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JOURNAL OF GEOPHYSICAL RESEARCH,
VOL. 114,
E04009,
10 PP., 2009
doi:10.1029/2008JE003287
Giant impacts on early Mars and the cessation of the Martian dynamo
Department of Earth and Planetary Sciences, University of California, Santa Cruz, California, USA
Space Sciences Laboratory, University of California, Berkeley, California, USA
Department of Earth and Planetary Science, University of California, Berkeley, California, USA
Although Mars currently has no global dynamo‐driven magnetic field, widespread crustal magnetization provides strong evidence that such a field existed in the past. The absence of magnetization in the younger large Noachian basins suggests that a dynamo operated early in Martian history but stopped in the mid‐Noachian. Within a 100 Ma period, 15 giant impacts occurred coincident with the disappearance of the global magnetic field. Here we investigate a possible causal link between the giant impacts during the early and mid‐Noachian and the cessation of the Martian dynamo at about the same time. Using three‐dimensional spherical mantle convection models, we find that impact heating associated with the largest basins (diameters >2500 km) can cause the global heat flow at the core‐mantle boundary to decrease significantly (10–40%). We suggest that such a reduction in core heat flow may have led to the cessation of the Martian dynamo.
Received 24 October 2008; accepted 11 February 2009; published 23 April 2009.
Citation: (2009), Giant impacts on early Mars and the cessation of the Martian dynamo, J. Geophys. Res., 114, E04009, doi:10.1029/2008JE003287.
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