^1,2Nandita Kumari, ¹John Mustard, ³Timothy D. Glotch
Icarus (in Press) Link to Article [https://doi.org/10.1016/j.icarus.2025.116721]
¹Department of Earth, Environmental and Planetary Sciences, Brown University, USA
²Planetary Science Institute, USA
³Department of Geosciences, Stony Brook University, USA
Copyright Elsevier

Visible/near-infrared (VNIR) and thermal infrared (TIR) spectroscopy have been widely used to detect and characterize the abundances of silicates across the solar system. Recently, intermediate infrared (IMIR) reflectance spectroscopy (~4 – 6 μm) has been proposed as a tool to quantify the Mg# in olivine and pyroxene with varying iron, magnesium and calcium content. The lunar surface is composed of rocks with mixed particle sizes and thus quantifying the effects of particle size is extremely important to increase the robustness of IMIR spectroscopy as a tool for lunar surface exploration. Similarly, space weathering has been known to cause optical darkening and affect the spectra of the lunar surface materials across a broad wavelength range. In this study, we have identified the emission features of lunar analog minerals/rocks and their variations with changes in particle sizes and albedo at IMIR wavelengths in simulated lunar environment (SLE). We find that the lunar analog minerals display an increase in emissivity and striking decrease in feature contrast with an increase in particle sizes or decrease in albedo. This study shows that while this wavelength range works well in reflectance space for sample characterization, using it for emissivity measurements via orbital remote sensing or in-situ rovers requires extensive study.

^1,2Tomoko Arai, ¹Takayuki Tomiyama, ²Takafumi Niihara, ³Tatsunori Yokoyama, ⁴Miwa Yoshitake, ^2,3Hiroshi Kaiden, ^2,3Keiji Misawa, ⁴Anthony J. Irving
Icarus (in Press) Open Access Link to Article [https://doi.org/10.1016/j.icarus.2025.116715]
¹Planetary Exploration Research Center, Chiba Institute of Technology, 2-17-1 Tsudanuma, Narashino, Chiba 275-0016, Japan
²National Institute of Polar Research, 10-3 Midoricho, Tachikawa, Tokyo 190-8518, Japan
³Graduate Institute for Advanced Studies, SOKENDAI, 10-3 Midoricho, Tachikawa, Tokyo 190-8518, Japan
⁴Department of Earth & Space Sciences, University of Washington, Seattle, WA 98195, USA
Copyright Elsevier

A lunar meteorite Northwest Africa (NWA) 4485 is a KREEP (potassium, rare earth elements and phosphorus)-rich polymict breccia, likely paired with NWA 4472. NWA 4485 includes mm-sized lithic clasts with variable textures and modal abundances. The lithic clasts share features with KREEP basalts, and consist dominantly of moderately Mg-rich pyroxene and less calcic plagioclase than those in the Apollo 17 KREEPy basalt with zircon and phosphates. Uranium‑thorium‑lead isotopic studies on zircon and baddeleyite in the lithic clasts and matrix of NWA 4485 revealed that the 207Pbsingle bond206Pb age spectrum (4350–3920 Ma) is compatible with that for apatite in the paired NWA 4472, broadly covering the ages of zircons in Apollo polymict breccia samples from multiple landing sites. The presence of a 4160 Ma zircon in a millimeter-sized lithic clast, a core of 4210 Ma in a detrital zircon with multiple rims of ~3960 Ma, and an individual zircon grain of 4350 Ma in the matrix clearly indicates that they are products of pre-mare multiple KREEP-related magmatism, predating the lunar cataclysm (~3900–4000 Ma).