Panspermia: life everywhere in the Universe

Life on the Earth surface is very abundant. Both on the continents and in the oceans biological organisms have developed and flourished, even in the atmosphere microorganisms have been identified to the higher stratospheric levels.  Another biological realm that has been observed during the last decades is situated in underground environments. In the bottom of wells, boreholes, caves and mine galleries a myriad of microorganisms, particularly bacteria, can be found.

When we examine the possibility of life on the surface of other planetary bodies we realize that they are all quite different from those on the earth, temperatures may be too hot (Venus) or too cold (i.e. Mars, most asteroids and satellites of the gas giant planets) the atmospheres may be absent or have a composition not amenable with life.

Howevere, the subsurface conditions within many planetary bodies may be similar to ours.

The relationship of pressure and temperature with depth will, of course, be different, but the chances of life having developed at some depth may be not too different from those here. Hydrocarbons (methane and others) have been spectroscopically detected on the surfaces and in the atmospheres of many of these bodies, and subsurface liquid water can be expected within most of them (water appears to have been plentiful in the circumsolar cloud that formed the planets, and ice has been identified on several other planetary bodies and comets that are colder than the earth). The rocks, like those of the earth, should contain some oxi-dized components that will serve as oxygen donors. The scene would thus be set for the existence of microbiology there.

Mars would be the least expensive planetary body to investigate for evidence of subsurface extraterrestrial life, because we might not need to launch any spacecraft to begin such an effort. Meteorites that occasionally fall to earth bear the chemical signature of Mars. Several meteorites collected from the ice fields of Antarctica appear to have come from Mars. Trace element ratios such as the sequence of noble gases from neon to xenon, as well as the rather unusual nitrogen isotope ratio of the Martian atmosphere, were measured by the earlier Viking landing craft, and very similar values for these quantities show up in these meteorites. It seems very unlikely that debris from any other body would match these quantities so closely. Millions of years after an impact on Mars caused the ejection of Martian material, the orbits of some of these ejecta led to collisions with the earth. In 1996, one such meteorite (denoted ALH84001) yielded strong evidence that the rock had been altered by microbial life while still in the source planet.

We can extend this reasoning further. Probably the subsurface condition of several planetary satellites (i.el the Moon, Io, Ganymedes, Titan, Europa, Enceladus, etc) as well as of the largest asteroids (Ceres, Pallas),may be also similar and therefoere might have active organisms inside.

Even smaller bodies, like comets, may have these types of conditions , particularly when they approach the Sun.

A final conclusion is that these deep environments probably do exist in many, if not most planets of the galaxy.

Regarding these thoughts we would like to quote Fred Hoyle when he said “Life is a property of matter".

Partly adapted from "The Deep Hot Biosphere" of Thomas Gold,