The search for extraterrestrial life-from simple organisms to intelligent beings-is one of the most fascinating fields of science.

Life Beyond?

Does life exist beyond our planet and, if so, is that life comparable to the life forms we know here on Earth? These are questions that ICTP has been involved in since the Centre launched its first conference on "chemical evolution and the origin of life" nearly a decade ago. The Centre's focus on this subject will continue this year with the Sixth Trieste Conference on Chemical Evolution: First Steps in the Origin of Life in the Universe, to be held at the Adriatico Guesthouse on 18-22 September.

Three strategies have been devised in the search for extraterrestrial life: the study of the cellular makeup of exotic organisms on Earth; the search for organic matter and living micro-organisms beyond Earth; and the use of radiotelescopes to detect signals of intelligent life in the heavens above.

The first strategy has focussed on understanding how life began on Earth. Research has concentrated on the makeup of exotic organisms living in such inhospitable environments as ocean-floor bottoms, glacial lakes, and volcanic lava streams--all of which display temperatures and pressures that may have been present during the Earth's formation about 4 billion years ago. The research not only broadens our appreciation of the enormous diversity of life here on Earth, but helps us understand the environmental extremes that simple organisms can tolerate. Such extremes may be found on other celestial bodies, making it more probable that life can exist there.

The second strategy for deciding if we are not alone in the universe is the search for the simplest forms of organic matter--aminoacids or proteins--that may be embedded in the ancient rock of planets, comets or meteorites, or suspended in the soupy mixture of interstellar clouds. The search has focussed on three celestial bodies: Mars, Europa (a moon of Jupiter), and Titan (a moon of Saturn).

For now, interest has shifted toward discovering fossilised remnants of life that existed billions of years ago when our solar system was an extremely violent environment in which only extremophilic organisms (those that withstand extreme pressures and temperatures) could survive. One of the primary goals of this extraterrestrial search is to determine whether life ever existed in places other than Earth and, if so, what were the environmental conditions that made it possible.

The radiotelescope at Arecibo

The third strategy used in the hunt for life beyond Earth relies on radiotelescopes such as the huge telescope at the National Astronomy and Ionosphere Center in Arecibo, Puerto Rico, USA. These 'mega-dishes' actually have two roles to play: First and foremost, they help to examine wavelengths that cannot be seen by the human eye--for example, radiowaves and microwaves. Such information has proven essential for understanding the movement and behaviour of planets, stars and galaxies. Second, radiotelescopes seek anomalies in microwaves and radiowaves wafting across the universe. Such anomalies may represent the imprint of intelligent life in the heavens beyond.

Astronomers have been scanning the micro- and radiowave spectrum for four decades with no reliable signal from an extraterrestrial civilisation. But that doesn't mean the initiative is likely to be abandoned. The public's fascination with the search for extraterrestrial life, combined with the vast reaches of outer space, where Earth-bound scientific research continues to uncover new extrasolar planets and even solar systems, keeps hope alive that 'somewhere out there' intelligent life exists that will some day send us a signal. If a signal is ever received, this much is certain: It will be one of the most remarkable and influential discoveries ever made, with profound implications for science, philosophy and even theology.

Julian Chela-Flores
ICTP Staff Associate
Physics of the Living State

For additional information about the Sixth Trieste Conference on Chemical Evolution: First Steps in the Origin of Life in the Universe, see http://www.ictp.it/~chelaf/trieste2000.

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