Search for extraterrestrial intelligence (SETI) was the subject of a recent RAS-sponsored conference of astronomers and planetary scientists at the astrophysical laboratory in Karachayevo-Circassia. It's a fact, the delegates agreed, that as many as 168 planets have now been discovered in 144 stellar systems. Most of these planets are giants like Jupiter, though-unlike Jupiter-they are very hot; their atmosphere contains but negligible amounts of oxygen. Yet according to Doctor of Biology Alexei Topunov, laboratory head of the A.N. Bach Institute of Biochemistry (Russian Academy of Sciences), billions of years ago, at the birth of life on earth, our planet looked "oxygen-free" if viewed from any star nearest to us. Indeed, the globe had all too little oxygen, a gas vital to advanced forms of life (subsequently it came to be generated by green plants through photosynthesis). Still and all, the "contemporaries" of those primeval times are still around here on earth, though few in number. These are the pristine microorganisms subsisting on nitrogen, sulfur and even iron. But aeons ago their population could be far more numerous, they found themselves on a par with oxygen-consuming organisms and (who knows?) could have overcome their rivals in the struggle for a "place in the sun"...

The American astronauts, who landed on the moon in 1969, dismantled the pilotless Surveyor-3 that had touched down on the lunar surface two years before, and brought some of its parts back to earth. It's amazing, but terrestrial bacteria had survived in air-free space fine! Planetary scientists believe that such microorganisms could inhabit other worlds, too.

As to high temperature, it is no obstacle: for instance, terrestrial microorganisms have adjusted to t = 100 - 150°C on volcanoes and or not springs. It's inconceivaible that they could accommodate to temperatures above l,000°C, but others could! To find out, we should promote space biochemistry at all points, and explore celestial bodies with most different conditions so as to learn what forms of life can occur there.

Thanks to American Mars rovers as well as European and Russian automatic space probes today we have an idea about the composition of the Martian atmosphere, surface temperatures and the like. Even though none of the space vehicles has discovered traces of life there*, many SETI scientists still believe: some tokens of life might be there after all, but only deep underground (because of the rarefied atmosphere and sharp fluctuations of day- and night-time temperatures). It has been proved that once the Red Planet had water and rivers.** Consequently, what we should do is to take Martian ground samples, and then the presence of primitive microorganisms could not be excluded either.

Both biochemists and biologists support the possibility of organic life on Mars. They think it could be discovered at relatively shallow depths, down to 10 meters. The pattern is different on Venus and Mercury, though: due to the scorching sunrays, the inhabited level could be as deep as 100 meters and even lower beneath the surface. Such is the situation on the "terrestrial" planets of the solar system. As to the cold "Jovian" planets-say, Neptune (which is an ice-bound sphere) - life might be detected in the upper layers of the atmosphere. Protists, faring quite well in the earth's mountain glaciers, might exist on "Jovian" planets as well. Why not?

According to informed expert opinion, the best chances for the existence of intelligent life have the Jovian satellites: Io (Jupiter I), Europe (JII), Ganymede (JIII) and Callisto (JIV). These bodies have an atmosphere and display vigorous seismic and volcanic activity, and the temperatures are quite tolerable there. Yet another promising object is Titan, the largest and brightest satellite of Saturn (SVI). It is like the earth in many respects, the way it was 5 billion years ago, at the very inception of terrestrial life.

Comets, too, may spring surprises.*** As the US space vehicle DEEP IMPACT crashed into the Tempel-Tuttle comet, there occurred a discharge of a vast mass of organic matter. Planetologists allow for the presence of water-filled cavities and fissures in the cores of similar heavenly bodies, the safe niches for microorganisms. We can check up on this hypothesis on the moon: its southern pole is covered with ice deposits formed by the impact of comets. SETI researchers might find extraterrestrial life in lunar polar probes after all.

URALPRESS- INFORM, 2005

Prepared by Olga BAZANOVA

* See: A. Portnov, "The Demise of Life on Mars", Science in Russia, No. 2, 2003. - Ed.

** See: A. Litvak, I. Mitrofanov, "Martian Seasons", Science in Russia, No. 4, 2004. - Ed.

*** See: A. Finkelstein, "Astronomy: Coordinate-Time Support", Science in Russia, No. 3, 2003. - Ed.

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