Liquid water in comets: implications for astrobiology

摘要

We show that radiogenic heating in primordial comets of radii in excess of ~10km could produce liquid water cores persisting for hundreds of thousands to millions of years. Supposing comets were seeded with even the smallest numbers of viable microbes at the time of their formation from pre-solar material, there is ample time for exponential amplification within the liquid interiors before refreezing occurs. Freeze-dried biological material is returned to interplanetary and interstellar space during cometary activity as the outer layers of comets are stripped away via sublimation, Modelling of the post-impact 8-12u.m spectra of Tempel 1 gives a strong indication of mixtures of clays and organics in comparable quantity, clays in turn providing evidence of a liquid water history of the comet The totality of comets in a galaxy or a cluster of galaxies, seems to provide a far more promising setting for an origin of life than any setting thus far proposed in relation to the primitive Earth Once life has originated in a comet mechanisms of interstellar panspermia that have recently been identified will disperse throughout the Galaxy within a few billion years.