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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
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,
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