[meteorite-list] NASA Mars Orbiters See Clues to Possible Water Flows

From: Ron Baalke <baalke_at_meteoritecentral.com>
Date: Mon, 10 Feb 2014 13:40:31 -0800 (PST)
Message-ID: <201402102140.s1ALeWjG011420_at_zagami.jpl.nasa.gov>

http://www.jpl.nasa.gov/news/news.php?release=2014-042

NASA Mars Orbiters See Clues to Possible Water Flows
Jet Propulsion Laboratory
February 10, 2014

NASA spacecraft orbiting Mars have returned clues for understanding
seasonal features that are the strongest indication of possible liquid
water that may exist today on the Red Planet.

The features are dark, finger-like markings that advance down some
Martian slopes when temperatures rise. The new clues include
corresponding seasonal changes in iron minerals on the same slopes and a
survey of ground temperatures and other traits at active sites. These
support a suggestion that brines with an iron-mineral antifreeze, such
as ferric sulfate, may flow seasonally, though there are still other
possible explanations.

Researchers call these dark flows "recurring slope lineae." As a result,
RSL has become one of the hottest acronyms at meetings of Mars scientists.

"We still don't have a smoking gun for existence of water in RSL,
although we're not sure how this process would take place without
water," said Lujendra Ojha, a graduate student at the Georgia Institute
of Technology, Atlanta, and lead author of two new reports about these
flows. He originally discovered them while an undergraduate at the
University of Arizona, Tucson, three years ago, in images from the High
Resolution Imaging Science Experiment (HiRISE) camera on NASA's Mars
Reconnaissance Orbiter.

Ojha and Georgia Tech assistant professor James Wray more recently
looked at 13 confirmed RSL sites using images from the same orbiter's
Compact Reconnaissance Imaging Spectrometer for Mars (CRISM) instrument.
They searched for minerals that RSL might leave in their wake as a way
of understanding the nature of these features: water-related or not?

They didn't find any spectral signature tied to water or salts. But they
did find distinct and consistent spectral signatures of ferric and
ferrous minerals at most of the sites. These iron-bearing minerals were
more abundant or featured distinct grain sizes in RSL-related materials
as compared to non-RSL slopes. These results are in a paper published in
the journal Geophysical Research Letters.

Ojha said, "Just like the RSL themselves, the strength of the spectral
signatures varies according to the seasons. They're stronger when it's
warmer and less significant when it's colder."

One possible explanation for these changes is a sorting of grain sizes,
such as removal of fine dust from the surface, which could result from
either a wet process or dry one. Two other possible explanations are an
increase in the more-oxidized (ferric) component of the minerals, or an
overall darkening due to moisture. Either of these would point to water,
even though no water was directly detected. The spectral observations
might miss the presence of water, because the dark flows are much
narrower than the area of ground sampled with each CRISM reading. Also,
the orbital observations have been made only in afternoons and could
miss morning moisture.

The leading hypothesis for these features is the flow of near-surface
water, kept liquid by salts depressing the freezing point of pure water.
"The flow of water, even briny water, anywhere on Mars today would be a
major discovery, impacting our understanding of present climate change
on Mars and possibly indicating potential habitats for life near the
surface on modern Mars," said Mars Reconnaissance Orbiter Project
Scientist Richard Zurek, of NASA's Jet Propulsion Laboratory, Pasadena,
Calif.

In related research, reported in a paper to be published by the journal
Icarus next month, the Georgia Tech scientists and colleagues at the
University of Arizona; U.S. Geological Survey, Flagstaff, Ariz.; and
Polish Academy of Sciences, Warsaw, used the Mars Reconnaissance Orbiter
and NASA's Mars Odyssey orbiter to look for patterns in where and when
the dark seasonal flows exist on Mars. Their results indicate that many
sites with slopes, latitudes and temperatures matching known RSL sites
do not have any evident RSL.

They hunted for areas that were ideal locations for RSL formation: areas
near the southern mid-latitudes on rocky cliffs. They found 200, but
barely any of them had RSL. "Only 13 of the 200 locations had confirmed
RSL," said Ojha. "The fact that RSL occur in a few sites and not others
indicates additional unknown factors such as availability of water or
salts may play a crucial role in RSL formation."

They compared new observations with images from previous years,
revealing that RSL are much more abundant some years than others.

"NASA likes to 'follow the water' in exploring the Red Planet, so we'd
like to know in advance when and where it will appear," Wray said. "RSL
have rekindled our hope of accessing modern water, but forecasting wet
conditions remains a challenge."

JPL, a division of the California Institute of Technology, manages the
Mars Reconnaissance Orbiter and Mars Odyssey projects for NASA's Science
Mission Directorate, Washington. Lockheed Martin Space Systems in Denver
built both orbiters. The University of Arizona operates the HiRISE
camera, which was built by Ball Aerospace & Technologies Corp. of
Boulder, Colo. The Johns Hopkins University Applied Physics Laboratory,
Laurel, Md., provided and operates CRISM.

For more about NASA's Mars exploration missions, see
http://www.nasa.gov/mars and http://mars.jpl.nasa.gov . The new research
reports about recurring slope lineae are available at
http://wray.eas.gatech.edu/Ojha_etal2013-acceptedGRL.pdf and
http://wray.eas.gatech.edu/Ojha_etal2014-acceptedIcarus.pdf .

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

Jason Maderer 404-385-2966
Georgia Institute of Technology, Atlanta
jason.maderer at comm.gatech.edu

2014-042
Received on Mon 10 Feb 2014 04:40:31 PM PST