Extraterrestrials

On the television program The X-Files, FBI agent Fox Mulder is always searching for proof of extraterrestrials, mostly by exploring old warehouses with his trusty flashlight and cell phone.

But as an article by Ron Cowen in the November 1 issue of Science News points out, the real search for non-terrestrial life is taking place in university and government laboratories, where scientists pore over data from space probes and conduct experiments that simulate conditions on the other planets and moons in our solar system.

At first glance, life on any of the other planets or moons in the solar system seems unlikely. Most are either very, very hot or very, very cold, either airless lumps of rock or bathed in corrosive chemicals. But life on Earth manages to survive in equally harsh environments, from slow-growing algae in the ice of Antarctica to bacteria in the unimaginable pressure and heat of volcanic vents at the bottom of the ocean.

You need three things for life: organic compounds, liquid water, and a source of energy. We know of only two places in the solar system that definitely have all three–Earth and Mars. Jupiter’s moon Europa probably also qualifies.

Saturn’s moon Titan has organic compounds and a source of energy, but lacks liquid water. Nevertheless, scientists are examining it closely, because its dense atmosphere of nitrogen and methane is similar to Earth’s early atmosphere of nitrogen and carbon dioxide.

Beneath its clouds, Titan may have pools of liquid ethane and methane, and perhaps short-lived pools of liquid water. When this mixture of chemicals is exposed to ultraviolet light in the laboratory (as James P. Ferris at the Rensselaer Polytechnic Institute in Troy, New York, has been doing for 15 years) they combine and recombine to form highly complex molecules–possibly the precursors of life. With more water, Titan might teem with life.

Europa apparently has lots of water. The spacecraft Galileo, orbiting Jupiter, has taken photographs of Europa’s ice-covered surface that show what some scientists interpret as vast fractures, out of which liquid water has welled and frozen. Other sections of the surface appear to have been pulled apart and rotated–as if they’re floating. Europa may boast a vast subterranean ocean, kept liquid (or at least slushy) by the moon’s internal heat, generated as Europa is constantly flexed by the competing gravitational pulls of Jupiter and its fellow moons. That internal heat could also mean volcanic activity…and as I noted, on Earth unique life forms live happily around volcanic vents in even the coldest, darkest depths.

So far, organic compounds haven’t been detected on Europa–but they have been on two colder moons of Jupiter, Ganymede and Callisto, which probably means Europa has them, too.

And then there’s Mars. Dry as a bone now, Mars appears to have once had lots of water–its oldest terrain boasts channels that look like river valleys. Scientists think Mars maintained a sizeable amount of surface water for a billion years or so. During the same time, Mars had volcanic activity (a source of energy), and the meteorite from Mars that made the news a few months ago contained carbonate deposits (organic compounds).

As yet we’ve found no evidence of life on the surface, but deep underground, where Mars is still warm and water may still linger–who knows?

Larger versions of Mars Sojourner will land on Mars in 2001 and 2003, scooping up samples that, in 2005, will be returned to Earth. Perhaps among those rocks we’ll find confirmation of ancient life, the traces of which some scientists believe have already turned up in the aforementioned Martian meteorite.

Finding life elsewhere in our solar system will raise a new question: did that life evolve separately from life on Earth? During the early history of the solar system, about 3.8 billion years ago, the planets and their moons were bombarded by all kinds of debris. Bits and pieces got knocked off and zoomed around to crash into other planets and moons. As Christopher P. McKay of Ames Research Center puts it, they were “swapping spit.”

Discovering that life on Earth and Mars shared a common biochemistry would indicate that they also shared a common ancestry. That could mean that life didn’t begin on Earth at all: that it arose somewhere else, then was splattered across the solar system by a celestial collision.

Eeven Fox Mulder would be surprised should it turn out that we have already met the aliens–and they are us.

Permanent link to this article: https://edwardwillett.com/1998/12/extraterrestrials/

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