The lunar surface exhibits an absorption band near 3 mu m due to hydration, either water or hydroxyl. In most analyses, the band is variable at least in latitude and temperature. Hypotheses for the variability include infilling of the band by thermal emission, migration of molecular water along temperature gradients, and formation and destruction of metastable hydroxyl as solar wind hydrogen diffuses through lunar surface grains. The degree to which lunar soil exhibits an inherent hydration feature in the absence of environmental influences is an open question. The recent opening of Apollo core sample 73001 that was sealed in vacuum on the lunar surface and curated in dry nitrogen since its return from the Moon affords an opportunity to determine if lunar soil exhibits a spectral feature due to hydration isolated from the lunar environment. To that end, near the close of dis of the core into samples for allocation to the lunar science community, we introduced an infrared spectrometer into the nitrogen purged curation cabinet and collected reflectance spectra of portions of the core between 2 and 4 mu m. We found no evidence of absorption due to hydration to 1.1% band depth uncertainty. The measurements were relative to a diffuse aluminum standard, which itself could possibly absorb light at 3 mu m due to a thin film of water; we estimate a possible negative bias of about 50 mu g/g equivalent water absorption, leading to a final estimate of core water abundance of 50 mu g/g +/- 50 mu g/g. This finding does not contradict prior estimates of lunar surface hydration as core sample 73001 is immature and may not have had sufficient opportunity to gather enough hydrogen from the solar wind or water from micrometeorites to form detectable hydration. After exposure of the core to laboratory atmosphere, a strong 3 mu m absorption developed, equivalent to over 1,000 mu g/g at a rate of about 5 mu g/g per minute, illustrating the sensitivity of lunar materials to water contamination, and the effectiveness of curation of the sample.

Imaging Infrared Spectrometer (IIRS) on-board Chandrayaan-2 is designed to measure lunar reflected and emitted solar radiation in 0.8-5.0 mu m spectral range. Its high spatial resolution (similar to 80 m) and extended spectral range is most suitable to completely characterize lunar hydration (2.8-3.5 mu m region) attributed to the presence of OH and/or H2O. Here we present initial results from IIRS reflectance data analysed to unambiguously detect and quantify lunar 3 mu m absorption feature. After pre-processing and data-reduction, a physics based thermal correction analysis of IIRS reflectance spectra has been done using co-located temperature measurements. Hydration absorption was observed at all latitudes and surface types with varying degrees for all pixels in the study area and its absorption depth shows distinct variability associated with mineralogy, surface temperature and latitude.

We present reaction balancing and thermodynamic modeling based on microtextural observations and mineral chemistry, to constrain the history of phosphate crystallization within two lunar mare basalts, 10003 and 14053. Phosphates are typically found within intercumulus melt pockets (mesostasis), representing the final stages of basaltic crystallization. In addition to phosphates, these pockets typically consist of Fe-rich clinopyroxene, fayalite, plagioclase, ilmenite, SiO2, and a residual K-rich glass. Some pockets also display evidence for unmixing into two immiscible melts: A Si-K-rich and an Fe-rich liquid. In these cases, the crystallization sequence is not always clear. Despite petrologic complications associated with mesostasis pockets (e.g., unmixing), the phosphates (apatite and merrillite) within these areas have been recently used for constraining the water content in the lunar mantle. We compute mineral reaction balancing for mesostasis pockets from Apollo high-Ti basalt 10003 and high-Al basalt 14053 to suggest that their parental magmas have an H2O content of 25 +/- 10 ppm, consistent with reported estimates based on directly measured H2O abundances from these samples. Our results permit to constrain in which immiscible liquid a phosphate of interest crystallizes, and allows us to estimate the extent to which volatiles may have partitioned into other phases such as K-rich glass or surrounding clinopyroxene and plagioclase using a non-destructive method.

Reflectance spectroscopy of Apollo lunar soil samples curated in an air- and water-free, sealed environment since recovery and return to Earth has been carried out under water-, oxygen-, CO2- and organic-controlled conditions. Spectra of these pristine samples contain features near 3 mu m wavelength similar to those observed from the lunar surface by the Chandrayaan-1 Moon Mineralogy Mapper (M-3), Cassini Visual and Infrared Mapping Spectrometer (VIMS), and Deep Impact Extrasolar Planet Observation and Deep Impact Extended Investigation (EPDXI) High-Resolution Instrument (HRI) instruments. Spectral feature characteristics and inferred OH/H2O concentrations are within the range of those observed by spacecraft instruments. These findings confirm that the 3 mu m feature from the lunar surface results from the presence of hydration in the form of bound OH and H2O. Implantation of solar wind H+ appears to be the most plausible formation mechanism for most of the observed lunar OH and H2O. (C) 2014 Elsevier B.V. All rights reserved.