| Alien Life Forms |
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Speculating about the existence of life on distant worlds, we invariably refer to "Life as We Know It".
Using our terrestrial model, this definition looks for central blue-prints (such as DNA and DNR), the tendency towards higher complexity. All of those are based on organic chemistry.
Invariably, the "aliens" we arrive at are depending on the consumption of what we call "lower forms of life". Following the food chain downwards, we finally reach the autonomous users of energy, the plants. Even vegetarians depend on the existence of other life for metabolism.
Would extrasolar life also depend on other life forms for their source of energy?
Not neccessarily.
Recently discovered microorganisms in deep-sea thermal vents seem to be capable of extracting their energy from inorganic chemicals, as do bacteria found in fossil fuel wells.
Yet nobody seems to consider extraterrestrial intelligence evolved from inorganic material.
Intelligent life on extrasolar planets may well be a far cry from the ridiculous allens with two legs, two arms and a humanoid body, whose difference from us is restricted to pointed ears, thick lobes on the neck, or corrugated foreheads as Hollywood likes to suggest.