Molecular biology's contributions to geobiology

Abstract

On August 7, 1996, US President Bill Clinton held a press conference to announce the possibility that the Allan Hills 84001 meteorite might provide insight into ancient life on Mars. With soaring rhetoric, he declared: 'Today, rock 84001 speaks to us across all those billions of years and millions of miles. It speaks of the possibility of life. If this discovery is confirmed, it will surely be one of the most stunning insights into our universe that science has ever uncovered. Its implications are as far-reaching and awe-inspiring as can be imagined. Even as it promises answers to some of our oldest questions, it poses still others even more fundamental.' Shortly thereafter, NASA expanded its support for astro-and geobiological research, which marked the beginning of a renaissance in geobiology. Seemingly overnight, geobiology was transformed from a somewhat arcane discipline to a glamorous field that promised to reveal the secrets of life. While today, most geobiologists would agree that the evidence for past life in AH84001 is inconclusive at best, and find the hype surrounding its discovery to be comical, nonetheless, the excitement it engendered has had a long-lasting and positive impact on our science. The enduring consequence of Clinton's press conference was that it called attention to the fact that life has been leaving signatures in its environment (be it earthly or extraterrestrial) for billions of years. In the years following the meteorite's discovery, it has become clear that to understand life's traces and-more importantly---effects on its environment, it is necessary to understand how life leaves its imprint and whether this can be distinguished from similar imprints left by abiotic processes. This is a central challenge in geobiology.