On the cooling rate evolution of asteroid fragments

Jialong Ren, Marc A. Hesse, Michael P. Lucas, Nicholas Dygert

In Press, Journal Pre-proof, Available online 24 February 2022



• Conductive cooling rate at constant temperature declines as 1/time.
• High-temperature cooling rate data provide constraint on cooling time.
• High-temperature cooling rate data provide constraint on fragment size.
• H-chondrite cooling times exceed dynamical estimates of reassembly time.”

“Recent observations of rapid cooling rates at high temperatures in several ordinary chondrite and primitive achondrite meteorite groups suggest the fragmentation of their parent bodies near peak temperatures. We use analytic models for conductive cooling of collisional fragments to show that the actively cooling part of a fragment experiences similar cooling rates over a large range of temperatures. This characteristic cooling rate decays inversely with time and the larger a fragment the longer this decay continues. Measurements of high temperature cooling rates therefore place a lower bound on the cooling time and size of collisional fragments. Applying this model to the cooling rates in H chondrites, which vary from 10^1 to 10^-2°C/yr at temperatures between 700 to 850 °C, we estimate cooling times of at least 10^2 and 10^3 years in fragments at least to m in radius.”