Seawater seeps down into the mantle and heats up. As the seawater hits the minerals, the olivine and pyroxene within the periodite turn into serpentine minerals and produce hydrocarbons.

"On Mars however, with its lack of plate tectonics and a basaltic crust dominated by dark minerals like olivine and pyroxene, white rocks are a rare find," NASA said in a Nov. 12 statement.

The meteorite mainly consists of olivine (Fa24.6), low-Ca pyroxene (Fs20.5), and troilite and Fe-Ni metal, with minor amounts of feldspar (Ab82.4-84.7). Three poorly metamorphosed porphyritic ...