There's vastly more water in Mars's mantle than previously thought - as much as on Earth, in fact - dramatically raising the chances that the planet might once have sustained life.
Until now, Earth was the only planet known to have vast reservoirs of water in its interior. But through an analysis of the water content of two Martian meteorites, Carnegie Institution scientists have established that water must have been present.
Shergottite meteorites are fairly young meteorites that originated by partial melting of the Martian mantle — the layer beneath the crust — and crystallized in the shallow subsurface and on the surface. They were ejected from Mars around 2.5 million years ago.
"We analyzed two meteorites that had very different processing histories. One had undergone considerable mixing with other elements during its formation, while the other had not," says investigator Erik Hauri.
"We analyzed the water content of the mineral apatite and found there was little difference between the two, even though the chemistry of trace elements was markedly different. The results suggest that water was incorporated during the formation of Mars and that the planet was able to store water in its interior during the planet's differentiation."
Based on the mineral's water content, the scientists estimate that the Martian mantle source from which the rocks were derived contained between 70 and 300 parts per million water - much the same as the Earth.
"There has been substantial evidence for the presence of liquid water at the Martian surface for some time," says Hauri.
"So it's been puzzling why previous estimates for the planet's interior have been so dry. This new research makes sense and suggests that volcanoes may have been the primary vehicle for getting water to the surface."