The physical appearance of intelligent aliens


A possibility often suggested by more radical exobiologists is that extraterrestrial life might depend on a chemistry that does not require the carbon atom. Bracewell [1] has proposed that life could make use of the chemistry of the silicon atom rather than the carbon atom. Silicon based organisms would, for example, breathe out silicon dioxide (sand) instead of carbon dioxide. The rock eating creature has often been suggested as a product of this biological system.

The problem is that silicon polymers of the protein type are unlikely to from the compounds essential for for chemical evolution. Bieri [2] points out that the energy requirements for duplicating a living system are fulfilled only by carbon and the hight energy phosphate bond.

It is very difficult to envisage any life other than that based on the carbon compounds forming in water. Unfortunately this limits the planetary considerations necessary for the evolution of larger sized organisms somewhat severely — in fact it restricts planets that may have intelligent to those with broadly Earth-like surface temperatures and pressures. (It also restricts the type of star that may shine on life producing planets — the DNA molecule is sensitive to high levels of radiation, particularly  the ultraviolet.

What of possible creatures that could get by without requiring the availability of an Earth-like oxygen rich atmosphere? The conjectured ‘balloon’ creatures floating in the gas belts of Jupiter and using, instead of oxygen, a metabolism of hydrogen — could they ever become intelligent ETs? And what is wrong with with Fred Hoyle’s “Black Cloud,” an intelligent gas cloud thousands of kilometers across? The answer lies in our prime question, “how could this creature become intelligent?” Intelligence, it is argued later, will probably only arise from stimulating predatory existence in a harsh but survivable physical environment.

Conceding defeat to the necessity for life to be based on carbon in a water medium, the exotic morphology ET supporters suggest that there are enormous variations open to chance evolution even under Earth-like conditions. Slight differences in surface pressure, temperature, gravity or solar radiation, they argue, will produce widely divergent evolutionary trends [3]. Steen[4] suggests that intelligent ETs might be insect like, bird like, fish like or even plant like. They may be spherical in shape, glutinou s, jelly-like creatures, such as as “Quatermass” might meet, or possibly even a planet sized oceanic intelligence such as that in Stanislaw Lem’s novel “Solaris.”

For less bizarre (but still very exotic) alien creatures proposed for extraterrestrial life bearing planets, the exhibits on display at the National Air and Space Museum’s “Life in the Universe” section in Washington, DC provides some good examples of exotic aliens [5]. Biologist Bonnie Dalzell has designed for a dry Earth-like world the “hexalope,” a six legged antelope. For a high gravity planet, we are presented with the “bandersnatch,” a monstrous herbivore with eight legs, a large mouth in its chest, two eyes on stalks and ears along the side of its body — the creature weighs 30,000 lbs. on its 3-G world! The intelligent ET that Dalzell presents us with is a six legged toad like creature.

Life on Earth shows us just how strange creatures can become in the chain of evolution. The giraffe is a good example of this. But it is highly unlikely that these creatures could ever become intelligent.

Braindrain by McKie Angus