Reconciling remote-sensing estimates of Ryugu’s albedo with laboratory measurements

Abstract The Japanese Hayabusa2 spacecraft returned samples from the asteroid Ryugu in December 2020, and several results on the properties of the particles have been published since. A detailed geochemical analysis determined that the total organic carbon abundance of the sample was on average 2.92 wt%. This value is much less than the 14.6–59.3 vol% estimated from remote-sensing data for Ryugu coupled with the albedos of irradiated meteorites and organic matter. Understanding the reasons for this discrepancy is paramount to accurately predict the composition of C-complex asteroids. Here we explore several factors that may affect the estimates of organic matter abundance made using remote-sensing data. Such factors include the distribution of organic matter, the porosity and roughness of the surfaces of asteroids, and inconsistencies between the observation geometries used by remote-sensing and laboratory investigations. We posit that discussing such factors may fuel further experimental investigations of the effects of irradiation on asteroid surfaces and, thus, improve predictions of their organic composition.