Ever since the first Australopithecine ape fell out of a tree and found he could stand upright,… Ever since the first Australopithecine ape fell out of a tree and found he could stand upright, hominids have looked upward with a sense of awe and wonder, and not without a sense of their own insignificance. The thousands of tiny specks we can see in the sky, and the modern realization of the countless more that cannot be seen unaided, reminds us that to those “thousand points of light,” we are undetectable. An appreciation for how vast space is — how distant its worlds and how frigid its vacuum — makes us feel lucky.

And very, very alone.

This loneliness has led storytellers and astronomers to “populate” our universe with all manner of fantastic creatures, from “little green men” to Keanu Reeves. Mars especially has attracted great attention. Perceval Lowell staked his entire reputation on Martian civilization, and the writers of science fiction H.G. Wells, Issac Asimov, Robert Heinlein, Ray Bradbury and others, make Mars a happening place indeed.

However, since Mariner 4 made its historic flyby in 1964, attention shifted away from what Mars is now — a cold, barren world — to what it once was. Indeed, the surface bears evidence of massive floods of water billions of years ago, and the northern plains of Mars, the Vastitas Borealis, might be the seabed of an ocean that once stretched over the top half of the planet. Four billion years ago, Mars was probably more hospitable than Earth at the same time. Lately, however, life seems long gone.

Or is it?

Methane is a gas formed by either biological or physical processes, and on Mars, you would not expect to find any. Solar radiation hammers Mars’ atmosphere, which is unprotected by a magnetic field. This destroys methane in a short period of time, so something would have to be actively producing methane for us to detect any.

Researchers at the Jet Propulsion Labs (JPL) think they have detected traces of methane in the Martian atmosphere. This might just be the result of planetal processes, but it also could mean bacteria exist deep in the Martian crust, shielded from the sun and in residual warmth from Mars’ cooling core.

Bacteria cannot be cited as the source of methane, but they cannot be ruled out, either. This development is exciting and problematic at the same time. It’s exciting because it lends credibility to the obscure field of astrobiology.

It also makes the idea of life on other moons of the solar system sound more plausible, like Saturn’s moons, Enceladus and Titan, and Jupiter’s moons, Europa and Ganymede. Now the odds of life elsewhere in the universe are overwhelming: There are so many stars, many that might have planets, that it is incredibly unlikely that only Earth is able to sustain life. However, this research brings it close to home, and it takes the idea of extraterrestrials from the realm of probability to the realm of possibility.

Of course, this does not mean that Will Smith will have to fly planes against gigantic flying saucers that vaporize the White House. A civilization 100 light-years away, which is an extraordinarily generous estimate, just heard Guglielmo Marconi’s first dots and dashes and probably aren’t impressed. Imagine our surprise if they show up in 300 years to answer the Titanic’s distress calls.

However, extraterrestrial life, no matter how primitive, could have large implications for philosophers and theologians. First, some people don’t want their children to read the first sentence of this article in a public school because it assumes Darwin was right. Now ask these folks to swallow instruction about space aliens in school — and not in the form of science fiction. Philosophically, we will have to come to grips with the loss of the final thing that allows us to claim a vague importance in the vastness of the firmament: of being the only intelligent life out there. Well, maybe not so intelligent …

Scientifically, how much evidence is needed to support the idea of a life form on a particular world? We can’t just say “Oh, there’s methane, ergo life,” as that’s not proper science. However, we are realizing that an analysis of conditions on a planet is not always enough to rule out life. Bacteria persist in some of the most inhospitable climates imaginable on Earth, outside of hot water vents, eating hydrogen sulfide — and all this under hundreds of atmospheres of pressure. So how can we conclusively disprove the existence of life on a given planet? We can probably rule out, say, Mercury, and especially Venus, but when can we rule out Europa?

No matter how we answer these questions, one thing is clear. We will never look at the stars the same way again. Yet it’s that sense of wonder and captivation that will keep us peering at the sky for as long as man walks the Earth.

E-mail Mark at [email protected].