Terrestrial Microbes as Candidates for Survival on Mars and Europa

Abstract

Mars and the ice-covered satellites of Jupiter are currently the most favourable sites for the search of extraterrestrial life. The motivation for the search for life in the Solar System is the evidence of liquid water in the early history of Mars and, at present, in the interior of at least two of the galilean satellites (Callisto and Europa). Hydrothermal vents on the Earth’s sea floor have been found to sustain life forms that can live without direct solar energy. Similar possible geologic activity on Europa, caused by tidal heating and decay of radioactive elements, makes this Jovian moon the best target for identifying a separate evolutionary line. This search addresses the main problem remaining in astrobiology, namely, the distribution of life in the universe. We explore ideas related to Europa’s likely degree of evolution, and discuss a possible experimental test. The total lack of understanding of the distribution of extraterrestrial life is particularly troublesome. Nevertheless, technical ability to search for extraterrestrial intelligence, by means of radioastronomy, has led to remarkable technological advances. In spite of this success, the theoretical bases for the distribution of life in the universe are still missing. The search for life in the Jovian satellites can provide a first step towards the still missing theoretical insight.