Dinosaur asteroid 'sent life to Mars and Jupiter'
The asteroid that wiped out the dinosaurs may have catapulted life to places as far off Mars and the moons of Jupiter, US researchers say.
They looked at rocks from Earth fired into space by asteroid impacts over the last 3.5 billion years.
The Chicxulub impact, thought to have wiped out the dinosaurs, may have been strong enough to reach Jupiter's moons.
This means tiny life-forms might have been carried elsewhere in the Solar System, and could even have survived.
It's only a theory, as the system has been worked out on a computer program that simulates the journeys asteroids make across space.
Transferring life between worlds
The idea is that that living organisms could "hitchhike" across the Solar System by becoming attached to comets and debris from meteor strikes.
Some astronomers say it could even work in reverse: that life from other planets, most likely Mars, was brought to Earth via meteorites.
In the study the researchers worked out how many Earth rocks bigger than 3m wide have been flung into space, because they believe only rocks of this size could shield life forms from the Sun, keeping them alive.
It found that 360,000 rocks of that size made it as far as Mars - and 83,000 as far as Jupiter.
The head researcher, Rachel Worth from Penn State University in America, said: "We find that rock capable of carrying life has likely transferred from both Earth and Mars to all of the terrestrial planets in the Solar System and Jupiter.
"Any missions to search for life on Titan or the moons of Jupiter will have to consider whether biological material is of independent origin, or another branch in Earth's family tree."
Mapping the meteors
Using the special computer program, the researchers mapped out the likely journeys of the Earth rocks thrown into space by meteors.
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 number made it all the way to alien worlds which might welcome life. "Enough that it matters," Ms Worth said.
About six rocks even made it as far as Europa, a satellite moon of Jupiter with a liquid ocean covered in an icy crust.
"It's still possible that organisms could be swimming around out there in the oceans of Europa," she said.
An object, thought to be a comet about six miles across, landed in Mexico about 65 million years ago, and has been blamed for the mass extinction of the dinosaurs, triggering volcanic eruptions and wildfires that choked the planet with smoke and dust.
Ms Worth and her team are interested in this impact because the sheer size of it meant it launched around 70 billion kg of rock into space.
The researchers say the chances of this rock carrying life out there with it are "better than 50/50."
But could living organisms actually survive these epic trips?
"I'd be surprised if life hasn't gotten to Mars," Ms Worth told BBC News.
"It's beyond the scope of our study. But it seems reasonable that at some point some Earth organisms have made it over there."