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.

July 5, 1999
See Explanation.  Clicking on the picture will download 
 the highest resolution version available.

Four Faces of Mars
Credit: S. Lee (U. Colorado) et al., WFPC2, HST, NASA

Explanation: As Mars rotates, most of its surface becomes visible. During Earth's recent pass between Mars and the Sun, the Hubble Space Telescope was able to capture the most detailed time-lapse pictures ever from the Earth. Dark and light sand and gravel create an unusual blotted appearance for the red planet. Winds cause sand-tinted features on the Martian surface to shift over time. Visible in the above pictures are the north polar cap, made of water ice and dry ice, clouds including an unusual cyclone, and huge volcanoes leftover from ancient times. The Mars Global Surveyor satellite orbiting Mars continues to scan the surface for good places to land future robot explorers.

Tomorrow's picture: A Sun Pillar

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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.