This image illustrates possible ways methane might
be added to Mars' atmosphere (sources) and removed from the atmosphere (sinks).
NASA's Curiosity Mars rover has detected fluctuations in methane concentration
in the atmosphere, implying both types of activity occur on modern
Mars.
Image Credit:
NASA/JPL-Caltech/SAM-GSFC/Univ. of
Michigan
Feature Link:
NASA's Mars Curiosity rover has measured a tenfold spike in methane, an
organic chemical, in the atmosphere around it and detected other organic
molecules in a rock-powder sample collected by the robotic laboratory’s
drill.
NASA's Mars rover Curiosity drilled into this rock
target, "Cumberland," during the 279th Martian day, or sol, of the rover's work
on Mars (May 19, 2013) and collected a powdered sample of material from the
rock's interior.
Image Credit:
NASA/JPL-Caltech/MSSS
This graphic shows the Tunable Laser Spectrometer,
one of the tools within the Sample Analysis at Mars laboratory on NASA's
Curiosity Mars rover. By measuring absorption of light at specific wavelengths,
it measures concentrations of methane, carbon dioxide and water vapor in Mars'
atmosphere.
This graphic shows tenfold spiking in the abundance
of methane in the Martian atmosphere surrounding NASA's Curiosity Mars rover, as
detected by a series of measurements made with the Tunable Laser Spectrometer
instrument in the rover's Sample Analysis at Mars laboratory
suite.
Image Credit:
NASA/JPL-Caltech
Feature Link:
Data graphed here are examples from the Sample
Analysis at Mars (SAM) laboratory's detection of Martian organics in a sample of
powder that the drill on NASA's Curiosity Mars rover collected from a rock
target called "Cumberland."
Image Credit:
NASA/JPL-Caltech
Feature Link:
This graphic offers comparisons between the amount
of an organic chemical named chlorobenzene detected in the "Cumberland" rock
sample and amounts of it in samples from three other Martian surface targets
analyzed by NASA's Curiosity Mars rover.
Image Credit:
NASA/JPL-Caltech
Feature Link:
This illustration portrays some of the reasons why
finding organic chemicals on Mars is challenging. Whatever organic chemicals may
be produced on Mars or delivered to Mars face several possible modes of being
transformed or destroyed.
Image Credit:
NASA/JPL-Caltech
Feature Link:
"This temporary increase in methane -- sharply up and then back down -- tells
us there must be some relatively localized source," said Sushil Atreya of the
University of Michigan, Ann Arbor, and Curiosity rover science team. "There are
many possible sources, biological or non-biological, such as interaction of
water and rock."
Researchers used Curiosity’s onboard Sample Analysis at Mars (SAM) laboratory
a dozen times in a 20-month period to sniff methane in the atmosphere. During
two of those months, in late 2013 and early 2014, four measurements averaged
seven parts per billion. Before and after that, readings averaged only one-tenth
that level.
Curiosity also detected different Martian organic chemicals in powder drilled
from a rock dubbed Cumberland, the first definitive detection of organics in
surface materials of Mars. These Martian organics could either have formed on
Mars or been delivered to Mars by meteorites.
Organic molecules, which contain carbon and usually hydrogen, are chemical
building blocks of life, although they can exist without the presence of life.
Curiosity's findings from analyzing samples of atmosphere and rock powder do not
reveal whether Mars has ever harbored living microbes, but the findings do shed
light on a chemically active modern Mars and on favorable conditions for life on
ancient Mars.
"We will keep working on the puzzles these findings present," said John
Grotzinger, Curiosity project scientist of the California Institute of
Technology in Pasadena (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 Cumberland 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 Sharp 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 Cumberland 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 Science
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. In 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 measurements.
The ratio that Curiosity found in the Cumberland 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 convention in 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.
A report on organics detection in the Cumberland rock by NASA scientist
Caroline Freissinet, of Goddard, and co-authors, is pending publication.
For copies of the new Science papers about Mars methane and water, visit:
For more information about Curiosity, visit:
and
Learn about NASA’s Journey to Mars at:
NASA
Guillermo Gonzalo Sánchez Achutegui
