Roll your watches back about 3.9 billion years, to the time when asteroids the size of Ireland were pummeling Earth and, as it was believed until now, vaporizing any forms of life. But now, thanks to a team of researchers at the University of Colorado at Boulder, it appears life forms existed before and after the asteroid bombardment--microbes that might well have thrived, reportsÂ Reuters. Though the Earth's crust was melty-hot,Â hydrothermal vents appear to have created sanctuaries for the small creatures, as well as serving as possible incubators for life, providing a clue to how life elsewhere in the universe might exist in planetary tough times. The question of when life first appeared on Earth is a strongly debated topic among scientists, but not so much for CU geological science professor Stephen Mojzsis, who toldÂ The Christian Science Monitor, "instead of chopping down the tree of life, our view is that the [asteroid] bombardment pruned it." As for the little guys that survived the bombardment--the "extremophiles"--Boulder'sÂ Daily CameraÂ compares them to the "unboilable bugs" found today in Yellowstone National Park.