Two Simulated Spectral Databases of Lunar Regolith: Method, Validation, and Application

Our simulated lunar regolith spectra database, based on the Hapke AMSA radiative transfer model (RTM), is a large supplement to the limited number of lunar spectra data. By analyzing the multiple solutions and applicable scopes of the Hapke model by means of Newton interpolation and the least square optimization method, an improved method was found for the simulation of spectra, but it remained challenging to use to invert mineral abundance. Then, we simulated the spectra, mineral abundance, particle size and maturity of 57 mare and highland samples of the Lunar Soil Characterization Consortium (LSCC) in size groups of 10 µm, 10–20 µm and 20–45 µm. The simulated and measured spectra fit well with each other, with correlation coefficients greater than 0.99 and root mean square errors at a magnitude of 10-3. The parameters of mineral abundance, particle size and maturity are highly consistent with the measured values. Having confirmed the reliability of our simulation method, we analyzed the mechanism, reliability and applicability of the “spectral characteristic angle parameter” proposed by Lucey using the simulated spectral data of lunar regolith. Lucey’s method is only suitable for macro analysis of the entire moon, and the error is large when it is used for areas with high abundance of forsterite or ilmenite. In the spectral simulation of lunar regolith, olivine was subdivided into forsterite and fayalite, and the two end-members were mixed to approximately estimate the effect of the chemical composition of olivine on the spectra, which has been confirmed to be feasible.

Dependence of the Hydration of the Lunar Surface on the Concentrations of TiO2, Plagioclase, and Spinel

We investigate the interrelation between the hydration of the lunar regolith and the mineral composition of the surface of the Moon with respect to the concentrations of plagioclase, TiO2 (highly correlated with the oxide mineral ilmenite), and Mg-spinel. The spectral properties of lunar regions with a low concentration of plagioclase or a high concentration of TiO2 or Mg-spinel show a significant reduction in hydration at lunar midday compared to other compositions. This suggests that these oxide minerals contain less of the strongly bound OH component, which is not removed at lunar midday. The time-of-day-dependent variation of the 3 μm band depth is greater in TiO2-rich areas compared to other mare regions. The TiO2-rich regions therefore appear to have a strong tendency to adsorb solar wind-induced hydrogen into binding states of low energy that can more readily desorb and readsorb OH/H2O on a daily basis.

Regolith and Radiation: The Cosmic Battle

This chapter discusses regolith utilization in habitat construction mainly from the point of view of radiation protection of humans on missions of long duration. It also considers other key properties such as structural robustness, thermal insulation, and micrometeoroid protection that all have to be considered in parallel when proposing regolith-based solutions. The biological hazards of radiation exposure on the Moon are presented and put in the context of lunar exploration-type missions and current astronaut career dose limits. These factors guide the research in radiation protection done with lunar regolith simulants, which are used in research and development activities on Earth due to the reduced accessibility of returned lunar samples. The ways in which regolith can be used in construction influence its protective properties. Areal density, which plays a key role in the radiation shielding capacity of a given material, can be optimized through different regolith processing techniques. At the same time, density will also affect other important properties of the construction, e.g. thermal insulation. A comprehensive picture of regolith utilization in habitat walls is drawn for the reader to understand the main aspects that are considered in habitat design and construction while maintaining the main focus on radiation protection.