"We will keep working on the puzzles these findings
present," said John Grotzinger, Curiosity project
scientist of the California Institute of Technology in
(Caltech). "Can we learn more about the active chemistry
causing such fluctuations in the amount of methane in
the atmosphere? Can we choose rock targets where
identifiable organics have been preserved?"
Researchers worked many months to determine whether any
of the organic material detected in the
sample was truly Martian. Curiosity’s SAM lab detected
in several samples some organic carbon compounds that
were, in fact, transported from Earth inside the rover.
However, extensive testing and analysis yielded
confidence in the detection of Martian organics.
Identifying which specific Martian organics are in the
rock is complicated by the presence of perchlorate
minerals in Martian rocks and soils. When heated inside
SAM, the perchlorates alter the structures of the
organic compounds, so the identities of the Martian
organics in the rock remain uncertain.
"This first confirmation of organic carbon in a rock on
Mars holds much promise," said Curiosity participating
scientist Roger Summons of the Massachusetts Institute
of Technology in
Cambridge. "Organics are
important because they can tell us about the chemical
pathways by which they were formed and preserved. In
turn, this is informative about Earth-Mars differences
and whether or not particular environments represented
by Gale Crater sedimentary rocks were more or less
favorable for accumulation of organic materials. The
challenge now is to find other rocks on Mount
that might have different and more extensive inventories
of organic compounds."
Researchers also reported that Curiosity's taste of
Martian water, bound into lakebed minerals in the
rock more than three billion years ago, indicates the
planet lost much of its water before that lakebed formed
and continued to lose large amounts after. SAM analyzed
hydrogen isotopes from water molecules that had been
locked inside a rock sample for billions of years and
were freed when SAM heated it, yielding information
about the history of Martian water. The ratio of a
heavier hydrogen isotope, deuterium, to the most common
hydrogen isotope can provide a signature for comparison
across different stages of a planet's history.
"It's really interesting that our measurements from
Curiosity of gases extracted from ancient rocks can tell
us about loss of water from Mars," said Paul Mahaffy,
SAM principal investigator of NASA’s Goddard Space
Flight Center in Greenbelt, Maryland, and lead author of
a report published online this week by the journal
The ratio of deuterium to hydrogen has changed because
the lighter hydrogen escapes from the upper atmosphere
of Mars much more readily than heavier deuterium.
order to go back in time and see how the
deuterium-to-hydrogen ratio in Martian water changed
over time, researchers can look at the ratio in water in
the current atmosphere and water trapped in rocks at
different times in the planet’s history.
Martian meteorites found on Earth also provide some
information, but this record has gaps. No known Martian
meteorites are even close to the same age as the rock
studied on Mars, which formed about 3.9 billion to 4.6
billion years ago, according to Curiosity’s
The ratio that Curiosity found in the
sample is about one-half the ratio in water vapor in
today's Martian atmosphere, suggesting much of the
planet's water loss occurred since that rock formed.
However, the measured ratio is about three times higher
than the ratio in the original water supply of Mars,
based on assumption that supply had a ratio similar to
that measured in Earth's oceans. This suggests much of
Mars' original water was lost before the rock formed.
Curiosity is one element of NASA's ongoing Mars research
and preparation for a human mission to Mars in the
2030s. Caltech manages the Jet Propulsion Laboratory in Pasadena, California, and
JPL manages Curiosity rover science investigations for
NASA's Science Mission Directorate in
Washington. The SAM
investigation is led by Paul Mahaffy of Goddard. Two of
SAM instruments key in these discoveries are the
Quadrupole Mass Spectrometer, developed at Goddard, and
the Tunable Laser Spectrometer, developed at JPL.
The results of the Curiosity rover investigation
into methane detection and the Martian organics in
an ancient rock were discussed at a news briefing
Tuesday at the American Geophysical Union's
San Francisco. The methane
results are described in a paper published online
this week in the journal Science by NASA scientist
Chris Webster of JPL, and co-authors.