Astronomy Picture of the Day Search Results for "( Opportunity OR Spirit ) AND rover"

APOD: 2019 March 14 - Perseverance Valley Panorama
Explanation: Mars exploration rover Opportunity's parting panorama from Perseverance Valley spans 360 degrees in this false color mosaic. The scene is composed of 354 individual images recorded through 3 different color filters by the rover's panoramic camera from May 13 through June 10, 2018. A few frames remain in black and white at the lower left though. Those were obtained through only one filter just before a dust storm engulfed Mars in June 2018, ultimately ending the solar-powered rover's trailblazing 15 year mission. Just right of center, the annotation identifies Opportunity's entry point to Perseverance Valley along the Endeavor crater's western rim. The rover's tracks begin there, extending from over the horizon toward the far right and its final resting spot on the Red Planet.

APOD: 2019 February 17 - Shadow of a Martian Robot
Explanation: What if you saw your shadow on Mars and it wasn't human? Then you might have been the Opportunity rover exploring Mars. Opportunity explored the red planet from 2004 to 2018, finding evidence of ancient water, and sending breathtaking images across the inner Solar System. Pictured here in 2004, Opportunity looks opposite the Sun into Endurance Crater and sees its own shadow. Two wheels are visible on the lower left and right, while the floor and walls of the unusual crater are visible in the background. Caught in a dust storm in 2018, last week NASA stopped trying to contact Opportunity and declared the ground-breaking mission, originally planned for only 92 days, complete.

APOD: 2019 February 15 - Opportunity at Perseverance Valley
Explanation: Opportunity had already reached Perseverance Valley by June of 2018. Its view is reconstructed in a colorized mosaic of images taken by the Mars Exploration Rover's Navcam. In fact, Perseverance Valley is an appropriate name for the destination. Designed for a 90 day mission, Opportunity had traveled across Mars for over 5,000 sols (martian solar days) following a January 2004 landing in Eagle crater. Covering a total distance of over 45 kilometers (28 miles), its intrepid journey of exploration across the Martian landscape has come to a close here. On June 10, 2018, the last transmission from the solar-powered rover was received as a dust storm engulfed the Red Planet. Though the storm has subsided, eight months of attempts to contact Opportunity have not been successful and its trailblazing mission ended after almost 15 years of exploring the surface of Mars.

APOD: 2018 October 4 - Opportunity After the Storm
Explanation: On Mars dust storms can't actually blow spacecraft over, but they can blot out the Sun. Over three months ago a planet-wide dust storm caused a severe lack of sunlight for the Mars rover Opportunity at its location near the west rim of Endeavour crater. The lack of sunlight sent the solar-powered Opportunity into hibernation and for over 115 sols controllers have not received any communication from the rover. The dust is clearing as the storm subsides though. On September 20th, when this image was taken by the Mars Reconnaissance Orbiter's HiRISE camera, about 25 percent of the sunlight was reaching the surface again. The white box marks a 47-meter-wide (154-foot-wide) area centered on a blip identified as the silent-for-now Opportunity rover.

APOD: 2018 June 23 - Curiosity's Dusty Self
Explanation: Winds on Mars can't actually blow spacecraft over. But in the low gravity, martian winds can loft fine dust particles in planet-wide storms, like the dust storm now raging on the Red Planet. From the martian surface on sol 2082 (June 15), this self-portrait from the Curiosity rover shows the effects of the dust storm, reducing sunlight and visibility at the rover's location in Gale crater. Made with the Mars Hand Lens Imager, its mechanical arm is edited out of the mosaicked images. Curiosity's recent drill site Duluth can be seen on the rock just in front of the rover on the left. The east-northeast Gale crater rim fading into the background is about 30 kilometers away. Curiosity is powered by a radioisotope thermoelectric generator and is expected to be unaffected by the increase in dust at Gale crater. On the other side of Mars, the solar-powered Opportunity rover has ceased its operations due to the even more severe lack of sunlight at its location on the west rim of Endeavour crater.

APOD: 2018 June 16 - Dusty With a Chance of Dust
Explanation: It's storm season on Mars. Dusty with a chance of dust is the weather report for Gale crater as a recent planet-scale dust storm rages. On June 10 looking toward the east-northeast crater rim about 30 kilometers away, the Curiosity rover's Mastcam captured this image of its local conditions so far. Meanwhile over 2,000 kilometers away, the Opportunity rover ceased science operations as the storm grew thicker at its location on the west rim of Endeavour crater, and has stopped communicating, waiting out the storm for now. Curiosity is powered by a radioisotope thermoelectric generator, but the smaller Opportunity rover uses solar panels to charge its batteries. For Opportunity, the increasingly severe lack of sunlight has caused its batteries to run low.

APOD: 2018 April 4 - Intrepid Crater on Mars from Opportunity
Explanation: The robotic rover Opportunity sometimes passes small craters on Mars. Pictured here in 2010 is Intrepid Crater, a 20-meter across impact basin slightly larger than Nereus Crater that Opportunity had chanced across previously. The featured image is in approximately true color but horizontally compressed to accommodate a wide angle panorama. Intrepid Crater was named after the lunar module Intrepid that carried Apollo 12 astronauts to Earth's Moon 49 years ago. Beyond Intrepid Crater and past long patches of rusty Martian desert lie peaks from the rim of large Endeavour Crater, visible on the horizon. The Opportunity rover continues to explore Mars, recently surpassing 5,000 Martian days on the red planet.

APOD: 2015 March 29 - Shadow of a Martian Robot
Explanation: What if you saw your shadow on Mars and it wasn't human? Then you might be the Opportunity rover currently exploring Mars. Opportunity has been exploring the red planet since early 2004, finding evidence of ancient water, and sending breathtaking images across the inner Solar System. Pictured above in 2004, Opportunity looks opposite the Sun into Endurance Crater and sees its own shadow. Two wheels are visible on the lower left and right, while the floor and walls of the unusual crater are visible in the background. Opportunity is continuing on its long trek exploring unusual terrain in Meridiani Planum which continues to yield clues to the ancient history of Mars, our Solar System, and even humanity.

APOD: 2014 September 29 - Unusual Rocks near Pahrump Hills on Mars
Explanation: How did these Martian rocks form? As the robotic Curiosity rover has approached Pahrump Hills on Mars, it has seen an interesting and textured landscape dotted by some unusual rocks. The featured image shows a curiously round rock spanning about two centimeters across. Seemingly a larger version of numerous spherules dubbed blueberries found by the Opportunity rover on Mars in 2004, what caused this roundness remains unknown. Possibilities include frequent tumbling in flowing water, sprayed molten rock in a volcanic eruption, or a concretion mechanism. The inset image, taken a few days later, shows another small but unusually shaped rock structure. As Curiosity rolls around and up Mount Sharp, different layers of the landscape will be imaged and studied to better understand the ancient history of the region and to investigate whether Mars could once have harbored life.

APOD: 2014 May 16 - Opportunity's Mars Analemma
Explanation: Staring up into the martian sky, the Opportunity rover captured an image at 11:02 AM local mean time nearly every 3rd sol, or martian day, for 1 martian year. Of course, the result is this martian analemma, a curve tracing the Sun's motion through the sky in the course of a year (668 sols) on the Red Planet. Spanning Earth dates from July, 16, 2006 to June 2, 2008 the images are shown composited in this zenith-centered, fisheye projection. North is at the top surrounded by a panoramic sky and landscape made in late 2007 from inside Victoria crater. The tinted martian sky is blacked out around the analemma images to clearly show the Sun's positions. Unlike Earth's figure-8-shaped analemma, Mars' analemma is pear-shaped, because of its similar axial tilt but more elliptical orbit. When Mars is farther from the Sun, the Sun progresses slowly in the martian sky creating the pointy top of the curve. When close to the Sun and moving quickly, the apparent solar motion is stretched into the rounded bottom. For several sols some of the frames are missing due to rover operations and dust storms.

APOD: 2014 March 2 - Martian Sunset
Explanation: What would it be like to see a sunset on Mars? To help find out, the robotic rover Spirit was deployed in 2005 to park and watch the Sun dip serenely below the distant lip of Gusev crater. Colors in the above image have been slightly exaggerated but would likely be apparent to a human explorer's eye. Fine martian dust particles suspended in the thin atmosphere lend the sky a reddish color, but the dust also scatters blue light in the forward direction, creating a bluish sky glow near the setting Sun. Because Mars is farther away, the Sun is less bright and only about two thirds the diameter it appears from Earth. Images like this help atmospheric scientists understand not only the atmosphere of Mars, but atmospheres across the Solar System, including our home Earth.

APOD: 2014 January 29 - Jelly Donut Shaped Rock Appears on Mars
Explanation: What if a rock that looked like a jelly donut suddenly appeared on Mars? That's just what happened in front of the robotic Opportunity rover currently exploring the red planet. The unexpectedly placed rock, pictured above, was imaged recently by Opportunity after not appearing in other images taken as recently as twelve Martian days (sols) before. Given the intriguing mystery, the leading explanation is somewhat tame -- the rock was recently scattered by one of the rover's tires. Even so, the rock's unusual light tones surrounding a red interior created interest in its composition -- as well as causing it to be nicknamed Jelly Donut. A subsequent chemical analysis showed the rock has twice the abundance of manganese than any other rock yet examined -- an unexpected clue that doesn't yet fit into humanity's understanding of the Martian geologic history. Opportunity, just passing its 10th anniversary on Mars, continues to explore the Murray Ridge section of the rim of 22-kilometer wide Endeavor Crater.

APOD: 2014 January 25 - Opportunity's Decade on Mars
Explanation: On January 25 (UT) 2004, the Opportunity rover fell to Mars, making today the 10th anniversary of its landing. After more than 3,500 sols (Mars solar days) the golf cart-sized robot from Earth is still actively exploring the Red Planet, though its original mission plan was for three months. This self-portrait was made with Opportunity's panoramic camera earlier this month. The camera's supporting mast has been edited out of the image mosaic but its shadow is visible on the dusty solar panels arrayed across the rover's deck. For comparison, a similar self-portrait from late 2004 is shown in the inset. Having driven some 39 kilometers (24 miles) from its landing site, Opportunity now rests at Solander Point at the rim of Endeavour Crater.

APOD: 2013 December 8 - Everest Panorama from Mars
Explanation: If you could stand on Mars -- what might you see? Scroll right to find out. The robotic Spirit rover that rolled around Mars from 2004 to 2009 Mars climbed to the top of a hill in 2005 and took a series of images over three days that were then digitally combined into a 360 degree panorama. Spirit was instructed to take images having the same resolution as a human with 20-20 eyesight. The full panoramic result can be found by clicking on the above image and has a level of detail unparalleled in the history of Martian surface photography. The panorama was taken from the pinnacle of Husband Hill and has been dubbed the Everest panorama, in honor of the view from the tallest mountain on Earth. Visible in Gusev Crater are rocks, rusting sand, a Martian sundial, vast plains, nearby peaks, faraway peaks, and sand drifts. In the distance, fast moving dust devils can be seen as slight apparitions of red, green, or blue, the colors of filters used to build up this natural color vista.

APOD: 2013 January 25 - Matijevic Hill Panorama
Explanation: On January 25 (UT) 2004, the Opportunity rover fell to Mars, making today the 9th anniversary of its landing. After more than 3,200 sols (Mars solar days) the golf cart-sized robot from Earth is still actively exploring the Red Planet, though its original mission plan was for three months. Having driven some 35 kilometers (22 miles) from its landing site, Opportunity's panoramic camera recorded the segments of this scene, in November and December of last year. The digitally stitched panorama spans more than 210 degrees across the Matijevic Hill area along the western rim of Endeavour Crater. Features dubbed Copper Cliff, a dark outcrop, appear at the left, and Whitewater Lake, a bright outcrop, at the far right. The image is presented here in a natural color approximation of what the scene would look like to human eyes.

APOD: 2012 September 25 - Unusual Spheres on Mars
Explanation: Why are these strange little spheres on Mars? The robotic rover Opportunity chanced across these unusually shaped beads earlier this month while exploring a place named Kirkwood near the rim of Mars' Endeavour Crater. The above image taken by Opportunity's Microscopic Imager shows that some ground near the rover is filled with these unusual spheres, each spanning only about 3 millimeters. At first glance, the sometimes-fractured balls appear similar to the small rocks dubbed blueberries seen by Opportunity eight years ago, but these spheres are densely compacted and have little iron content. Although it is thought that these orbs formed naturally, which natural processes formed them remain unknown. Opportunity, an older sibling to the recently deployed Curiosity rover, will continue to study these spheres with the hope that they will provide a new clue to the ancient history of the surface of the red planet.

APOD: 2012 July 11 - A Morning Line of Stars and Planets
Explanation: Early morning dog walkers got a visual treat last week as bright stars and planets appeared to line up. Pictured above, easily visible from left to right, were the Pleiades open star cluster, Jupiter, Venus, and the "Follower" star Aldebaran, all seen before a starry background. The image was taken from the Atacama desert in western South America. The glow of the rising Sun can be seen over the eastern horizon. Jupiter and Venus will continue to dazzle pre-dawn strollers all over planet Earth for the rest of the month, although even now the morning planets are seen projected away from the line connecting their distant stellar sky mates.

APOD: 2012 July 9 - Greeley Panorama on Mars
Explanation: What did you do over your winter vacation? If you were the Opportunity rover on Mars, you spent four months of it stationary and perched on the northern slope of Greeley Haven -- and tilted so that your solar panels could absorb as much sunlight as possible. During its winter stopover, the usually rolling robot undertook several science activities including snapping over 800 images of its surroundings, many of which have been combined into this 360-degree digitally-compressed panorama and shown in exaggerated colors to highlight different surface features. Past tracks of Opportunity can be seen toward the left, while Opportunity's dust covered solar panels cross the image bottom. Just below the horizon and right of center, an interior wall of 20-kilometer Endeavour Crater can be seen. Now that the northern Martian winter is over, Opportunity is rolling again, this time straight ahead (north). The rover is set to investigate unusual light-colored soil patches as it begins again to further explore the inside of Endeavour, a crater that may hold some of the oldest features yet visited.

APOD: 2012 January 25 - Opportunity Rover Spots Greeley Haven on Mars
Explanation: Where on Mars should you spend the winter? As winter approached in the southern hemisphere of Mars last November, the Opportunity rover had just this problem -- it needed a place to go. The reduced amount of sunlight impacting Opportunity's solar panels combined with the extra power needed to keep equipment warm could drain Opportunity's batteries. Therefore Opportunity was instructed to climb onto the 15 degree incline of Greeley's Haven, shown as the rocky slope ahead. The incline increased power input as Opportunity's solar panels now have greater exposure to sunlight, while also giving the rolling robot some interesting landscape to explore. Visible in the distance, beyond Greeley Haven, lies expansive Endeavour Crater, the ancient impact basin that Opportunity will continue exploring as the Martian winter concludes in a few months, if it survives.

APOD: 2011 December 12 – An Unusual Vein of Deposited Rock on Mars
Explanation: What could create this unusual vein of rock on Mars? A leading hypothesis is that this thin rock layer dubbed "Homestake" was deposited by a running liquid -- like most mineral veins are here on Earth. And the running liquid of choice is water. Therefore, this mineral streak -- rich in calcium and sulfur -- is the latest in the growing body of evidence that part of Mars had a watery past. This, in turn, increases the speculation that Mars was once hospitable to life. Pictured above is a vista taken near the western rim of Endeavour Crater by the Opportunity rover currently exploring Mars. The inset image shows a close up of the recently discovered mineral vein.

APOD: 2011 November 30 - Curiosity Rover Lifts Off for Mars
Explanation: Next stop: Mars. This past weekend the Mars Science Laboratory carrying the Curiosity Rover blasted off for the red planet atop an Atlas V rocket from Cape Canaveral, Florida, USA, as pictured above. At five times the size of the Opportunity rover currently operating on Mars, Curiosity is like a strange little car with six small wheels, a head-like camera mast, a rock crusher, a long robotic arm, and a plutonium power source. Curiosity is scheduled to land on Mars next August and start a two year mission to explore Gale crater, to help determine whether Mars could ever have supported life, and to help determine how humans might one day visit Earth's planetary neighbor.

APOD: 2011 September 12 - Tisdale 2 Rock Formation on Mars
Explanation: Why does this Martian rock have so much zinc? Roughly the size and shape of a tilted coffee-table, this oddly flat, light-topped rock outcropping was chanced upon a few weeks ago by the robotic Opportunity rover currently rolling across Mars. Early last month Opportunity reached Endeavour crater, the largest surface feature it has ever encountered, and is now exploring Endeavour's rim for clues about how wet Mars was billions of years ago. Pictured above and named Tisdale 2, the unusual rock structure was probed by Opportunity last week and is now thought to be a remnant thrown off during the impact that created nearby Odyssey crater. The resulting chemical analysis of Tisdale 2, however, has shown it to have a strangely high amount of the element zinc. The reason for this is currently unknown, but might turn out to be a clue to the history of the entire region. Opportunity is already finding rocks older than any previously studied and will continue to explore several other intriguing rock formations only now glimpsed from a distance.

APOD: 2011 August 15 - Rover Arrives at Endeavour Crater on Mars
Explanation: What can the present-day terrain in and around large Endeavour crater tell us about ancient Mars? Starting three years ago, NASA sent a coffee-table sized robot named Opportunity on a mission rolling across the red planet's Meridiani Planum to find out. Last week, it finally arrived. Expansive Endeavour crater stretches 22 kilometers from rim to rim, making it the largest crater ever visited by a Mars Exploration Rover (MER). It is hypothesized that the impact that created the crater exposed ancient rock that possibly formed under wet conditions, and if so, this rock may yield unique clues to the watery past of Mars. Pictured above, the west rim of Endeavour looms just ahead of the Opportunity rover. Opportunity may well spend the rest of its operational life exploring Endeavour, taking pictures, spinning its wheels, and boring into intriguing rocks.

APOD: 2011 July 31 - Metal on the Plains of Mars
Explanation: What has the Opportunity rover found on Mars? While traversing a vast empty plain in 2005 in Meridiani Planum, one of Earth's rolling robots on Mars found a surprise when visiting the location of its own metallic heat shield discarded last year during descent. The surprise is the rock visible on the lower left, found to be made mostly of dense metals iron and nickel. The large cone-shaped object behind it -- and the flank piece on the right -- are parts of Opportunity's jettisoned heat shield. Smaller shield debris is also visible. Scientists do not think that the basketball-sized metal "Heat Shield Rock" originated on Mars, but rather is likely an ancient metallic meteorite. In hindsight, finding a meteorite in a vast empty dust plain on Mars might be considered similar to Earth meteorites found on the vast empty ice plains of Antarctica. The finding raises speculations about the general abundance of rocks on Mars that have fallen there from outer space.

APOD: 2011 May 30 - The Last Panorama of the Spirit Rover on Mars
Explanation: This is the last thing that the Spirit rover on Mars ever saw. Operating years beyond original expectations, Spirit eventually got mired in martian dirt and then ran out of power when investigating the unusual Home Plate surface feature on Mars. Visible in the above panorama are numerous rocks and slopes of the surrounding Columbia Hills of Mars. The strange hill with the light colored top, visible near the top center of the image, has been dubbed von Braun and was a future destination when Spirit got bogged down. A leading hypothesis holds that von Braun is related to martian volcanism. Last week, NASA stopped trying to contact Spirit after numerous attempts. Half a world away, Spirit's sister rover Opportunity continues to roll toward Endeavour Crater, which could become the largest crater yet visited by an earthling-created robot.

APOD: 2011 May 8 - Shadow of a Martian Robot
Explanation: What if you saw your shadow on Mars and it wasn't human? Then you might be the Opportunity rover currently exploring Mars. Opportunity and sister robot Spirit have been probing the red planet since early 2004, finding evidence of ancient water, and sending breathtaking images across the inner Solar System. Pictured above, Opportunity looks opposite the Sun into Endurance Crater and sees its own shadow. Two wheels are visible on the lower left and right, while the floor and walls of the unusual crater are visible in the background. Although the Spirit rover is now stuck, Opportunity is continuing on its long trek to expansive Endeavor crater.

APOD: 2011 January 29 - Opportunity at Santa Maria Crater
Explanation: Celebrating 7 years on the surface of the Red Planet, Mars exploration rover Opportunity now stands near the rim of 90 meter wide Santa Maria crater. Remarkably, Opportunity and its fellow rover Spirit were initially intended for a 3 month long primary mission. Still exploring, the golf cart-sized robot and shadow (far right) appear in the foreground of this panoramic view of its current location. The mosaic was constructed using images from the rover's navigation camera. On its 7 year anniversary, Opportunity can boast traversing a total of 26.7 kilometers along the martian surface. After investigating Santa Maria crater, controllers plan to have Opportunity resume a long-term trek toward Endeavour crater, a large, 22 kilometer diameter crater about 6 kilometers from Santa Maria. The rim of Endeavour is visible in the mosaic on the horizon at the right, just above the shadow of the rover's mast. During coming days, communication with the rover will be more difficult as Mars moves close to alignment with the Sun as seen from planet Earth's perspective.

APOD: 2010 December 8 - Intrepid Crater on Mars
Explanation: The robotic rover Opportunity has chanced across another small crater on Mars. Pictured above is Intrepid Crater, a 20-meter across impact basin slightly larger than Nereus Crater that Opportunity chanced across last year. The above image is in approximately true color but horizontally compressed to accommodate a wide angle panorama. Intrepid Crater was named after the lunar module Intrepid that carried Apollo 12 astronauts to Earth's Moon 41 years ago last month. Beyond Intrepid Crater and past long patches of rusty Martian desert lie peaks from the rim of large Endeavour Crater, visible on the horizon. If Opportunity can avoid ridged rocks and soft sand, it may reach Endeavour sometime next year.

APOD: 2010 October 4 - Rolling Across the Rocky Plains of Mars
Explanation: You stare out across the rocky plains of Mars. Before you, in every direction, is dark sand and bright rock. Although little has changed here for millions of years, no one has ever seen this view before. You are being sent on a long journey to a distant crater, the largest crater in the region. Your human overlords back on planet Earth wonder if the impact that created this distant crater might have also uncovered unique clues to the distant past of Earth's neighboring planet, clues that might reveal if life ever existed here. Breaking the monotony, visible toward the image center, an unusual rock sticks out from the landscape. Quite possibly, this rock is not from this world, and you divert to inspect it. You are the robotic Opportunity rover, and you are the eyes for countless humans following your trek back on planet Earth. Rolling about a football field a day, you might reach Endeavour crater sometime in 2012. If you survive.

APOD: 2010 August 30 - Comanche Outcrop on Mars Indicates Hospitable Past
Explanation: Could life once have survived on Mars? Today, neither animal nor plant life from Earth could survive for very long on Mars because at least one key ingredient -- liquid water -- is essentially absent on the red planet's rusty surface. Although evidence from the martian rovers indicates that long ago Mars might once have had liquid water on its surface, that water might also have been too acidic for familiar life forms to thrive. Recently, however, a newly detailed analysis of an unusual outcropping of rock and soil chanced upon in 2005 by the robotic Spirit rover has uncovered a clue indicating that not all of Mars was always so acidic. The mound in question, dubbed Comanche Outcrop and visible near the top of the above image, appears to contain unusually high concentrations of elements such as magnesium iron carbonate. The above image is shown in colors exaggerated to highlight the differences in composition. Since these carbonates dissolve in acid, the persistence of these mounds indicates that water perhaps less acidic and more favorable for life might have once flowed across Mars. More detailed analyses and searches for other signs will surely continue.

APOD: 2010 May 25 - Looking Back Across Mars
Explanation: It's been a long trip for the Martian rover Opportunity. Last week Opportunity surpassed Viking 1 as the longest running mission on Mars, now extending well over six years. Pictured above, Opportunity's tire tracks cross a nearly featureless Martian desert, emanating from a distant horizon. Landing in 2004 in Meridiani Planum, the robotic Opportunity has embarked on its longest and most dangerous trek yet, now aiming to reach large Endeavor Crater sometime next year. Endeavor, it is hoped, holds new clues to the ancient geology of Mars and whether Mars could once have harbored life.

APOD: 2010 March 7 - Spirit Rover at Engineering Flats on Mars
Explanation: Is it art? If so, the paintbrush was the Spirit robotic rover, the canvas was the soil on Mars, and the artists were the scientists and engineers of the Mars Exploration Rover Mission. This panoramic picture, created in 2004 and shown above compressed horizontally, was mostly unintentional -- the MERS team was primarily instructing Spirit to investigate rocks in and around Hank's Hollow in a location called Engineering Flats on Mars. After creating the ground display with its treads, the Spirit rover was instructed to photograph the area along with itself in shadow. In 2010 as winter approaches in northern Mars, Spirit, still mired in sand, has been placed in an energy saving "hibernating" mode until spring arrives and more direct sunlight might be used to power the robotic explorer.

APOD: 2009 October 19 - Nereus Crater on Mars
Explanation: It was along the way. The robotic rover Opportunity currently rolling across the Meridiani Plain on Mars has a destination of Endeavour Crater, a large crater over 20 kilometers across which may yield additional clues about the cryptic past of ancient Mars. Besides passing open fields of dark soil and light rock, Opportunity has chanced upon several interesting features. One such feature, pictured above in a digitally stitched and horizontally compressed panorama, is Nereus Crater, a small crater about 10 meters across that is surrounded by jagged rock. Besides Nereus, Opportunity recently also happened upon another unusual rock -- one that appears to be the third large meteorite found on Mars and the second for Opportunity during only this trip. Opportunity has been traveling toward Endeavour Crater for over a year now, and if it can avoid ridged rocks and soft sand along the way, it may reach Endeavour sometime next year.

APOD: 2009 August 13 - Block Island Meteorite on Mars
Explanation: What is this strange rock on Mars? Sitting on a smooth plane, the rock stands out for its isolation, odd shape, large size and unusual texture. The rock was discovered by the robotic Opportunity rover rolling across Mars late last month. Pictured, Opportunity prepares to inspect the unusual rock. After being X-rayed, poked, and chemically analyzed, the rock has now been identified by Opportunity as a fallen meteorite. Now dubbed Block Island, the meteorite has been measured to be about 2/3 of a meter across and is now known to be composed mostly of nickel and iron. This is the second meteorite found by a martian rover, and so far the largest. Vast smooth spaces on Mars and Earth can make large meteorites stand out. Opportunity continues its trip across Meridiani Planum on Mars and is on schedule to reach expansive Endeavour Crater next year.

APOD: 2009 June 1 - Spirit Encounters Soft Ground on Mars
Explanation: Will Spirit be able to free itself from soft ground on Mars? The robotic Spirit rover currently rolling across Mars ran into unexpectedly soft ground last month while exploring the red planet. A worry is that the ground is so soft that Spirit won't be able to free itself, will have to stay put and thereafter study what it can from its current position near an unusual martian land feature named Home Plate. Pictured above, the front left wheel appears to be primarily digging itself in when spun, while on the other side, the front right wheel no longer spins and is dragged by the five year old mechanical explorer. In the distance, rocks and rusty dirt fill the alien landscape in front of the distant Husband Hill. NASA continues to study the situation, and engineers and scientists have not yet run out of ideas of how to use Spirit's six wheels. Far across Mars, Spirit's twin Opportunity continues on its two year trek toward Endeavour crater.

APOD: 2009 March 24 - Martian Dunes and the Shadow of Opportunity
Explanation: Human made robots continue to roll across the surface of Mars. Both Opportunity and its sister rover Spirit are in their sixth year on Mars, exploring the red planet for years longer than original expectations. Pictured above is a composite of recent images taken by the navigation camera on top of the Opportunity rover in Meridiani Planum. Visible are parallel rover tracks, rippling sand dunes, light-colored bedrock protrusions, metallic rover parts, and the dark shadow of the sometimes-artistic robotic photographer. Currently, Opportunity is on its way toward huge Endeavor crater, while Spirit is trying to climb an unusual rock structure known as Home Plate. If it can survive the harsh martian environment, Opportunity should arrive at Endeavor crater in about two years, at which time it may revolutionize human knowledge of this ancient martian landform.

APOD: 2009 January 20 - Bonestell Panorama from Mars
Explanation: If you could stand on Mars -- what could you see? One memorable vista might be the above 360-degree panoramic image taken by the robotic Spirit rover over the last year. The above image involved over 200 exposures and was released as part of Spirit's five year anniversary of landing on the red planet. The image was taken from the spot that Spirit stopped to spend the winter, near an unusual plateau called Home Plate. Visible on the annotated image are rocks, hills, peaks, ridges, plains inside Gusev crater, and previous tracks of the rolling Spirit rover. The image color has been closely matched to what a human would see, and named for the famous space artist Chesley Bonestell.

APOD: 2009 January 10 - Martian Sunset
Explanation: This month, the Mars Exploration Rovers are celebrating their 5th anniversary of operations on the surface of the Red Planet. The serene sunset view, part of their extensive legacy of images from the martian surface, was recorded by the Spirit rover on May 19, 2005. Colors in the image have been slightly exaggerated but would likely be apparent to a human explorer's eye. Of course, fine martian dust particles suspended in the thin atmosphere lend the sky a reddish color, but the dust also scatters blue light in the forward direction, creating a bluish sky glow near the setting Sun. The Sun is setting behind the Gusev crater rim wall some 80 kilometers (50 miles) in the distance. Because Mars is farther away, the Sun is less bright and only about two thirds the size seen from planet Earth.

APOD: 2008 June 29 - Shadow of a Martian Robot
Explanation: What if you saw your shadow on Mars and it wasn't human? Then you might be the Opportunity rover currently exploring Mars. Opportunity and sister robot Spirit have been probing the red planet since early 2004, finding evidence of ancient water, and sending breathtaking images across the inner Solar System. Pictured above, Opportunity looks opposite the Sun into Endurance Crater and sees its own shadow. Two wheels are visible on the lower left and right, while the floor and walls of the unusual crater are visible in the background. Opportunity and Spirit have now spent over four years exploring the red world, find new clues into the wet ancient past of our Solar System's second most habitable planet.

APOD: 2008 May 19 - Flying Over the Columbia Hills of Mars
Explanation: What it would be like to fly over Mars? Combining terrain data from the orbiting Mars Reconnaissance Orbiter spacecraft with information about the robotic Spirit rover currently rolling across Mars has resulted in a digital movie that shows what a flight over the Columbia Hills might look like. Dark rippled sand dunes are highlighted against the Columbia Hills in the above opening image. Clicking on the above image, though, will launch you across Mars, approaching the Columbia Hills. On the far side of the hills, the dark sand dunes come into view. Soon you pass an unusual white-rimmed structure, slightly raised, known as Home Plate, the origin of which is currently unknown and being researched. Turning, you re-approach the hills from a different angle, this time zooming in on Spirit, a curious alien rover sent from planet Earth. A final zoom pans out over the region. This coming Sunday, NASA's Phoenix Lander will attempt to set down near the icy North Pole of Mars and search for signs of ancient life.

APOD: 2008 January 29 - West Valley Panorama from the Spirit Rover on Mars
Explanation: What does Mars look like from here? Last September, before hiking across rugged and slippery terrain to reach its winter hibernation point, the robotic Spirit rover climbed a small plateau known as Home Plate and captured the spectacular vista pictured above. Part of the curious flat-topped Home Plate is visible as the light colored landscape across the panorama's foreground. On the image left, visible about eight kilometers in the distance, is Grissom Hill, while on the left foreground is rock strewn Tsiolkovski Ridge. On the right, at about 800 meters distant, is Husband Hill, already explored by Spirit and notable as the highest point visible in the westward looking panorama. In the inset is a close-up of a tiny motionless feature informally dubbed Little Bigfoot that has drawn some attention for it superficial appearance to a humanoid life form. Tenacious image explorers might locate Little Bigfoot towards the front left of the high resolution panorama. Spirit successfully reached its energy-conserving winter haven in December.

APOD: 2007 December 18 - Unusual Silica Rich Soil Discovered on Mars
Explanation: You're rolling across Mars when you unexpectedly uncover some unusually light soil. You stop. You turn. You return to inspect the soil and find out it is almost purely silica -- the main ingredient in quartz and glass. Such soil has never been found on Mars before. What created this soil? Since you are the robotic rover Spirit currently rolling across Mars, you send the images and data back to Earth for analysis. Your scientist friends from the blue water planet say that such soil on Earth is usually created by either volcanic steam or a hot spring. The second hypothesis in particular indicates, once again, a wet past for part of Mars, as possibly hot water saturated with silica deposited the white soil. Intriguingly, on Earth, living microbes typically flourish under either condition. Pictured above, the uncovered light soil is visible on the right.

APOD: 2007 December 12 - Mars Rover Races to Survive
Explanation: The Martian rover Spirit is now in the race of its life. The rolling robot is trying to reach an outpost to spend the winter, but it keeps getting bogged down in soft sand on Mars. Earth scientists hope that Spirit can reach a slope on the northern edge of the unusual feature dubbed Home Plate, before the end of this month when northern winter will be phasing in on Mars. Reaching this slope will likely allow the rover to tilt enough toward the Sun to create a needed increase in the efficiency of its energy-absorbing solar panels. This map shows the path of Spirit from July 2004 until just last month.

APOD: 2007 October 22 - Victoria Crater on Mars
Explanation: Scroll right to see the largest crater yet visited by a rover on Mars. Reaching the expansive Victoria Crater has been a goal for the robotic Opportunity rover rolling across Mars for the past two years. Victoria crater has about five times the diameter of Endurance Crater, which Opportunity spent six months exploring. Opportunity reached Victoria last year, and was cautiously probing the edges of the stadium-sized crevice while waiting for large dust storms to clear. A safe path was found, and Opportunity has slowly entered into Victoria Crater. It is hoped that Victoria Crater will show a deep stack of layers uncovered by the initial impact, and hence new clues into the ancient surface history of Mars. Visible in the distance in the above mosaic is the far rim of Victoria Crater, lying about 800 meters away and rising about 70 meters above the crater floor. The alcove in front has been dubbed Duck Bay.

APOD: 2007 September 17 - Inside Victoria Crater on Mars
Explanation: NASA's Opportunity rover is now inside Victoria Crater on Mars. Last week the robot rolled about 20 meters into the largest crater any Martian rover has yet encountered, the crater next to which Opportunity has been perched for months. Currently, the rolling explorer is situated in Duck Bay alcove, peering across at the internal crater wall dubbed Cape St. Vincent. The above wide-angle view is from Opportunity's front hazard-identification camera. Over the next few weeks, Opportunity is scheduled to explore this telling alien indentation, searching for clues to the ancient past of Mars before the huge impact that created Victoria Crater ever took place.

APOD: 2007 September 4 - A Path Into Victoria Crater
Explanation: What's inside Victoria Crater? Now that the dust has settled from the regional Martian dust storms that immobilized the rolling Martian rovers, the task ahead has become clear. Opportunity arrived at Victoria Crater last month and was poised to enter when the dust storms flared up unexpectedly. The above image was taken last week by the Opportunity rover perched at a possibly traversable slope into the 750-meter impact feature. Victoria Crater is the largest crater that either Martian rover has come across during their explorations. The crater walls might hold clues about the Martian surface before the tremendous impact that created Victoria Crater.

APOD: 2007 July 25 - Global Dust Storms Threaten Mars Rovers
Explanation: Will global dust storms terminate the robotic Martian rovers? Over the past month, windy dust storms have blocked much needed sunlight from reaching the solar panels of both the Spirit and Opportunity rovers exploring Mars. At times, as much as 99 percent of direct sunlight has been obscured, causing worry that the batteries might run out of energy before the storms end -- which may be as long as weeks. In an effort to weather these storms, Earth controllers have programmed the rovers to restrict movements and to use as little power as possible. Although the rovers have been working for a remarkable three years past their planned three month lifetimes, their immediate future is now uncertain. Pictured above, the Opportunity rover perched on the edge of Victoria Crater peered for a month into the distance as dust made the Martian air increasingly opaque.

APOD: 2007 July 3 - At the Edge of Victoria Crater
Explanation: We're going in. The robotic Opportunity rover currently rolling across Mars has been prowling around the edge of the largest crater it has visited since landing over three years ago. It has been studying Victoria crater and looking for a way in. Now scientists on Earth have decided to take a calculated risk and plan to send Opportunity right into this ancient Martian crater over the next few weeks. Pictured is Cape St. Vincent, part of the wall of Victoria Crater next to where Opportunity will descend. The wall itself appears to contain clues about the Martian terrain before the impact that created Victoria crater, and so will be studied during the daring descent. Above the crater wall, far in the distance, lies a relatively featureless Martian horizon.

APOD: 2007 March 13 - Attacking Mars
Explanation: The Spirit rover attacked Mars again in 2005 September. What might look, above, like a military attack, though, was once again just a scientific one - Spirit was instructed to closely inspect some interesting rocks near the summit of Husband Hill. Spirit's Panoramic Camera captured the rover's Instrument Deployment Device above as moved to get a closer look at an outcrop of rocks named Hillary. The Spirit rover, and its twin rover Opportunity, have now been exploring the red planet for over three years. Both Spirit and Opportunity have found evidence that parts of Mars were once wet.

APOD: 2007 February 4 - Shadow of a Martian Robot
Explanation: What if you saw your shadow on Mars and it wasn't human? Then you might be the Opportunity rover currently exploring Mars. Opportunity and sister robot Spirit have been probing the red planet since early 2004, finding evidence of ancient water, and sending breathtaking images across the inner Solar System. Pictured above, Opportunity looks opposite the Sun into Endurance Crater and sees its own shadow. Two wheels are visible on the lower left and right, while the floor and walls of the unusual crater are visible in the background. Opportunity and Spirit have now spent over three years exploring the red world, find new clues into the wet ancient past of our Solar System's second most habitable planet.

APOD: 2006 December 6 - Spirit Rover on Mars Imaged from Orbit
Explanation: If you have the right equipment, you can see the Spirit rover currently rolling across Mars. The right equipment, however, is currently limited to the High Resolution Imaging Science Experiment onboard the Mars Reconnaissance Orbiter (MRO). MRO arrived at Mars in March and just started science observations of the red planet last month. Visible in the above spectacularly high resolution image is the Spirit rover in the Columbia Hills of Mars. Objects as small as one meter are resolved. Also visible are the tracks made by the robot explorer and a large plateau of layered rock dubbed Home Plate. MRO will continue to image the red planet in unprecedented detail, creating images that will likely be important in better understanding the geology and weather on Mars, as well as indicating good candidate landing sites for future missions to Mars.

APOD: 2006 November 1 - McMurdo Panorama from Mars
Explanation: This was Spirit's view on Martian-day 1,000 of its 90-Martian-day mission. The robotic Spirit rover has stayed alive so long on Mars that it needed a place to wait out the cold and dim Martian winter. Earth scientists selected Low Ridge hill, a place with sufficient slant to give Spirit's solar panels enough sunlight to keep powered up and making scientific observations. From its Winter Haven, Spirit has been able to build up the above 360-degree panorama, which has been digitally altered to exaggerate colors and compressed horizontally to fit your screen. The long winter is finally ending in the south of Mars, and with the increasing sunlight plans are now being made for Spirit to further explore the rocky Columbia Hills inside intriguing Gusev crater.

APOD: 2006 October 17 - Clouds and Sand on the Horizon of Mars
Explanation: If you could stand on Mars -- what might you see? Like the robotic Opportunity rover rolling across the red planet, you might well see vast plains of red sand, an orange tinted sky, and wispy light clouds. The Opportunity rover captured just such a vista after arriving at Victoria Crater earlier this month, albeit in a completely different direction from the large crater. Unlike other Martian vistas, few rocks are visible in this exaggerated color image mosaic. The distant red horizon is so flat and featureless that it appears similar to the horizon toward a calm blue ocean on Earth. Clouds on Mars can be composed of either carbon dioxide ice or water ice, and can move quickly, like clouds move on Earth. The red dust in the Martian air can change the sky color above Mars from the blue that occurs above Earth toward the red, with the exact color depending on the density and particle size of the floating dust particles.

APOD: 2006 October 9 - Mars Rover at Victoria Crater Imaged from Orbit
Explanation: An unusual spot has been found on Mars that scientists believe is not natural in origin. The spot appears mobile and is now hypothesized to be a robot created by an intelligent species alien to Mars. In fact, the spot appears to be NASA's robotic Opportunity rover currently rolling across Mars. The ability to see the Martian rover from orbit has recently been demonstrated by the High Resolution Imaging Science Experiment on NASA's Mars Reconnaissance Orbiter (MRO). The new spacecraft achieved orbit around Mars in 2006 March. Last week, MRO imaged the location of Victoria Crater and the rover Opportunity that had just arrived there. In the above image at spectacularly high resolution, objects about one meter in size are resolved, and this includes the rolling rover. Such images may help scientists better determine if any safe path exists for Opportunity to enter large crater. In the inset image on the upper left, the whole of Victoria Crater was also imaged by MRO.

APOD: 2006 October 2 - Victoria Crater on Mars
Explanation: Scroll right to see the largest crater yet visited by a rover on Mars. Reaching the expansive Victoria Crater has been a goal for the robotic Opportunity rover rolling across Mars for the past 21 months. Opportunity reached Victoria last week, and is cautiously probing the stadium-sized crevice. It is hoped that Victoria Crater will show a deep stack of layers uncovered by the initial impact, and hence new clues into the ancient surface history of Mars. Visible in the distance of the above image mosaic is the far rim of Victoria Crater, lying about 800 meters away and rising about 70 meters above the crater floor. The alcove in front has been dubbed Duck Bay. Victoria crater has about five times the diameter of Endurance Crater, which Opportunity spent six months exploring. If a safe path is found, Opportunity may actually attempt to enter Victoria Crater.

APOD: 2006 September 19 - Beagle Crater on Mars
Explanation: What have we found on the way to large Victoria Crater? Smaller Beagle Crater. The robotic Opportunity rover rolling across Mars stopped at Beagle Crater early last month and took an impressively detailed 360-degree panorama of the alien Martian landscape. Beagle crater appears in the center as a dip exposing relatively dark sand. Surrounding 35-meter Beagle Crater are many of the rocks ejected during its creation impact. Opportunity's detailed images show significant erosion on the rocks and walls of Beagle Crater, indicating that the crater is not fresh. Beagle Crater's unofficial name derives from the ship HMS Beagle where Charles Darwin observations led him to postulate his theory of natural selection. That ship was named after the dog breed of beagle. Opportunity is scheduled to roll up to expansive Victoria Crater this week.

APOD: 2006 August 4 - Burns Cliff Anaglyph
Explanation: Get out your red/blue glasses and gaze across Burns Cliff along the inner wall of Endurance crater on Mars! The view from the perspective of Mars rover Opportunity is a color anaglyph - two different images are presented to the left and right eyes by color filters to produce the 3D effect. Scroll the picture to the right to see the full 180 degree panorama. Still returning science data and images, both Spirit and Opportunity rovers completed 2 years of Mars exploration in January. Opportunity spent the month of July on the road to Victoria crater. The stereo pair of images used to create this view are based on image data recorded in November 2004.

APOD: 2006 July 21 - Strangers on Mars
Explanation: This view from the winter station of Mars Exploration Rover Spirit, looks across the rock strewn landscape of Gusev Crater. The dark boulders and distant hills are characteristic of the region, but the two light colored rocks in the foreground of this cropped image are - like Spirit itself - most probably strangers to the Red Planet, believed to be iron meteorites. Informally named for sites in Antarctica they have been dubbed "Zhong Shan" and "Allan Hills." Zhong Shan is the Antarctic base of the People's Republic of China. Allan Hills is the icy location where many Martian meteorites have been found on planet Earth, including the controversial ALH84001, suggested to contain evidence for fossilized Martian microbial life.

APOD: 2006 July 3 - The View toward Husband Hill on Mars
Explanation: This Martian vista is only part of one of the greatest panoramic views of Mars that has ever been attempted. The expansive mosaic is helping to keep the robotic Spirit rover busy over the energy draining winter in the southern hemisphere of Mars. During the winter, Spirit is constrained to stay on the side of McCool Hill in order to keep its solar panels pointed toward the Sun. The panorama has so far involved over 800 exposures, very little digital compression, and will take over a month to complete. The view shown is toward Husband Hill, a hill that Spirit climbed last year. A careful inspection of the above image shows tracks crossing from the center to the right.

APOD: 2006 June 5 - The Road to Victoria Crater on Mars
Explanation: Here is a road never traveled. To get to Victoria Crater on Mars, the rolling robotic rover Opportunity must traverse the landscape shown above. Victoria Crater lies about one kilometer ahead. The intervening terrain shows a series of light rock outcrops that appears like some sort of cobblestone road. Surrounding this naturally-occurring Martian road, is Martian sand ripples that must be navigated around. Inspection of the outcrop road shows it to be sprinkled with many small round rocks dubbed blueberries. Opportunity and its sister robot Spirit continue their third year exploring Mars. Within the next month, planetary scientists hope to maneuver Opportunity across Meridiani Planum to get a good view of 800-meter diameter Victoria Crater.

APOD: 2006 May 15 - Volcanic Bumpy Boulder on Mars
Explanation: What created this unusually textured rock on Mars? Most probably: a volcano. Dubbed Bumpy Boulder, the strange stone measuring just under a half-meter high was found by the robotic Spirit rover currently rolling across Mars. Pits on the ragged rock are likely vesicles and arise from hot gas bubbling out of hot rock ejected by an active Martian volcano. Several similar rocks are visible near Bumpy Boulder that likely have a similar past. The above true-color image was taken about one month ago. The Spirit rover, now in its third year of operation on Mars, is weathering the low sunlight winter of Mar's northern hemisphere on a hillside slope in order to maximize the amount of absorbable battery-refreshing sunlight.

APOD: 2006 April 6 - Unusual Bright Soil on Mars
Explanation: What is this bright soil on Mars? Several times while rolling across Mars, the treads of the robotic rover Spirit have serendipitously uncovered unusually bright soil. Spirit uncovered another batch unexpectedly last month while rolling toward its winter hibernation location on McCool Hill. The physics and chemistry instruments on Spirit have determined the soil, shown above, contains a high content of salts including iron-bearing sulfates. A leading hypothesis holds that these salts record the presence of past water, with the salts becoming concentrated as the water evaporated.

APOD: 2006 March 15 - McCool Hill on Mars
Explanation: You can make it. Winter is rapidly advancing on the southern hemisphere on Mars, and the lack of sunlight could be dangerous unless you find a good place to hibernate. There it is ahead: McCool Hill. As the robotic Spirit rover rolling across Mars, you are told that this will be a good place to spend the Martian winter. On the north slope of McCool Hill, you can tilt your solar panels toward the Sun enough to generate the power you need to keep running through the winter. Between you and McCool Hill is an unusual reddish outcropping of rocks. Also visible above, unusual layered rocks lie to your right, while other scattered rocks appear either smooth or sponge-like. Fortunately, there is still some time to explore, and the landscape before you may hold more clues to the history of ancient Mars.

APOD: 2006 January 26 - An Unusual Two Toned Rock on Mars
Explanation: How did this unusual Martian rock form? The atypical two-toned rock, visible in the lower right of the above image, was photographed a few days ago by the robotic Spirit rover currently rolling across Mars. For now, the environmental processes that created the rock remain a matter of speculation. Finding unusual rocks is not unusual for Spirit or its twin rover Opportunity, however. Over the past two years, for example, the rovers have unexpectedly discovered very small gray pebbles dubbed blueberries, and a rock out in the middle of nowhere now thought to be a meteorite. Having investigated alien terrain and having found clear evidence that part of Mars had a wet past, the Earth-launched Martian rovers are now entering their third spectacular year exploring the red planet.

APOD: 2006 January 5 - New Year Mars Panorama
Explanation: According to an Earth-based calendar, the Spirit rover spent the first day of 2006 gathering data to complete this panoramic view from Gusev crater on Mars. That day corresponded to Spirit's 710th Martian day or sol on the Red Planet. Scrolling right the view spans 160 degrees, looking up a slope and across rippled sand deposits in a dark field dubbed "El Dorado". The Spirit rover is traveling in a down hill direction after reaching the summit of Husband Hill. This month, both Spirit and Opportunity rovers will celebrate two years of Mars exploration, a remarkable achievement considering their original 90 day warranty. During that time Spirit has traveled over 3.5 miles and Opportunity over 4 miles across the Martian surface.

APOD: 2005 December 14 - A Digital Opportunity Rover on Mars
Explanation: If you could see one of the robot rovers currently rolling across Mars, what would it look like? To gain this perspective useful in planning explorations, the above synthetic image was produced digitally. Above, a digital model of the Opportunity rover was added to a real image of the inside of Endurance Crater on Mars taken earlier by Opportunity itself. The size of the six-wheeled robot was scaled to the size of the tracks that the Opportunity rover actually created. In actuality, both the Opportunity and Spirit rovers currently rolling across Mars each span about two meters and so are similar in size to a large rolling desk. Also visible in the image is dark soil, ancient light rock and numerous small gray pellets known as blueberries.

APOD: 2005 November 28 - Vista Inside Gusev Crater on Mars
Explanation: What is the geologic history of Mars? To help find out, the robot Spirit rover explored the terrain on the way up to the top of Husband Hill and took pictures along the way. Earth-bound team members later combined images from one camera with colors from another to create this semi-realistic vista from near the top of the rugged hill. Many rock faces were imaged and probed along the way. The above image captures not only a high and distant Mars inside Gusev crater, but also more of the refrigerator-sized Spirit rover than other similar vistas. Visible technology includes a wide array of energy-absorbing solar panels, a sundial, and the circular high gain communications antenna.

APOD: 2005 November 14 - Everest Panorama from Mars
Explanation: If you could stand on Mars -- what might you see? Scroll right to find out. The robotic Spirit rover currently rolling across Mars climbed to the top of hill and took a series of images that were digitally combined into a 360 degree panorama over three days early last month. Spirit was instructed to take images having the same resolution as a human with 20-20 eyesight. The full panoramic result can be found by clicking on the above image and has a level of detail unparalleled in the history of Martian surface photography. The panorama was taken from the pinnacle of Husband Hill and has been dubbed the Everest panorama, in honor of the view from the tallest mountain on Earth. Visible in Gusev Crater are rocks, rusting sand, a Martian sundial, vast plains, nearby peaks, faraway peaks, and sand drifts. In the distance, fast moving dust devils can be seen as slight apparitions of red, green, or blue, the colors of filters used to build up this natural color vista.

APOD: 2005 November 8 - The Drifts of Mars
Explanation: What would it be like to walk across Mars? The robot Opportunity rover is currently experiencing what it is like to roll across part of the red planet. It's not always easy -- the rover is being instructed to dodge the deeper drifts of dark sand. During its exploration of Erebus Crater, the rover stopped and took the above picture. Inside this part of Erebus Crater, the surface of mars is covered not only by dark sand but also light outcrops of rock. Scattered across the exposed rock are numerous small round pebbles known as blueberries . Typically smaller than marbles, these unexpected and unusual rocks likely formed by accretion in an ancient wet environment. Also visible are some strange protruding edges known as razorbacks. The above image was taken early last month.

APOD: 2005 October 24 - Angular Sand on Martian Hills
Explanation: Why isn't this sand round? The robotic Spirit rover currently rolling across Mars has found notably angular sand in the Columbia Hills on Mars. Previously, small bits of sand found in the plains of Gusev Crater were significantly more round. The finding indicates that angular hill sand has tumbled less and likely traveled a shorter distance than the corresponding round plain sand. Such tumbling has the general effect of making sand and rocks increasingly round and with fewer sharp edges. Pictured above, as taken last month, are angular sand grains magnified by Spirit's Microscopic Imager. The above frame spans about three centimeters.

APOD: 2005 September 7 - The View from Husband Hill on Mars
Explanation: Scroll right to see a breathtaking panorama of Mars from the top of Husband Hill. The image was taken by the robotic rover Spirit now exploring the red planet. Spirit, situated in expansive Gusev Crater, has been exploring the Columbia Hills for some time including climbing Husband Hill over the last few months. On the way up, Spirit took in a color vista from Larry's Lookout. Visible in the above image is the vast eastern landscape previously blocked from view by the Columbia Hills themselves. The horizon is mostly defined by the rim of Thira crater visible some 15 kilometers in the distance. Spirit will now examine rocks and soil at the top of Husband Hill, looking for clues as to how the hills and local rocks formed in the distant past.

APOD: 2005 August 22 - Desolate Mars: Rub al Khali
Explanation: Sometimes on Mars, there is nothing to see but red sand. Traveling two kilometers south of Endurance Crater, the robotic rover Opportunity now exploring Mars stopped and took a 360 degree panorama of a desolate and rusted Martian landscape. The site was dubbed Rub al Khali for its similarity to a barren part of the Saudi Arabian desert on Earth. In the center of the frame, the tracks from the rover's grated wheels can be seen receding far into the distance. Near the bottom, several parts of Opportunity itself are recorded, including, on the far right, a Martian sundial. Nearly 100 images in three colors to generate the above spectacular real-color image mosaic. To display the full high-resolution image would require about 300 computer monitors -- or one good large format printer.

APOD: 2005 June 20 - Sunset Over Gusev Crater
Explanation: What would it be like to see a sunset on Mars? To help find out, the robotic rover Spirit was deployed last month to park and serenely watch the Sun dip below the distant lip of Gusev crater. It was a tough job, but some robot had to do it. Now on Earth a red sunset is caused by two effects -- by blue light being preferentially scattered out of sunlight by oxygen and nitrogen molecules in the atmosphere, and by scattering off a small amount of impurities like volcanic dust. (The magnitude of the first effect was computed in one of Albert Einstein's most cited papers.) Although Mars lacks oxygen and nitrogen, it is covered in red dust frequently hoisted into the atmosphere by fast but thin winds. Analyses of images like the above photograph show that at least some Martian days are capped by a sunset significantly longer and redder than typical on Earth. For up to two hours after twilight, sunlight continued to reflect off Martian dust high in the atmosphere, casting a diffuse glow. The result helps atmospheric scientists understand not only the atmosphere of Mars, but atmospheres across the Solar System, including our home Earth.

APOD: 2005 May 17 - A Panorama of Mars from Larrys Lookout
Explanation: Scroll right to see a breathtaking panorama of Mars from Larry's Lookout. The lookout occurs near the peak of Husband Hill in the Columbia Hills. The summit of Husband Hill is visible 200 meters in the distance toward the center of the 360-degree near-true-color picture. The robot rover Spirit took images that compose the above mosaic over four Martian days. After taking the image sequence, Spirit carefully picked its way to toward Husband Hill's summit. On the far right, near distant rover tracks, is a recently investigated area dubbed Paso Robles that was found to contain high amounts of sulfur.

APOD: 2005 May 2 - Methuselah Outcrop on Mars
Explanation: What is the history of the outcropping of rock called Methuselah? The unusual rock group is visible on the left of the above image taken by the robot Spirit rover current exploring Mars. Methuselah was discovered while maneuvering over hilly terrain and shows unusual multiple layering that caught the attention of the rover science team. Since the above representative color image was taken about three weeks ago, Spirit has moved in to get a closer look. Also visible in the above image are another rock outcrop dubbed Larry's Lookout on the upper right and a larger Clark Hill in the left background. On the far right is a more distant peak of the Columbia Hills.

APOD: 2005 April 26 - A Martian Dust Devil Passes
Explanation: What goes there across the plains of Mars? A dust devil. For the first time, definitive movies of the famous spinning dust towers have been created from ground level. The robot rover Spirit has now imaged several dust devils from its hillside perch just within the past two months. Each image in the above sequence was taken about 20 seconds apart. Inspection of the digitally resized images show the passing dust devil raising Martian dust so thick that it casts a shadow. The new dust devil movies have been made possible by a new hybrid interaction system where the robot Spirit on Mars takes many images and humans on Earth inspect thumbnails and decide which full resolution images to send back.

APOD: 2005 April 12 - Earth or Mars?
Explanation: Which image is Earth, and which is Mars? One of the above images was taken by the robot Spirit rover currently climbing Husband Hill on Mars. The other image was taken by a human across the desert south of Morocco on Earth. Both images show vast plains covered with rocks and sand. Neither shows water or obvious signs of life. Each planet has a surface so complex that any one image does not do that planet justice. Understanding either one, it turns out, helps understand the other. Does the one on the left look like home? Possibly not, but it is Earth.

APOD: 2005 March 23 - A Dust Devil Swirling on Mars
Explanation: What is that wisp on the horizon? Scientists think that the slight white apparition is actually a Martian dust devil that was caught swirling across Mars. The above image was taken earlier this month by the robotic rover Spirit. The swirling cloud was found by comparing the above image to a previous image of the same area. Fresh dust devil tracks have been seen on Mars before, but actually seeing one up close was a surprise. The most similar phenomena to Martian dust devils on Earth are terrestrial dust devils, tornadoes and waterspouts. The ultimate cause of Martian dust devils remains unknown, but might be related to rising air heated by sun-warmed rocks and soil. Just the previous day, Spirit's power acquisition increased unexpectedly, possibly the result of a dust devil passing near or over the Spirit rover and effectively cleaning its solar panels.

APOD: 2005 February 9 - Heat Shield Impact Crater on Mars
Explanation: Broken metal and scorched Mars make the impact site of Opportunity's heat shield one of the more interesting sites inspected by the rolling robot. Visible on the image left is the conical outer hull of the shattered heat shield expelled by Opportunity as it plummeted toward Mars last year. Scrolling right will show not only another section of the heat shield but the impact site itself. The site is of interest partly because its creation was relatively well understood. The impact splattered subsurface light red dirt, while a darker material appears to track toward the large debris. Behind the impromptu space exhibit lies a vast alien landscape of featureless plains and rust-tinted sky.

APOD: 2005 January 21 - Metal on the Plains of Mars
Explanation: What has the Opportunity rover found on Mars? While traversing a vast empty plain in Meridiani Planum, one of Earth's yearling rolling robots found a surprise when visiting the location of its own metallic heat shield discarded last year during descent. The surprise is the rock visible on the lower left, found to be made mostly of dense metals iron and nickel. The large cone-shaped object behind it -- and the flank piece on the right -- are parts of Opportunity's jettisoned heat shield. Smaller shield debris is also visible. Scientists do not think that the basketball-sized metal "Heat Shield Rock" originated on Mars, but rather is likely an ancient metallic meteorite. In hindsight, finding a meteorite in a vast empty dust plain on Mars might be considered similar to Earth meteorites found on the vast empty ice plains of Antarctica. The finding raises speculations about the general abundance of rocks on Mars that have fallen there from outer space.

APOD: 2004 December 31 - A Year of Mars Roving
Explanation: Landing on Mars in January, NASA's twin rovers Spirit and Opportunity have now each spent over 330 sols roving the martian surface. Still healthy and well in to extended missions, the golfcart sized robots have operated five times longer than planned. Ranging across the floor of Gusev crater, the Spirit rover has reached the Columbia Hills and journeyed nearly four kilometers. Half a planet away, Opportunity has spent much of its tour on Meridiani Planum exploring the 130 meter wide Endurance Crater. Opportunity recently returned this panoramic view of rock outcrops and steep crater walls. Both rovers have uncovered strong evidence that ancient salty oceans left their mark on the alluring Red Planet.

APOD: 2004 December 15 - Looking Back Over Mars
Explanation: Pictured above, the path of the robot rover Spirit on Mars can be traced far into the distance. Spirit has now crossed kilometers of plains covered with rocks and sand, approached the lip of a crater 200-meters across, and climbed a series of hills. Spirit's path has been not only one of adventure but discovery. Landing inside vast Gusev crater near the beginning of this year, Spirit, along with its sister robot Opportunity across the planet, has uncovered key evidence for ancient Martian water. The recent discovery of goethite, a mineral only known to form on Earth in the presence of water, bolsters the case. Spirit and Opportunity continue to roam the red planet in search of different and more detailed clues to the unfolding ancient past of Mars.

APOD: 2004 November 15 - Burns Cliff on Mars
Explanation: The majestic walls of Endurance Crater contain layers of clues about the ancient past of Mars. In fact, the deeper the layer, the older the clue. The particular crater wall imaged above was dubbed Burns Cliff and was in front of the robot rover Opportunity last week. Close inspection of different layers has found slightly different compositions as well as interesting trends in relative compositions. For example, deeper layers contain similarly decreasing amounts of both magnesium and sulfur, indicating a common reason for their decline -- possibly dissolution in water. Today, more practically, Burns Cliff blocks one exit direction for Opportunity to leave Endurance Crater. When combined with slippery sand elsewhere on the crater floor, controllers have decided to program Opportunity to back out of the crater the way it came in - after a few more days exploration.

APOD: 2004 October 11 - Mosaic of Endurance Crater on Mars
Explanation: Where should this Martian rover explore next? Possible choices for the Opportunity rover team on Earth in early August were to send the Martian robot inside Endurance crater toward the arc-shaped sand dunes on the left, the unusually shaped rock on the right slope dubbed Wopmay, and lower parts of Burns Cliff at the top of the craters inner slopes. The Opportunity rover team on Earth chose 1-meter diameter rock Wopmay as their next target, and closer photographs are already being returned. Below center of the above mosaic is an area already explored by the rover. Opportunity has recently found rocks in Endurance crater with a network of cracks potentially indicative of dried mud, bolstering the case that Mars had a wet ancient past.

APOD: 2004 September 22 - Spirit Rover at Engineering Flats on Mars
Explanation: Is it art? Here the paintbrush was the Spirit robotic rover, the canvas was the soil on Mars, and the artists were the scientists and engineers of the Mars Exploration Rover Mission. The picture created was mostly unintentional -- the MERS team was primarily instructing Spirit to investigate rocks in and around Hank's Hollow in a location called Engineering Flats on Mars. After creating the ground display with its treads, the Spirit rover was instructed to photograph the area along with itself in silhouette. Both Mars rovers, Spirit and Opportunity, are now back in contact after an expected radio blackout caused by Mars moving behind the Sun. NASA has also announced that it is extending the rovers missions for six months, so long as they keep working.

APOD: 2004 August 23 - Looking Out Over Mars
Explanation: What would it be like to climb a hill and look out over Mars? That opportunity was afforded the Spirit rover earlier this month as it rolled to a high perch in the Columbia Hills. Peering out, the rolling robot spied the interior plains and distant rim of Gusev Crater, beyond an outcrop of rocks called Longhorn. Spirit continues to find evidence that many rock shapes have been altered by ancient water. Both Spirit and her sister robot Opportunity have completed their primary three-month mission but remain in good enough condition to continue to explore Mars.

APOD: 2004 August 17 - The Unusual Blueberries at Bylot Rock
Explanation: Why aren't these Martian rocks round? Small rocks dubbed blueberries have been found by the Opportunity rover all over Meridiani Planum on Mars, but the ones perched on Bylot rock have unusually non-spherical shapes. The strangely shaped blueberry rocks are shown above in an image taken by Opportunity's microscopic imager on August 9. Dark sand also covers much of Bylot rock. One hypothesis for the lack of blueberry roundness here is a coating relatively resistant to erosion. The average diameter of a blueberry is about 4 millimeters. The study of these and other rock features is allowing a better understanding of the wet past of ancient Mars.

APOD: 2004 August 3 - Shadow of a Martian Robot
Explanation: What if you saw your shadow on Mars and it wasn't human? Then you might be the Opportunity rover currently exploring Mars. Opportunity and sister robot Spirit have been probing the red planet since January, finding evidence of ancient water, and sending breathtaking images across the inner Solar System. Pictured above, Opportunity looks opposite the Sun into Endurance Crater and sees its own shadow. Two wheels are visible on the lower left and right, while the floor and walls of the unusual crater are visible in the background. Opportunity is cautiously edging its way into this enigmatic crater, hoping to find new clues into the wet ancient past of our Solar System's second most habitable planet.

APOD: 2004 July 27 - Razorbacks in Endurance Crater
Explanation: Over one year after its launch, robot geologist Opportunity has been spending recent sols on Mars inching its way down the slopes of Endurance crater. Littered with martian blueberries, some flat rocks within the crater also seem to have surprising razorbacks -- narrow slabs sticking up along their edges. Like the blueberries, it's possible that the sharp, narrow features are related to water. They could be formed by minerals deposited by water in cracks, with the surrounding softer material subsequently eroded away. How narrow are they? The ones pictured here in an enhanced color image from Opportunity's panoramic camera are actually only a few centimeters high and about half a centimeter wide. Impressive 3D views have been constructed by stereo experimenter P. Vantuyne based on the camera's left and right eye images of the region.

APOD: 2004 July 19 - Attacking Mars
Explanation: The Spirit rover attacked Mars again late last month. What might look, above, like a military attack, though, was once again just a scientific one - Spirit was instructed to closely inspect some interesting rocks near Columbia Hills. Spirits Front Hazard Avoidance Camera captured the rover's Instrument Deployment Device above as it guided the Microscopic Imager to get a closer look at a rock dubbed Breadbox. Images taken by the Microscopic Imager show a rock surface consistent with basalt corroded by ancient groundwater. Structures with similar origins can be found, for example, in the Western Desert of Egypt on Earth. The above picture taken on June 30, the 175th Martian day that the Spirit rover has been on the red planet.

APOD: 2004 June 28 - Spirit Rover Reaches the Columbia Hills on Mars
Explanation: The Spirit robotic rover on Mars has now reached the Columbia Hills on Mars. Two of the hills are shown on approach near the beginning of June. The above true-color picture shows very nearly what a human would see from Spirit's vantage point. The red color of the rocks, hills, and even the sky is caused by pervasive rusting sand. Spirit has now traveled over 3 kilometers since it bounced down onto the red planet in January. The robotic explorer, controlled and programmed remotely from Earth, is now investigating a rock called Pot of Gold. On the other side of Mars, Spirit's twin Opportunity is now inspecting unusual rocks inside a pit dubbed Endurance crater.

APOD: 2004 May 10 - Endurance Crater on Mars
Explanation: Scroll right to see the inside of Endurance Crater, the large impact feature now being investigated by the Opportunity rover rolling across Mars. The crater's walls show areas of light rock that might hold clues about the ancient watery past of this Martian region. Inspection of this true-color image shows, however, that much of this interesting rock type is confined to crater walls that might be hard for even this wily robot to access. Both of the Mars rovers have now successfully completed their original mission and are now exploring topical opportunities.

APOD: 2004 May 4 - Missoula Crater on Mars
Explanation: Scroll right to see the rocks, craters, and hills that were in view for the Spirit rover last week as it continued its trek across Mars. Missoula crater, taking up much of the above frame, appeared from orbit to have ejecta from Bonneville crater inside it. Upon closer inspection, however, Spirit finds only evidence for wind-blown drifts. The rocks show numerous blisters and small cavities that may have occurred as ancient water vapor evaporated from hot cooling lava. Columbia Hills in the distance is now planned as the ultimate destination for the Spirit rover. Both of the Mars rovers have now successfully completed their original mission and are now exploring topical opportunities.

APOD: 2004 April 5 - A Berry Bowl of Martian Spherules
Explanation: How were these unusual Martian spherules created? Thousands of unusual gray spherules, made of iron and rock but dubbed blueberries, were found embedded in and surrounding rocks near the landing site of the robot Opportunity rover on Mars. To help investigate their origin, Opportunity found a surface dubbed the Berry Bowl with an indentation that was rich in the Martian orbs. The Berry Bowl is pictured above, imaged during rover's 48th Sol on Mars. The average diameter of a blueberry is only about 4 millimeters. By analyzing a circular patch in the rock surface to the left of the densest patch of spherules, Opportunity obtained data showing that the underlying rock has a much different composition than the hematite rich blueberries. This information contributes to the growing consensus is that these small, strange, gray orbs were slowly deposited from a bath of dirty water.

APOD: 2004 April 1 - April Fools Day More Intense On Mars
Explanation: Today, April 1st, astrophysicists have announced a surprising discovery - April Fools Day is more intense on Mars! Though the discovery is contrary to accepted theories of April Fools Day, researchers note that there are several likely causes for the severe martian April Fools phenomenon. For starters, gravity, the force that opposes comedy throughout the universe, is only about 3/8ths as strong on Mars' surface as it is on planet Earth. Also, a martian day, called a sol, lasts nearly 40 minutes longer than an earth day. And furthermore ... well, as soon as they think of some more reasons, they've promised to tell us. Happy April Fools day from the editors at APOD! Editors note: Mars rover Spirit recorded this image looking out toward the eastern horizon and the Columbia Hills over 2 kilometers in the distance. Its journey across this rocky martian terrain could take from 60 to 90 sols.

APOD: 2004 March 24 - Intriguing Dimples Near Eagle Crater on Mars
Explanation: What are those unusual looking dimples? Looking back toward Eagle crater, its landing place on Mars, the robot rover Opportunity has spotted some unusual depressions in the Martian soil. The dimples, visible above on the image left, each measure about one meter across and appear to have light colored rock in their interior. The nearest dimple has been dubbed "Homeplate", while the next furthest one out is called "First Base." Scrolling right will reveal a magnificent panorama including the rover in the foreground, the backshell and parachute that detached from Opportunity before it landed near the horizon, Eagle crater in the center, Opportunity's tracks as it rolled away from Eagle crater, and wind blown ripples of Martian soil in every direction. Further analysis of rocks photographed by Opportunity has yielded evidence that Opportunity has landed on an evaporated shoreline of an ancient salt-water ocean.

APOD: 2004 March 18 - Spirit Pan from Bonneville Crater's Edge
Explanation: Scroll right and follow this breathtaking view of the martian surface from the southern edge of a small crater dubbed Bonneville. NASA's Spirit rover recorded the sharp 180-degree panorama on sols 68 and 69 of its stay on the Red Planet, following the completion of a 300+ meter journey from its landing site within Mars' expansive Gusev Crater region. Bonneville crater itself is about 200 meters across. Rocks scattered about the area are potentially "ejecta" from Bonneville, debris blasted from below the martian surface by the impact which created the crater. Researchers are eager to confirm this scenario since such material could be a guide to the geological history of the area. So what's that shiny patch on the left, just beyond the crater's far rim? It's the Spirit lander's heat shield.

APOD: 2004 March 10 - Humphrey Rock Indicates Ancient Martian Water
Explanation: How prevalent was water on Mars? Results from the Spirit rover now indicate that Gusev crater likely had a wet past, a result that comes shortly after Spirit's twin rover Opportunity uncovered clear evidence of past water at Meridiani Planum on the other side of Mars. Evidence uncovered by Spirit and released last week focussed on a large rock of unusual shape nicknamed Humphrey, shown above near the image bottom. Detailed inspection of the rock revealed a bright material filling internal cracks. Such material may have crystallized from water trickling through the volcanic rock. The amount of Mars once covered by ancient water remains unknown, as both rovers landed in regions thought likely to once be underwater. Spirit continues to roll across Mars, recently passing the 300-meter mark on its way to Bonneville crater.

APOD: 2004 March 3 - Opportunity Rover Indicates Ancient Mars Was Wet
Explanation: Was Mars ever wet enough to support life? To help answer this question, NASA launched two rover missions to the red planet and landed them in regions that satellite images indicated might have been covered with water. Yesterday, mounting evidence was released indicating that the Mars Opportunity rover had indeed uncovered indications that its landing site, Meridiani Planum, was once quite wet. Evidence that liquid water once flowed includes the physical appearance of many rocks, rocks with niches where crystals appear to have grown, and rocks with sulfates. Pictured above, Opportunity looks back on its now empty lander. Visible is some of the light rock outcropping that yielded water indications, as well as the rim of the small crater where Opportunity landed. The rover will continue to explore its surroundings and try to determine the nature and extent that water molded the region.

APOD: 2004 February 25 - White Boat Rock on Mars
Explanation: What caused this rock to have an unusual shape? Earlier this month the robot Spirit rover on Mars stopped to examine a rock dubbed "white boat", named for its unusually light color and shape. White boat, the large rock near the image center of the above color-composite image, was examined by Spirit just after Adirondack, a football-sized rock determined to be composed of volcanic basalt. Spirit resumed scientific operations two weeks ago after recovering from a computer memory problem. Spirit and its twin rover Opportunity, on the other side of Mars, continue to roam the red planet in search of clues to the ancient past of Earth's most hospitable neighbor.

APOD: 2004 February 16 - A Patch of Spherules on Mars
Explanation: Some patches of Mars are full of mysterious tiny spherules. The microscopic imager on board the Opportunity rover on Mars recorded, last week, the above image showing over a dozen. The image was taken near a rock outcrop called Stone Mountain and spans roughly 6 centimeters across. A typical diameter for one of the pictured spherules is only about 4 millimeters, roughly the size of a small blueberry. The spherules appear to be much grayer and harder than surrounding rock. Debate rages on the origin of the tiny spherules, and whether their shape has to do with a slow accumulation of sediments suspended in water, or flash-frozen rock expelled during a meteor impact or volcanic eruption. A layered spherule, if ever found, would favor a water-based origin. Meanwhile, Opportunity is being programmed to dig into the Martian surface of Meridiani Planum to see what is there.

APOD: 2004 February 10 - Unusual Spherules on Mars
Explanation: What are those unusual spherules on Mars? The Mars Opportunity rover has now photographed several unusual nodules on Mars that have a nearly spherical shape. Many times these spherules are embedded in larger rock outcroppings but appear grayer. Pictured in the inset is one such spherule embedded in a rock dubbed Stone Mountain, visible to the Opportunity rover now rolling inside a small crater on Meridiani Planum. Opportunity was directed to go right up to Stone Mountain to get a better look. The inset picture spans only 3 centimeters across, revealing the rock to be named more for shape than actual size. Scientists are currently debating the origin of the spherules. One leading hypothesis holds that the beads were once-molten rock that froze in mid-air after an impact or a volcanic eruption. Another hypothesis holds that the spherules are concretions, hard rock that slowly accumulates around a central core. Opportunity will work to solve this mystery and others over the next few days.

APOD: 2004 February 6 - Magnified Mars
Explanation: At first glance, this sharp, color close-up gives the strong impression of pebbles strewn over a sandy beach. But the picture is one of the first microscopic images of another planet, captured by the Opportunity rover on its tenth sol on the martian surface at Meridiani Planum. The patch of soil measures about 3 centimeters (1.2 inches) across. It is shown in shades approximating what the eye might see, obtained by combining pictures of the soil with and without the microscopic imager's orange-tinted dust cover in place. Searching for evidence of past water on Mars, researchers note that both volcanic and water-related accretion processes could have produced the striking circular grain at the lower left. However, other investigations now indicate the soil near the lander contains olivine, an iron-bearing mineral common in volcanic rocks, while a signature of the iron mineral hematite was found in soil around a nearby rocky outcrop. On planet Earth, hematite often forms in association with liquid water.

APOD: 2004 February 4 - Opportunity's Horizon
Explanation: Remarkably, the Opportunity Mars rover lies in a small martian impact crater about 3 meters deep and 22 meters wide. For 360 degrees, Opportunity's horizon stretches to the right in this new color mosaic image from the rover's panoramic camera. Notable in this view of the generally dark, smooth terrain are surface imprints left by the lander's airbags and an outcropping of light-colored, layered rock about 8 meters away toward the northwest. Though they look imposing, the rocks in the tantalizing outcrop are only a few centimeters high and will be dwarfed by the cart-sized rover itself during future close-up investigations. Opportunity has now rolled off its lander and, along with the restored Spirit rover, is directly exploring the martian surface.

APOD: 2004 January 27 - Opportunity on Mars
Explanation: You've just woken up in a small crater on Mars. The surrounding landscape is barren, strange, and alien. You've never been on this world before. You transmit pictures that are instantly rebroadcast all over your home world. You are the eyes for billions of people. You seek adventure. Your mission is to explore this strange new world and search for signs of pre-historic life. You have six wheels, one arm, and X-ray eyes. Surrounding you, pictured above, is iron sand and light-colored protrusions that might be bedrock. You are the Opportunity Rover that landed on Mars just this past weekend.

APOD: 2004 January 26 - A Landing at Meridiani Planum
Explanation: After an interplanetary journey of nearly 300 million miles, Opportunity bounced down on the martian surface at about 9:05 pm PST Saturday, its final plunge cushioned by airbags. Now the second NASA rover on Mars, Opportunity's landing site at Meridiani Planum is on the opposite side of the red planet from its twin rover Spirit. Described as unlike any ever seen on Mars, the dark, undulating terrain at Meridiani Planum (aka Terra Meridiani) is pictured above in the first stunning color view from Opportunity. This area is thought to be rich in gray hematite, an iron-bearing mineral which can form in watery environments. Part of the rover's deck is in the foreground while circular impressions and drag marks made by the airbags are visible just beyond it.

APOD: 2004 January 24 - Valles Marineris from Mars Express
Explanation: Looking down from orbit on January 14, ESA's Mars Express spacecraft scanned a 1700 by 65 kilometer swath across Valles Marineris - the Grand Canyon of Mars - with its remarkable High Resolution Stereo Camera. This spectacular picture reconstructs part of the scanned region from the stereo colour image data recording the rugged terrain with a resolution of 12 metres per pixel. Joining Mars Global Surveyor and Mars Odyssey, Mars Express has been orbiting the red planet since December 25th, returning scientific data, acting as a communications relay, and even making coordinated atmospheric observations with NASA's Spirit rover on the surface. The Beagle 2 lander was released from Mars Express making a landing attempt also on December 25th, but no signal has been received so far.

APOD: 2004 January 22 - Columbia Memorial Station
Explanation: After leaving its nest, the Spirit rover turned to capture this spectacular view over the Columbia Memorial Station and the floor of Gusev crater on the 16th sol of its visit to Mars. The sharp picture looks toward the northeast. Over 2 meters wide, the lander platform surrounded by deflated airbags, and the egress ramp used by the rover to complete its journey to the martian surface, are in the foreground. In the background lie Spirit's likely future waypoints and destination - initially toward a ridge on the left bordering an impact crater about 200 meters across and finally toward the hills visible on the horizon at the right. The crater is about 250 meters away while the hills are about 3 kilometers distant. Searching for evidence of ancient watery environments, Spirit's scientific instruments have begun to return data on the composition of the surface in the lander's vicinity, suggesting that iron-bearing volcanic minerals are present.

APOD: 2004 January 21 - Adirondack Rock on Mars
Explanation: Is this a great pyramid on Mars? Actually, the pictured rock dubbed Adirondack has an irregular shape, is only about the size of a football, and has formed by natural processes. Still, its relatively large size and dust-free surface made it the first destination for the robotic Spirit rover currently roving Mars. Spirit, itself the size of a golf cart, will now attempt to determine the rock's composition and history by prodding it with its sophisticated mechanical arm. Spirit's arm, programmed remotely from Earth, has the capability to bend, grind, and photograph the rock in minute detail. Spirit's twin rover Opportunity is scheduled to land on the other side of Mars this coming weekend.

APOD: 2004 January 18 - A Close-Up of Martian Soil
Explanation: Make your background the closest image of Mars yet. The Spirit Rover currently rolling on Mars has taken the highest resolution image to date of another planet. The above black and white image spans only about 1.5 centimeters across, with details smaller than 1/10 of a millimeter visible. A microscope attached to the Spirit rover's instrument arm took the image. Up close, the Martian soil appears to planetary geologists to have clumping properties similar to cocoa powder. As more images come in and as the Spirit Rover continues to explore Mars, more information about the unusual floor of Gusev Crater are likely to emerge.

APOD: 2004 January 16 - Martian Surface in Perspective
Explanation: Spirit moved across Mars yesterday as the rover successfully maneuvered down off its lander, driving its six wheels onto the floor of Gusev crater. As planned, the robotic geologist will now begin a close-up examination of the rocks and soil around the landing site for clues to the processes that formed them. A perspective projection of Spirit's local martian rocks and soil is shown above, based on 3D color image data recorded when rover was still perched on its landing platform. Dark-colored airbag drag marks stretch across the soil in this view of the surface. For scale, the triangular-faced rock in the upper left corner is about 20 centimeters (8 inches) high. Scientists anticipate that the rover's investigation will yield valuable evidence helping to confirm or refute the possibility that the floor of Gusev crater is an ancient lake bed.

APOD: 2004 January 14 - A Mars Panorama from the Spirit Rover
Explanation: If you could stand on Mars -- what would you see? Scrolling right will reveal a full color 360-degree panoramic view from NASA's Spirit Rover that landed on Mars just 10 days ago. The image is a digital mosaic from the panoramic camera that shows the view in every direction. Annotated on the image are the directions and distances to various hills along the horizon. These hills are valuable for orienting Spirit since they are also visible to the Mars Global Surveyor and Mars Odyssey spacecraft orbiting high overhead. Visible in the foreground are several instruments and airbags around Columbia Memorial Station. Spirit will attempt to roll onto the red planet in the next few days and explore interesting features.

APOD: 2004 January 10 - Two Worlds, One Sun
Explanation: Two Worlds, One Sun, is the legend emblazoned on the Spirit rover's camera calibration target. Resting on the rover's rear deck, it also doubles as a sundial, allowing students to determine the solar time at Spirit's landing site on Mars. Examples of the sundial or Marsdial are shown above where the left image, captured near local noon, shows the effect of the Sun high in the martian sky. The right image from later in the afternoon with the Sun lower in the sky, shows a long shadow cast by the Marsdial's 3.5 centimeter high central post. Based on the computer generated grid overlay, students determined the local time in the central inset image to be about 12:17 pm local solar time. The face of the Marsdial was designed by astronomy artist Jon Lomberg in collaboration with other team members. Did you know, the Marsdial idea was a brainchild of Bill Nye, the Science Guy? Now you know ...

APOD: 2004 January 9 - Sol 5 Postcard from Mars
Explanation: A martian Sol - the average martian solar day - is about 39 minutes longer than Earth's familiar 24 hour day. Operating on martian time, the Spirit rover recently sent back this color postcard image, recorded on Sol 5 of its stay on the martian surface. This cropped version of the full, high-resolution mosaic looks north across Gusev crater floor. The smooth-looking, 9 meter wide circular feature dubbed Sleepy Hollow lies at the center of the scene. Within it are round dark markings which may have been left by the lander swaddled in airbags as it bounced across the martian surface. Other examples of disturbances, likely made by the lander's retracting airbags, can be seen in the foreground just beyond Spirit's solar cell covered deck.

APOD: 2004 January 8 - The Hills of Mars
Explanation: Distant hills rise above a rocky, windswept plain in this sharp stereo scene from the Spirit rover on Mars. When viewed with red/blue glasses, the picture combines left and right images from Spirit's high resolution panoramic camera to yield a dramatic 3D perspective. The hills were estimated to lie about 2 kilometers away and be approximately 50 to 100 meters high. Along with other features of the landscape, determining their direction and distance will help pinpoint the exact location of the Spirit landing site when compared with high resolution images of the region taken from Mars orbit. Much stereo image data, allowing important estimates of three dimensional shapes, sizes, and distances, is anticipated from the rover's cameras. (Editor's note: Red/blue glasses for viewing stereo pictures can be purchased or simply constructed using red and blue plastic for filters. Try it! To view this image, the red filter is used for the left eye.)

APOD: 2004 January 7 - Red Mars from Spirit
Explanation: Rocks are strewn across the broad, flat Gusev crater floor in this sharp color picture from NASA's Spirit rover. Recorded by the rover's panoramic camera, the picture is part of Spirit's first color image of Mars - the highest resolution picture yet taken on the surface of another planet. Already revealing alluring and perplexing details of an apparently windswept plain thought to be an ancient lake bed, this stunning view represents only a small fraction of the color image data mission scientists expect to be transmitted in the coming days. As the robotic Spirit rover is preparing to stand up, roll off the lander, and explore the geology of the crater floor, NASA has announced plans to rename the landing site the Columbia Memorial Station in honor of the astronauts lost in the Columbia space shuttle accident.

APOD: 2004 January 6 - Spirit's 3D View Toward Sleep Hollow
Explanation: Working late, tired mission members nicknamed the smooth-looking depression to the left of center in this image from the martian surface, Sleepy Hollow. The picture is a portion of the 3D panorama of the Spirit rover's landing site released yesterday, constructed with data from the Mars rover's navigation cameras. Use red/blue glasses, red for the left eye, to get the 3D effect. Sleepy Hollow is estimated to be around 9 meters (30 feet) in diameter and about 12 meters (40 feet) away. Possibly an impact crater, the martian surface feature is a tantalizing potential site for a future visit when the golf cart-sized robotic rover ventures forth. Covered with solar arrays, the rear deck of the rover is also visible in this view along with the top of an antenna at the right. An innovative camera calibration target, a martian sundial, can be seen left of the antenna, mounted near the edge of the rover's deck.

APOD: 2004 January 5 - Spirit Pan from Gusev Crater
Explanation: After a seven month voyage of nearly 500 million kilometers through interplanetary space, NASA's Spirit Rover has reached the surface of Mars. Scroll right and see a mosaic panorama of Spirit's first images returned from its landing site in Gusev Crater! Taken by Spirit's navigation camera, the panorama covers 360 degrees, with the spacecraft in the foreground and the floor of Gusev Crater, thought to be an ancient lake bed, extending to the horizon. The entry, descent, and landing phase of Spirit's mission - referred to by mission planners as "Six Minutes of Terror" - began Saturday night around 8:30pm PST as Spirit entered the martian atmosphere at about 20,000 kilometers per hour. Updates on Spirit's status will be posted throughout the day.

APOD: 2004 January 4 - Spirit Rover Bounces Down on Mars
Explanation: After a seven month voyage through interplanetary space, NASA's Spirit Rover has reached the surface of the Red Planet and returned the first images from its landing site in Gusev crater! The entry, descent, and landing phase of its mission - referred to by mission planners as "Six Minutes of Terror" - began Saturday night around 8:30pm PST as Spirit entered the martian atmosphere at about 12,000 miles per hour. Depicted in the above artist's illustration, the spacecraft is in the final stages of its landing sequence, swaddled in large, protective airbags and bouncing to a soft landing on Mars. The same type of airbags were used for the Mars Pathfinder landing in 1997. Updates on Spirit's status will be posted throughout the day.

APOD: 2003 September 22 - Opportunity Rockets Toward Mars
Explanation: Next stop: Mars. Two months ago, the second of two missions to Mars was launched from Cape Canaveral, Florida, USA above a Boeing Delta II rocket. The Mars Exploration Rover dubbed Opportunity is expected to arrive at the red planet this coming January. Pictured above, an attached RocketCam (TM) captures Opportunity separating from lower booster stages and rocketing off toward Mars. Upon arriving, parachutes will deploy to slow the spacecraft and surrounding airbags will inflate. The balloon-like package will then bounce around the surface a dozen times or more before coming to a stop. The airbags will then deflate, the spacecraft will right itself, and the Opportunity rover will prepare to roll onto Mars. A first rover named Spirit was successfully launched on June 10 and will arrive at Mars a few weeks earlier. The robots Spirit and Opportunity are expected to cover as much as 40 metres per day, much more than Sojourner, their 1997 predecessor. Spirit and Opportunity will search for evidence of ancient Martian water, from which implications might be drawn about the possibility of ancient Martian life.

APOD: 2003 July 28 - Launch of the Spirit Rover Toward Mars
Explanation: Next stop: Mars. Last month the first of two missions to Mars was launched from Cape Canaveral, Florida, USA above a Boeing Delta II rocket. Pictured above, solid fuel boosters are seen falling away as light from residual exhaust is reflected by the soaring rocket. The Mars Exploration Rover dubbed Spirit is expected to arrive at the red planet this coming January. Upon arriving, parachutes will deploy to slow the spacecraft and surrounding airbags will inflate. The balloon-like package will then bounce around the surface a dozen times or more before coming to a stop. The airbags will then deflate, the spacecraft will right itself, and the Spirit rover will prepare to roll onto Mars. The robotic Spirit is expected to cover as much as 40 meters per day, much more than Sojourner, its 1997 predecessor. Spirit will search for evidence of ancient Martian water, from which implications might be drawn about the possibility of ancient Martian life. A second rover named Opportunity was successfully launched on July 7 and will arrive at Mars a few weeks later.