They then mapped the likely fate of these voyagers. Many simply hung around in Earth orbit, or were slowly drawn back down.
Others were pulled into the Sun, or sling-shotted out of the Solar System entirely.
Yet a small but significant number made it all the way to alien worlds which might welcome life. "Enough that it matters," Ms Worth told BBC News.
About six rocks even made it as far as Europa, a satellite of Jupiter with a liquid ocean covered in an icy crust.
"Even using conservative, realistic estimates... it's still possible that organisms could be swimming around out there in the oceans of Europa," she said.
Travel to Mars was much more common. About 360,000 large rocks took a ride to the Red Planet, courtesy of historical asteroid impacts.
Big bang theory
Perhaps the most famous of these impacts was at Chicxulub in Mexico about 66 million years ago - when an object the size of a small city collided with Earth.
The impact has been blamed for the mass extinction of the dinosaurs, triggering volcanic eruptions and wildfires which choked the planet with smoke and dust.
It also launched about 70 billion kg of rock into space - 20,000kg of which could have reached Europa. And the chances that a rock big enough to harbour life arrived are "better than 50/50", researchers estimate.
But could living organisms actually survive these epic trips?
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