Forming Earths and Mercuries: solids less volatile than water

by Alexander Hubbard (Nordita)

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Life requires a variety of chemicals and elements. The question of water, how it was delivered to Earth and how it would be delivered to exoplanets, has taken a central position. However, other chemicals and elements are also important. Earth is significantly (~80%) depleted in elements important for life like sodium and potassium, both much less volatile than water, but much more volatile than silicon, magnesium, or iron. Part of the composition of planets is set during their formation process, when the solids are still in sub-cm dust grains. I will discuss both the supply of moderately volatile elements to the proto-Earth, and why Mercury is extremely iron rich. Both processes should play major roles in exoplanet formation, with consequences for their chemistry and hence any possible biology.