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.

Last year, researchers excitedly announced that they had found two organic compounds essential for living organisms in samples retrieved from an asteroid called Ryugu. The Japanese Space Agency's Hayabusa2 spacecraft obtained the samples from the space rock in 2019.

Imagine that, for billions of years, you're a grain of material unbothered on asteroid Ryugu. All of a sudden, a spacecraft flies down, shoots you with a pellet to kick you up, and collects you, taking you back to Earth.