[meteorite-list] Mars Orbiter Imagery Boots Curiosity Rover's Life Search

[Ron Baalke]

http://www.spaceflightnow.com/news/n0905/31mromsl/

Mars orbiter imagery boosts Curiosity rover's life search
BY CRAIG COVAULT
SPACEFLIGHT NOW
May 31, 2009

NASA and university scientists reviewing data from the Mars
Reconnaissance Orbiter (MRO) say evidence is growing that the planet
harbored life in its past or that Martian microbes exist now.

They say their views are based on the growing body of data on the
diversity of water related minerals discovered by MRO. It is also
supported by findings from other spacecraft such as Europe's Mars
Express orbiter and NASA's Phoenix lander and twin Mars rovers.

The MRO data is being used to narrow the best sites to locate life
related evidence, while also being safe enough for the Mars Science
Laboratory rover "Curiosity" set for launch in 2011.

MRO's high resolution mineralogy data resulted in, for example, the
addition of Gale crater to MSL's final landing target list.

The Curiosity rover will carry 10 times the science payload mass of the
coffee-table sized Spirit and Opportunity rovers still operating on Mars.

MSL's much larger size is evident by the scale of the Jet Propulsion
Laboratory MSL development rover that is the same size of the flight
vehicle (see above). Called the "Scarecrow" (because it does not have a
computer brain) the MSL developmental rover here--stripped of all but
its wheels and chassis--shows the scale of the vehicle far better than
more complex mockups with pseudo instrumentation in place because those
versions hide chassis details. The new MRO data is being used
specifically for final MSL landing site selection as well as assessing
evidence for current or past life across Mars.

"Every time we go and look at new data from the planet I have gotten
more encouraged that the possibility for life at least in Mars' past,"
says Mike Meyer NASA's lead scientist for Mars exploration.

"There is encouraging new MRO evidence that makes the pursuit of present
day life very worthwhile," says Scott Murchie of the Applied Physics
Laboratory at Johns Hopkins University, principal investigator of the
MRO Compact Reconnaissance Imaging Spectrometer.

"I definitely think there could have been life on Mars," says Richard
Zurek, MRO project scientist at JPL.

All three scientists commented on the life issues at a NASA Headquarters
briefing on MRO highlights, as the orbiter has just completed its
primary science mission and is beginning and extended science mission
phase.

"I think there is very encouraging evidence not just to look in the
present, but also for what [past life may have come] before during
planets evolution," Murchie says. His team's CRISM instrument has
returned extensive new evidence on the diversity of water related
mineral locations on the planet.

Meyer said the discovery of methane in the current Martian atmosphere as
well as evidence of liquid water on the planet today are positive
factors toward the potential for current life on Mars.

On Earth methane is a common byproduct of metabolism by life forms. It
has been discovered at specific locations in the Martian atmosphere by
the European Mars Express Orbiter. In addition Phoenix lander scientists
believe their spacecraft splashed up actual liquid water on Mars during
its landing on an arctic water ice plane in 2008. Phoenix also detected
carbonate related soil chemistry that could support life. MRO is finding
similar carbonate chemistry at other locations on Mars.

"I think life could have developed on Mars but whether it is there today
I am not so sure," Zurek cautioned however,

Zurek said that MRO and other data has become so compelling on positive
factors for at least past Martian life, that an important questions is
if no life is found on Mars , why has it not formed, he asked? That
would force a major new branch of study on the assessment for diminished
chances for life on other bodies besides Earth, in or outside of the
solar system he says.

He said that the same ingredients present on Earth when life began to
form just a billion years after the planet formed were also present at
the same time on Mars, when its climate was warmer and more hospitable
to surface life than it is now.

Those include surface and underground water, solar energy and heat and
heat from within the planet . All three scientists said underground Mars
life may be more likely than surface life just as on Earth where there
is more biomass underground than on the surface.

A major emphasis in the new MRO phase will be to search for near real
time geologic and aqueous processes that could bear on the current life
question, such as detection of real time or recent outbursts of water
from the sides of crater walls.

MRO has made some spectacular discoveries that relate to the presence of
water or ancient Mars and its abundance at specific locations.

One such site is at Nili Fossae, where there is remarkable mineral
evidence relating to water.

The area, based on CRISM data was initially considered as an MSL landing
area but rejected as too hazardous. That does not diminish its
significance, however, as an area where life could have formed. Some
future rover beyond MSL or even a manned lander may some day visit Nili
Fossae based on the MRO imagery.

That MRO imagery shows carbonate minerals (color coded green) indicating
that Mars had neutral to alkaline water when the minerals formed at
these locations more than 3.6 billion years ago.

Carbonates, which on Earth include limestone and chalk, dissolve quickly
in acid. Therefore, their survival until today on Mars challenges
suggestions that an exclusively acidic environment later dominated the
planet. Instead, it indicates that different types of watery
environments existed. The greater the variety of wet environments, the
greater the chances one or more of them may have supported life,
scientists agree.

"We're excited to have finally found carbonate minerals because they
provide more detail about conditions during specific periods of Mars'
history," said Murchie.

The best-exposed rocks occur along a Nili Fossae trough system 414 mi.
long at the edge of a large basin. The region has rocks rich in olivine,
(color coded yellow) a mineral that can react with water to form the
carbonate.

"This discovery of carbonates in an intact rock layer, in contact with
clays, is an example of how joint observations by CRISM and the
telescopic cameras on MRO are revealing details of distinct environments
on Mars," said Sue Smrekar, deputy project scientist for the orbiter at
JPL. They point to specific locations where future rovers and landers
could search for possible evidence of past life, she says.

Gale crater and three other potential MSL sites, already picked based on
earlier data, and reexamination by MRO , will be narrowed to a final
target site by late next year.

The image of Gale shown above also shows the candidate MSL landing
ellipse within the crater.

CRISM data indicate that water once in the crater left a detailed and
layered mineralogical record on the crater walls and around the crater's
giant central peak. The peak documents what took place there from the
time a giant meteorite initially formed the crater 3 billion years ago,
to later periods in Mars history. The oldest exposed rocks are at the
top of the central peak. Layering all up and down the peak indicate
different water layers in the crater through more recent time since the
crater was formed.

If Gale crater is selected, Murchie says MSL rover instruments will look
for fossils of past Martian life there as well as less spectacular
evidence, like organic bearing rocks that could have been formed with
microorganisms present and preserved the chemical signitures of past life.

MRO is also continuing to image three other MSL landing site candidates
equally compelling says Zurek. They are:

*Marwth Valley:* The only MSL candidate landing site in the northern
hemisphere is the Marwth Valley area. " It too is important because of
the diversity of the mineral signatures that you see," Zurek says. A
large channel carved by water cuts across the valley below highlands out
of where the water flowed. The highlands also show the effects of water,
Zurek says. "There we see different mineral signatures in different
layers indicating the episodic activity of water or the mixing of soils
by impacts in the early history of Mars," he says.

*Holden Crater:* In the southern hemisphere of Mars the 60 mi. dia.
Holden crater area is also a landing site finalist because of a channel
that goes into that crater. MRO data indicate water once flowed into
that crater, then formed a lake before it breached the far wall and ran
out, leaving layers. "In those layers we would expect to find evidence
of the past chemistry, the action of water, and how long it was there,"
says Zurek. "They may also have the potential of preserving bio
signature evidence of past life if life ever developed on the planet and
flourished in this area."

*Eberswalde Crater:* "The outstanding characteristic of Eberswalde
crater is that it has a delta formation like that formed by the
Mississippi river," Zurek says. The delta is highly structured and
layered, "meaning that there were many episodes of water flowing into
the crater," he says. Those layers are the kind of formation that could
preserve evidence of past life if that life had developed on the planet,
Zurek says.