Scientists have found microorganisms crawling over a sample retrieved from the 200 million-mile-distant asteroid Ryugu. But they almost certainly came from Earth.

Panspermia is the hypothesis that life can survive the transfer between planetary bodies as a secondary path for life to get started on planets throughout a solar system. The discovery of extraterrestrial life on asteroids or within meteorites would have profound implications for understanding the origins and distribution of life in the universe.