The first billion years on Earth and Mars: A geologist’s perspective – Clark M. Johnson

Despite the likelihood of early habitability on both Earth and Mars, the geologic evolution of these two planets, and the rock record they preserve, is quite different. Plate tectonics on Earth played a central role in evolution of our biosphere, and yet has destroyed much of the early Earth rock record, creating great challenges for finding evidence for early life on Earth. Mars did not have Earth-style plate tectonics, but the evidence is clear that Mars was habitable very early in its history. Preservation of the early Mars geologic record is excellent, raising the possibility that it might contain evidence for the earliest life in the Solar System...