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NASA's Phoenix Mars Lander
Minerals in the soil of Mars show it was covered once by lakes, rivers and
other bodies of water that could have supported life, U.S. researchers reported
on Wednesday.
NASA's Phoenix Mars Lander
Last month the Mars Phoenix Lander found ice on the surface of the planet, but
it is frozen hard and covered by red dust. Writing in the journal Nature, a team
of scientists shows that the ice is left over from warmer, wetter times.
"This is really exciting because we're finding dozens of sites where future
missions can land to understand if Mars was ever habitable and if so, to look
for signs of past life," said John Mustard of Brown University in Providence,
Rhode Island, who worked on the study.
"The minerals present in Mars' ancient crust show a variety of wet
environments," Mustard said.
His team used the Compact Reconnaissance Imaging Spectrometer for Mars (CRISM)
and other instruments on board NASA's Mars Reconnaissance Orbiter to look at
colors in reflected sunlight. This helps determine what minerals are there.
"Water must have been creating minerals at depth to get the signatures we see,"
Mustard said in a statement.
The clay minerals would have to have been formed at low temperatures, the
researchers said.
"What does this mean for habitability? It's very strong," Mustard said. "It
wasn't this hot, boiling cauldron. It was a benign, water-rich environment for a
long period of time."
The findings fit with the analysis from the Phoenix Mars Lander mission, which,
besides ice, found alkaline soil that could have supported life.
"The big surprise from these new results is how pervasive and long-lasting Mars'
water was, and how diverse the wet environments were," said Scott Murchie,
CRISM's principal investigator at the Johns Hopkins University Applied Physics
Laboratory in Laurel, Maryland.
The clay-like minerals, called phyllosilicates, suggest water interacted with
rocks dating back to what is called the Noachian period on Mars, about 4.6
billion to 3.8 billion years ago.
"In most locations the rocks are lightly altered by liquid water, but in a few
locations they have been so altered that a great deal of water must have flushed
though the rocks and soil," Mustard said.
Another study, published in Nature Geosciences, found that the wet conditions
persisted for a long time. It found evidence of river channels forming a delta
where the river emptied into a crater lake.
"The distribution of clays inside the ancient lakebed shows that standing water
must have persisted for thousands of years," said Brown University's Bethany
Ehlmann.
"Clays are wonderful at trapping and preserving organic matter, so if life ever
existed in this region, there's a chance of its chemistry being preserved in the
delta."
NASA's Phoenix Mars Lander has successfully drilled into the rock-hard ice
layer below the Martian surface and collected the frozen shavings in its robotic
arm scoop, NASA said on Wednesday.
NASA's Phoenix Mars Lander
The ice is too hard for Phoenix's scoop to dig into it, so the craft used a
powered rasp on the back of the scoop to drill into the ice, loosen the material
and kick it up into the scoop.
Images and data sent from Phoenix back to Earth on Wednesday confirmed that the
material was in the scoop and showed that it had changed slightly during the
hours after it was collected.
When ice is exposed to the air on Mars, it starts to sublimate, or convert into
water vapor (whereas ice exposed to air on Earth tends to melt).
The rasp made two separate holes in the trench informally named Snow White,
which Phoenix enlarged over the weekend and early in the week.
This ice collection trial was a test of the rasping method of gathering a
sample. The same method will be used in the coming days to collect a sample for
Phoenix's Thermal and Evolved-Gas Analyzer, which bakes samples in its tiny
ovens and analyzes the vapors they give off to determine the composition of the
sample.
"This was a trial that went really well," said Richard Morris, a Phoenix science
team member from NASA's Johnson Space Center in Houston. "While the putative ice
sublimed out of the shavings over several hours, this shows us there will be a
good chance ice will remain in a sample for delivery" to Phoenix's ovens.
Mission scientists will command Phoenix to continue scraping and enlarging the
Snow White trench and conduct another series of rasp tests on Wednesday. | |
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