[meteorite-list] Mars Rovers Sharpen Questions About Livable Conditions

[Ron Baalke]

http://www.jpl.nasa.gov/news/news.cfm?release=2008-026

Mars Rovers Sharpen Questions About Livable Conditions
Jet Propulsion Laboratory
February 15, 2008

BOSTON -- Like salt used as a preservative, high concentrations of
dissolved minerals in the wet, early-Mars environment known from
discoveries by NASA's Opportunity rover may have thwarted any microbes
from developing or surviving.

"Not all water is fit to drink," said Andrew Knoll, a member of the
rover science team who is a biologist at Harvard University, Cambridge,
Mass.

Opportunity and its twin, Spirit, began their fifth year on Mars last
month, far surpassing their prime missions of three months. Today, at a
meeting of the American Association for the Advancement of Science in
Boston, scientists and engineers discussed new observations by the
rovers, recent analysis of some earlier discoveries, and perspectives on
which lessons from these rovers' successes apply to upcoming missions to
Mars.

"The engineering efforts that have enabled the rovers' longevity have
tremendously magnified the science return," said Steve Squyres of
Cornell University, Ithaca, N.Y., principal investigator for the rovers'
science payload. "All of Spirit's most important findings, such as
evidence for hot springs or steam vents, came after the prime mission."

Opportunity spent recent months examining a bright band of rocks around
the inner wall of a crater. Scientists previously hypothesized this
material might preserve a record of the ground surface from just before
the impact that excavated the crater. Inspection suggests that, instead,
it was at the top of an underground water table, Squyres reported.

Experiments with simulated Martian conditions and computer modeling are
helping researchers refine earlier assessments of whether the long-ago
conditions in the Meridiani area studied by Opportunity would have been
hospitable to microbes. Chances look slimmer. "At first, we focused on
acidity, because the environment would have been very acidic," Knoll
said. "Now, we also appreciate the high salinity of the water when it
left behind the minerals Opportunity found. This tightens the noose on
the possibility of life."

Conditions may have been more hospitable earlier, with water less briny,
but later conditions at Meridiani and elsewhere on the surface of Mars
appear to have been less hospitable, Knoll said. "Life at the Martian
surface would have been very challenging for the last 4 billion years.
The best hopes for a story of life on Mars are at environments we
haven't studied yet -- older ones, subsurface ones," he said.

NASA's current rovers and orbiters at Mars pursue the agency's "follow
the water" theme for Mars exploration. They decipher the roles and fate
of water on a planet whose most striking difference from Earth is a
scarcity of water. "Our next missions, Phoenix and Mars Science
Laboratory, mark a transition from water to habitability -- assessing
whether sites where there's been water have had conditions suited to
life," said Charles Elachi, director of NASA's Jet Propulsion
Laboratory, Pasadena, Calif. "Where conditions were habitable, later
missions may look for evidence of life."

Elachi cited the achievements of Spirit and Opportunity. "They have
worked 16 times longer than planned, driven 20 times farther than
planned, and, most important, found diverse geological records of the
effects of water in ancient Martian environments," he said. "We must not
let these successes lull us into thinking this type of exploration is
easy. Fifty years into the Space Age, we are still in the golden age of
robotic exploration of our solar system, when each mission is
unprecedented in some way as we push the limits of what is possible.
Each mission presents new challenges."

The Phoenix lander, on course to reach Mars on May 25, will assess
habitability of a shallow subsurface environment of icy soil farther
north than any earlier mission has landed. It revives technology from
missions launched before Spirit and Opportunity. The following mission,
the Mars Science Laboratory rover, will incorporate many lessons from
the current rovers, said that project's manager, Richard Cook of JPL.
"The next rover will be much bigger to carry the instruments necessary
for meeting its goals, but it would be laughable to consider doing Mars
Science Laboratory without the experience gained from doing the Mars
Exploration Rovers," he said.

The Mars Science Laboratory rover will weigh about four times as much as
Spirit or Opportunity. "There's no way we could use an airbag landing,"
said JPL's Rob Manning, chief engineer for the future rover. Instead, a
rocket-powered hovering stage will lower it to the surface on a tether.
Lessons from Spirit and Opportunity will come into play when it starts
driving, though. "With the current rovers, we've learned we can trust
the autonomous navigation technology to a level we never expected, so
now we can include that as a capability in our mission design for Mars
Science Laboratory," Manning said.

JPL, a division of the California Institute of Technology, Pasadena,
built and manages the rovers for NASA's Science Mission Directorate. For
images and information about Spirit and Opportunity, visit
www.nasa.gov/rovers and http://marsrovers.jpl.nasa.gov.

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Media Contact: Guy Webster 818-354-6278
Jet Propulsion Laboratory, Pasadena, Calif.
guy.webster at jpl.nasa.gov

2007-026