¹V. Payré,¹K. L. Siebach,¹R. Dasgupta,²A. Udry,³E. B. Rampe,⁴S. M. Morrison
Journal of Geophysical Research (Planets) (In Press) Link to Article [https://doi.org/10.1029/2020JE006467]
¹Department of Earth, Environmental and Planetary Sciences, Rice University, Houston, TX, USA
²Department of Geoscience, University of Nevada, Las Vegas, NV, USA
³Astromaterials Research and Exploration Science Division, NASA Johnson Space Center, Houston, TX, USA
⁴Geophysical Laboratory, Carnegie Institution for Science, Washington, D.C., USA
Published by arrangement with John Wiley & Sons

Understanding magmatic processes is critical to understanding Mars as a system, but Curiosity’s investigation of dominantly sedimentary rocks has made it difficult to constrain igneous processes. Igneous classification of float rocks is made difficult by: (1) the possibility that they have been affected by sedimentary processes or weathering, and (2) grain size heterogeneity in the observed rock textures makes the small‐scale compositions measured by rover instruments unreliable for bulk classification We avoid these ambiguities by using detrital igneous mineral chemistry to constrain models of magmatic processes in the source region for the fluvio‐deltaic Bradbury group. Mineral chemistry is obtained from X‐ray diffraction of three collected samples and a new stoichiometric and visual filtering of ~5,000 laser induced breakdown spectroscopy (LIBS) spots to identify compositions of individual igneous minerals. Observed mineral chemistries are compared to those produced by MELTS thermodynamic modeling to constrain possible magmatic conditions. Fractionation of two starting primary melts derived from different extent of adiabatic decompression melting of a primitive mantle composition could result in the crystallization of all minerals observed. Crystal fractionation of a subalkaline and an alkaline magma is required to form the observed minerals. These results are consistent with the collection of alkaline and subalkaline rocks from Gale as well as clasts from the martian meteorite Northwest Africa 7034 and paired stones. This new method for constraining magmatic processes will be of significant interest for the Mars2020 mission, which will also investigate an ancient volcaniclastic‐sedimentary environment and will include a LIBS instrument.

^1,2Matthew A. Siegler,^1,2Jianqing Feng,³Paul G. Lucey,^1,2Rebecca R. Ghent,⁴Paul O. Hayne,¹Mackenzie N. White
Journal of Geophysical Research (Planets) (in Press) Link to Article [https://doi.org/10.1029/2020JE006405]
¹Planetary Science Institute, USA
²Southern Methodist University, USA
³University of Hawaii, USA
⁴University of Colorado, Boulder, USA
Published by arrangement with John Wiley & Sons

Passive microwave frequency (~300 MHz‐300 GHz) observations of the Moon have a long history and have been suggested as a plausible orbital instrument for the Moon and other bodies. However, global, orbital multi‐frequency measurements of lunar passive microwave emission have only recently been made by the Chinese Chang’E 1 and 2 Microwave RadioMeter instruments (MRM). These missions carried nearly identical 4‐channel (3.0, 7.8, 19.35, and 37 GHz) instruments into lunar orbit in 2007‐2009 and 2010‐2011, respectively. Over the same time period, the ongoing Lunar Reconnaissance Orbiter mission carried the Diviner Lunar Radiometer, which collected surface temperature measurements in the far‐infrared (~7.8‐400μm) from 2009 to present. By combining these data and associated thermal models, we provide new constraints on the relationship between physical temperature and microwave brightness temperature to reveal novel information about regolith thermal and dielectric properties which can reveal unique geologic information about the Moon. Here we describe several first‐order global results to come from this combined data set, focusing primarily on the ability to detect, map and quantify dielectric loss tangent variations of the Moon, including those from the presence of titanium‐bearing ilmenite. We update the loss tangent models for both highlands and mare and identify a clear frequency dependence that differs in sign between the two. We use the correlation with visible wavelength TiO₂ mapping to provide a means to separate out the loss from rocks and from that of composition.