NASA’s Curiosity rover has detected bursts of methane. At this stage scientists are hedging their bets as to its source, but few can contain their excitement over the potential implications: there may be life on the red planet.
W hat scientists have found on Mars could change our conception of the universe. We may not be alone.
NASA’s Curiosity rover has recorded a burst of methane that lasted at least two months. It may not be in quite the same league as making first contact with an alien race or finding the remains of a long-lost civilisation on a distant world, but the discovery has thrown scientists into a frenzy of excitement. Why? Because they have only two possible explanations.
One is that the methane could have been created by the geological process of serpentinisation, which requires both heat and liquid water - in themselves significant discoveries that could lead to the discovery of hydrothermal systems which would be prime locations in the search for life. But the other, even more exciting possibility scientists are considering is that the methane is the waste product of living microbes.
“It is one of the few hypotheses that we can propose that we must consider as we go forward,” said John P. Grotzinger, the mission’s project scientist.
Vladimir Krasnopolsky of the Catholic University of America points out that as Mars has been volcanically dead for at least the past few million years, bacteria are indeed the most plausible source of methane on Mars. On Earth, 95% of methane comes from microbial organisms.
As methane molecules would be broken up within a few hundred years by sunlight and chemical reactions in the Martian atmosphere, the gas Curiosity reported must have been created relatively recently, suggesting that if it was created by microbes they are not long extinct.
“Scientists have always expected that some tiny amount of methane would be found on Mars,” writes Kenneth Chang in the New York Times. “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, 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.”
In November 2013, Curiosity 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.
Methane levels remained high until at least the end of January, then fell to less than one part per billion. The rapid appearance and then disappearance suggests the methane was a relatively small burst.
Mr. Chang writes: “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.”
At the time, many scientists thought it was simpler to conclude that the measurements were mistaken. After all, as philosopher of science Thomas Kuhn explained, scientific paradigms are littered with anomalous results that are frequently brushed away as errors. It is only when sufficient unexplained results build up that we see a paradigm shift. Could the latest results lead to a paradigm shift in our conception of Mars as a lifeless planet? At the very least, the bursts of methane, according to Dr. Grotzinger, are “back on the table”.
NASA also reported that for the first time it can confirm the presence of carbon-based organic molecules in a rock sample. These are not themselves direct signs of life, but they do add to the growing body of evidence that suggests Mars once had the ingredients required for life. It may still have them. Curiosity also found water bound in the fine-grained soil within the Gale crater formed by a meteor strike about 3.5 billion years ago. There were believed to be around two pints of water in each cubic foot of Martian soil, although it is attached to minerals and not freely accessible.
With each new discovery our conception of Mars as a barren, lifeless planet is slowly changing. We now know it to be far less barren than we first assumed. Could it be far less lifeless too?