London, September 27 : An international team of researchers has suggested that planets orbiting the sun's stellar siblings might have planted the seeds of life on Earth.
According to a report in New Scientist, most of the stars in the Milky Way got their start in clouds of dust and gas that eventually formed clusters of stars.
If our Sun started life in such a scenario, the cluster would most likely have drifted apart after a few hundred million of years.
But that might have been enough time for life to travel between the rocky debris surrounding each nascent star, according to a study led by astronomer Mauri Valtonen at the Turku University in Finland.
Rock-smashing experiments have suggested that microbes could certainly survive a massive crash that sandwiches them in debris and jettisons them into space.
A recent study by Edward Belbruno and colleagues at Princeton University showed that planets in densely packed star clusters could throw out as many as 1018 rocks in the first 100 million years or so, at speeds slow enough for other stars to capture them.
The new research suggests that microbes from other planetary systems, if they existed, could very well have hitched a ride in such rocks - as long as the rocks were large enough to protect the organisms from cosmic rays and the heat of impact.
According to the researchers, if the Sun was born in a cluster, there would have been time for around 100 life-bearing rocks to be captured by our star before the cluster drifted apart, thus transporting the microbes to Earth.
Valtonen's result means we might improve our chances of finding something similar to terrestrial life if we can track down the Sun's former siblings.
Finding such stars may be possible with the European Space Agency's Gaia telescope, set to launch in 2011.
The orbiting satellite will measure the proper motion of roughly a billion stars. That should allow astronomers to backtrack the star's positions to where they sat billions of years ago.