Serpentine
Serpentine is a water-bearing sheet silicate formed when water altered rock on carbonaceous chondrite parent bodies.
Serpentine is a group of magnesium and iron silicates whose crystal structure contains hydroxyl, water locked inside the mineral as hydrogen and oxygen. Its atoms form sheets, so it belongs to the phyllosilicates, or sheet silicates. On Earth it forms green, sometimes snakeskin-patterned rock.
Serpentine is the dominant mineral in CM chondrites and a major one in CI chondrites, where it formed as liquid water reacted with olivine, pyroxene, glass and metal inside the parent asteroid within a few million years of its formation. A similar mineral mix makes up the samples returned from the asteroids Ryugu and Bennu.
Because serpentine holds water, carbonaceous chondrites can contain up to about 10 per cent water by weight, mostly in this form. That makes such asteroids a possible source of Earth's oceans. Serpentine also releases water when heated, a property that future space missions may use to extract water from asteroids.
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