Glaciopanspermia: Seeding the Terrestrial Planets with Life?

Abstract

The question whether life originated on Earth or elsewhere in the solar system has no obvious answer since the Earth was sterilized by the Moon-forming impact and possibly also during the LHB, about 700 Ma after the formation of the solar system. Seeding by lithopanspermia has to be considered: Possible sources of life include Earth itself, Mars, Venus (if it had a more benign climate than today), and the icy bodies of the solar system. The first step of lithopanspermia is the ejection of fragments of the surface into space, which requires achieving at least escape velocity. As the velocity distribution of impact ejecta falls off steeply, attention is drawn to bodies with lower escape velocities. Ceres has had, or still has, an ocean more than 100 km deep, with hydrothermal activity at its rocky core. The possible presence of life, its relative closeness to the terrestrial planets, and Ceres’ low escape velocity of 510 m/s suggest that Ceres could well be a parent body for life in the solar system.

Icy impact ejecta—hence glaciopanspermia—from Ceres will be subject to evaporation of volatiles. Spores may be loosened by evaporation and enter the atmospheres of the terrestrial planets as micrometeorites.

The seeding of the terrestrial planets from Ceres would result in (1) detection of life in the crustal layers of Ceres, (2) a commonality of Cerean life with Terran and possible Martian and Venusian life, and (3) biomarkers of Cerean life which might be found in the ices at the Moon’s poles and on the surface of other main-belt asteroids.