September 20, 2013
Life On Mars? Lack Of Methane Makes That Improbable, But Not Impossible
[ Watch the Video: Curious Case Of Methane On Mars ]
Lee Rannals for redOrbit.com - Your Universe Online
Previous data reported by scientists indicated that methane was present on Mars, but the latest evidence derived from extensive tests by the rover shows the planet lacks traces of the gas.
Finding methane would be a big indicator for scientists looking to see if Mars holds any sign of life, because the gas can be produced by microbes. One thing this finding doesn't do is put the possibility of finding evidence of life on Mars completely out of question.
"This important result will help direct our efforts to examine the possibility of life on Mars," Michael Meyer, NASA's lead scientist for Mars exploration, said in a recent statement. "It reduces the probability of current methane-producing Martian microbes, but this addresses only one type of microbial metabolism. As we know, there are many types of terrestrial microbes that don't generate methane."
Curiosity analyzed samples of the Martian atmosphere using the Tunable Laser Spectrometer. The rover performed this analysis six times from October 2012 through June this year, none of which yielded a result that showed the presence of methane. NASA said that given the sensitivity of this instrument, the amount of methane that could be in the Martian atmosphere today is no more than 1.3 parts per billion, which is about one-sixth as much as some earlier studies predicted.
"It would have been exciting to find methane, but we have high confidence in our measurements, and the progress in expanding knowledge is what's really important," said Chris Webster, NASA's Jet Propulsion Laboratory in Pasadena, Calif and lead author of the study published in the journal Science Express. "We measured repeatedly from Martian spring to late summer, but with no detection of methane."
The Martian rover's spectrometer, part of Curiosity's Sample Analysis at Mars (SAM) Laboratory, can be tuned specifically for the detection of trace methane. NASA said its rover team will now be using the laboratory to try and detect methane at concentrations well below 1 part per billion.
Methane is the most abundant hydrocarbon in our solar system, and previous reports showed localized methane concentrations of up to 45 parts per billion on Mars. These findings were based on observations from Earth and from orbit around the Red Planet. NASA said these results are not consistent with what its Martian resident has discovered, even if the methane had dispersed globally.
"There's no known way for methane to disappear quickly from the atmosphere," said one of the paper's co-authors, Sushil Atreya of the University of Michigan. "Methane is persistent. It would last for hundreds of years in the Martian atmosphere. Without a way to take it out of the atmosphere quicker, our measurements indicate there cannot be much methane being put into the atmosphere by any mechanism, whether biology, geology, or by ultraviolet degradation of organics delivered by the fall of meteorites or interplanetary dust particles."
He said the highest concentration of methane that could be present without being detected by Curiosity would amount to no more than 10 to 20 tons per year of methane entering the Martian atmosphere. This equals about 50 million times less than the rate of methane entering Earth's atmosphere.