It is not obvious that life on Mars would be a separate origin than life on Earth, as the two planets exchange tons of rocks each year and it is at least theoretically possible that life could have formed on one planet and been subsequently transferred to the other (McKay 2010). Since Mars is a smaller body than Earth, it coalesced before Earth and thus it is conceivable that life might have formed there first, although this is a relatively marginal view in the astrobiology community. Meteorites from Mars and other planetary bodies have also been the source of purported biosignatures. The Martian meteorite ALH84001 was instrumental in forming the science of astrobiology in 1996, after NASA scientists discovered bacteria-like structures (McKay et al. 1996). Subsequent meteorites have also garnered scientific interest (e.g. White et al. 2014).