HYDROTHERMAL SYSTEMS AND THE SEARCH FOR EXTRATERRESTRIAL LIFE
Hydrothermal systems probably played an important role in the early history of the dark asteroids, which are considered the most likely parent bodies for the C-1 (carbonaceous) chondrites. These meteorites, which show evidence for extensive aqueous alteration over a temperature range of 50 - 100 °C, were an important source of exogenous prebiotic organics on the early Earth. Given the potential for abundant water, sustained heat sources, and reduced compounds, hydrothermal systems on Europa could have provided long-term habitats for chemotrophic microbial ecosystems, similar to those found in deep sea vent environments on Earth. Hydrothermal environments were probably also widespread on Mars early in the planet's history. Their deposits have been cited as important targets in the search for a Martian fossil record. Small channel networks located on steep, poleward-facing slopes at high latitudes on Mars, may have been formed by recent outflows of near surface hydrothermal brines, thus providing potentially habitable environments for a subsurface biosphere on Mars today.
(1) Farmer, Jack D. 2000. Hydrothermal Systems: Doorways to Early Biosphere Evolution, GSA Today 10(7), 1-9.
(2) Farmer, J.D. 2000, Exploring for a fossil record of extraterrestrial life, p. 10-15 In Derek Briggs and P. Crowther (eds.) Palaeobiology II, Blackwell Science Publishers, Oxford.