Nili Fossae
A large exposure of olivine is in Nili Fossae. In December 2008, NASA's Mars Reconnaissance Orbiter found that rocks at Nili Fossae contain carbonate minerals, a geologically significant discovery. Other minerals found by MRO are aluminum smectite, iron/magnesium smecite, hydrated silica, kaolinite group minerals, and iron oxides. NASA scientists discovered that Nili Fossae is the source of plumes of methane, raising the question of whether this source originates from biological sources.
Researchers in July 2010 suggested that carbonate bearing rocks found in the Nili Fossae region of Mars are made up of hydrothermally altered ultramafic rocks. Consequently, hydrothermal activity would have provided sufficient energy for biological activity. Evidence of living organisms could have been preserved.
Nili Fossae trough is thought to have resulted from the impact that formed the nearby Isidis basin.