Scientists Report That Labs on Lander Reveal Many Nutrients, Lack of Acidity
By Marc Kaufman
Washington Post Staff Writer
Friday, June 27, 2008
Early results from the first-ever "wet" chemical analysis of the surface soil of Mars show the planet harbors many of the nutrients needed for life and none of the acidity that some feared would make life highly unlikely.
"There's nothing about it that would preclude life. In fact, it seems very friendly," said mission scientist Samuel P. Kounaves of Tufts University. "We were flabbergasted."
Kounaves said that the soil was similar to what people would find in their back yards on Earth and that if organic material was added, "you could probably grow asparagus, but not strawberries."
Carbon-based organic material, however, has not been found and may be impossible to detect with the equipment now on Mars. The Viking missions to Mars in the 1970s failed to find evidence of carbon.
The new findings come from the suite of chemistry labs on the Phoenix lander, which has been digging up soil from the northern polar area of Mars since it touched down late last month.
In the wet lab experiments -- the first ever conducted beyond Earth -- the lander's analyzers moisten the soil samples and then superheat them to the point that the component elements can be analyzed, Kounaves said. The researchers hope to perform similar tests on subsurface ice samples the Phoenix has yet to collect.
The chemicals identified by the instruments included magnesium, sodium, potassium and chloride.
The experiments found a pH level of 8 to 9, which is on the alkaline side. Some researchers had predicted a Martian pH of 1, which would be acidic to the point of being most likely uninhabitable.
Kounaves and Michael Hecht of NASA's Jet Propulsion Laboratory said the soil seemed similar to that found in dry valleys of Antarctica. The team has also been intrigued to see that the surface where Phoenix landed shows polygonal patterns remarkably similar to some seen in Antarctica. Scientists speculate that they could be the result of cycles of freezing and thawing.
The Phoenix has dug two small trenches, called Wonderland and Snow White, with its eight-foot robotic arm. Yesterday's results came from samples taken about an inch deep in Wonderland.
The most dramatic results came from MECA, the microscopy, electrochemistry and conductivity analyzer, which determined the pH of the soil and identified numerous salts in it.
Another instrument, the thermal and evolved-gas analyzer (TEGA), used its eight tiny ovens to bake the soil to 1,800 degrees Fahrenheit and found water that had been chemically bound to elements of the soil long ago.
"This soil clearly has interacted with water in the past," said William V. Boynton of the University of Arizona in Tucson.
Phoenix was aimed at the north polar region because earlier surveys showed that is where water ice is most likely to be present. Scientists are convinced that surface water flowed on Mars billions of years ago, a conclusion reached by studying geologic features of the Martian landscape. Today, conditions on Mars do not allow for liquid water, in large part because the atmosphere is only 1 percent as dense as Earth's.
In 2002, the Mars Odyssey orbiter discovered that large amounts of water ice lay just beneath the surface in permafrost that covers much of the planet's far north. The region, which is notably flat and smooth, may have once been the bottom of a large ocean.
Scientists generally believe that water is necessary for life, but the recent discovery of microbes and bacteria living in extreme environments on Earth has led to a rethinking of where life can survive. Kounaves said, for instance, that some microbes have been discovered on Earth that live without water and, in effect, "eat rocks." He said similar organisms could be living below the Martian surface.
In describing the soil as compatible with life, Kounaves said he was not suggesting anything could grow on the Martian surface, which is bombarded by deadly ultraviolet rays. Any existing life forms would have to be in the soil and ice below.
The soil was deemed to be promising because, he said, "there's nothing about it that's toxic."
Hecht said the makeup of the soil -- or at least the sample tested so far -- could be important for future manned exploration because, if properly protected, the soil could be used to grow vegetables for astronauts.
"So far, we've found nothing extreme," Kounaves said. "It's all amazingly similar to what you might find on Earth."
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