Impact Effects on Iron Meteorite Cooling Rates
With: Tim Bowling, Fred Ciesla, Tom Davison, Gareth Collins
Iron meteorites provide a record of the thermal evolution of their parent bodies, with cooling rates inferred from the structures of their minerals. While models have been developed to link cooling rates to sizes of parent bodies that they originate from, issues remain. In particular, some iron meteorite groups exhibit significant scatter in their cooling rates that require multiple parent bodies or appear to cool too rapidly to be consistent with ideas on sizes of planetesimals. Further, these models largely ignore high-energy impacts that are expected to occur when parent bodies still retain their radiogenic heat.
We've used numerical simulations to investigate the effects impacts have on cooling rates of the cores of differentiated planetesimals. We find that very early and late impacts will not significantly affect the recorded cooling rates. However, impacts that occur when the core is still largely fluid but the mantle has begun to solidify, can expose the cores leading to more rapid and non-uniform cooling (as seen in the video and figures to the left). These collisions should be considered when interpreting the histories of iron meteorite parent bodies.