Blueberries, Add Water and Stir
The Soup on Mars
|Cover of Science Magazine devoted to Opportunity rover initial results.
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.
|Cover of Science Magazine devoted to Spirit rover initial results.
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.
"These machines just keep going and going," said Squyres, "so the science just keeps coming and coming."
"It’s an incredibly rich data set," Squyres told Astrobiology Magazine. "The data from the first 90 sols of both landing sites is now out there in the Planetary Data System, and anybody can access it and do science with it. To a certain extent, it’s going to be very satisfying to just sit back and watch people do science with this data. We worked very hard to build these rovers, and we’ve worked very hard to collect the data.
But I don’t think this is going to be it for me as far as Mars exploration is concerned. I’m on the imaging team for the Mars Reconnaissance Orbiter mission, which launches in less than a year. So I intend to keep doing science at Mars for a long time."
Related Web Pages
Cornell Mars Site
Mars Exploration Rovers, JPL
NASA’s RATs Go Roving on Mars
Pancam– Surveying the Martian Scene
Alpha Proton X-ray Spectrometer