The Effect of Iron "Snow" Layers on Magnetic Field Generation in Mercury

Measurements of Mercury's magnetic field from the Mariner 10 and MESSENGER flybys show a field of internal origin, with a dipole moment on the order of 250 nT-RM3 RM is the radius of Mercury). Although the field is likely caused by a planetary dynamo, a field as weak as Mercury's is difficult to produce with an Earth like dynamo. Owing to its anomalously weak dipole signature, the origin of the Mercurian magnetic field remains a mystery. Recently, Chen et al. (2008) performed experiments which indicate that convection in Mercury's outer core may be driven at multiple locations by an iron precipitate or "snow". Using the Kuang-Bloxham numerical dynamo model, we investigate the effects of these iron snow zones on the dynamo to determine whether these layers can help explain Mercury's weak field. We find that when snow zones are placed both midway through the core, and at the core mantle boundary, the observed dipole field strength is reproduced. Because the geometry of these layers is dependent on the chemical makeup of the core, the results can be used to provide constraints on the sulphur content in Mercury's core.