Scientific goals: we seek to better understand the relative rates of the two main agents of lunar space weathering: micrometeoroid bombardment and the solar wind. Many recent studies have pointed to…

The Johns Hopkins University was awarded a $309,452 grant by the National Aeronautics and Space Administration (NASA) for a research project focused on better understanding the relative rates of the two main lunar space weathering agents - micrometeoroid bombardment and solar wind. The project aims to improve knowledge of the spectral properties of lunar soil agglutinates and use that information to model the evolution of the lunar regolith over the Copernican period. This work will leverage lunar data from the Kaguya, Chandrayaan-1, and Lunar Reconnaissance Orbiter missions. The grant does not have a set-aside designation and has an ultimate completion date of August 8, 2023.

Scientific goals: we seek to better understand the relative rates of the two main agents of lunar space weathering: micrometeoroid bombardment and the solar wind. Many recent studies have pointed to the importance of the solar wind in altering the lunar soil by creating amorphous rims that contain nanophase-sized grains of iron metal. The nanophase iron metal, in particular, alters the spectral properties of the soil in ways that are well known. But micrometeoroid bombardment is also a key component of lunar space weathering, and is responsible for the production of agglutinates, glassy agglomerations of mineral fragments and iron metal particles. Agglutinates comprise approximately half of typical mature lunar soils, and are thus highly important for understanding the changes in spectral properties that result from micrometeoroid bombardment. Surprisingly, the detailed spectral characteristics of agglutinates and how those characteristics vary with soil composition are not well known. This knowledge GAP hinders the ability to pursue scientific investigations related to space weathering. In the work proposed here, we will improve our knowledge of the spectral properties of agglutinates so that we can separately model the rates of space weathering due to the solar wind (nanophase iron production) and micrometeoroid bombardment (agglutinate production) in order to understand the evolution of the lunar regolith throughout the copernican period. Further, the new understanding of agglutinate spectra will permit US to examine recent work that suggests IT is the flux of solar wind rather than total dose that determines how a soil matures. Methodology: our proposed work is separated into four tasks. In the first task, we will characterize agglutinates separated from apollo soil samples that bracket the major range of lunar composition and collect reflectance spectra of these separates. The second task will seek to understand what properties control the observed spectral reflectance characteristics of the separates using electron and xray petrography and electron microprobe analyses to determine glass and mineral chemistry and fraction. Our third task is to use the information collected in the laboratory to determine the best way to treat agglutinates in radiative transfer models of lunar soil spectra by testing several methods of varying complexity. Our fourth task will use the improvements to radiative transfer models developed in task 3 to address our main scientific investigation, understanding the relative rates of lunar space weathering due to the solar wind and micrometeoroid bombardment. We will select both kaguya spectral profiler (SP) data and moon mineralogy mapper (M3) spectra of craters of a range of ages, and model the agglutinate and nanophase iron abundance within the ejecta of these craters. Ages of the craters will be taken from the literature or determined using the correlation between crater age and the 95TH percentile value of ejecta rock abundance determined from diviner data. These rates will be compared to new determinations of rates of regolith gardening, and will be compared to special locations such as at high latitudes and crustal magnetic anomalies. Relevance: this proposal focuses on a scientific analysis of lunar data (primarily kaguya SP, M3, and diviner) to understand the rates of space weathering processes on the moon. This work is not currently possible without a better understanding of lunar agglutinate spectral properties, and thus in support of our scientific investigation we will pursue "nondata analysis" tasks (laboratory work and radiative transfer model improvements), which are responsive to the ldap call because they "are necessary to analyze (or help analyze) the lunar mission data." as the main goal of this work is a scientific study of lunar data, IT is not appropriate for solar system workings ("solar system workings does not accept proposals that are eligible for submission to a DAP").