I was watching a documentary on the planets. During the show, it was brought up that there might have been life on Venus before the run away greenhouse effect turned it into what it is today. <br /><br />There is always a point that these shows never bring up however, and that is the position of the planets and their distance from the sun millions of years ago. Was Venus once in the "habitable zone" where life could have emerged? If this is the case, then maybe life on Venus may have been more possible than life on Mars. My logic is that Mars was probably much colder millions of years ago than it is today since it was farther away from the sun in the solar system than it is today.<br /><br />My other question would be, how much closer do planets get to the sun each year generally?