New Clues Suggest Wet Era on Early Mars Was Global

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

Guy Webster
Jet Propulsion Laboratory, Pasadena, Calif.
818-354-6278
guy.webster@jpl.nasa.gov

Kristi Marren
Johns Hopkins University Applied Physics Laboratory, Laurel, Md.
240-228-6268
Kristi.marren@jhu.edu

News release: 2010-209 June 24, 2010

New Clues Suggest Wet Era on Early Mars Was Global

The full version of this story with accompanying images is at:
http://www.jpl.nasa.gov/news/news.cfm?release=2010-209&cid=release_2010-209

PASADENA, Calif. -- Minerals in northern Mars craters seen by two orbiters suggest that a phase in
Mars' early history with conditions favorable to life occurred globally, not just in the south.

Southern and northern Mars differ in many ways, so the extent to which they shared ancient
environments has been open to question.

In recent years, the European Space Agency's Mars Express orbiter and NASA's Mars
Reconnaissance Orbiter have found clay minerals that are signatures of a wet environment at
thousands of sites in the southern highlands of Mars, where rocks on or near the surface are about
four billion years old. Until this week, no sites with those minerals had been reported in the northern
lowlands, where younger volcanic activity has buried the older surface more deeply.

French and American researchers report in the journal Science this week that some large craters
penetrating younger, overlying rocks in the northern lowlands expose similar mineral clues to ancient
wet conditions.

"We can now say that the planet was altered on a global scale by liquid water about four billion years
ago," said John Carter of the University of Paris, the report's lead author.

Other types of evidence about liquid water in later epochs on Mars tend to point to shorter durations
of wet conditions or water that was more acidic or salty.

The researchers used the Compact Reconnaissance Imaging Spectrometer for Mars (CRISM), an
instrument on the Mars Reconnaissance Orbiter, to check 91 craters in the northern lowlands. In at
least nine, they found clays and clay-like minerals called phyllosilicates, or other hydrated silicates
that form in wet environments on the surface or underground.

Earlier observations with the OMEGA spectrometer on Mars Express had tentatively detected
phyllosilicates in a few craters of the northern plains, but the deposits are small, and CRISM can
make focused observations on smaller areas than OMEGA.

"We needed the better spatial resolution to confirm the identifications," Carter said. "The two
instruments have different strengths, so there is a great advantage to using both."

CRISM Principal Investigator Scott Murchie of Johns Hopkins University Applied Physics
Laboratory, Laurel, Md., a co-author of the new report, said that the findings aid interpretation of
when the wet environments on ancient Mars existed relative to some other important steps in the
planet's early history.

The prevailing theory for how the northern part of the planet came to have a much lower elevation
than the southern highlands is that a giant object slammed obliquely into northern Mars, turning
nearly half of the planet's surface into the solar system's largest impact crater. The new findings
suggest that the formation of water-related minerals, and thus at least part of the wet period that may
have been most favorable to life, occurred between that early giant impact and the later time when
younger sediments formed an overlying mantle.

"That large impact would have eliminated any evidence for the surface environment in the north that
preceded the impact," Murchie said. "It must have happened well before the end of the wet period."

The report's other two authors are Francois Poulet and OMEGA Principal Investigator Jean-Pierre
Bibring, both of the University of Paris.

NASA's Jet Propulsion Laboratory, a division of the California Institute of Technology, Pasadena,
manages the Mars Reconnaissance Orbiter for NASA. Johns Hopkins University Applied Physics
Laboratory provided and operates CRISM, one of six instruments on that orbiter.

For more information about the Mars Reconnaissance Orbiter, visit http://www.nasa.gov/mro .

-end-

To remove yourself from this mailing, please go to http://www.kintera.org/TR.asp?a=lkIVJdPTKgLYImI&s=ffKSISOtGbLEJRNzHpE&m=bkJSL7PNKhKXImK

To remove yourself from all mailings from NASA Jet Propulsion Laboratory, please go to http://www.kintera.org/TR.asp?a=enJHKSNrE9KLK2L&s=ffKSISOtGbLEJRNzHpE&m=bkJSL7PNKhKXImK