Dr. Katherine Shirley (she/her)

Abstract:

Hydration on the Moon’s surface is widely detected in orbital datasets (e.g. M3 on Chandrayan-1), yet its abundance and physical form (-OH, H2O, frost, and/or ice) remain poorly constrained. The lunar surface is covered in regolith fines, which impacts local thermophysical conditions, obscures underlying volatiles and modifies detectable hydration bands. Our interpretation of hydration form and abundance on the lunar surface is further limited by existing experimental constraints of water-ice spectral behaviour at the regolith interface (photometric effects) and by the restriction of current orbital datasets to the near-infrared (< ~3 µm O–H stretching mode). We are developing a laboratory approach to quantify how dust layering, regolith maturity, grain size, composition, and ice abundance control the spectral expression of water-ice across the near- and mid-infrared (1.8–20 µm), with emphasis on the ~3 and 6 µm diagnostic regions. This poster presents a preliminary experimental set-up developed ahead of the full operation of a custom-built vacuum chamber, Polar Analogue of Dust Overlying Regolith–Ice (PANDOR-I), intended to simulate airless-body and cryogenic polar conditions. In this initial laboratory set-up, the sample compartment of a Bruker 70V Fourier Transform Infrared (FTIR) spectrometer is isolated using potassium bromide (KBr) windows to enable controlled, low-pressure (~0.2 mbar) reflectance measurements of anhydrous and hydrated analogue configurations to (i) characterise the spectral expression of hydration-related structure in the ~3 and 6 µm regions under regolith simulant fines, and (ii) provide benchmark spectra for direct comparison with a Mie–Hapke forward model (band shape,depth, and mixing trends) prior to cryogenic and airless body simulations with PANDOR-I. This preliminary work will establish an empirical reference for model validation and for designing the subsequent PANDOR-I cryogenic experiments, enabling a more robust interpretation of spectrally mixed hydration signatures in forthcoming lunar datasets.

Abstract:

Abstract Laboratory spectral analysis of well‐characterized meteorite samples can be employed to more quantitatively analyze asteroid remote sensing data in conjunction with returned extraterrestrial samples. In this work, we examine the combined effects of physical (temperature, particle size) and chemical (petrologic type, metal fraction) variables on visible and near‐infrared (VNIR) spectra of ordinary chondrite meteorite powders. Six equilibrated ordinary chondrite meteorite falls were prepared at a variety of particle sizes to capture the spectral diversity associated with asteroid regoliths dominated by various grain sizes. Mineral compositions and abundance were determined from electron microprobe analysis of meteorite thick sections to precisely characterize changes in spectral features due to variations in mineralogy. VNIR spectra of the ordinary chondrites were measured under simulated asteroid surface conditions at a series of temperatures chosen to mimic near‐Earth asteroid surfaces. The resulting spectra show minimal variation in both major absorption bands across the simulated near‐Earth asteroid temperature regime. Changes in particle size result in variations in band centers and band area ratios for material of the same composition, two key parameters typically used to derive asteroid composition. Unlike previous spectral investigations of ordinary chondrites, we retained the metal fraction in our powders instead of analyzing only the silicate fraction. Metal has a subtle but non‐negligible effect on the VNIR spectra of ordinary chondrites. The more petrologically pristine samples from each ordinary chondrite group display relatively weaker absorption bands than their more thermally altered counterparts. The band centers shift to longer wavelengths as grain size and petrologic type increase. Plain Language Summary Remote interpretation of asteroid composition can be complicated by the physical (grain size, temperature) and chemical (mineral composition and abundance) properties of the asteroids themselves. To aid in understanding the effects of these variables and improve our remote interpretation of asteroid compositions from their spectra, we have systematically evaluated the effects of these variables on the visible‐near‐infrared spectra of well‐characterized asteroid samples (e.g., ordinary chondrite meteorites) measured in a simulated asteroid environment. Our results show that while the effect of near‐Earth asteroid temperatures on the spectra appears to be minimal, changes in particle size can mimic changes in spectral band parameters that are typically attributed to composition. It is therefore essential to account for particle size when interpreting composition from silicate‐dominated asteroid spectra. Key Points Near‐Earth asteroid temperatures (∼10–100°C) have a minimal effect on the visible and near‐infrared (VNIR) spectra of olivine and pyroxene dominated ordinary chondrite meteorites Particle size is a critical variable to account for when trying to derive composition from remotely sensed asteroid VNIR spectra Metal content has a subtle but non‐trivial effect on the VNIR spectra of ordinary chondrites

Abstract:

Abstract The Lunar Trailblazer smallsat mission High‐resolution Volatiles and Minerals Moon Mapper (HVM 3 ) science instrument was designed to acquire targeted spectral image cubes of the lunar surface at visible to shortwave infrared (VSWIR) wavelengths (0.6–3.6 μm) in an effort to understand the distribution, abundance, and form (OH, H 2 O, ice) of lunar water, as well as the lunar water cycle. The Lunar Trailblazer mission end was declared in July 2025. Here, we describe the formulation and testing of VSWIR spectral parameters in preparation for previously anticipated returned data from HVM 3 using global image cubes and mosaic data from the Moon Mineralogy Mapper (M 3 ) imaging spectrometer, HVM 3 's predecessor, and the Deep Impact spacecraft. We expand upon the existing M 3 global spectral parameter library, test the efficacy of presented parameters individually and alongside existing M 3 spectral parameters, provide examples of quantitative thresholds intended to indicate robust mineral detections, and discuss the spectral parameter limitations. We demonstrate that newly formulated and existing parameters capture lunar mineral diversity well and serve as a reliable indicator of lunar surface hydration, making them useful for existing and future scientific analysis using lunar orbital remote sensing data sets. Plain Language Summary The High‐resolution Volatiles and Minerals Moon Mapper (HVM 3 ) is one of two science instruments on the Lunar Trailblazer smallsat mission, whose science goal is to understand the distribution, abundance, and form of water on the Moon, as well as the lunar water cycle. HVM 3 uses patterns in infrared light reflection and absorption at different wavelengths to detect water and minerals in rocks and soils on the Moon's surface. In July 2025 the Lunar Trailblazer mission end was declared. Here, we detail the formulation and testing of algorithms for making water and mineral maps in preparation for the anticipated HVM 3 returned data using existing Moon Mineralogy Mapper (M 3 ) and Deep Impact spacecraft lunar data sets, which are similar types of instruments. We demonstrate that presented spectral parameters can distinguish lunar minerals of interest and therefore, capture lunar mineral diversity well. We also show that a newly developed water spectral parameter can be used as a reliable indication of lunar surface water presence, thereby demonstrating the value of expected HVM 3 maps for the broader scientific community as well as planning future exploration of the Moon. Key Points Legacy M 3 and updated visible‐shortwave infrared spectral parameters were formulated and tested for the Lunar Trailblazer mission Spectral parameters capture lunar mineral diversity well and are readily distinguished particularly in conjunction with each other A newly presented water parameter serves as a reliable indicator of lunar surface hydration

Abstract:

Research into compositions of small bodies and planetary surfaces, such as asteroids, is key to understanding the origin of water and organics on Earth [1], as well as placing constraints on planetary dynamics and migration models [2] that can help understand how planetary systems around other stars may form and evolve. Compositional estimates can be found with thermal infrared (TIR; 5-25μm) spectroscopy, as the TIR region is rich in diagnostic information and can be used in remote sensing observations and laboratory measurements. However, TIR spectra of the same material may appear differently depending on several factors, such as particle size, surface roughness, porosity etc. This work quantifies the changes in spectral morphology (i.e., shapes and depths of spectral features) as particle size transitions from fine (90%), at several size fractions, aimed to be