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

[Ron Baalke]

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