The planetary scientist said he has no concrete evidence that life hitchhiked to Earth on an asteroid, but the scenario is possible. Life could have been exchanged from Earth to Mars and Mars to Earth if conditions on Mars were ever hospitable. If Mars was once warmer and wetter, then there's a chance there has been that kind of exchange. Millions of years ago, the Earth was bombarded by large meteorites whose impact likely blasted chunks of the planet out into space. Some of that material could have made it to Mars and to other places in the solar system.
Scientists say Earth was bombarbed by large meteorites millions of years ago.
Last fall, a group of scientists claimed that they had collected an alien bacterium 10 miles above the surface of Earth. The idea that the seeds of life fell from space has been a theory of astronomers Fred Hoyle and Indian astronomer Chandra Wickramasinghe since the 1970s. At the NASA conference, researchers noted that the earliest records of life coincide with the period when impacts to the Earth from space debris first began to subside some 3.5 billion years ago, before bombardment began again.