Lunar Volatiles and Solar System Science

Understanding the origin and evolution of the lunar volatile system is not only compelling lunar science, but also fundamental Solar System science. This white paper (submitted to the US National Academies' Decadal Survey in Planetary Science and Astrobiology 2023-2032) summarizes recent advances in our understanding of lunar volatiles, identifies outstanding questions for the next decade, and discusses key steps required to address these questions

Spectroscopy of synthetic Mg-Fe pyroxenes I: Spin-allowed and spin-forbidden crystal field bands in the visible and near-infrared

Understanding the fundamental crystal chemical controls on visible and near-infrared reflectance spectra of pyroxenes is critical to quantitatively assessing the mineral chemistry of pyroxenes viewed by remote sensing. This study focuses on the analysis ofspectroscopic measurements of a comprehensive set of synthetic Mg-Fe pyroxenes from the visible through the near-infrared (0.3-2.6 micrometers) to address the constraints of crystal structure and Fe^2+ content on spin-forbidden and spin-allowed crystal field absorptions in Ca-freeorthopyroxenes. The chemistry and oxidation state of the synthetic pyroxenes are characterized. Coordinated Mössbauer spectroscopy is used to determine site occupancy of Fe^2+ in the M1 and M2 crystallographic sites. Properties of visible and near-infrared absorption bands of the synthetic pyroxenes are quantified using the modified Gaussian model. The 1 and 2 m spin-allowed crystal field absorption bands move regularly with increasing iron content, defining a much tighter trend than observed previously. A spin-allowed crystal field absorption band at 1.2 micrometers is explicitly verified, even at low total iron contents, indicating that some portion of Fe^2+ resides in the M1 site. The 1.2 micrometers band intensifies and shifts to longer wavelengths with increasing iron content. At visible wavelengths, spin-forbidden crystal field absorptions are observed in all iron-bearing samples. The most prominent absorption near 506 nm, attributed to iron in the M2 site, shifts to slightly longer wavelengths with iron content. The purity and extent of this pyroxene series allows visible wavelength absorption bands to be directly assigned to specific transitions of Fe^2+ in the M1 and M2 sites.The Meteoritics & Planetary Science archives are made available by the Meteoritical Society and the University of Arizona Libraries. Contact [email protected] for further information.Migrated from OJS platform February 202

Carle Pieters (Interviewed by Emma Bernstein)

Interview conducted with an MIT alumna as part of the Margaret MacVicar Memorial AMITA (Association of MIT Alumnae) Oral History Project. The purpose of the project is to document the life histories of women graduates of the Massachusetts Institute of Technology

Regional elemental abundances within South Pole-Aitken basin as measured with lunar prospector gamma-ray spectrometer data.

South Pole-Aitken (SPA) basin has been a target of intense study since it is one of the largest impact basins in the solar system. It is thought that SPA basin excavated deep into the lunar crust and possibly even the mantle. Such conclusions have been supported by the observed mafic and thorium composition anomalies seen across the entire basin. One of the major goals of lunar and planetary science has been to measure and understand the composition of the non-mare materials within SPA basin. It is expected that this information will help to increase our understanding of the formation and differentiation processes that occurred early on the Moon

Low-temperatureand low atmospheric pressure infrared reflectance spectroscopy of Mars soil analog materials

Infrared reflectance spectra of carefully selected Mars soil analog material have been measured under low atmospheric pressures and tempertures. Chemically altered montmorillonites containing ferrihydrite and hydrated ferric sulfate complexes are examinated, aswel as synthetic ferrihydrite and a palagonitic soil from Haleakala, Maui. Reflectance spectra of these analog materials exhibit subtle visible to near-infrared features, which are indicative of nanophase ferric oxides or oxyhydroxides and are similar to features observed in the spectra of the bright regions of Mars. Infrared reflectance spectra of these analgs include hydration features due to structural OH, bound H2O and adsorbed H2O. The spectral character of these hydration features is highly dependent on the sample environment and on the nature of the H2O/OH in the analogs. The behavior of the hydration featuresnear 1.9 muem, 2.2 muem, 2.7 muem, 3 muem, and 6 muem are reported in spectra measured under a Marslike atmospheric environment. In spectra of these analogs measured under dry Earth atmospheric conditions the 1.9-muem band depth is 8-17%; this band ismuch stronger under moist conditions. Under Marslike atmospheric conditions the 1.9-muem feature is broad and barely disverible (1-3% band depth) in spectra of the ferrihydrite and palagonitic soil samples. In comparale spectra of the ferric-sulfate-bearing montmorillonite the 1.9 muem feature is also broad, but stronger (6% band depth). In the low atmospheric pressureand temperature spectra of the ferrihydrite-bearing montmorillonite this feature is sharper than the other analogs and relatively stronger (6% band depth). Although the intensity of the 3-muemband is weaker in spectra of each of the analogs when measured under MArslike conditions, the 3- muem band remains a dominant feature and is especially broad in spectra of the ferrihydrite and palagonitic soil