A year after reporting that NASA’s
Curiosity rover had found no evidence
of methane gas on Mars , all but
dashing hopes that organisms might
be living there now, scientists
reversed themselves on Tuesday.
Curiosity has now recorded a burst of
methane that lasted at least two
months.
For now, scientists have just two
possible explanations for the methane.
One is that it is the waste product of
certain living microbes
Curiosity rover had found no evidence
of methane gas on Mars , all but
dashing hopes that organisms might
be living there now, scientists
reversed themselves on Tuesday.
Curiosity has now recorded a burst of
methane that lasted at least two
months.
For now, scientists have just two
possible explanations for the methane.
One is that it is the waste product of
certain living microbes
The scientists also reported that for
the first time, they had confirmed the
presence of carbon-based organic
molecules in a rock sample. The so-
called organics are not direct signs of
life, past or present, but they lend
weight to the possibility that Mars had
the ingredients required for life, and
may even still have them.
“This is really a great moment for the
mission,” Dr. Grotzinger told a news
conference here at the fall meeting of
the American Geophysical Union.
The presence of methane is significant
because the gas cannot exist for long.
Calculations indicate that sunlight and
chemical reactions in the Martian
atmosphere would break up the
molecules within a few hundred years,
so any methane there now must have
been created recently.
It could have been created by a
geological process known as
serpentinization, which requires both
heat and liquid water. Or it could be a
product of life in the form of microbes
known as methanogens, which release
methane as a waste product.
Even if the explanation for the
methane turns out to be geological, the
hydrothermal systems would still be
prime locations to search for signs of
life.
Scientists have always expected that
some tiny amount of methane would
be found on Mars. Cosmic dust falling
on the planet contains organic
compounds that are broken up by
ultraviolet light from the sun,
producing methane.
But the new findings, which are
described in detail in a paper this
week in the journal Science, are a 180-
degree flip from a year ago, when
mission scientists said that Curiosity
had found no signs of methane,
placing an upper limit of 1.3 parts per
billion by volume.
Since then, the scientists refined their
measurements, detecting a
background level of 0.7 parts per
billion. That is half of what was
predicted, raising another mystery
that somehow methane is also being
destroyed.
But in November 2013, two months
after the scientists reported the
absence of methane on Mars, the
rover measured methane levels 10
times as high. “It was an ‘oh my gosh’
moment,” said Christopher R. Webster
of the NASA Jet Propulsion
Laboratory, the lead author of the
Science paper.
The methane levels stayed high
through at least the end of January.
They subsequently fell, to less than
one part per billion.
An earlier measurement in July had
also been high, although it dropped by
half a week later, and the margin of
error made it unclear what was going
on. Curiosity made no methane
measurements between July and
November 2013.
Sushil K. Atreya of the University of
Michigan, a member of the science
team, said it was possible that elevated
methane levels lasted from July
through January. “It could have been
over six months,” he said, “but we
don’t know that.”
Given its quick appearance and quick
disappearance, the newly discovered
methane was a relatively small burst,
mission scientists suspect.
A decade ago, three teams of scientists
reported that they had detected
methane in the Martian atmosphere —
two using observations from Earth ,
one using the European Space
Agency’s Mars Express orbiter.
All of the measurements were at the
edge of the instruments’ capabilities,
and the methane appeared to
disappear two years later. If true, that
meant not only that was something
creating methane on Mars, but also
that something else was quickly
destroying it.
Many Mars scientists decided that a
simpler solution to the methane
mystery was that the measurements
were mistaken, a conclusion bolstered
by the absence reported by the
Curiosity team last year.
Now, Dr. Grotzinger said, “It’s back on
the table.”
Michael J. Mumma of NASA’s Goddard
Space Flight Center in Greenbelt, Md.,
who led one of the teams that reported
much larger methane plumes in the
Mars atmosphere in 2003 based on
measurements from Earth — and has
found no methane since 2005 — said
the new data was “pleasant” after
years of doubts from critics.
The new Curiosity measurements
“confirmed this startling reality that
methane is being released,
sporadically, and it is being destroyed
quickly,” he said. “Both events are
surprising.”
As for the organic molecules, they
showed up in a mudstone nicknamed
Cumberland that Curiosity drilled in
May 2013.
Within Curiosity is a miniature
chemistry laboratory that detected
significant amounts of the organic
molecule chlorobenzene, in much
higher concentrations than had been
seen in other rocks it had examined.
Scientists spent months analyzing
whether the organic compounds came
from Cumberland or contamination
Curiosity had brought from Earth.
“You don’t want to be faked out,” Dr.
Grotzinger said.
The scientists are still unsure whether
Cumberland contained chlorobenzene,
which is not a naturally occurring
compound on Earth, or if that was the
end product of chemical reactions
involving other organic molecules in
the rock as it was heated. But they
convinced themselves that the organic
carbon is Martian.
“In part, Curiosity was built to explore
for organics,” Dr. Grotzinger said,
“and we found them.”
the first time, they had confirmed the
presence of carbon-based organic
molecules in a rock sample. The so-
called organics are not direct signs of
life, past or present, but they lend
weight to the possibility that Mars had
the ingredients required for life, and
may even still have them.
“This is really a great moment for the
mission,” Dr. Grotzinger told a news
conference here at the fall meeting of
the American Geophysical Union.
The presence of methane is significant
because the gas cannot exist for long.
Calculations indicate that sunlight and
chemical reactions in the Martian
atmosphere would break up the
molecules within a few hundred years,
so any methane there now must have
been created recently.
It could have been created by a
geological process known as
serpentinization, which requires both
heat and liquid water. Or it could be a
product of life in the form of microbes
known as methanogens, which release
methane as a waste product.
Even if the explanation for the
methane turns out to be geological, the
hydrothermal systems would still be
prime locations to search for signs of
life.
Scientists have always expected that
some tiny amount of methane would
be found on Mars. Cosmic dust falling
on the planet contains organic
compounds that are broken up by
ultraviolet light from the sun,
producing methane.
But the new findings, which are
described in detail in a paper this
week in the journal Science, are a 180-
degree flip from a year ago, when
mission scientists said that Curiosity
had found no signs of methane,
placing an upper limit of 1.3 parts per
billion by volume.
Since then, the scientists refined their
measurements, detecting a
background level of 0.7 parts per
billion. That is half of what was
predicted, raising another mystery
that somehow methane is also being
destroyed.
But in November 2013, two months
after the scientists reported the
absence of methane on Mars, the
rover measured methane levels 10
times as high. “It was an ‘oh my gosh’
moment,” said Christopher R. Webster
of the NASA Jet Propulsion
Laboratory, the lead author of the
Science paper.
The methane levels stayed high
through at least the end of January.
They subsequently fell, to less than
one part per billion.
An earlier measurement in July had
also been high, although it dropped by
half a week later, and the margin of
error made it unclear what was going
on. Curiosity made no methane
measurements between July and
November 2013.
Sushil K. Atreya of the University of
Michigan, a member of the science
team, said it was possible that elevated
methane levels lasted from July
through January. “It could have been
over six months,” he said, “but we
don’t know that.”
Given its quick appearance and quick
disappearance, the newly discovered
methane was a relatively small burst,
mission scientists suspect.
A decade ago, three teams of scientists
reported that they had detected
methane in the Martian atmosphere —
two using observations from Earth ,
one using the European Space
Agency’s Mars Express orbiter.
All of the measurements were at the
edge of the instruments’ capabilities,
and the methane appeared to
disappear two years later. If true, that
meant not only that was something
creating methane on Mars, but also
that something else was quickly
destroying it.
Many Mars scientists decided that a
simpler solution to the methane
mystery was that the measurements
were mistaken, a conclusion bolstered
by the absence reported by the
Curiosity team last year.
Now, Dr. Grotzinger said, “It’s back on
the table.”
Michael J. Mumma of NASA’s Goddard
Space Flight Center in Greenbelt, Md.,
who led one of the teams that reported
much larger methane plumes in the
Mars atmosphere in 2003 based on
measurements from Earth — and has
found no methane since 2005 — said
the new data was “pleasant” after
years of doubts from critics.
The new Curiosity measurements
“confirmed this startling reality that
methane is being released,
sporadically, and it is being destroyed
quickly,” he said. “Both events are
surprising.”
As for the organic molecules, they
showed up in a mudstone nicknamed
Cumberland that Curiosity drilled in
May 2013.
Within Curiosity is a miniature
chemistry laboratory that detected
significant amounts of the organic
molecule chlorobenzene, in much
higher concentrations than had been
seen in other rocks it had examined.
Scientists spent months analyzing
whether the organic compounds came
from Cumberland or contamination
Curiosity had brought from Earth.
“You don’t want to be faked out,” Dr.
Grotzinger said.
The scientists are still unsure whether
Cumberland contained chlorobenzene,
which is not a naturally occurring
compound on Earth, or if that was the
end product of chemical reactions
involving other organic molecules in
the rock as it was heated. But they
convinced themselves that the organic
carbon is Martian.
“In part, Curiosity was built to explore
for organics,” Dr. Grotzinger said,
“and we found them.”
Posted by kenics and team
Posted by kenics and team
