The Quest for Mars and the Search for a Second Earth

Mars is of particular interest for the study of the origins of life because of its similarity to the early Earth. This is especially so since Mars has a cold climate and lacks plate tectonics or continental drift, so has remained almost unchanged since the end of the Hesperian period. NASA's Curiosity rover has found new evidence preserved in rocks on Mars that suggests that the planet could have supported ancient life. It has also found evidence for methane in the Martian atmosphere that could hold a clue for current life on the red planet. In 2018, scientists reported the discovery of a subglacial lake on Mars, 1.5 km (0.93 mi) below the southern polar ice cap, with a horizontal extent of about 20 km (12 mi), the first known stable body of liquid water on the planet. However, doing this for the entire planet may not be feasible. NASA conducted a feasibility study in 1976 that concluded it would take at least a few thousand years for even extremophile organisms specifically adapted for the Martian environment to make a habitable atmosphere out of the Red Planet.