The Red Planetin 3D
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Right: A false-color animation of Mars showing four hemispheric views at 90 degree intervals. Colors correspond to elevations measured by the Mars Orbiter Laser Altimeter on the Mars Global Surveyor spacecraft. Red and white colors denote high elevations; blue denotes low.
Generated by the Mars Orbiter Laser Altimeter (MOLA), an instrument aboard NASA's Mars Global Surveyor, the high-resolution map represents 27 million elevation measurements gathered in 1998 and 1999. The data were assembled into a global grid with each point spaced 37 miles (60 kilometers) apart at the equator, and less elsewhere. Each elevation point is known with an accuracy of 42 feet (13 meters) in general, with large areas of the flat northern hemisphere known to better than six feet (two meters).
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"The most curious aspect of the topographic map is the striking difference between the planet’s low, smooth Northern Hemisphere and the heavily cratered Southern Hemisphere," which sits, on average, about three miles (five kilometers) higher than the north, Smith added. The MOLA data show that the Northern Hemisphere depression is distinctly not circular, and suggest that it was shaped by internal geologic processes during the earliest stages of martian evolution.
This ring of material, likely thrown out of the basin during the impact of an asteroid, has a volume equivalent to a two-mile (3.5-kilometer) thick layer spread over the continental United States, and it contributes significantly to the high topography in the Southern Hemisphere.
The difference in elevation between the hemispheres results in a slope from the South Pole to North Pole that was the major influence on the global-scale flow of water early in martian history. Scientific models of watersheds using the new elevation map show that the Northern Hemisphere lowlands would have drained three-quarters of the martian surface.
On a more regional scale, the new data show that the eastern part of the vast Valles Marineris canyon slopes away from nearby outflow channels, with part of it lying a half-mile (about one kilometer) below the level of the outflow channels.
"While water flowed south to north in general, the data clearly reveal the localized areas where water may have once formed ponds, " explained Dr. Maria Zuber of the Massachusetts Institute of Technology, Cambridge, MA, and Goddard.
The amount of water on Mars can be estimated using the new data about the south polar cap and information about the North Pole released last year. While the poles appear very different from each other visually, they show a striking similarity in elevation profiles. Based on recent understanding of the North Pole, this suggests that the South Pole has a significant water ice component, in addition to carbon dioxide ice.
The upper limit on the present amount of water on the martian surface is 800,000 to 1.2 million cubic miles (3.2 to 4.7 million cubic kilometers), or about 1.5 times the amount of ice covering Greenland. If both caps are composed completely of water, the combined volumes are equivalent to a global layer 66 to 100 feet (22 to 33 meters) deep, about one-third the minimum volume of a proposed ancient ocean on Mars.
During the ongoing Mars Global Surveyor mission, the MOLA instrument is collecting about 900,000 measurements of elevation every day. These data will further improve the global model, help engineers assess the area where NASA's Mars Polar Lander mission will set down on Dec. 3, and aid the selection of future landing sites. MOLA was designed and built by the Laser Remote Sensing Branch of the Laboratory for Terrestrial Physics at Goddard. The Mars Global Surveyor mission is managed for NASA's Office of Space Science, Washington, DC, by the Jet Propulsion Laboratory, Pasadena, CA, a division of the California Institute of Technology.
More details about the MOLA instrument and science investigation can be found at: http://ltpwww.gsfc.nasa.gov/tharsis/mola.html Web Links
FIRST GLOBAL 3-D VIEW OF MARS REVEALS DEEP BASIN AND PATHWAYS FOR WATER FLOW - NASA HQ Press Release
The Planet Mars - from the SEDS Nine Planets web site
Life on Mars - A review of evidence of signs of life in the Allen Hills meteorite
Mars Global Surveyor - home page
Mars - by Percival Lowell, 1895
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Stormy weather on Mars -- During the recent close approach of Mars to Earth, NASA's Hubble Space Telescope spotted a gigantic storm swirling near the Red Planet's north pole. May 19, 1999 NASA NASA Science News
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A close encounter with the Red Planet -- Mars makes its closest approach to Earth in 1999. Apr 23, 1999 NASA NASA Science News
Summer snow on Mars -- New Mars Global Surveyor images reveal snowy slopes. Mar. 25, 1999 NASA NASA Science News
A new face on Mars has scientists smiling -- MGS beams back pictures of the "Happy Face Crater". Mar. 12, 1999 NASA NASA Science News
Mars mapping begins in earnest -- MGS achieves its final orbit. Mar. 12, 1999 NASA NASA Science News
A steamy cover-up on the red planet -- New evidence for active volcanism on Mars. Feb. 18, 1999 NASA NASA Science News
The Sands of Mars -- Oct. 29, 1998 NASA NASA Science News
New NASA images of the Martian North Pole -- Oct. 23, 1998 NASA NASA Science News
New images of volcanoes on Mars and Io -- Oct. 14, 1998 NASA NASA Science News
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