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

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.

Excitement turned to surprise when scientists studying asteroid Ryugu samples found elongated microorganisms. Were they alien life? Not quite. Despite rigorous handling, the samples were contaminated with Earth-based bacteria.