Measuring the fidelity of asteroid regolith and cobble simulants

Abstract

NASA has developed a "Figure of Merit" method to grade the fidelity of lunar simulants for scientific and engineering purposes. Here we extend the method to grade asteroid simulants, both regolith and cobble variety, and we apply the method to the newly developed asteroid regolith and cobble simulant UCF/DSI-CI-2. The reference material that is used to evaluate this simulant for most asteroid properties is the Orgueil meteorite. Those properties are the mineralogical and elemental composition, grain density, bulk density of cobbles, magnetic susceptibility, mechanical strength of cobbles, and volatile release patterns. To evaluate the regolith simulant's particle sizing we use a reference model that was based upon the sample returned from Itokawa by Hayabusa, the boulder count on Hayabusa, and four cases of disrupted asteroids that indicate particle sizing of the subsurface material. Compared to these references, the simulant has high figures of merit, indicating it is a good choice for a wide range of scientific and engineering applications. We recommend this methodology to the wider asteroid community and in the near future will apply it to additional asteroid simulants currently under development.

Simulated asteroid materials based on carbonaceous chondrite mineralogies

“…c) with several MPa in unconfined compressive strength, matching measurements from CI chondrites (Metzger et al. ; Pohl and Britt Forthcoming). The clay species appear to be responsible for most of this strength, because we found mixtures with less clay were much less coherent upon drying.…”

“…In terms of quantitative metrics, Metzger et al. () adopted the figure‐of‐merit (FoM) system developed by NASA, and they evaluated the fidelity of the CI Asteroid Simulant as an example. In this system, numerical scores are given from 0 (lowest fidelity) to 1 (highest fidelity) based on comparisons to a reference material, in this case the meteorite Orgueil and asteroid models for some properties like particle size distribution.…”

“…Metzger et al. () performed an in‐depth analysis of the particle size distribution of the CI Asteroid Simulant in regolith form and compared it to available constraints from meteorite and asteroid observations.…”

“…A companion paper (Metzger et al. ) describes a rigorous effort to quantitatively assess the fidelity of the CI simulant using a modified version of the “Figure‐of‐Merit” approach developed by NASA for lunar simulants. That paper focused more on physical properties, while the analyses below address microscopic textures, bulk chemistry, VNIR reflectance spectra, thermal emission spectra, and volatile release properties for all three simulant varieties.…”

“…Metzger et al. () provided a detailed list of past efforts to simulate asteroid surface materials: in many cases, these are low‐fidelity substitutes such as glass beads, lunar simulant, and bread flour, among others. In the first effort to systematically create high‐fidelity asteroid simulants, the University of Central Florida (UCF) and Deep Space Industries (DSI; now part of Bradford Space) developed a series of prototypes with physical forms including solid cobbles and regolith.…”