Astronomy Picture of the Day 6-27-02

Explanation: Just as erosion from the Colorado River carved the Grand Canyon on Earth, a river of flood water may have carved Ma'adim Vallis, one of the largest canyons on Mars. Researchers have presented strong evidence for such a scenario based on elevation data recorded by the MOLA (Mars Orbiter Laser Altimeter) experiment on the Mars Global Surveyor spacecraft. This false-color, detailed, topographical map of MOLA data shows in blue the area of an enormous complex of lakes that are thought to have existed over three and a half billion years ago in the southern highlands of Mars. As the largest lake spilled over the low point in its boundary a torrential flood would have moved north, along the direction indicated by the arrow, carving the sinuous Ma'adim Vallis. At the north end of Ma'adim Vallis, the flood waters would have poured into large, round Gusev Crater. Since standing bodies of surface water are thought to be favorable for ancient martian microbial life, Gusev Crater has been suggested as a landing site for future Mars missions.

"Ma'adim" is the Hebrew word for Mars.

MOLA's Top Ten Scientific Accomplishments

1) The most accurate global topographic map of any planet in the solar system, including a two-order-of-magnitude improvement in the geodetic grid (latitude/longitude system) of Mars.

(2) Recognition of the flat northern hemisphere of Mars.

(3) The pole-to-pole slope and Tharsis control the shape of the planet.

(4) Detection of buried basins beneath the northern hemisphere plains that has clarified the large impact basin population and the age of the northern hemisphere crust.

(5) The first reliable inversion for the crustal structure of Mars (using both MOLA and MGS gravity data from the Radio Science Experiment).

(6) Establishment of the pathways for the flow of past water and the locations, sizes, and volumes of watersheds.

(7) All craters greater than a few kilometers in size display ramparts, indicating that water was pervasive in the Martian subsurface.

(8) Present-day surface water inventory from polar cap/layered terrain volumes.

(9) Detection of the heights of clouds and identification of dynamical features in the atmosphere, such as gravity waves.

(10) Seasonal changes in the height of the Martian surface (aka, snow depth) that represented the first direct global measurement of the amount and distribution of condensed CO₂.

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