Life on other planets


is there extraterrestrial life no answer to this eternally fascinating question currently exists, but astronomers have gathered a significant amount of relevant information. bruce jakosky argues that we have every reason to believe that there could be life elsewhere in the universe. reviewing the development of life on earth, he considers the likelihood of comparable processes having taken place on mars and venus, on moons around jupiter and saturn, and on planets orbiting other distant stars. the argument suggesting that there is life on other planets is very simple and straightforward. it begins with life on earth as that is, of course, the only life that we know about. the fossil record and the genetic record tell us that life on earth is very old, having originated somewhere before 3.5 billion years ago b.y.a. and possibly before 3.85 b.y.a. the oldest known life forms were at once both very simple and remarkably complex. the simple aspect...