What’s more, we know that meteorites can (and did!) bang into Mars, knock off planetary chunks, and send them hurtling Earthward. And young Mars of 4 billion years ago was a much friendlier environment than young Earth, with a pleasant temperature and a nice combination of land and water. A number of scientists believe it is possible—even probable—that life, either complex molecules or actual cells, evolved first on Mars and then seeded Earth.
