Venus

For a long time thought the "twin" of the Earth, Venus has instead some environmental characteristics which are entirely unsuitable to the life. The temperature at the surface varies from 300°C of the zone in shade to 480°C of the illuminated one: such temeperatures are caused by the greenhouse effect due to the dense and turbulent atmosphere, that is constituted for 97% by carbonic dioxide and exerts over the ground a pressure 90 times superior to the terrestrial one.

Around 60% of the surface is weakly undulated, while an other 15% is occupied by ample depressed basins. The remaining fourth is a thousand of meters more elevated than the lowland: in such plateaus there are mountainous chains, such as the Maxwell Mounts, that reach the 11.000 meters. The lowlands are cut by long valleys and shows many circular structures, identified as impact craters.

Venus was studied by numerous American and Soviet probes. Some of them went down on the surface gathering photos of the Venusian landscape: because of the atmospheric pressure and of the corrosive rains, none of the landed probes has succeeded in withstanding more than few ten minutes.