Panspermia

Panspermia is the hypothesis that life or its precursors can travel between celestial bodies, naturally or deliberately, and seed life in new environments.

Lithopanspermia: The hypothesis that microorganisms travel between worlds inside rocks ejected by impacts. It describes the best-studied natural route: impact ejecta carrying microbes between planets.
Anaxagoras: A fifth-century BCE Greek philosopher who proposed that seeds of life are distributed throughout the cosmos. His cosmic-seed idea is an ancient antecedent of panspermia.
Astrobiology: The study of life’s origins, evolution, distribution, and future in the universe. Panspermia is one hypothesis within this broader investigation of life beyond Earth.
Planetary protection: Policies and practices that prevent biological contamination of celestial bodies and Earth during space missions. The possibility of natural or spacecraft-mediated transfer makes contamination a scientific concern.
Panspermia evidence: Observations and experiments bearing on whether life or its precursors can move between celestial bodies. No confirmed discovery establishes that life has completed an extraterrestrial transfer.
Radiopanspermia: The hypothesis that microscopic life travels through space on radiation pressure. It proposes that stellar light, rather than impact ejecta, propels microbes between worlds.
Hermann von Helmholtz: A German physicist and physician who argued that meteorites might carry life between worlds. He helped formulate a scientific version of cosmic life transport in the nineteenth century.
Extremophile: An organism adapted to conditions that are hostile to most life. Its resilience helps define which environmental stresses a traveling microbe might endure.
Mars meteorite ALH84001: A meteorite from Mars that became a focus of debate over possible signs of ancient microbial life. Its proposed fossils prompted discussion of whether Martian material could carry evidence of life to Earth.
Space exposure experiment: An experiment that exposes biological or chemical samples to the space environment. Such experiments test survival under selected stresses, not whether natural transfer actually occurs.

Linked from 15 pages