[meteorite-list] NASA Mars Rover Will Check for Ingredients of Life (Curiosity)

From: Ron Baalke <baalke_at_meteoritecentral.com>
Date: Wed, 19 Jan 2011 17:06:28 -0800 (PST)
Message-ID: <201101200106.p0K16S3g025207_at_zagami.jpl.nasa.gov>

http://www.jpl.nasa.gov/news/news.cfm?release=2011-018

NASA Mars Rover Will Check for Ingredients of Life
Jet Propulsion Laboratory
January 18, 2011

PASADENA, Calif. -- Paul Mahaffy, the scientist in charge of the largest
instrument on NASA's next Mars rover, watched through glass as
clean-room workers installed it into the rover.

The specific work planned for this instrument on Mars requires more
all-covering protective garb for these specialized workers than was
needed for the building of NASA's earlier Mars rovers.

The instrument is Sample Analysis at Mars, or SAM, built by NASA's
Goddard Space Flight Center, Greenbelt, Md. At the carefully selected
landing site for the Mars rover named Curiosity, one of SAM's key jobs
will be to check for carbon-containing compounds called organic
molecules, which are among the building blocks of life on Earth. The
clean-room suits worn by Curiosity's builders at NASA's Jet Propulsion
Laboratory, Pasadena, Calif., are just part of the care being taken to
keep biological material from Earth from showing up in results from SAM.

Organic chemicals consist of carbon and hydrogen and, in many cases,
additional elements. They can exist without life, but life as we know it
cannot exist without them. SAM can detect a fainter trace of organics
and identify a wider variety of them than any instrument yet sent to
Mars. It also can provide information about other ingredients of life
and clues to past environments.

Researchers will use SAM and nine other science instruments on Curiosity
to study whether one of the most intriguing areas on Mars has offered
environmental conditions favorable for life and favorable for preserving
evidence about whether life has ever existed there. NASA will launch
Curiosity from Florida between Nov. 25 and Dec. 18, 2011, as part of the
Mars Science Laboratory mission's spacecraft. The spacecraft will
deliver the rover to the Martian surface in August 2012. The mission
plan is to operate Curiosity on Mars for two years.

"If we don't find any organics, that's useful information," said
Mahaffy, of NASA's Goddard Space Flight Center. "That would mean the
best place to look for evidence about life on Mars may not be near the
surface. It may push us to look deeper." It would also aid understanding
of the environmental conditions that remove organics.

"If we do find detectable organics, that would be an encouraging sign
that the immediate environment in the rocks we're sampling is preserving
these clues," he said. "Then we would use the tools we have to try to
determine where the organics may have come from." Organics delivered by
meteorites without involvement of biology come with more random chemical
structures than the patterns seen in mixtures of organic chemicals
produced by organisms.

Mahaffy paused in describing what SAM will do on Mars while engineers
and technicians lowered the instrument into its position inside
Curiosity this month. A veteran of using earlier spacecraft instruments
to study planetary atmospheres, he has coordinated work of hundreds of
people in several states and Europe to develop, build and test SAM after
NASA selected his team's proposal for it in 2004.

"It has been a long haul getting to this point," he said. "We've taken a
set of experiments that would occupy a good portion of a room on Earth
and put them into that box the size of a microwave oven."

SAM has three laboratory tools for analyzing chemistry. The tools will
examine gases from the Martian atmosphere, as well as gases that ovens
and solvents pull from powdered rock and soil samples. Curiosity's
robotic arm will deliver the powdered samples to an inlet funnel. SAM's
ovens will heat most samples to about 1,000 degrees Celsius (about 1,800
degrees Fahrenheit).

One tool, a mass spectrometer, identifies gases by the molecular weight
and electrical charge of their ionized states. It will check for several
elements important for life as we know it, including nitrogen,
phosphorous, sulfur, oxygen and carbon.

Another tool, a laser spectrometer, uses absorption of light at specific
wavelengths to measure concentrations of selected chemicals, such as
methane and water vapor. It also identifies the proportions of different
isotopes in those gases. Isotopes are variants of the same element with
different atomic weights, such as carbon-13 and carbon-12, or oxygen-18
and oxygen-16. Ratios of isotopes can be signatures of planetary
processes. For example, Mars once had a much denser atmosphere than it
does today, and if the loss occurred at the top of the atmosphere, the
process would favor increased concentration of heavier isotopes in the
retained, modern atmosphere.

Methane is an organic molecule. Observations from Mars orbit and from
Earth in recent years have suggested transient methane in Mars'
atmosphere, which would mean methane is being actively added and
subtracted at Mars. With SAM's laser spectrometer, researchers will
check to confirm whether methane is present, monitor any changes in
concentration, and look for clues about whether Mars methane is produced
by biological activity or by processes that do not require life. JPL
provided SAM's laser spectrometer.

SAM's third analytical tool, a gas chromatograph, separates different
gases from a mixture to aid identification. It does some identification
itself and also feeds the separated fractions to the mass spectrometer
and the laser spectrometer. France's space agency, Centre National
d'??tudes Spatiales, provided support to the French researchers who
developed SAM's gas chromatograph.

NASA's investigation of organics on Mars began with the twin Viking
landers in 1976. Science goals of more recent Mars missions have tracked
a "follow the water" theme, finding multiple lines of evidence for
liquid water -- another prerequisite for life -- in Mars' past. The Mars
Science Laboratory mission will seek more information about those wet
environments, while the capabilities of its SAM instrument add a
trailblazing "follow the carbon" aspect and information about how well
ancient environments may be preserved.

The original reports from Viking came up negative for organics. How,
then, might Curiosity find any? Mahaffy describes three possibilities.

The first is about locations. Mars is diverse, not uniform. Copious
information gained from Mars orbiters in recent years is enabling the
choice of a landing site with favorable attributes, such as exposures of
clay and sulfate minerals good at entrapping organic chemicals. Mobility
helps too, especially with the aid of high-resolution geologic mapping
generated from orbital observations. The stationary Viking landers could
examine only what their arms could reach. Curiosity can use mapped
geologic context as a guide in its mobile search for organics and other
clues about habitable environments. Additionally, SAM will be able to
analyze samples from interiors of rocks drilled into by Curiosity,
rather than being restricted to soil samples, as Viking was.

Second, SAM has improved sensitivity, with a capability to detect less
than one part-per-billion of an organic compound, over a wider mass
range of molecules and after heating samples to a higher temperature.

Third, a lower-heat method using solvents to pull organics from some SAM
samples can check a hypothesis that a reactive chemical recently
discovered in Martian soil may have masked organics in soil samples
baked during Viking tests.

The lower-heat process also allows searching for specific classes of
organics with known importance to life on Earth. For example, it can
identify amino acids, the chain links of proteins. Other clues from SAM
could also be hints about whether organics on Mars -- if detected at all
-- come from biological processes or without biology, such as from
meteorites. Certain carbon-isotope ratios in organics compared with the
ratio in Mars' atmosphere could suggest meteorite origin. Patterns in
the number of carbon atoms in organic molecules could be a clue.
Researchers will check for a mixture of organics with chains of carbon
atoms to see if the mix is predominated either by chains with an even
number of carbon atoms or with an odd number. That kind of pattern,
rather than a random blend, would be typical of biological assembly of
carbon chains from repetitious subunits.

"Even if we see a signature such as mostly even-numbered chains in a mix
of organics, we would be hesitant to make any definitive statements
about life, but that would certainly indicate that our landing site
would be a good place to come back to," Mahaffy said. A future mission
could bring a sample back to Earth for more extensive analysis with all
the methods available on Earth.

JPL, a division of the California Institute of Technology in Pasadena,
manages the Mars Science Laboratory mission for the NASA Science Mission
Directorate, Washington.

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

2011-018
Received on Wed 19 Jan 2011 08:06:28 PM PST