Can a chondrule precursor survive a shock wave?

Earth and Environmental Sciences, Graduate School of Environmental Studies, Nagoya University, Nagoya 464-8602, Japan e-mail: sirono@eps.nagoya-u.ac.jp

Received: 9 March 2006
Accepted: 28 April 2006

Abstract

In a shock-wave heating model, a chondrule is formed due to frictional heating between its precursor and gas. If the tensile stress inside the precursor derived from the gas dynamic pressure, is greater than the tensile strength of the precursor, the precursor is broken into smaller pieces. The yield (onset of plastic deformation) and breaking (onset of fracturing) strengths of the precursor when sintering is taken into account was calculated. The timescale of sintering is estimated. The model in Sirono & Greenberg (2000, Icarus 145, 230), in which a grain aggregate is assumed to comprise chains of spherical grains of uniform size was used. The critical packing fraction above which an aggregate can survive a shock wave is obtained. If the degree of sintering is low, the breaking strength of the aggregate decreases due to sintering. When sintering has sufficiently occurred, the aggregate can avoid breaking up. Sintering can proceed upstream of the shock wave before the passage of the shock wave.