FIRST
GLOBAL 3-D VIEW OF MARS REVEALS DEEP BASIN AND PATHWAYS
FOR WATER FLOW
May 27, 1999
Picture above is a flat map 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.
FIRST GLOBAL 3-D VIEW OF MARS REVEALS
DEEP BASIN AND PATHWAYS FOR WATER FLOW
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.
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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| Images
above represent 90 degree 3D global views of
Mars. Click on each globe for a
larger view. Hi-Resolution website
identified at end of story. |
"This incredible database means that we
now know the topography of Mars better than many
continental regions on Earth," said Dr. Carl
Pilcher, Science Director for Solar System Exploration
at NASA Headquarters, Washington, DC. "The data
will serve as a basic reference book for Mars scientists
for many years, and should inspire a variety of new
insights about the planet's geologic history and the
ways that water has flowed across its surface during the
past four billion years."
"The full range of topography on Mars is
about 19 miles (30 kilometers), one and a half times the
range of elevations found on Earth," noted Dr.
David Smith of NASA's Goddard Space Flight Center,
Greenbelt, MD, the principal investigator for MOLA and
lead author of a study to be published in the May 28,
1999, issue of Science.
"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.
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.
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.
Related Links:
The
Mars Page
MOLA topographic images may be viewed
at the following web address:
http://pao.gsfc.nasa.gov/gsfc/spacesci/pictures/mola/mars3d.htm
More details about the MOLA instrument
and science investigation can be found at:
http://ltpwww.gsfc.nasa.gov/tharsis/mola.html
Hi-Resolution Images can be found at:
ftp://pao.gsfc.nasa.gov/Newsmedia/mola
http://svs.gsfc.nasa.gov/~gshirah/mola/jpg/
