NASA designated Reiner Gamma (RG) as the landing site for the first Payloads and Research Investigations on the Surface of the Moon (PRISM) delivery (dubbed PRISM-1a). Reiner Gamma is home to a magnetic anomaly, a region of magnetized crustal rocks. The RG magnetic anomaly is co-located with the type example of a class of irregular high-reflectance markings known as lunar swirls. RG is an ideal location to study how local magnetic fields change the interaction of an airless body with the solar wind, producing stand-off regions that are described as mini-magnetospheres. The Lunar Vertex mission, selected by NASA for PRISM-1a, has the following major goals: 1) Investigate the origin of lunar magnetic anomalies; 2) Determine the structure of the mini-magnetosphere that forms over the RG magnetic anomaly; 3) Investigate the origin of lunar swirls; and 4) Evaluate the importance of micrometeoroid bombardment vs. ion/electron exposure in the space weathering of silicate regolith. The mission goals will be accomplished by the following payload elements. The lander suite includes: The Vertex Camera Array (VCA), a set of fixed-mounted cameras. VCA images will be used to (a) survey landing site geology, and (b) perform photometric modeling to yield information on regolith characteristics. The Vector Magnetometer-Lander (VML) is a fluxgate magnetometer. VML will operate during descent and once on the surface to measure the in-situ magnetic field. Sophisticated gradiometry allows for separation of the natural field from that of the lander. The Magnetic Anomaly Plasma Spectrometer (MAPS) is a plasma analyzer that measures the energy, flux, and direction of ions and electrons. The lander will deploy a rover that conducts a traverse reaching ≥500 m distance, obtaining spatially distributed measurements at locations outside the zone disturbed by the lander rocket exhaust. The rover will carry two instruments: The Vector Magnetometer-Rover (VMR) is an array of miniature COTS magnetometers to measure the surface field. The Rover Multispectral Microscope (RMM) will collect images in the wavelength range ~0.34–1.0 um. RMM will reveal the composition, texture, and particle-size distribution of the regolith.

A planetary surface’s thermal infrared (TIR) emissions provide insight into the surface’s composition. Different minerals can be identified by their characteristic TIR spectral signatures. Therefore one can retrieve surface mineral composition by comparing TIR observations of a planetary surface against a library of known mineral TIR spectra measured on Earth. However for airless bodies such as the Moon, creating such a spectral library poses a challenge: minerals exhibit different TIR characteristics when measured in typical terrestrial conditions versus in lunar surface-like environments. We work to overcome this challenge by measuring TIR emission spectra of mineral samples in a chamber that simulates the lunar environment. The Simulated Airless Body Emission Laboratory (SABEL) chamber heats particulate samples under vacuum to generate a thermal gradient akin to that found in the upper regolith (i.e. epiregolith) of airless bodies. The presence of this thermal gradient—modeled to be as steep as ~60K/100 μm for the Moon—is due to airless bodies lacking the convective heat transfer provided by an atmosphere. This thermal gradient is responsible for the altered TIR spectral emission characteristics of the lunar surface, so simulating it in SABEL allows us to measure TIR spectra that are directly comparable to remotely sensed TIR observations from the Diviner Lunar Radiometer (Diviner) instrument aboard the Lunar Reconnaissance Orbiter (LRO). The work presented here focuses on one particular application of SABEL: characterizing the TIR emission spectra of silicate mineral mixtures with the endmembers plagioclase, pyroxene, and olivine. These endmembers bound the typical mineral compositions of the lunar surface. By understanding the TIR characteristics of these endmembers’ mixtures, and in particular how the wavelength position of the Christiansen feature—an emissivity maximum sensed by Diviner—changes for different mixtures, we can better interpret TIR data and their implications for surface composition.