Exobiology

Exobiology, also known as astrobiology in contemporary usage, is the interdisciplinary study of life beyond Earth. It investigates the origin, evolution, distribution, and potential future of life in the universe, drawing on biology, chemistry, geology, astronomy, and planetary science.

The field addresses fundamental questions such as what physical and chemical conditions are compatible with living systems, how life began on Earth, whether life could arise in environments very different from our planet, and how to recognize signs of life elsewhere. It encompasses exploration of possible habitats for life and the biosignatures that living systems might leave behind, whether in an atmosphere, on a surface, or within a subsurface ocean.

Research methods combine observational astronomy and planetary science to identify habitable environments and potential biosignatures on exoplanets and Solar System bodies with laboratory experiments that model prebiotic chemistry and metabolism, alongside theoretical work on planetary habitability, biosignature detection, and the likelihood of various forms of life.

Key domains include planetary habitability, focusing on the presence of liquid water, energy sources, and essential elements; the search for biosignatures in atmospheres and surfaces; and the study of extreme life on Earth to inform models of extraterrestrial life. Target bodies commonly considered include Mars, icy moons such as Europa and Enceladus, and exoplanets in or near the habitable zone.

Exobiology emerged in the mid-20th century as scientists framed life beyond Earth as a scientific question rather than science fiction. Today it is usually encompassed within astrobiology, reflecting its broad, interdisciplinary scope. Planetary protection and ethical considerations accompany exploration to minimize contamination and to responsibly interpret findings.