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How does astrobiology differ from exobiology?

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Planet TOI 700e — extraterrestrial life An illustration of the Earth-size planet TOI 700e orbiting within the habitable zone of its star. The habitable zone is the area around a star where liquid water, and thus possibly life, can survive on a planet's surface. Its Earth-size sibling, TOI 700d, can be seen in the distance.

Astrobiology and exobiology are often used interchangeably to describe the scientific study of life beyond Earth. While the terms are synonymous in many contexts, they reflect different historical and disciplinary emphases.1

Exobiology is defined as a branch of biology specifically focused on the search for life outside of Earth and the investigation of how extraterrestrial environments affect living organisms.2

Astrobiology is a broader, multidisciplinary field that encompasses the nature, existence, and search for extraterrestrial life. It integrates insights from biology, astronomy, and geology to understand the conditions under which life can arise, identify habitable worlds, and search for biological signatures.3

In modern scientific practice, astrobiology is the more commonly used term, as it captures the comprehensive, collaborative nature of the research—ranging from the study of extremophiles on Earth to the analysis of extrasolar planets and the search for extraterrestrial intelligence.3