Technology Review – About 65 million years ago, the Earth was struck by an asteroid some 10 km in diameter with a mass of well over a trillion tons. We now know the immediate impact of this event—megatsunamis, global wildfires ignited by giant clouds of superheated ash, and, of course, the mass extinction of land-based life on Earth.
But in recent years, astrobiologists have begun to study a less well known consequence: the ejection of billions of tons of life-bearing rocks and water into space. By some estimates, the impact could have ejected as much mass as the asteroid itself.
The probability is investigated that the meteorites originating on Earth are transferred to other planets in our Solar System and to extra solar planets. We take the collisional Chicxulub crater event, and material that was ejected as an example of Earth-origin meteors. If we assume the appropriate size of the meteorites
as 1cm in diameter, the number of meteorites to reach the exoplanet system (further than 20 ly) would be much greater than one. We have followed the ejection and capture rates estimated by Melosh (2003) and the discussion by Wallis and Wickramasinghe (2004). If we consider the possibility that the fragmented ejecta (smaller than 1cm) are accreted to comets and other icy bodies, then buried fertile material could make the interstellar journey throughout Galaxy. If life forms inside remain viable, this would be evidence of life from Earth seeding other planets. We also estimate the transfer velocity of the micro-organisms in the interstellar space. In some assumptions, it could be estimated that, if life has originated 10 billion years ago anywhere in our Galaxy as theorized by Joseph and Schild (2010a, b), it will have since propagated throughout our Galaxy and could have arrived on Earth by 4.6 billion years ago. Organisms disperse.
* Almost as much ejecta would have ended up on Europa as on the Moon: around 100 million individual Earth rocks in some scenarios. That’s because the huge gravitational field around Jupiter acts as a sink for rocks, which then get swept up by the Jovian moons as they orbit.
About a thousand Earth-rocks from this event would have made its way to Gliese 581 (a red dwarf some 20 light years from here that is thought to have a super-Earth orbiting at the edge of the habitable zone), taking about a million years to reach their destination.
Life-bearing ejecta from Earth would take a trillion years for ejecta to spread through a volume of space the size of the Milky Way
If life evolved at just 25 different sites in the galaxy 10 billion years ago, the combined ejecta from these places would now fill the Milky Way.
The probability is almost 1 (close to certain) that our solar system is visited by microorganisms that originated outside our solar system.
An example of how the ejecta get spread out into space and then captured by planets and moons