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John Bluck                                            Feb.12, 2003
NASA Ames Research Center, Moffett Field, Calif.
Phone: 650/604-5026 or 650/604-9000
E-mail: jbluck{at}mail.arc.nasa.gov

RELEASE: 03-12AR

NASA STUDY SHOWS HOW WATER MAY HAVE FLOWED ON ANCIENT MARS

NASA scientists have discovered how an intricate martian network of 
streams, rivers and lakes may have carried water across Mars.

Using new three-dimensional data from the Mars Global Surveyor 
spacecraft and a powerful state-of-the-art computer code that 'models' 
overland water flow, scientists visualized the complex flow of martian 
water. These data, acquired by the laser altimeter on board the 
spacecraft, provided highly accurate, three-dimensional topographic 
views of Mars.

"We've known for some time that Mars contains lakebed and stream-like 
surface features, and that many of these stream features run into 
depressions, then end abruptly," said Marc G. Kramer, a visiting 
National Research Council scientist at NASA Ames Research Center in 
California's Silicon Valley. Kramer is principal author of a 
peer-reviewed news article about the study that recently appeared in 
EOS, a weekly American Geophysical Union publication. "A new aspect of 
this study shows how these two features link to one another as a 
single, integrated water network that may have existed on Mars at some 
time in the past," he said.

The study spans portions of the equatorial region on the martian 
highlands that extend from the northern mid latitudes to the southern 
mid latitudes. Kramer's co-authors are Christopher Potter, David Des 
Marais and David Peterson, all from NASA Ames.

Scientists have long been puzzled as to why some ancient river-like 
features on the red planet do not seem to connect to one another and 
often lack smaller stream features.

"If you look at a photograph of the surface of Mars, the river 
features begin and end abruptly, and often lack small-scale features," 
Kramer said. "Many scientists have argued that these features were 
formed from localized groundwater seeping to the surface. Others have 
argued that these features formed from precipitation during a time 
when Mars may have had a thicker atmosphere."

"What we found in this study, is that many of these apparently 
fragmented river features may have connected or flowed into 
depressions that resemble ancient lake beds," Kramer explained. "Some 
of the larger depressions are comparable in size to the Great Lakes in 
North America in terms of surface area."

In addition, some of the larger depressions of the main channel system 
are comparable in volume to Lake Erie, the smallest of the Great Lakes 
in North America, Kramer added.

Large lakes and rivers on Mars once may have formed water systems that 
included many streams and smaller lakes, according to the scientists. 
The study found that the areas near the Great Lakes on Earth bear a 
strong resemblance to features on Mars. Although the areas appear to 
be similar, they formed in different ways, according to Kramer.

The study of surface depressions in conjunction with river features, 
provides a more complete picture of a surface water network that may 
have existed on what must have been a warmer early Mars, according to 
Potter. The researchers excluded fresh impact crater areas during the 
analysis in order to study older drainage patterns.

"The larger shallow depressions in the main channel system often 
contain multiple, highly eroded craters and show evidence of stream 
features in the extensive upland regions draining into them," Kramer 
said. These depressions become increasingly shallow downstream, 
suggesting that increased sedimentation may have been deposited by 
water or ice that once may have flowed through them, according to the 
scientists.

"Still unclear is how long such a water system may have persisted, and 
under exactly what climate conditions," he said. "The answers to these 
questions may lie in further examination of the sediments that have 
accumulated across the depressions of the surface water network."

"New instruments on the Mars Odyssey spacecraft, including the Thermal 
Emission Imaging System (THEMIS) instrument, address these questions," 
Kramer said. THEMIS infrared and visible light images have revealed a 
diversity of surface types and features. Nighttime temperature images 
show complex patterns of rock layers, rocky debris, sand and dust 
produced by impact cratering, wind erosion, volcanism and deposition.

"The data coming out of the Mars Global Surveyor and Mars Odyssey 
Mission are quite revealing," Kramer said. "We were able to study the 
planet in ways that were previously not possible."

"With an abundance of ice recently detected just below the surface of 
Mars, the possibility that life has existed or still may exist may 
hinge on its past climate and the duration of surface water flows," 
Potter said. "Was Mars ever a warm and wet planet, or has it always 
been cold and dry?" he asked.

The Jet Propulsion Laboratory, Pasadena, Calif., manages the Mars 
Global Surveyor and Mars Odyssey missions. The NASA Astrobiology 
Institute, based at NASA Ames, funded the study that resulted in the 
peer-reviewed article. Publication size images are available at:

http://amesnews.arc.nasa.gov/releases/2003/03images
  /marslake/marslakes.html

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