Astrobiology of comets

Abstract

We review the current state of knowledge concerning microbial extremophiles and comets and the potential significance of comets to Astrobiology. We model the thermal history of a cometary body, regarded as an assemblage of boulders, dust, ices and organics, as it approaches a perihelion distance of ~ 1AU. The transfer of incident energy from sunlight into the interior leads to the melting of near surface ices, some under stable porous crust, providing possible habitats for a wide range of microorganisms. We provide data concerning new evidence for indigenous microfossils in CI meteorites, which may be the remains of extinct cometary cores. We discuss the dominant microbial communities of polar sea-ice, Antarctic ice sheet, and cryoconite environments as possible analogs for microbial ecosystems that may grow in sub-crustal pools or in ice/water films in comets.

Liquid Water and Organics in Comets: Implications for Exobiology

“…Transient sub-surface pools with organic nutrients and viable microbes allow biological activity to restart seasonally at the periodic returns of comets. Hoover et al (2004) have suggested on the basis of Antarctic flora that a wide range of species which can withstand periodic deep freezing could potentially flourish. The pools in our model are maintained a few tens of centimetres below a sealed outer crust that is continually regenerated due to condensation of diffusing organic materials.…”

Liquid water and organics in Comets: implications for exobiology

“…Transient sub-surface pools with organic nutrients and viable microbes allow biological activity to restart seasonally at the periodic returns of comets. Hoover et al (2004) have suggested on the basis of Antarctic flora that a wide range of species which can withstand periodic deep freezing could potentially flourish. The pools in our model are maintained a few tens of centimetres below a sealed outer crust that is continually regenerated due to condensation of diffusing organic materials.…”

The cometary biosphere and the origin of life

“…Then those nucleated galaxies spin off more comets so that a phase transition marches through the universe at the speed of cometary diffusion, much as a comet undergoes a phase transition the first time it melts. [41][42][43] This shows how information flow is bidirectional in Fourier space, flowing from large to small and back to large, so that comets are not just a unidirectional flow, but a diffusion flow, a redistribution of information throughout all Fourier space. Thus the early universe shows a reverse flow, or an emergence, whereas late universe shows a concentrating flow.…”

“…In actuality, the first evidences of fossil life are stromatolites, 14 which are not only multicellular but also ecologically stratified communities. In partial resolution of this conundrum, we note that stromatolites are composed of prokaryotic cyanobacteria, which are viable as single cells but have the genes for loose multicellular organization as well as the unique ability to both photosynthesize and fix nitrogen.…”