Viking’s Astrobiological Legacy: A Philosophical Framework for Searching for Molecular Biosignatures

James Lovelock was the first to lay out a physical and chemical basis for searching for life beyond Earth, based on the observation that the molecular features and patterns in classes of organics differ for compounds formed through biological versus nonbiological processes. This approach shaped the Viking molecular analysis experiment designed to search for organics, including potential signs of extinct or extant life, and it still remains fundamentally viable today. In the five decades since Viking, many missions have uncovered new information about the martian organic inventory, geological landscape, and changes to habitability over time, while advances in organic geochemistry on Earth enabled scientists to identify even more differences between biotic and abiotic organics, solidifying the utility of Lovelock’s physical and chemical approach in the search for extraterrestrial life. Key Words: Search for Mars’ Organics—Mars—Biosignatures—Life detection—Biomarkers. Astrobiology 00, 000–000