[meteorite-list] NASA'S Curiosity Rover Provides Clues to Changes in Martian Atmosphere

[Ron Baalke]

Nov. 02, 2012

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

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

Nancy Neal Jones 
Goddard Space Flight Center, Greenbelt, Md. 
301-286-0039 
nancy.n.jones at nasa.gov 


RELEASE: 12-387

NASA'S CURIOSITY ROVER PROVIDES CLUES TO CHANGES IN MARTIAN ATMOSPHERE

PASADENA, Calif. -- NASA's car-sized rover, Curiosity, has taken 
significant steps toward understanding how Mars may have lost much of 
its original atmosphere. 

Learning what happened to the Martian atmosphere will help scientists 
assess whether the planet ever was habitable. The present atmosphere 
of Mars is 100 times thinner than Earth's. 

A set of instruments aboard the rover has ingested and analyzed 
samples of the atmosphere collected near the "Rocknest" site in Gale 
Crater where the rover is stopped for research. Findings from the 
Sample Analysis at Mars (SAM) instruments suggest that loss of a 
fraction of the atmosphere, resulting from a physical process 
favoring retention of heavier isotopes of certain elements, has been 
a significant factor in the evolution of the planet. Isotopes are 
variants of the same element with different atomic weights. 

Initial SAM results show an increase of 5 percent in heavier isotopes 
of carbon in the atmospheric carbon dioxide compared to estimates of 
the isotopic ratios present when Mars formed. These enriched ratios 
of heavier isotopes to lighter ones suggest the top of the atmosphere 
may have been lost to interplanetary space. Losses at the top of the 
atmosphere would deplete lighter isotopes. Isotopes of argon also 
show enrichment of the heavy isotope, matching previous estimates of 
atmosphere composition derived from studies of Martian meteorites on 
Earth. 

Scientists theorize that in Mars' distant past its environment may 
have been quite different, with persistent water and a thicker 
atmosphere. NASA's Mars Atmosphere and Volatile Evolution, or MAVEN, 
mission will investigate possible losses from the upper atmosphere 
when it arrives at Mars in 2014. 

With these initial sniffs of Martian atmosphere, SAM also made the 
most sensitive measurements ever to search for methane gas on Mars. 
Preliminary results reveal little to no methane. Methane is of 
interest as a simple precursor chemical for life. On Earth, it can be 
produced by either biological or non-biological processes. 

Methane has been difficult to detect from Earth or the current 
generation of Mars orbiters because the gas exists on Mars only in 
traces, if at all. The Tunable Laser Spectrometer (TLS) in SAM 
provides the first search conducted within the Martian atmosphere for 
this molecule. The initial SAM measurements place an upper limit of 
just a few parts methane per billion parts of Martian atmosphere, by 
volume, with enough uncertainty that the amount could be zero. 

"Methane is clearly not an abundant gas at the Gale Crater site, if it 
is there at all. At this point in the mission we're just excited to 
be searching for it," said SAM TLS lead Chris Webster of NASA's Jet 
Propulsion Laboratory (JPL) in Pasadena, Calif. "While we determine 
upper limits on low values, atmospheric variability in the Martian 
atmosphere could yet hold surprises for us." 

In Curiosity's first three months on Mars, SAM has analyzed atmosphere 
samples with two laboratory methods. One is a mass spectrometer 
investigating the full range of atmospheric gases. The other, TLS, 
has focused on carbon dioxide and methane. During its two-year prime 
mission, the rover also will use an instrument called a gas 
chromatograph that separates and identifies gases. The instrument 
also will analyze samples of soil and rock, as well as more 
atmosphere samples. 

"With these first atmospheric measurements we already can see the 
power of having a complex chemical laboratory like SAM on the surface 
of Mars," said SAM Principal Investigator Paul Mahaffy of NASA's 
Goddard Space Flight Center in Greenbelt, Md. "Both atmospheric and 
solid sample analyses are crucial for understanding Mars' 
habitability." 

SAM is set to analyze its first solid sample in the coming weeks, 
beginning the search for organic compounds in the rocks and soils of 
Gale Crater. Analyzing water-bearing minerals and searching for and 
analyzing carbonates are high priorities for upcoming SAM solid 
sample analyses. 

Researchers are using Curiosity's 10 instruments to investigate 
whether areas in Gale Crater ever offered environmental conditions 
favorable for microbial life. JPL manages the project for NASA's 
Science Mission Directorate in Washington. The SAM Instrument was 
developed at Goddard with instrument contributions from Goddard, JPL 
and the University of Paris in France. 

For more information about Curiosity and its mission, visit: 

http://www.nasa.gov/msl 

You can follow the mission on Facebook and Twitter at: 

http://www.facebook.com/marscuriosity 

and 

http://www.twitter.com/marscuriosity 
	
-end-