In a blow to the theory that life could still exist on Mars, the U.S. space agency, NASA, announced
Thursday that the Curiosity rover has not detected any methane gas on the red planet.
The discovery of methane could have been a potential sign that microbial life still exists on Mars. Scientists note, however, that the lack of methane doesn’t necessarily mean the planet is devoid of life.
Previous reports of localized methane concentrations up to 45 parts per billion on Mars, which sparked interest in the possibility of a biological source on the planet, were based on observations from Earth and from orbit around Mars. However, the measurements from Curiosity were not consistent with such concentrations, even if the methane had dispersed globally.
"This important result will help direct our efforts to examine the possibility of life on Mars," said Michael Meyer, NASA's lead scientist for Mars exploration. "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 for methane six times between October, 2012 and June of this year and detected none. Given the sensitivity of the instrument used, the Tunable Laser Spectrometer, and not detecting the gas, scientists calculate the amount of methane in the Martian atmosphere today, if any, could be no more than 1.3 parts per billion.
"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 the report's lead author, Chris Webster of NASA's Jet Propulsion Laboratory in Pasadena, California. "We measured repeatedly from Martian spring to late summer, but with no detection of methane."
Methane, researchers said, would not disappear from the atmosphere quickly, meaning there can’t be much of the gas being added to the atmosphere by any mechanism, whether biology, geology, or by ultraviolet degradation of organics delivered by the fall of meteorites or interplanetary dust particles.
Curiosity landed inside Gale Crater on Mars in August of last year and is investigating evidence about possibly habitable environments there.
Details of the findings appear in the Thursday edition of Science Express