- PASADENA, Calif. -- Scientists
are puzzled about a patch of soil near the Mars rover Spirit lander that
they now call "Magic Carpet". The intrigue has been stirred up
by how soil behaved when the lander's airbags scraped across the martian
soil. That soil appears to have been peeled away.
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- This odd performance of the soil, some speculate, could
provide a window into the existence of subsurface water and, maybe, clues
about whether Mars could sustain life.
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- There's one thing for sure. Whatever the lander's airbags
have caused, the result is a "spirited" debate.
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- Airbag retraction
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- Wrapped in protective airbags, the Spirit rover came
to rest within Gusev Crater, bouncing and skimming across the landscape
nearly 30 times, eventually rolling to full-stop.
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- Once the airbags deflated, motors and a rib and cable
network worked together to tug on the tough fabric, pulling those bags
underneath the lander's set of petals. Doing so permits the rover to drive
off its landing perch onto Mars' surface.
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- Early images relayed from Spirit showed a patch of soil
near the lander, clearly perturbed by the airbag retraction activity.
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- That small area of martian landscape was later labeled
Magic Carpet for how it behaved when scraped by a deflated and then retracting
airbag.
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- Magic carpet ride
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- "It has been detached and folded like a piece of
carpet sliding across the floor," said Mars Exploration Rover science-team
member John Grotzinger of Massachusetts Institute of Technology in Cambridge.
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- Rocks were also dragged by the airbags, leaving impressions
and "bow waves" in the soil, Grotzinger reported during a press
gathering here at the Jet Propulsion Laboratory (JPL).
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- "We don't understand itwe're dying to get a close-up
look," said Steve Squyres, principal investigator for Spirit's Athena
package of scientific tools. He was early in his view that the airbags
have uncovered "bizarre" subsurface material. The "weird
stuff", Squyres said, appears to be "strangely cohesive."
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- Spirit scientists had been repeatedly pressed on whether
the cohesive nature of the disturbed soil may be water-related -- a mud,
in fact. So far, that idea doesn't appear to hold, well what else to say
-- water.
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- Super-fine particles clumped together under the influence
of the martian environment could act in the manner that's being seen, suggest
Spirit investigators.
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- Wheel action
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- Initially, Spirit's mission planners indicated interest
in driving the rover over to this site to look for additional clues about
the composition of the martian soil. Those plans seem to have been nixed,
however, by cautious rover engineers anxious to avoid getting snagged by
lander hardware.
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- It is within the Spirit rover's ability, however, to
use its wheels to trench the martian terrain. An array of science gear
toted by the robot can then be focused on the result of wheel action.
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- When Spirit rolled off its lander pedestal, it was quickly
noted that the rover's wheels had begun to be caked in martian surface
material.
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- Sand and brine?
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- "I think we're seeing, already, preliminary evidence
for a variety of materials, just within the soil," said David Des
Marais, an astrobiologist from NASA 's Ames Research Center. He is also
a lead member of the long-term planning group that is charting future use
of the Mars rovers, Spirit and the yet-to-land Opportunity.
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- Finer grain material is seemingly globally uniform on
Mars, Des Marais told SPACE.com . But then more coarse material is available
locally too, he said.
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- "That darker stuff that's beneath the fines is a
step in that direction. This funny peeling that's occurred, he added, could
be, as hypothesized, the result of very fine grain material.
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- "But another thing that could do something like
that, in my opinion, is a mixture of sand and brine," Des Marais explained.
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- Gully connection
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- Brines on Mars have been part of the debate regarding
gully formation on the planet, now documented to exist at numbers of locations
on Mars. Some experts suggest they are the result of water action.
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- Research suggests that some brines could be sort of fluid-like
down to temperatures way below zero, Des Marais said. At Gusev crater,
he added, temperatures are such that very concentrated brine could be what
is now being tagged as Magic Carpet.
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- "We can't go there with the rover. Engineers have
an exclusion zone because it's a navigation hazard. That area is too close
to the lander, unfortunately," Des Marais said. "There is a general
sense of the group that this type of deposit might not be everywhere. But
it certainly has got to be elsewhere," he noted.
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- With Earth at one end and a very dry place at the other
end, Mars is somewhere in-between. The ratio of water to rock material
is a scientific objective of the Mars Exploration Rovers.
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- "These very concentrated brines could be one example
of that intermediate domain, such as you might see in desertsplaces like
Death Valley in California where water is limited - but it is there,"
Des Marais said.
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- If indeed if Magic Carpet is brine, this material could
be processed to get water out of it -- a resource that could help sustain
a future human expedition to the red planet, Des Marais concluded.
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- Mars muck
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- "What I really see is mud," suggests Gilbert
Levin, a former Mars Viking life detection experimenter in the 1970s. He
is now Executive Officer for Science at Spherix Incorporated in Beltsville,
Maryland.
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- Levin said that the formation of liquid water can happen
under the environmental conditions of Mars. Indeed, that water can even
exist in liquid form on the surface of the red planet.
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- Furthermore, the detection by NASA's Mars Odyssey of
the widespread presence of near-surface ice means liquid water is on the
martian surface, Levin told SPACE.com via email.
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- "Liquid water is generally acknowledged to be necessary
for the presence of life on Mars," Levin said, hence the importance
of addressing the issue that the so-called Magic Carpet has raised on Mars,
he said.
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- Levin added: "If it looks like muck, and it puddles
like muck, and it tracks like muck -- it must be muck."
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