Perhaps a safer way for seed to spread would be for whole rocks to travel other worlds. Previous research has showed that, theoretically, a massive meteorite impact could blast up and scatter tonnes of rock across the solar system.

In their recent paper, Hara and colleagues considered one of the biggest meteorite hits known in Earth’s history: the Chicxulub impact 65 million years ago, usually blamed for killing off the dinosaurs. The 10-kilometre-wide asteroid weighed well over a trillion tonnes, and could have excavated as much mass from the surface of the Earth.

The team calculated how much of that stuff could have ended up on the bodies in the solar system thought most likely to be hospitable to life: Saturn’s moon Enceladus and Jupiter’s moon Europa, both of which are thought to have subsurface oceans of liquid water.

Under certain conditions, as many as 300 million individual rocks could have ended up on Europa, and 500 on Enceladus, they calculated. Even more could have ended up on the moon and Mars. The team write:

“Although it is uncertain how rocks enter the presumed sea under the surface, for example, of Enceladus and Europa, the probability may be high that microorganisms transferred from Earth would be adapted and grow there.”

A handful of rocks could even have made it to planets around other stars. Once such could be Gliese 581, a red dwarf 20 light years away with a super-Earth orbiting at the outer edge of its habitable zone, where water could be liquid. Hana and colleagues calculated that about 1000 rocks from the Chicxulub impact could have reached that far in about a million years, meaning any life that made it would have had 64 million years to develop – or die off.

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