[meteorite-list] NASA Scientists Find Evidence of Water in Mars Meteorite, Reviving Debate Over Life on Mars

From: Ron Baalke <baalke_at_meteoritecentral.com>
Date: Thu, 27 Feb 2014 16:36:11 -0800 (PST)
Message-ID: <201402280036.s1S0aBTm006129_at_zagami.jpl.nasa.gov>

http://www.jpl.nasa.gov/news/news.php?release=2014-065

NASA Scientists Find Evidence of Water in Meteorite,
Reviving Debate Over Life on Mars
Jet Propulsion Laboratory
February 27, 2014

A team of scientists at NASA's Johnson Space Center in Houston and the
Jet Propulsion Laboratory in Pasadena, Calif., has found evidence of
past water movement throughout a Martian meteorite, reviving debate in
the scientific community over life on Mars.

In 1996, a group of scientists at Johnson led by David McKay, Everett
Gibson and Kathie Thomas-Keprta published an article in Science
announcing the discovery of biogenic evidence in the Allen Hills
84001(ALH84001) meteorite. In this new study, Gibson and his colleagues
focused on structures deep within a 30-pound (3.7-kilogram) Martian
meteorite known as Yamato 000593 (Y000593). The team reports that newly
discovered different structures and compositional features within the
larger Yamato meteorite suggest biological processes might have been at
work on Mars hundreds of millions of years ago.

The team's findings have been published in the February issue of the
journal Astrobiology. The lead author, Lauren White, is based at the Jet
Propulsion Laboratory. Co-authors are Gibson, Thomas-Keprta, Simon
Clemett and McKay, all based at Johnson. McKay, who led the team that
studied the ALH84001 meteorite, died a year ago.

"While robotic missions to Mars continue to shed light on the planet's
history, the only samples from Mars available for study on Earth are
Martian meteorites," said White. "On Earth, we can utilize multiple
analytical techniques to take a more in-depth look into meteorites and
shed light on the history of Mars. These samples offer clues to the past
habitability of this planet. As more Martian meteorites are discovered,
continued research focusing on these samples collectively will offer
deeper insight into attributes which are indigenous to ancient Mars.
Furthermore, as these meteorite studies are compared to present day
robotic observations on Mars, the mysteries of the planet's seemingly
wetter past will be revealed."

Analyses found that the rock was formed about 1.3 billion years ago from
a lava flow on Mars. Around 12 million years ago, an impact occurred on
Mars which ejected the meteorite from the surface of Mars. The meteorite
traveled through space until it fell in Antarctica about 50,000 years ago.

The rock was found on the Yamato Glacier in Antarctica by the Japanese
Antarctic Research Expedition in 2000. The meteorite was classified as a
nakhlite, a subgroup of Martian meteorites. Martian meteoritic material
is distinguished from other meteorites and materials from Earth and the
moon by the composition of the oxygen atoms within the silicate minerals
and trapped Martian atmospheric gases.

The team found two distinctive sets of features associated with
Martian-derived clay. They found tunnel and micro-tunnel structures that
thread their way throughout Yamato 000593. The observed micro-tunnels
display curved, undulating shapes consistent with bio-alteration
textures observed in terrestrial basaltic glasses, previously reported
by researchers who study interactions of bacteria with basaltic
materials on Earth.

The second set of features consists of nanometer- to-micrometer-sized
spherules that are sandwiched between layers within the rock and are
distinct from carbonate and the underlying silicate layer. Similar
spherical features have been previously seen in the Martian meteorite
Nakhla that fell in 1911 in Egypt. Composition measurements of the
Y000593 spherules show that they are significantly enriched in carbon
compared to the nearby surrounding iddingsite layers.

A striking observation is that these two sets of features in Y000593,
recovered from Antarctica after about 50,000 years residence time, are
similar to features found in Nakhla, an observed fall collected shortly
after landing.

The authors note that they cannot exclude the possibility that the
carbon-rich regions in both sets of features may be the product of
abiotic mechanisms: however, textural and compositional similarities to
features in terrestrial samples, which have been interpreted as
biogenic, imply the intriguing possibility that the Martian features
were formed by biotic activity.

"The unique features displayed within the Martian meteorite Yamato
000593 are evidence of aqueous alterations as seen in the clay minerals
and the presence of carbonaceous matter associated with the clay phases
which show that Mars has been a very active body in its past," said
Gibson. "The planet is revealing the presence of an active water
reservoir that may also have a significant carbon component.

"The nature and distribution of Martian carbon is one of the major goals
of the Mars Exploration Program. Since we have found indigenous carbon
in several Mars meteorites, we cannot overstate the importance of having
Martian samples available to study in earth-based laboratories.
Furthermore, the small sizes of the carbonaceous features within the
Yamato 000593 meteorite present major challenges to any analyses
attempted by remote techniques on Mars," Gibson added.

"This is no smoking gun," said JPL's White. "We can never eliminate the
possibility of contamination in any meteorite. But these features are
nonetheless interesting and show that further studies of these
meteorites should continue."

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

2014-065
Received on Thu 27 Feb 2014 07:36:11 PM PST