A few hundred thousand billion free-floating life-bearing earth-sized planets may exist in the space between stars in the Milky Way, says a study.
The idea is being propounded by an international team of astronomers led by Chandra Wickramasinghe, professor and director of the Buckingham Centre for Astrobiology at the University of Buckingham.
They have proposed that these life-bearing planets originated in the early universe within a few million years of the Big Bang, and that they make up most of the so-called "missing mass" of galaxies, the journal Astrophysics and Space Science reported.
The scientists calculate that such a planetary body would cross the inner solar system every 25 million years on the average and during each transit, zodiacal dust, including a component of the solar system's living cells, becomes implanted at its surface.
The free-floating planets would then have the added property of mixing the products of local biological evolution on a galaxy-wide scale, according to a statement of Buckingham University.
Since 1995, when the first extra solar planet was reported, interest in searching for planets has reached a feverish pitch. The 750 or so detections of exo-planets are all of planets orbiting stars, and very few, if any, have been deemed potential candidates for life.
The possibility of a much larger number of planets was first suggested in earlier studies where the effects of gravitational lensing of distant quasars (most distant objects) by intervening planet-sized bodies were measured.
Recently several groups of investigators have suggested that a few billion such objects could exist in the galaxy.
Wickramasinghe and team have increased this grand total of planets to a few hundred thousand billion (a few thousand for every Milky Way star) - each one harbouring the legacy of cosmic primordial (beginning) life.