In findings that are as scientifically significant as they are crushing to the popular imagination, NASA reported Thursday that its Mars rover, Curiosity, which has been trundling across the red planet for a little over a year, has deflated hopes that life could be thriving on Mars today.
The conclusion, published in the journal Science, comes from the fact that Curiosity has been looking for methane, a gas that is considered a possible calling card of microbes, and has so far found none of it. While the absence of methane does not entirely preclude the possibility of present-day life on Mars, it does return the idea to the realm of pure speculation without any hopeful data to back it up.
“You don’t have direct evidence that there is microbial process going on,” as Sushil K. Atreya, a professor of atmospheric and space science at the University of Michigan and a member of the science team, put it.
The history of human fascination with the possibility of life on Mars is rich, encompassing myriad works of science fiction, Percival Lowell’s quixotic efforts to map what turned out to be imaginary canals, Orson Welles’ panic-inducing 1938 “Attack by Mars” radio play, and of course Bugs Bunny’s nemesis Marvin the Martian.
But NASA scientists are going strictly by their data, and they are having none of it. Asked the same question once posed by David Bowie — “Is there life on Mars?” — John Grotzinger, the project scientist for the Curiosity mission, would only go so far as to say that the lack of methane “discounts” the possibility of living creatures going about their business on Mars.
“It does diminish the argument that there are methanogenic organisms there,” Dr. Grotzinger said.
A decade ago, observations from telescopes on Earth and a spacecraft orbiting Mars suggested that vast plumes of methane were rising from certain regions, but Curiosity’s readings now bring the earlier claims into question.
“It just isn’t there,” said Dr. Atreya, referring to methane.”
– The New York Times, "Mars Rover Comes Up Empty In Search for Methane"