Microbial habitability of the Hadean Earth during the late heavy bombardment

Life on a hostile Earth Between about 4.1 and 3.8 billion years ago, conditions on Earth might be expected to have been pretty extreme. Data from lunar crust samples, meteorites and other Solar System materials all point to this as a time — known as the late heavy bombardment — when the Earth and other inner planets were subjected to cataclysmic impact events. Habitats on the early Earth would have almost certainly been repeatedly destroyed, prompting suggestions that life might not have survived. In fact the thermal effects of this bombardment on the young Earth have remained poorly constrained, leaving the field leaving the field a fertile one for speculation. Now Oleg Abramov and Stephen Mojzsis report results from computer models constructed to study the thermal effects of impacts on the terrestrial lithosphere during the late heavy bombardment. They find no plausible scenario in which Earth's habitable zone was fully sterilized, and conclude that the evidence from ribosomal RNA ancestry that terrestrial life arose from thermophiles or hyperthermophiles is consistent with the prevalence of hydrothermal activity suggested by the model.