Astronomy Picture of the Day

Discover the cosmos! Each day a different image or photograph of our fascinating universe is featured, along with a brief explanation written by a professional astronomer.

March 19, 1999
See Explanation.  Clicking on the picture will download 
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Mapping Mars
Credit: Malin Space Science Systems, MGS, JPL, NASA

Explanation: This month, the Mars Global Surveyor (MGS) spacecraft began its primary mission to the red planet. Orbiting about once every two hours at an altitude of over 200 miles, instruments onboard MGS now regularly explore the Martian surface and atmosphere. This MGS polar mapping orbit was set up to achieve a favorable "afternoon" sun-angle for imaging as the spacecraft crosses over the day side of the planet. Mars' rotation will allow complete coverage of the surface roughly once every week with mapping operations planned for one Martian year (687 Earth days). These two opposite hemisphere views of Mars were pieced together from MGS wide-angle camera scans made in early March (blue and red lines mark the scan edges). Water-ice clouds can be seen hovering over the surface while the north polar cap is visible at the top of each image.

Tomorrow's picture: Aurora and Orion

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Authors & editors: Robert Nemiroff (MTU) & Jerry Bonnell (USRA)
NASA Technical Rep.: Jay Norris. Specific rights apply.
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& Michigan Tech. U.