PING Gamma ray and neutron measurements of a meter-sized carbonaceous asteroid analog

The only main source of elemental composition information for carbonaceous (spectral type C or C-type) asteroids is from their optical, near-infrared and infrared properties, which include their spectral reflectance characteristics, albedo, polarization, and the comparison of optical spectroscopy with meteorite groups corresponding to asteroids of every spectral type. However, these sources reflect observations from widely contrasting spatial scales presently yielding a void in the continuum of microscopic and macroscopic evidence, a lack of in situ measurement confirmation, and require deeper sensing techniques to discern the nature of carbonaceous asteroids. The Probing In situ with Neutrons and Gamma rays (PING) instrument is ideally suited to address these issues because it can be used to determine the bulk elemental composition of asteroids. One aspect of the current work includes experimentally testing and optimizing PING on a known meter-sized basalt and polyethylene layered C-type asteroid analog sample that has the same neutron response as that of a C-type asteroid. To insure that the neutron response for the asteroid analog sample is like that of a C-type asteroid, the key elements are that the thermal and epithermal neutron fluxes, as a function of depth beneath the surface, need to closely approximate those of a C-type asteroid. In this paper, we will present the PING basalt layering experimental data and Monte Carlo computer simulations.