Astronomy Picture of the Day Index - Solar System: Mars

APOD: 1999 October 30 - Mars Rocks, Sojourner Rolls
Explanation: This sharp color image featuring Mars rock Yogi and the rolling Sojourner robot shows off Yogi's two-toned surface. Yogi appears to be leaning into the prevailing winds causing some to suggest that its color contrast may be caused by the accumulation of rust colored dust on its windward face. The Pathfinder spacecraft, now the Sagan Memorial Station, has ended the primary mission phase after returning a scientific bonanza from the surface of Mars. The Sojourner robot rolled hundreds of feet on the martian surface, circumnavigated the lander, and produced a wealth of data and images. Mars Pathfinder and Soujourner landed on July 4, 1997 and lasted about 3 months, well beyond their designed lifetime.

APOD: 1999 July 5 - Four Faces of Mars
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.

APOD: 1999 May 28 - Topographical Mars
Explanation: Contrasting colors trace changing elevations in this new high-resolution topographic map of Mars. Just released, the data were gathered in 1998 and 1999 by the Mars Orbiter Laser Altimeter (MOLA) onboard the Mars Global Surveyor spacecraft. The martian topography is seen to range over 19 miles between the highest volcanic peaks (white) and the lowest regions (purple). Along with the striking difference between the Red Planet's low northern hemisphere (top) and high southern regions, one of the most noticeable features on the map is the large blue-purple southern depression corresponding to the Hellas basin. Likely the result of an asteroid impact, Mars' deepest basin is about 1300 miles across making it one of the largest impact features in the Solar System. Explorations of MOLA's rich topographic database are expected to produce insights into water flows and the geologic history of Mars.