In: Biology
No evidence for the presence of past or present life have been found on Mars. The possibility of life on Mars has been a subject of research due to its proximity and similarities to Earth. The Martian surface is presently cold and dry, but there are plenty of evidence suggesting of the past existence of surface liquid water. This increases the possibility of life on Mars. It is proposed that life might have evolved on Mars when there was water, and life could be there even now. Searches for evidence for past biosphere are based on mainly autotrophic, chemotrophic, or chemolithoautotrophic microorganisms. To survive on Mars, bacteria need to be tolerant for salt and cold.
Methane is detected in the Martian atmosphere. The major candidates for the origin of Mars' methane include non-biological processes. This methane could be produced by living microorganisms, such as methanogens too. Methanogens require no oxygen or organic nutrients. They are anaerobes. Being non-photosynthetic they use hydrogen as their energy source and carbon dioxide as their carbon source. Methanogens are among the simplest and most ancient organisms on Earth. These facts could make the Methanogens an ideal candidate for life on Mars. They could exist in subsurface environments on Mars shielded from harsh levels of ultraviolet radiation.