Life from Earth may have been carried to moons of Jupiter and Saturn on rocks that blasted off our planet, scientists say.
The notion that life might travel on rocks knocked off a world's surface is known as lithopanspermia.
Researchers say if these meteoroids encase hardy enough organisms, they could seed life on another planet or moon.
Although lithopanspermia might seem far-fetched, a number of meteorite discoveries suggest it might at least be possible, 'Astrobiology Magazine' reported.
Rachel Worth, an astrophysicist at Pennsylvania State University and study lead author and her colleagues analysed where batches of several thousand rocks travelled once ejected off both Earth and Mars.
"We ended up simulating over 100,000 individual fragments," Worth said.
While most of these meteoroids slammed back into their home planet, a great many rocks also were either swallowed by the Sun or left the solar system entirely.
Researchers calculated that over the course of 3.5 billion years, about 200 million meteoroids large enough to potentially shield life from the rigours of space were blasted off Earth.
Roughly 800 million such rocks were ejected off Mars during the same period.
Scientists calculated about 83,000 meteoroids from Earth and 320,000 from Mars could have struck Jupiter after travelling 10 million years or less.
Also, roughly 14,000 from Earth should have hit Saturn in that time, and no more than 20,000 from Mars.
Since the moons of those giant worlds are relatively close to their planets, many of them might get peppered by these meteoroids as well.
Researchers calculated that Saturn's moons Titan and Enceladus and Jupiter's moons Io, Europa, Ganymede and Callisto should each have received between one and 10 impacts both from Earth and from Mars.
These findings suggest the possibility of transfer of life from the inner solar system to the outer moons, although very rare, currently cannot be ruled out.
However, researchers cautioned they are not saying "that life has made it to any of these moons, just that it could."