The amazing trajectories of life-bearing meteorites from Earth

April 12, 2012

Earth ejecta (credit: Tetsuya Hara, Kazuma Takagi, Daigo Kajiura)

The asteroid that killed the dinosaurs 65 million years ago (10 km in diameter, mass greater than 1 trillion tons) must have ejected billions of tons of life-bearing meteorites into space. Now Kyoto Sangyo University physicists have calculated this could have seeded life in the solar system and even as far as Gliese 581,  Technology Review Physics arXiv Blog reports.

Their results contain a number of surprises:

  • 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.
  • A previous study found that more Earth ejecta must end up in interstellar space than all the other planets combined.
  • 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.


Ref.: Tetsuya Hara, Kazuma Takagi, Daigo Kajiura,Transfer of Life-Bearing Meteorites from Earth to Other Planets,