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The Origin, Accretion and Differentiation of Extreme Volatiles in Terrestrial Planets

Final Report Summary - NOBLE (The Origin, Accretion and Differentiation of Extreme Volatiles in Terrestrial Planets)

The main goal of the NOBLE project was to develop new and enhanced analytical techniques to measure halogens and noble gases in meteorites and lavas and use these results to investigate how Earth gained and evolved the volatile elements and compounds essential for life and shaping the planet we see around us today.

We successfully built a system capable of analysing halogens (Cl, Br, I) in very small rock samples with little background interference. From rocks made in laboratory experiments we have calibrated, using our new analytical system, how much halogen transfers into any molten rock and how much stays behind in the solid phase. We used this information when analysing the halogen content of natural samples to identify where and how much of the halogens are in the deep Earth and how they are cycled from the surface, into the Earth's mantle, and back out again. This information tells us about the processes that control how volatile elements over Earth's history and the importance of subduction in limiting volatile element transfer back into the mantle. In addition we have measured the halogen content of meteorites that would have been similar to those that formed the Earth. A surprising result was that the halogens in the meteorites were in concentrations far lower that expected. This result shows that the halogens have behaved in the same way as other elements with similar volatility and, contrary to that previously thought, do not need any special early processes to have formed the Earth. This result greatly simplifies our understanding of Earth's accretion and how it acquired its volatile elements and compounds.