[meteorite-list] Reports Detail Rover Discoveries of Wet Martian History

[Ron Baalke]

Donald Savage 
Headquarters, Washington            Dec. 2, 2004
(Phone: 202/358-1727)

Guy Webster 
Jet Propulsion Laboratory, Pasadena, Calif.
(Phone: 818/354-6278)

RELEASE: 04-385

REPORTS DETAIL ROVER DISCOVERIES OF WET MARTIAN HISTORY 

     The most dramatic findings so far from NASA's twin Mars 
rovers -- telltale evidence for a wet and possibly habitable 
environment in the arid planet's past -- passed rigorous 
scientific scrutiny for publication in a major research 
journal.

Eleven reports by 122 authors in Friday's issue of the 
journal Science present results from Opportunity's three-
month prime mission, fleshing out headline discoveries 
revealed earlier.  

Opportunity bounced to an airbag-cushioned landing on Jan. 
24. It is exploring a region called Meridiani Planum, halfway 
around Mars from where its twin, Spirit, landed three weeks 
earlier. Sedimentary rocks Opportunity examined, "clearly 
preserve a record of environmental conditions different from 
any on Mars today," report 50 rover-team scientists led by 
Dr. Steve Squyres of Cornell University, Ithaca, N.Y. and Dr. 
Ray Arvidson of Washington University, St. Louis, Mo.

"Liquid water was once intermittently present at the Martian 
surface at Meridiani, and at times it saturated the 
subsurface. Because liquid water is a key prerequisite for 
life, we infer conditions at Meridiani may have been 
habitable for some period of time in Martian history," 
according to Squires, Arvidson and other co-authors.

"Formal review and publication this week of these amazing 
discoveries further strengthens the need for continued 
exploration by orbiters, surface robots, sample-return 
missions and human explorers. There are more exciting 
discoveries awaiting us on the red planet," said Dr. Michael 
Meyer, chief scientist for Mars exploration at NASA 
Headquarters, Washington.  

Opportunity and Spirit have driven a combined 5.75 kilometers 
(3.57 miles), nearly five times their mission-success goal. 
They continue in good health after operating more than three 
times as long as the three-month prime missions for which 
they were designed. 

NASA's rover team makes the resulting scientific discoveries 
available quickly to the public and the science community. 
One type of evidence that Meridiani was wet is the 
composition of rocks there.

The rocks have a high and variable ratio of bromine to 
chlorine; indicating "the past presence of large amounts of 
water," write Dr. Rudi Rieder and Dr. Ralf Gellert of Max-
Planck-Institute for Chemistry, Mainz, Germany, and co-
authors. Their paper and another by Dr. Phil Christensen of 
Arizona State University, Tempe, and collaborators report an 
abundance of sulfur-rich minerals in the rocks, another clue 
to a watery past. Clinching the case is identification of a 
hydrated iron-sulfate salt called jarosite in the rocks, as 
reported by Dr. Goestar Klingelhoefer of the University of 
Mainz, and Dr. Richard Morris of NASA's Johnson Space Center, 
Houston, and co-authors.

Structures within the rocks add more evidence according to 
Dr. Ken Herkenhoff of the U.S. Geological Survey, Flagstaff, 
Ariz., and co-authors. Plentiful cavities, about the size of 
shirt buttons, indicate crystals formed inside the rocks then 
dissolved. Minerals carried by water formed peppercorn-size 
gray spheres, nicknamed "blueberries," that are embedded in 
the rocks. Certain angled patterns of fine layers in some 
rocks tell experts a flowing body of surface water shaped the 
sediments that became the rocks. 

Several characteristics of the rocks suggest water came and 
went repeatedly, as it does in some shallow lakes in desert 
environments on Earth. That fluctuation, plus the water's 
possible high acidity and saltiness, would have posed 
challenges to life, but not necessarily insurmountable ones, 
according to researchers. If life ever did exist at 
Meridiani, the type of rocks found there could be good 
preservers of fossils, according to Squyres, Dr. John 
Grotzinger of the Massachusetts Institute of Technology, 
Cambridge, and co-authors. 

NASA's Jet Propulsion Laboratory, Pasadena, Calif., has 
managed the Mars Exploration Rover project since it began in 
2000. Images and additional information about the rovers and 
their discoveries are available on the Internet at:

http://www.nasa.gov/vision/universe/solarsystem/mer_main.html

Information about NASA and agency programs is available on 
the Web at:

http://www.nasa.gov

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