Even though many exotic systems appear to be no more likely in extraterrestrial biospheres, by no means is all lost.
Physical scientists have historically held a deterministic view of the possibility of extraterrestrial life.
It was the first seminal scientific text on the question of extraterrestrial intelligence.
It is thus possible to distinguish extraterrestrial from terrestrial kerogens using this technique.
Extreme salinity levels feature biota dependent upon "abnormal" conditions, which may represent forms of life that could possibly inhabit extraterrestrial planets.
These organisms are clearly relevant as an analogue for possible complex extraterrestrial life as well as for terraforming planets or moons in our solar neighbourhood.
We will describe the steps taken to determine which candidates are most likely to be extraterrestrial in origin, and present examples of the best candidates.
However, these extraterrestrial invaders of suburbia have breached humanity's ultimate boundary, that between itself and the universe.
