Spectral characteristics of ordinary chondrite impact melts

Introduction: Impacts are the most ubiquitous of all the processes that shape solar system bodies. Evidence for these collisions is visible on a macro scale in the form of impact craters and collisional fragments (i.e. asteroids). Impacts on larger bodies such as terrestrial planets and our own Moon modify the initial target material texture and composition creating impact melts that can be detected from remote sensing and also in returned samples. The production of impact melt is a function of impact velocity. Most asteroidal collisions take place at velocities of ~5 km/sec [1], which is sufficient to produce impact melt deposits as seen on the Moon where the impact velocities are much higher (~15 km/sec). However, porosity and composition (presence of metal/metal sulfides) play an equally important role as impact velocity [2]. Several meteorites derived from asteroidal sources show evidence for shock-darkening and impact melt. Ordinary chondrites (H, L and LL subtypes) are the most common type of meteorites that fall on Earth making up about 86% of all meteorites in terrestrial collections. A subset of S-type asteroids has been suggested to be the source of ordinary chondrites. In this work we present results of our laboratory spectral measurements of impact melts and unaltered material from the three ordinary chondrite types (H, L, and LL). Our goal is to understand the spectral changes between the unaltered and the impact melt materials and quantify its effects on taxonomic classification of asteroids.