The Red Planetin 3D
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The Red Planet in 3D
New data from Mars Global Surveyor
reveal the topography of Mars
better than many continental regions on Earth
May 27, 1999:
An impact basin deep enough to swallow Mount Everest and surprising slopes
in Valles Marineris highlight a global map of Mars that will influence scientific
understanding of the red planet for years.
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).
December 3: Mars Polar Lander nears touchdown  December 2: What next, Leonids? November 30: Polar Lander Mission Overview November 30: Learning how to make a clean sweep in space |
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"The most curious aspect of the topographic map is the striking difference between the planets 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.
The massive Hellas impact basin in the Southern Hemisphere is another
striking feature of the map. Nearly six miles (nine kilometers) deep and 1,300
miles (2,100 kilometers) across, the basin is surrounded by a ring of material that
rises 1.25 miles (about two kilometers) above the surroundings and stretches out
to 2,500 miles (4,000 kilometers) from the basin center.
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.
Right:
This dramatic three-dimensional visualization of Mars' north pole is based on elevation measurements
made by an orbiting laser. During the Spring and Summer of 1998 the Mars Orbiter Laser Altimeter (MOLA) flashed laser
pulses toward the Martian surface from the Global Surveyor spacecraft and recorded the time it took to detect the reflection.
This timing data has now been translated to a detailed topographic map of Mars' north polar terrain.
More information.
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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For more information, please contact: Dr. John M. Horack , Director of Science Communications |
Source: NASA HQ Press Release Editor: Dr. Tony Phillips Curator: Bryan Walls NASA Official: John M. Horack |