[meteorite-list] Curiosity Rover Finds Biologically Useful Nitrogen on Mars

[Ron Baalke]

http://www.jpl.nasa.gov/news/news.php?feature=4516

Curiosity Rover Finds Biologically Useful Nitrogen on Mars
Jet Propulsion Laboratory
March 24, 2015

A team using the Sample Analysis at Mars (SAM) instrument suite aboard 
NASA's Curiosity rover has made the first detection of nitrogen on the 
surface of Mars from release during heating of Martian sediments.

The nitrogen was detected in the form of nitric oxide, and could be released 
from the breakdown of nitrates during heating. Nitrates are a class of 
molecules that contain nitrogen in a form that can be used by living organisms. 
The discovery adds to the evidence that ancient Mars was habitable for 
life.

Nitrogen is essential for all known forms of life, since it is used in 
the building blocks of larger molecules like DNA and RNA, which encode 
the genetic instructions for life, and proteins, which are used to build 
structures like hair and nails, and to speed up or regulate chemical reactions.

However, on Earth and Mars, atmospheric nitrogen is locked up as nitrogen 
gas (N2) - two atoms of nitrogen bound together so strongly that they 
do not react easily with other molecules. The nitrogen atoms have to be 
separated or "fixed" so they can participate in the chemical reactions 
needed for life. On Earth, certain organisms are capable of fixing atmospheric 
nitrogen and this process is critical for metabolic activity. However, 
smaller amounts of nitrogen are also fixed by energetic events like lightning 
strikes.

Nitrate (NO3) - a nitrogen atom bound to three oxygen atoms - is a source 
of fixed nitrogen. A nitrate molecule can join with various other atoms 
and molecules; this class of molecules is known as nitrates.

There is no evidence to suggest that the fixed nitrogen molecules found 
by the team were created by life. The surface of Mars is inhospitable 
for known forms of life. Instead, the team thinks the nitrates are ancient, 
and likely came from non-biological processes like meteorite impacts and 
lightning in Mars' distant past.

Features resembling dry riverbeds and the discovery of minerals that form 
only in the presence of liquid water suggest that Mars was more hospitable 
in the remote past. The Curiosity team has found evidence that other ingredients 
needed for life, such as liquid water and organic matter, were present 
on Mars at the Curiosity site in Gale Crater billions of years ago.

"Finding a biochemically accessible form of nitrogen is more support for 
the ancient Martian environment at Gale Crater being habitable," said 
Jennifer Stern of NASA's Goddard Space Flight Center in Greenbelt, Maryland. 
Stern is lead author of a paper on this research published online in the 
Proceedings of the National Academy of Science March 23.

The team found evidence for nitrates in scooped samples of windblown sand 
and dust at the "Rocknest" site, and in samples drilled from mudstone 
at the "John Klein" and "Cumberland" drill sites in Yellowknife Bay. Since 
the Rocknest sample is a combination of dust blown in from distant regions 
on Mars and more locally sourced materials, the nitrates are likely to 
be widespread across Mars, according to Stern. The results support the 
equivalent of up to 1,100 parts per million nitrates in the Martian soil 
from the drill sites. The team thinks the mudstone at Yellowknife Bay 
formed from sediment deposited at the bottom of a lake. Previously the 
rover team described the evidence for an ancient, habitable environment 
there: fresh water, key chemical elements required by life, such as carbon, 
and potential energy sources to drive metabolism in simple organisms.

The samples were first heated to release molecules bound to the Martian 
soil, then portions of the gases released were diverted to the SAM instruments 
for analysis. Various nitrogen-bearing compounds were identified with 
two instruments: a mass spectrometer, which uses electric fields to identify 
molecules by their signature masses, and a gas chromatograph, which separates 
molecules based on the time they take to travel through a small glass 
capillary tube -- certain molecules interact with the sides of the tube 
more readily and thus travel more slowly.

Along with other nitrogen compounds, the instruments detected nitric oxide 
(NO -- one atom of nitrogen bound to an oxygen atom) in samples from all 
three sites. Since nitrate is a nitrogen atom bound to three oxygen atoms, 
the team thinks most of the NO likely came from nitrate which decomposed 
as the samples were heated for analysis. Certain compounds in the SAM 
instrument can also release nitrogen as samples are heated; however, the 
amount of NO found is more than twice what could be produced by SAM in 
the most extreme and unrealistic scenario, according to Stern. This leads 
the team to think that nitrates really are present on Mars, and the abundance 
estimates reported have been adjusted to reflect this potential additional 
source.

"Scientists have long thought that nitrates would be produced on Mars 
from the energy released in meteorite impacts, and the amounts we found 
agree well with estimates from this process," said Stern.

The SAM instrument suite was built at NASA Goddard with significant elements 
provided by industry, university, and national and international NASA 
partners. NASA's Mars Science Laboratory Project is using Curiosity to 
assess ancient habitable environments and major changes in Martian environmental 
conditions. NASA's Jet Propulsion Laboratory in Pasadena, California, 
a division of the California Institute of Technology, built the rover 
and manages the project for NASA's Science Mission Directorate in Washington. 
The NASA Mars Exploration Program and Goddard Space Flight Center provided 
support for the development and operation of SAM. SAM-Gas Chromatograph 
was supported by funds from the French Space Agency (CNES). Data from 
these SAM experiments are archived in the Planetary Data System (pds.nasa.gov).

For more information about Curiosity, visit:

http://www.nasa.gov/msl

and

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


Media Contact

Nancy Neal-Jones / William Steigerwald
NASA Goddard Space Flight Center, Greenbelt, Maryland
Nancy.N.Jones at nasa.gov / William.A.Steigerwald at nasa.gov
301-286-0039 / 301-286-5017 

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 

2015-096