[meteorite-list] Curiosity Mars Rover's Weather Data Bolster Case for Brine

From: Ron Baalke <baalke_at_meteoritecentral.com>
Date: Tue, 14 Apr 2015 08:59:09 -0700 (PDT)
Message-ID: <201504141559.t3EFx9qO011789_at_zagami.jpl.nasa.gov>

http://www.jpl.nasa.gov/news/news.php?feature=4549

NASA Mars Rover's Weather Data Bolster Case for Brine
Jet Propulsion Laboratory
April 13, 2015

Fast Facts:

* Conditions that might produce liquid brine in Martian soil extend closer
to the equator than expected

* Perchlorate salt in soil can pull water molecules from the atmosphere
and act as anti-freeze

* Presence of brine would not make Curiosity's vicinity favorable for
microbes

Martian weather and soil conditions that NASA's Curiosity rover has measured,
together with a type of salt found in Martian soil, could put liquid brine
in the soil at night.

Perchlorate identified in Martian soil by the Curiosity mission, and previously
by NASA's Phoenix Mars Lander mission, has properties of absorbing water
vapor from the atmosphere and lowering the freezing temperature of water.
This has been proposed for years as a mechanism for possible existence
of transient liquid brines at higher latitudes on modern Mars, despite
the Red Planet's cold and dry conditions.

New calculations were based on more than a full Mars year of temperature
and humidity measurements by Curiosity. They indicate that conditions
at the rover's near-equatorial location were favorable for small quantities
of brine to form during some nights throughout the year, drying out again
after sunrise. Conditions should be even more favorable at higher latitudes,
where colder temperatures and more water vapor can result in higher relative
humidity more often.

"Liquid water is a requirement for life as we know it, and a target for
Mars exploration missions," said the report's lead author, Javier Martin-Torres
of the Spanish Research Council, Spain, and Lulea University of Technology,
Sweden, and a member of Curiosity's science team. "Conditions near the
surface of present-day Mars are hardly favorable for microbial life as
we know it, but the possibility for liquid brines on Mars has wider implications
for habitability and geological water-related processes."

The weather data in the report published today in Nature Geosciences come
from the Cuirosity's Rover Environmental Monitoring Station (REMS), which
was provided by Spain and includes a relative-humidity sensor and a ground-temperature
sensor. NASA's Mars Science Laboratory Project is using Curiosity to investigate
both ancient and modern environmental conditions in Mars' Gale Crater
region. The report also draws on measurements of hydrogen in the ground
by the rover's Dynamic Albedo of Neutrons (DAN) instrument, from Russia.

"We have not detected brines, but calculating the possibility that they
might exist in Gale Crater during some nights testifies to the value of
the round-the-clock and year-round measurements REMS is providing," said
Curiosity Project Scientist Ashwin Vasavada of NASA's Jet Propulsion Laboratory,
Pasadena, California, one of the new report's co-authors.

Curiosity is the first mission to measure relative humidity in the Martian
atmosphere close to the surface and ground temperature through all times
of day and all seasons of the Martian year. Relative humidity depends
on the temperature of the air, as well as the amount of water vapor in
it. Curiosity's measurements of relative humidity range from about five
percent on summer afternoons to 100 percent on autumn and winter nights.

Air filling pores in the soil interacts with air just above the ground.
When its relative humidity gets above a threshold level, salts can absorb
enough water molecules to become dissolved in liquid, a process called
deliquescence. Perchlorate salts are especially good at this. Since perchlorate
has been identified both at near-polar and near-equatorial sites, it may
be present in soils all over the planet.

Researchers using the High Resolution Imaging Science Experiment (HiRISE)
camera on NASA's Mars Reconnaissance Orbiter have in recent years documented
numerous sites on Mars where dark flows appear and extend on slopes during
warm seasons. These features are called recurring slope lineae, or RSL.
A leading hypothesis for how they occur involves brines formed by deliquesence.

"Gale Crater is one of the least likely places on Mars to have conditions
for brines to form, compared to sites at higher latitudes or with more
shading. So if brines can exist there, that strengthens the case they
could form and persist even longer at many other locations, perhaps enough
to explain RSL activity," said HiRISE Principal Investigator Alfred McEwen
of the University of Arizona, Tucson, also a co-author of the new report.

In the 12 months following its August 2012 landing, Curiosity found evidence
for ancient streambeds and a lakebed environment more than 3 billion years
ago that offered conditions favorable for microbial life. Now, the rover
is examining a layered mountain inside Gale Crater for evidence about
how ancient environmental conditions evolved. JPL, a division of the California
Institute of Technology in Pasadena, manages the Mars Science Laboratory
and Mars Reconnaissance Projects for NASA's Science Mission Directorate,
Washington.

For more information about Curiosity, visit:

http://www.nasa.gov/msl

and

http://mars.jpl.nasa.gov/msl/

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

Dwayne Brown
NASA Headquarters, Washington
202-358-1726
dwayne.c.brown at nasa.gov

2015-127
Received on Tue 14 Apr 2015 11:59:09 AM PDT