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

From: Ron Baalke <baalke_at_meteoritecentral.com>
Date: Tue, 24 Mar 2015 14:42:45 -0700 (PDT)
Message-ID: <201503242142.t2OLgjkT001513_at_zagami.jpl.nasa.gov>

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
Received on Tue 24 Mar 2015 05:42:45 PM PDT