June 23rd, 2012 by James Ayre
Researchers analyzing the water content of two Martian meteorites have found that the amount of water in parts of Mars’ mantle must be vastly higher than previously estimated, nearly the same as the Earth’s. Until this discovery, the Earth was the only planet known to have very large reservoirs of water in its interior.
This finding affects not only our knowledge of the geologic history of Mars, but it also has implications for how water got to the Martian surface; further supporting the possibility that Mars could have sustained life, and maybe still does.
The research was done by analyzing shergottite meteorites, which are “fairly young meteorites that originated by partial melting of the Martian mantle—the layer under the crust—and crystallized in the shallow subsurface and on the surface. They came to Earth when ejected from Mars approximately 2.5 million years ago.” Researchers can use meteorite geochemistry to learn a great deal about the geological processes that a planet underwent earlier in its history.
“We analyzed two meteorites that had very different processing histories,” explained Hauri. “One had undergone considerable mixing with other elements during its formation, while the other had not. 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.”
Using the mineral’s water content, the researchers estimated that the mantle source “from which the rocks were derived contained between 70 and 300 parts per million (ppm) water.” The upper mantle of the Earth by comparison contains approximately 50-300 ppm water.
The research team was then able to “determine these values with new techniques and new standards they developed that can quantify water in apatite using a technology called secondary ion mass spectrometry (SIMS).”
“There has been substantial evidence for the presence of liquid water at the Martian surface for some time,” Hauri said. “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.”
McCubbin concluded, “Not only does this study explain how Mars got its water, it provides a mechanism for hydrogen storage in all the terrestrial planets at the time of their formation.”
The research was led by Carnegie postdoctoral scientist Francis McCubbin. And the analysis was performed by Carnegie Institution investigator Erik Hauri and his research team. The research has just been published in the journal Geology.
Source: Carnegie Institution For Science
Image Credits: NASA, JPL
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