Thermal History of Micrometeoroids during the atmospheric entry

INTRODUCTION Micrometeoroids (MMs) represent the largest mass flux of extraterrestrial matter to the present-day Earth (Love S. G. and Brownlee D. E. 1993 Icarus, 89, 26) and their flux was probably even larger during the heavy bombardment period, betweem 4 and 3.8 Gy ago. Micrometeoroids may have been the dominant source of organic carbon and may have contributed significantly to the delivery of water on the primitive Earth (Gounelle M. et al. 2005 GCA, 69, 3431). Upon atmospheric entry micrometeoroids suffer a frictional heating because of which their surface temperature rapidly reaches values as high as 1000 °K or greater. At these temperatures organic compounds evaporate or decompose. Most of the current models pertaining this topic assume the temperature of the particle as homogeneous through the whole volume. However, micrometeorites collected on the Earth’s surface show evidences that thermal gradients developed during the atmospheric passage (Genge M. J. et al. 1997 GCA, 61, 5149). The existence of these gradients may allow the survival of organic species in the interior of micrometeorites.