In the desert areas of Namibia, Oman, and Saudi Arabia, research work has revealed unusual structures that are probably due to the activity of an unknown microbiological life form. Unusually small burrows, i.e., tiny tubes that run through the rock in a parallel arrangement from top to bottom, were discovered in marble and limestone of these desert regions. "We were surprised because these tubes are clearly not the result of a geological process," said Professor Cees Passchier from Johannes Gutenberg University Mainz (JGU), who first came across the phenomenon during geological field work in Namibia. During subsequent sample investigations, evidence...