[meteorite-list] Geologists Finding a Different Mars Underneath

[Ron Baalke]

MEDIA RELATIONS OFFICE
JET PROPULSION LABORATORY
CALIFORNIA INSTITUTE OF TECHNOLOGY
NATIONAL AERONAUTICS AND SPACE ADMINISTRATION
PASADENA, CALIFORNIA 91109. TELEPHONE (818) 354-5011
http://www.jpl.nasa.gov

Guy Webster 818-354-6278
Jet Propulsion Laboratory, Pasadena, Calif.

Dwayne Brown 202-358-1726
NASA Headquarters, Washington, D.C.

Peter Golkin 202-633-2374
National Air and Space Museum, Washington, D.C.			

NEWS RELEASE: 2006-149 	     		 December 13, 2006

Geologists Finding a Different Mars Underneath

Mars is showing scientists its older, craggier face 
buried beneath the surface, thanks to a pioneering 
sounding radar co-sponsored by NASA aboard the 
European Space Agency's Mars Express orbiter.
Observations by the first project to explore a planet 
by sounding radar strongly suggest that ancient impact 
craters lie buried beneath the smooth, low plains of 
Mars' northern hemisphere. The technique uses echoes of 
waves that have penetrated below the surface. 

"It's almost like having X-ray vision," said Dr. Thomas R. 
Watters of the National Air and Space Museum's Center for 
Earth and Planetary Studies, Washington. "Besides finding 
previously unknown impact basins, we've also confirmed 
that some of the subtle topographic depressions mapped 
previously in the lowlands are related to impact features."

Studies of how Mars evolved aid understanding of early 
Earth. Some signs of the forces at work a few billion 
years ago are more evident on Mars because, on Earth, 
many of them have been obliterated during Earth's more 
active resurfacing by tectonic activity.

Watters and nine co-authors report the findings in the 
Dec. 14, 2006 issue of the journal Nature. 

The researchers used the orbiter's Mars Advanced Radar 
for Subsurface and Ionospheric Sounding, which was 
provided to the European Mars mission by NASA and the 
Italian Space Agency. The instrument transmits radio 
waves that pass through the Martian surface and bounce 
off features in the subsurface with electrical 
properties that contrast with those of materials that 
buried them. 

The findings bring planetary scientists closer to 
understanding one of the most enduring mysteries about 
the geologic evolution of the planet. In contrast to 
Earth, Mars shows a striking difference between its 
northern and southern hemispheres. Almost the entire 
southern hemisphere has rough, heavily cratered 
highlands, while most of the northern hemisphere is 
smoother and lower in elevation.

Since the impacts that cause craters can happen 
anywhere on a planet, the areas with fewer craters are 
generally interpreted as younger surfaces where 
geological processes have erased the impact scars. The 
abundance of buried craters that the radar has detected 
beneath Mars' smooth northern plains means the 
underlying crust of the northern hemisphere is extremely 
old, "perhaps as ancient as the heavily cratered 
highland crust in the southern hemisphere."  

Learning about the ancient lowland crust has been 
challenging because that crust was buried first by vast 
amounts of volcanic lava and then by sediments carried by 
episodic flood waters and wind.

Co-authors are Carl J. Leuschen, Johns Hopkins University 
Applied Physics Laboratory, Laurel, Md.; Jeffrey J. Plaut, 
Ali Safaeinili and Anton B. Ivanov of NASA's Jet Propulsion 
Laboratory, Pasadena, Calif.; Giovanni Picardi, "La 
Sapienza" University of Rome, Italy; Stephen M. Clifford, 
Lunar and Planetary Institute, Houston; William M. Farrell, 
NASA's Goddard Space Flight Center, Greenbelt, Md.; 
Roger J. Phillips, Washington State University, St. Louis; 
and Ellen R. Stofan, Proxemy Research, Laytonsville, Md.

Additional information about the Mars Advanced Radar for 
Subsurface and Ionospheric Sounding is available at 
http://www.marsis.com .  JPL, a division of the California 
Institute of Technology, Pasadena, manages NASA's roles in 
Mars Express for the NASA Science Mission Directorate, 
Washington. 

The Center for Earth and Planetary Studies is the scientific 
research unit within the Collections and Research Department 
of the Smithsonian Institution's National Air and Space 
Museum. The Center's scientists perform original research 
and outreach activities on topics covering planetary science, 
terrestrial geophysics and the remote sensing of 
environmental change.

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