[meteorite-list] Curiosity Tasked with Hunting for Elusive Martian Organics

From: Ron Baalke <baalke_at_meteoritecentral.com>
Date: Tue, 28 May 2013 12:21:26 -0700 (PDT)
Message-ID: <201305281921.r4SJLRAN002491_at_zagami.jpl.nasa.gov>

http://www.spaceflightnow.com/mars/msl/130527organics/

Curiosity tasked with hunting for elusive Martian organics
BY STEPHEN CLARK
SPACEFLIGHT NOW
May 27, 2013

Back in action after a month out of contact with Earth, NASA's Curiosity
rover is renewing its quest to excavate a definitive signal of organic
molecules - the building blocks of life - from the red planet's regolith
and bedrock after a first taste of Martian soil turned up inconclusive
results.
 
Scientists say there should be plenty of organic molecules on Mars. The
red planet has been pummeled by asteroids and comets since it formed,
delivering organics to the surface over billions of years.

So far, Curiosity has not encountered the levels of organic material
scientists expected to find, but the mission has a long way to go before
reaching a verdict on the presence of organics at the rover's Gale
Crater exploration site.

The six-wheeled robot's drill bored into a slab of Martian mudstone
Sunday to collect the mission's second sample of rock powder. The
rover's drill and scoop, mounted on the craft's robotic arm, will
deliver the sample to Curiosity's analytical instruments to scrutinize
the material for the signature of life-forming organic molecules.

The drill site is at a rock named "Cumberland" about 9 feet away from
the location where Curiosity extracted the mission's first powder rock
sample from a target called "John Klein."

The drill campaign at Cumberland is the rover's first major scientific
research activity since it renewed full communications with Earth in
early May. Mars was on the opposite side of the sun from Earth for most
of April, and managers instituted a moratorium on commands to the rover
in case the sun disrupted or corrupted signals passing between Curiosity
and ground antennas.

Scientists will use the Cumberland sample to confirm results from an
analysis of Curiosity's John Klein sample collected in February, which
showed the rover is in a region that was once habitable for life on
ancient Mars.

The second drill sample will help ensure the findings from the John
Klein analysis were not affected by contamination from other types of
Martian soil.

"The idea is to follow up on all these discoveries we've been making at
this John Klein drill site," said Ashwin Vasavada, the rover's deputy
project scientist, in an interview before the May 19 drill at
Cumberland. "The team has done a really extensive analysis of the first
powder that was acquired during the drilling, but to confirm some of
those results and maybe slightly tweak some of experiments for even
better analysis, we'd like to do a second drill hole somewhere around
the current drill site."

Both drill locations are in a shallow depression named Yellowknife Bay,
where Curiosity has explored rocks and soil since autumn. Scientists
believe the Yellowknife Bay site is at the end of an ancient river system.

Despite the promising discovery that Yellowknife Bay was once habitable
for microbial life, studies of drill and scoop samples gathered by
Curiosity have been inconclusive on the hunt for organic compounds - the
chemical building blocks necessary for the formation of life.

Vasavada said he expects Curiosity will spend a few more weeks at
Yellowknife Bay, then drive toward Mount Sharp, a three-mile-high peak
nearby that might offer a more definitive measurement for Curiosity's
instruments sensitive to organic molecules.

Since landing on Mars in August, Curiosity has driven about a half-mile
across rocks and dusty soil to the Yellowknife Bay region. The rover's
on-board instruments tasted powder from mudstone and found an array of
elements essential for life.

Carbon? Check. Hydrogen? Absolutely. Oxygen? Yep. Nitrogen? Sure.
Phosphorus? You bet. Sulfur? Plenty.

"You add it all up, and the presence of minerals in various states of
oxidation would provide a source of energy for primitive biology," said
John Grotzinger, Curiosity's lead scientist from NASA's Jet Propulsion
Laboratory.

That finding is enough for Curiosity's mission to be considered a
success, Grotzinger told a NASA advisory panel in April.

"This meets our mission success criteria, and we're having a good time,"
he said.

But in its first thorough check of Martian soil, Curiosity's SAM
sample-analyzing instrument, designed to sniff out the building blocks
of life, did not detect the kind of complex organic molecules many
scientists hoped to find.

"So far, we detected some carbon in the rocks and some very simple
carbon-containing molecules, but nothing you would call the organics
that people were excited to find," Vasavada said. "That's kind of a
mystery because we expect there to be carbon or even organics on Mars
delivered naturally. We know that, for example, asteroids and comets
have organic molecules in them. They form naturally in space and would
be delivered to Mars."

Grotzinger and Vasavada have directed their science team to develop a
systematic search for organic molecules, driving the rover to locations
thought to best sustain carbon. Curiosity is not equipped to find extant
life, but there is much to learn about the red planet's ability to
preserve organics and how to uncover them.

It won't be easy, Grotzinger said.

"I just think we'd be nuts to go around promising people that we have
even a good chance of finding organics," Grotzinger said in April. "On
the other hand, I think, as a mission, we have to undertake this search
systematically, so that if we don't find anything, we can do a proper
post-mortem and say here's what we tried, here's what we discovered, and
here's our best attempt to explain why we might have failed."

And if scientists are lucky, the rover could make a discovery, he said.

Curiosity is first continuing the work at Yellowknife Bay.

Managers selected the Cumberland drill site because it is near the
location Curiosity retrieved the mission's first powder sample.

But one difference is the Cumberland rock is covered with tiny spherical
concretions, which look similar to 'blueberries' discovered by NASA's
Opportunity rover on the other side of Mars.

Opportunity found the blueberry concretions were made of hematite - a
strongly oxidized iron-bearing mineral - left behind as water saturated
Martian bedrock in an earlier wetter period in the red planet's history.

While Curiosity's finding looks similar to Opportunity's blueberries,
scientists say the granules are made of different material. One
possibility is the concretions are made of magnetite - an iron-based
mineral with less oxidation than hematite - and formed in an aquatic
environment in a similar way to the hematite blueberries.

Curiosity's chemical and mineralogical instrument indicated the rocks
near the rover are rich in magnetite, and trailings from both of the
rover's drill holes are gray, suggesting the material is less oxidized
than the reddish rock present at Opportunity's landing site.

Scientists will have to wait several weeks to learn whether Curiosity's
instruments find organic molecules in the Cumberland concretions. Their
wait is even longer before Curiosity searches for organics amid the
layers of clay on Mount Sharp, which researchers suspect holds the
mission's best shot for finding more complex organic molecules than
found so far.

Curiosity will start driving toward Mount Sharp as soon as June, making
brief stops to investigate rocks and other interesting research targets
before beginning the climb up the flank of the central peak of Gale
Crater, the rover's landing site.

When NASA selected the Curiosity landing site, the prevailing theory was
Mount Sharp was formed in a long-gone lake. But new research from
scientists at Princeton University and the California Institute of
Technology suggests Mount Sharp was assembled over eons by silt lifted
into the Martian sky by winds.

The theory of wind formation for Mount Sharp would throw into doubt
whether Mount Sharp is the best spot on Mars for a rover to seek
evidence for past life, according to Kevin Lewis, a Princeton associate
research scholar in geosciences and a participating scientist on the
Curiosity rover mission.

Based on researchers' understanding of how organics are transported
through the solar system, Vasavada said there should be many more carbon
compounds than what Curiosity has discovered to date.

Paul Mahaffy, principal investigator for Curiosity's Sample Analysis at
Mars instrument package, said ancient stream systems and layered clays
like Yellowknife Bay and Mount Sharp are typically good preservers of
organics on Earth.

"We do believe that there should be a background rain of abiotic carbon
that comes in from the cosmos," Grotzinger said. "We would expect, at
some point, to actually find, and be able to measure, something more
complicated than a single chlorine chlorohydrocarbon - just a one-carbon
atom structure."

Although Curiosity's first tastes of soil produced no conclusive results
for organics, officials are not close to giving up. But scientists are
questioning why the rover did not detect as much carbon as expected.

"Are we even able to detect that background amount we expect to be
there, apart from life or anything else? If not, why not? The team has
been discussing various ways that organics are destroyed on Mars,"
Vasavada said. "One possibility is that this particular site we're at
wasn't conducive to preserving organics over time. There could be things
like UV light, natural high-energy radiation, or different chemical
oxidants, all of which could destroy the evidence before we get a chance
to detect it with our instruments.

"That's where we're at with this particular site, not having seen much
of a signal," Vasavada said. "Now the job is to take out the pencil and
paper and figure out what we would have expected to see even from
natural sources. Is it telling us this is not a place that would
preserve that kind of evidence for us? That would point us to look
elsewhere."

Michael Meyer, chief scientist for NASA's Mars program, said the rover's
results will not be the final ruling on whether life or organic material
existed in the red planet's distant past.

"Even if you understand everything and you don't find any evidence, that
doesn't mean there wasn't something going on when those rocks were laid
down," Meyer said May 6 in a public discussion at the Humans 2 Mars
Summit in Washington.

According to Grotzinger, the rover's science team is thinking of ways
"up the bar" and explore for carbon with an eye toward informing
upcoming missions of where organics tend to reside on Mars.

"We're learning about how to find areas and samples that would preserve
that kind of evidence," Vasavada said. "That helps not only us, but a
sample return mission."

NASA's next Mars rover, due for launch in 2020, will likely carry
equipment to collect and store soil samples for retrieval by a future
spacecraft for return to Earth.

"I see this as something important for us to do because this isn't going
to be easy," Grotzinger said. "Somewhere there should be something
preserved. I think as we go to Mount Sharp, we'll be able to push more
buttons there, and not only explore different habitability scenarios but
also explore options that may have preserved organic carbon differently."
Received on Tue 28 May 2013 03:21:26 PM PDT