Scientists have discovered microbes and other microscopic life in extreme conditions on Earth. For example, the ocean floor and deep in the Earth’s crust. This illustration shows micro-organisms in underground tunnels and fissures (lower frame) on Mars. Also, water ice is pictured at centre right below the surface of Mars. The micro-organisms pictured are based on extremophiles found on Earth. More specifically, a range of eukaryotic organisms found in biofilms deep in mines of South Africa.