Science / Medicine : Ocean: Shield for First Life?

Life may have begun 4.2 billion years ago in the ocean’s depths, where it developed free of the disruption caused by massive meteorites bombarding Earth, researchers said last week in the journal Nature.

David Stevenson and Kevin A. Maher, planetary scientists at Caltech, said that for complicated molecules to develop on the young planet they needed an environment free of trauma caused by meteorites or “planetesimals”--minute planets--striking the Earth.

“These environments were subjected to impacts that, very early in the history of the Earth, were spaced close together in time so that the chemical complexity was prevented from developing,” Stevenson said.

But life in the ocean’s depths was protected from the disruptions and was able to develop without the trauma. “We’re talking about something that’s even earlier than single-celled organisms. We’re not really talking about biology at all; it’s called pre-biotic,” he said.

Pre-biotic molecules would have spread, he said, along the regions of volcanic activity in the ocean. “That area is nice and hot and has lots of energy input. Once life started there, it would have propagated,” he said.