Coordinating Diverse Lines of Evidence for In Situ Life Detection Beyond Earth

Detecting Extant Life

After the Viking and Apollo missions of a quarter-century ago, biologists largely turned away from developing research programs designed specifically to look for life on another planetary body. Only in the last 6 years, with more insight from reconnaissance missions and the controversy over the martian meteorite ALH84001, has interest in extraterrestrial life detection—and sterilization of spacecraft—been renewed. This rising interest comes, in a sense, on the heels of a revolution in the field of microbiology, extraordinary progress in understanding the geobiological history of Earth, and detection of life in extreme environments. In the past decade alone, more than 1,500 new species of microorganisms have been discovered and genetically sequenced. In the next decade, it can be expected that phylogenetic trees will be redrawn and restructured and that genomics—the listing of an organisms entire genetic code—will become economical for all molecular microbial geologists to undertake. What remains to complete the picture regarding terrestrial life is to understand what microorganisms are doing, where and when they are doing it, and how these organisms and their metabolisms have evolved within Earths environment over geologic time.