Ever wondered if we are not alone in the universe?
As this truly nerdgasmic crash-course by Robert A. Freitas Jr speculates, the scope for alien life could be positively astronomical. Via xenology.info:
Xenology is the study of all aspects of life, intelligence, and civilization indigenous to environments other than Earth. Over the last three decades xenology has advanced rapidly on many fronts. Biochemists have studied the origin of life on this planet, knowing that if they can duplicate the major early steps of “abiogenesis” in the laboratory then the evolution of alien life is a very likely – maybe inevitable – event. NASA biologists have spent much time developing sophisticated life detection instruments such as the miniature biochemical automated test laboratories carried to Mars by Viking in 1976. There is growing interest in SETI, the Search for Extraterrestrial Intelligence, in which radio scientists look for powerful transmissions or leakage radiation from advanced extraterrestrial supercivilizations. (Most recently the search has been broadened, by myself and a few others, to include the possible observation of alien interstellar probes and artifacts here in the Solar System.) Astronomers are also looking for direct evidence of planets circling nearby stars, a task which will be much easier once the Space Telescope is launched into Earth orbit as early as 1983.
Xenobiology – the study of alien lifeforms – is a major subdiscipline within the xenological sciences. Its subject matter is the set of all possible life systems in the universe, rather than just the biology of a single world. The common assertion that xenobiology is “a science in search of a subject” because no extraterrestrials have yet been found ignores the long evolutionary history of our planet. From the cosmic point of view, Earth is an alien world as exotic as any in the Galaxy.
The term “chauvinism” derives from the name of Nicolas Chauvin, a highly jingoistic soldier born at Rochefort in the late 18th century. In 1815 Chauvin achieved notoriety by his stubborn, bellicose attachment to the lost cause of Napoleon’s crumbling empire. Since that time the word has come to be associated with any absurd, unreasoning, single-minded devotion to one’s own race, nationality, sex, religious persuasion. or, more generally, to one’s own peculiar point of view. Chauvinisms usually are associated with ignorance – in view of our lack of hard knowledge about lifeforms elsewhere in the universe, chauvinisms are predictably common in xenobiology.
For instance, there used to be the notion that oxygen (O2) is absolutely required for higher life. Many xenobiologists today categorically reject this proposition. Oxygen was largely absent during the first few billion years of evolution on Earth, and many organisms today still do not need this element to survive. Experiments have shown that plants grow better in air containing only about half the normal amount of oxygen, and the presence of O2in the nuclear regions of contemporary living cells is usually fatal. Human scuba divers are poisoned by the gas at more than a few atmospheres pressure. Large creatures on any world may need some strong oxidant to power their bodies, but it may not have to be oxygen.
Another early biological chauvinism was the insistence that life is an especially fragile phenomena limited to a very narrow range of environments. During the 1960s scientists examined the extremes of terrestrial life and found that the flora and fauna of Earth (especially microorganisms and other simple lifeforms) resist death even when subjected to conditions that would quickly kill a human being.
For example, Thiobacillus microbes flourish in some of the strongest acids known to man whereas the blue-green algae Plectonema nostocorum thrives in the strongest bases. The rugged tardigrade can survive periods of total dehydration and may be frozen to near absolute zero or heated to more than 120 °C without dying. Biological growth and reproduction have been demonstrated in the laboratory from -243 °C up to 104 °C, and deep sea bacteria and other animal lifeforms survive exposure to pressures in excess of 8000 atm (Earth-normal at sea level is 1 atm). Micrococcus radiodurans and several algal species are found happily growing in the core water of nuclear power plants, enduring radiation that would kill a person almost instantly. When a TV camera was retrieved from the American lunar probe Surveyor 3 by Apollo astronauts, a colony of Streptococcus mitis bacteria was found growing inside the lens. These hardy microbes evidently survived three years of hard vacuum, no food or water, exposure to cosmic rays, and temperatures ranging from well above the boiling point of water in the daytime to -160 °C during the night.
Spacecraft sent to other planets in the last decade have returned a fascinating wealth of information about our nearest neighbors in space. Jupiter, long considered too cold for life, is now believed to have an atmosphere rich in organic compounds and cloud temperatures warm enough to permit liquid water to exist. The Jovian moon Europa may have an ocean of water as deep as Earth’s seas trapped beneath its frozen surface (which could harbor life), and Io, another Jovian satellite, is thought to possess great underground pools of molten sulfur and tenuous sulfur dioxide air outgassed from the interior by active volcanoes. Titan, the largest moon of Saturn, has a thick atmosphere possibly containing hydrocarbons and other organic substances, and the presence of ammonia may produce a warming “greenhouse effect” which could raise surface temperatures up into the range of Earthly biology. The Viking mission to Mars found no unequivocal evidence for life, though some may have survived from an earlier, wetter epoch, yet escaped detection by hibernating in the Martian polar regions or deep underground. Finally, the Pioneer Venus spacecraft discovered water vapor in the Venusian atmosphere just under the main cloud deck in concentrations up to 0.5%. This is somewhat dry by terrestrial standards but still plenty wet for biology to retain a precarious foothold if it exists. The search for life in our Solar System is only beginning…
Continues at xenology.info