There may not actually be life on mars, but “life on Mars” is an apparently immortal concept. Every time you think you’ve killed it off, it comes springing back into your face, cackling like a lunatic. We all remember when astronomer Giovanni Schiaparelli first saw those “canali” through his telescope. He meant “channels,” but we quickly translated that into “canals.” Obviously, Mars was a desert planet with a dying civilization that in its desperation for survival would soon invade our watery world.
The great astronomer Percival Lowell was particularly, and almost uniquely, adept at seeing these canals, and mapping them, practically all the way down to individual flood gates and little tug boats on the water — and even Martian mule-skinners on the tow-paths. But then the scientific method intruded: Annoyingly, other astronomers couldn’t see the canals. In science one is supposed to replicate findings, and in this case the unsettling notion arose that the canals simply were not there.
Then NASA, really confusing the issue, sent a spacecraft to Mars, and saw that it looked a lot like the moon. It was pocked with craters. The canals didn’t exist.
Of course, the dreamers didn’t give up. Carl Sagan clung to the hope that Mars had life. This was a man who had “PHOBOS” on his license plate because he thought the Martian moon might be a hollow, artificial object. (Cool.) He made sure he was part of the imaging team working on the epic Viking mission — two probes to Mars that would land on the planet and look for life. Here’s what I wrote in my book on extraterrestrial life:
[Sagan] privately told colleagues that he believed the probe might well find more than just simple life — it might find animated creatures, Martian animals. Sagan complained, in fact, that the cameras were not ideally designed to capture a moving object: They might not notice a lumbering beast. In his book The Cosmic Connection, published three years before the Viking mission, he acknowledged that on Mars, which has no protective ozone layer, life would have to cope with the harsh, germicidal ultraviolet radiation blasting down upon the surface. But Sagan said Martian life might simply adapt to that. “We can easily imagine organisms walking around with small ultraviolet-opaque shields on their backs: Martian turtles.” [Pages 79-80]
Sagan at one point asked Gerald Soffen, the lead scientist for Viking, if the mission could include a flashlight that could be switched on to see if anything was attracted to the light — such as Martian moths. That idea didn’t fly.
Viking found no turtles or anything else. One scientist, Gil Levin, felt that one experiment found signs of life, but most of his colleagues, included Sagan, interpreted the results of the suite of life experiments as negative.
But we didn’t give up hope. About a decade ago, scientists renewed the life-on-Mars question by announcing that they’d detected methane in the Martian atmosphere. Methane can be produced by living organisms.
Another setback came a year ago, when NASA annnounced that Curiosity couldn’t detect any methane in the thin air of Mars.
Now the NASA folks have made another big announcement: Methane on Mars after all!
Biological? Geological? The top scientist for Curiosity, John Grotzinger, says he doesn’t know, but the detection of methane, as well as organic molecules in the rocks of Mars, is suggestive of something. From Rachel Feltman’s Speaking of Science blog:
“We now have full confidence that there is methane,” Grotzinger said. “And that there are organics preserved in rocks [around the planet]… those things are both consistent with the former or existing presence of life.”
Lee Billings in Scientific American points out that there’s another explanation other than “biological” or “geological”: contamination.
That source, however, could also be the rover itself, which has components known to have outgassed small amounts of methane in the past. “The rover has a lot of methane in it, that is not disputed,” says Zahnle, who is authoring a forthcoming commentary in Science on the findings. “The real issue is what is the source of the methane in the samples: rover or Mars?”
I’m going to keep believing there’s life on Mars, and possibly entire Martian subterranean cities with the equivalent of Martian Starbuckses. Because I’m a believer. Cognition should be motivated: You start with the conclusion and work backward. Life on Mars is more interesting than life not being on Mars, and I vote for the more interesting version of the universe, hard evidence be damned. Believing is seeing — a concept Percival Lowell would surely understand.
[From the archive, here’s a conversation with colleague Marc Kaufman about extraterrestrial life.]
[And here’s an A-blog on why there are no fish on Saturn’s moon Enceladus.]