Scientists from Princeton University, the University of Arizona and the Centro de Astrobiologia in Spain, writing in the journal Astrobiology, said there is a possibility that life came to Earth -- or spread from Earth to other planets -- during the solar system's infancy when Earth and planetary neighbors orbiting other stars would have been close enough to each other to exchange lots of solid material.
The scientists said their research provides support for "lithopanspermia," the idea basic life forms are distributed throughout the universe via meteorite-like planetary fragments cast forth by disruptions such as volcanic eruptions and collisions with other matter.
Eventually, another planetary system's gravity traps these roaming rocks, which can result in a mingling that transfers any living cargo, they said.
Lithopanspermia could happen under a process called weak transfer wherein solid materials meander out of the orbit of one large object and happen into the orbit of another, a Princeton release reported.
Our solar system and its nearest planetary-system neighbor could have swapped rocks at least 100 trillion times well before the sun journeyed away from its native star cluster, the researchers said.
"If this mechanism is true, it has implications for life in the universe as a whole," lead study author Edward Belbruno said.
"This could have happened anywhere."