Spaceborne VIR spectroscopy of small planetary bodies and inherent clues to their composition: a review and discussions of future requirements

Abstract

The possibility to study small bodies in the planetary system by means of flybys, orbital observations, and sample return by space missions has potentiated our knowledge about them. Compared to differentiated objects, whose materials have been greatly altered during the evolution of the solar system, they belong to those objects which allow the determination of the state of matter of the early planetary system. Depending on the heliocentric distance of their origin and their further development they exhibit different pristine compositions that include minerals, ices, and organics. Space missions such as Rosetta to comet 67P/Churyumov-Gerasimenko, Hayabusa2 operating at 162173 Ryugu, and Osiris-REx exploring 101955 Bennu have delivered and are delivering comprehensive data including Visible and Infrared/VIR (i.e. Visible and Near-Infrared/VNIR and Mid-Infrared/MIR) spectral information. However, the compositional analysis from VIR spectra is not straightforward. Dark and fine-grained materials influence the spectral properties considerably. Comparative laboratory investigations of analog materials and spectro-photometric modeling form the basis for a data analysis related to the respective planetary body. This paper summarizes selected results of these studies and discusses the scientific and instrumental requirements for future spaceborne VIR spectral studies of minor bodies like Comet Interceptor, AIDA, MMX, Lucy and further planned missions in the solar system.