Earth in the days when life was just beginning had no protective ozone layer, so light-dependent, iron-oxidizing bacteria formed iron minerals around themselves to protect them from damaging ultraviolet rays. In this way, living beings were able to survive in the rough environment of 3-4 billion years ago. This is the conclusion reached by Tübingen geomicrobiologists Tina Gauger and Professor Andreas Kappler following a series of laboratory experiments in collaboration with Professor Kurt Konhauser of the University of Alberta in Edmonton, Canada. The results of this research have been published in the latest issue of Geology.