Are there aliens on other planets?

By Gwynne Dyer

LONDON (JP): The riddle of intelligent aliens deepens. On one hand, evidence is piling up that life is as common as dirt in the universe. On the other hand, there is a deafening silence on all radio frequencies where you might expect to hear from technologically advanced aliens, if indeed they are out there.

Last August, scientists reported evidence (from meteor fragments found in Antarctica) that primitive life-forms once flourished on Mars. The possibility that their descendants might still survive there, despite the severe desiccation and loss of atmosphere that Mars has undergone in the past billion or so years, has lent urgency to a planned manned mission to Mars.

More recently, reports of carbon-nitrogen compounds, which are key signs of organic life, in the core of the Hale-Bopp comet added weight to astronomer Fred Hoyle's argument that the halo of comets orbiting the sun far beyond Pluto (known as the Oort cloud), like interstellar space itself, is rife with organic compounds.

An image is strengthening of a universe where the seeds of life are as ubiquitous as mold spores on a Hong Kong summer, ready to blossom on any remotely suitable surface. And now the 'Galileo' mission to Jupiter is sending back evidence that the most suitable planetary surfaces in our solar system (apart from Earth itself) are probably also contaminated with life.

'Galileo' entered the Jovian system in December 1995 to investigate the giant planet and its family of moons. It has already found complex organic molecules on Jupiter's largest moons, Ganymede and Callisto. Now it has sent back even more striking evidence from Europa, the smallest of the major moons.

"I'm sure there's life there," says oceanologist John Delvaney at a briefing held at the Jet Propulsion Laboratory in California on April 9. "The discovery of life on another planet will surpass anything that has ever taken place in human history."

What so excited Delvaney were pictures sent back by 'Galileo' after its recent flyby of Europa, showing a reddish sea with a crust of ice (which appears to be slowly melting), with huge icebergs floating in it. Not the most hospitable environment, but one which, on Earth, would contain a lot of living things.

Jupiter is very far from the Sun, and the Jovian system gets only a tiny fraction of the solar warming that makes Earth so hospitable toward life. However, Delvaney points out, he and other scientists believe that the waters under the ice crust are being warmed by volcanic activity -- and when volcanoes erupt under the ocean on Earth, they cause bacteria to "bloom at a massive level."

At the same time, as evidence accumulates for life taking root on any available surface, we are also getting more and more indications that planets themselves are as common as dirt. Planets are too small to be observed directly from interstellar distances, but in the past year there have been three claims by astronomers who believe they have detected planets orbiting nearby stars: 51 Pegasus, 70 Virginis, and 47 Ursis Majoris.

Put all this together, and it makes a pretty good prima facie case for a universe that is positively seething with life. So the burning question is: where is everybody?

Our sun is only halfway through its life cycle, and living things have already become established on one or more of its planets. On Earth, an intelligent species with a considerable mastery of technology has emerged. Is this strange or normal?

This galaxy alone contains 100 billion stars. If only one in a thousand has a planet with intelligent life, there ought to be a hundred million planets where intelligent bipeds, millipedes, or mollusks have their own technological civilizations. Hundreds of these planets ought to be within a few hundred light-years of us.

We have only had the wheel for 5,000 years, and we are already sending out signals saying "here we are". If the average technological civilization lasts a long time, most of them should be far more advanced than us. So why have not any of them said hello?

One chilling possibility is that they are simply not there any more. Maybe the average technological civilization does not make it past the first 10,000 years. Perhaps it's quite normal for such civilizations to pollute their environment, breed themselves into famine, and finally blow themselves up as a grand finale.

If developing a technological civilization is an automatic death sentence, and the way hi-tech civilizations die destroys the possibility of another intelligent species evolving in the same ecosphere, then maybe there really is nobody out there.

Vast as the number of stars are, the time scale is equally vast. If the average technological civilization lasts only 10,000 years and then destroys itself, at any given time there may be only one such civilization, or none, in the entire galaxy.

Another possible explanation for the missing aliens, much beloved by science fiction writers, is that nobody answers our calls because we have been placed in quarantine. Some benevolent confederation of civilized species bans premature contact with emerging technological civilizations. And finally, there is the possibility that everybody is in hiding.

Stephen Hawking, the celebrated expert on black holes, suggests, on a recent CD-Rom, that making contact with another intelligent species, even at interstellar distances, could be bad for the health of the human race. For all we know, there might be serious predators out there.

Our current knowledge of physics tells us that interstellar travel would be so enormously expensive and slow that there could never be any profit in interstellar trade, colonization, or conquest. It is not absolutely certain, however, that we already know everything that could ever be known about physics.

So maybe there are a lot of intelligent species out there, but they're all keeping their heads down to avoid attracting unwelcome attention. Maybe they are also feeling sorry for the poor, naive newcomers who are broadcasting their location to the entire cosmos.