Astrobiology Timeline (image) Princeton University Caption The researchers suggest that ideal conditions for lithopanspermia in the sun's birth cluster, in the solar system and on Earth overlapped for several hundred million years (blue shaded area). Rock evidence suggests that the Earth (bottom line) contained surface water during a period when the relative velocities between the sun and its closest cluster neighbors (top line) were small enough to allow weak transfer to other planetary systems, and when the solar system (middle line) experienced high meteorite activity within the sun's weak gravitational boundary. If life arose on Earth shortly after surface water was available, life could have journeyed from Earth to another habitable world during this time, or vice versa if life had an early start in another planetary system. Credit Image by Amaya Moro-Martín Usage Restrictions None Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.