Post-impact thermal evolution of iron-rich planetesimals

Iron-rich bodies have been proposed to be the result of high-energy collisions removing most of the silicate mantle from differentiated bodies [1]. Here we use the results of high velocity sub-catastrophic collisions at 10 km/s into differentiated planetesimals with initially 30-40 km thick mantles and 100 km radius iron cores performed using the iSALE-2D shock physics code [2]. In order to study the long-term thermal evolution of these iron-rich remnant bodies, we employ a 1D finite-difference code considering material-dependent heat diffusion, latent heat of crystallization and time-dependent radiogenic heating by 26Al and 60Fe in the leftover mantle and the iron core, respectively. For the thermal evolution calculations, we use an initial composition and temperature structure based on radial profiles through the center of the post-impact bodies. The start time after CAI formation of the long-term models is based on the Pd-Ag dating for various iron meteorites [3]. Finally, we compare the results with the cooling rate constraints for various iron meteorite types based on Widmanstätten pattern formation [4] and Pd-Ag data [3] with both methods covering different temperature intervals during the body’s cooling.

 

References:

[1] Asphaug, E., C. B. Agnor & Q. Williams (2006). Nature 439, 155–160.

[2] Raducan, S. D., M. Jutzi, T. M. Davison & G. S. Collins (2022). 85th Annual Meeting of The Meteoritical Society, 2695.

[3] Hunt, A. C., K. J. Theis, M. Rehkämper, G. K. Benedix, R. Andreasen & M. Schönbächler (2022). Nat. Astron. 6, 812-818.

[4] Goldstein, J. I., E. R. D. Scott & N. L. Chabot (2009). Chem. Erde 69, 293–325.