Free Astronomy Magazine March-April 2015

ASTROBIOLOGY G limpses of the Pongola Supergroup (South Africa), a rock formation 2.9 billion years old. The petrified undulations seen on the surface were caused by the interference between colonies of cyanobacteria and moving water. Similar processes may have taken place also on Mars. [Nora Noffke] full Paleoarchean age, to which belong the MISS of the Dresser Formation, Pilbara region, Western Australia, discovered in 2008 by the same Noffke (with Robert M. Hazen, of the Carnegie Institution, Wash- ington, D.C.) and presently considered the oldest evidence of life on Earth. Obviously the older the MISS are, and the harder it is to recognize the traces left by the biological activity to which they were subjected, given that erosion processes of various kinds (mainly induced by water) in- tervene to change their appearance. This has not however stopped researchers from discov- ering that the various types of MISS and their specific characteristics are invariably related to the peculiarities of the environments in which they form and evolve. This implies that already from an initial investigation (of the morphological type for example) it is possible