A "bite mark" where NASA's Mars Curiosity rover's robotic
arm scooped up Martian soil is shown in this NASA
Initial analysis of the atmosphere of Mars from NASA's
rover Curiosity has shown no sign of methane, a gas detected
previously by remote sensors, researchers said.
On Earth, more than 90 percent of the methane in the
atmosphere results from living organisms and its presence in
the Martian atmosphere, first detected in 2003, raised the
prospect of microbial life on the planet.
Although no methane was detected during Curiosity's first
detailed atmospheric analysis, scientists working under the
auspices of the US space agency plan to keep looking.
"The search goes on," Curiosity scientist Paul Mahaffy, from
NASA's Goddard Space Flight Center in Greenbelt, Maryland,
In addition to chemically analyzing soil and rocks, Curiosity
is equipped to sample and study gases in the planet's thin
The rover's onboard laboratory looked for methane in
concentrations as small as five parts per billion. Scientists
so far have no explanation as to why Curiosity has found no
methane, when orbiting probes and ground-based telescopes
have previously found evidence of the gas on Mars.
As well as being produced by living organisms, methane is
also generated by geological activity.
Methane would not have to be released at Curiosity's landing
site inside Gale Crater for the rover to detect it, according
to atmospheric chemist Sushil Atreya of the University of
Michigan at Ann Arbor.
"If there is a source of methane elsewhere, it does not take
very long for it to get distributed over the planet - about
three months," Atreya said.
"As we monitor (for) methane over time, we may be able to say
more about the possibility about any sources in the Gale
Crater region," he said.
Measurements of other atmospheric gases have proven more
An analysis of carbon, argon and other isotopes, which are
variations of particular chemical elements, indicates that
Mars, as suspected, has lost significant amounts of its
atmosphere to space over time.
"The gases in the current atmosphere are a product of Mars'
entire history," said Curiosity scientist Laurie Leshin of
the Rensselaer Polytechnic Institute in Troy, New York.
The goal of the two-year, $2.5 billion Curiosity mission is
to determine whether Mars, which is cold and dry today, ever
had the chemical and environmental conditions to support and
preserve microbial life.
"Did Mars once have abundant flowing water, and if so why is
the climate so cold and the atmosphere so thin today as to
preclude this?" Leshin said.
"By studying today's atmosphere, we can gain clues to how
Mars' environment has changed," she said.
Curiosity, which landed on Mars in August, is NASA's first
astrobiology mission since the 1970s-era Viking probes.