Weak Transfer Diagram (image) Princeton University Caption Researchers based at Princeton University, the University of Arizona and the Centro de Astrobiología in Spain used a low-velocity process called weak transfer to provide the strongest support yet for "lithopanspermia," the idea that the microorganisms that sprout life came to Earth -- or spread from Earth to other developing planets -- via collisions with meteorite-like planetary fragments. Under weak transfer, a slow-moving planetary fragment meanders into the outer edge of the gravitational pull, or weak stability boundary, of a planetary system. The system has only a loose grip on the fragment, meaning the fragment can escape and be propelled into space, drifting until it is pulled in by 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.