PLANETARY MUSINGS

Iron snow on Mercury

One of the active areas of research in our group is developing understanding of mechanisms that can drive convection inside the metallic cores of solid planets and moons. Why? To understand what may be driving magnetic fields. Previously, we had demonstrated that in contrast to the Earth, Ganymede's magnetic field could be the result of solid iron precipitating at the core-mantle boundary and "snowing" inward, driving compositional convection. Based on new experimental results by colleagues Bin Chen and Jie Li at the University of Illinois we have shown that a similar set of results is possible for Mercury. The effect at Mercury is pronounced by non-ideal melting behavior of the Fe-FeS system at modest pressures. Indeed, it turns out that Mercury could also evolve to a state of having to distinct and separated zones of snowing iron in its core. All of these results will be useful in understanding the results that will be gained by the MESSENGER mission to Mercury once it gets into orbit.

Citation:
Chen, Bin, Jie Lie, and Steven A. Hauck, II, Non-ideal liquidus curve in the Fe-FeS system and Mercury's snowing core , Geophys. Res. Lett., 35, L07201, doi: 10.1029/2008GL033311 (2008). Article