Shock processes in lunar meteorites, Apollo samples and terrestrial analogue materials

The overall goal of the CLRN’s research on lunar meteorites, Apollo samples and terrestrial analogue materials is to understand the effect of shock on lunar materials. Several CLRN researchers are examining lunar meteorites for evidence of shock deformation of minerals via reflectance spectroscopy, in situ micro-XRD, Raman spectroscopy, SEM, and SEM-CL. Other research focuses on understanding bulk physical properties of lunar meteorites (density, porosity, magnetic susceptibility, magnetic remnance) for the purpose of determining these objects’ bulk responses to impact events, thermal changes, paleomagnetic fields, cosmic ray irradiation and passage through the atmosphere as meteors.

A major goal of the work at the CLRN is also to provide support to the analysis of lunar spectroscopic data, whether acquired by earth- or space-based telescopes, orbiter or landers. Dr. Cloutis has been looking at the ultraviolet spectral properties of terrestrial analogues of lunar minerals, and the use of ultraviolet observations for lunar mapping (particularly of oxides). In addition, Dr. Cloutis has recently received approval from the NASA Astromaterials Curator for the loan of six pristine 1-gram samples of lunar soils (highlands, low-Ti mare, high-Ti mare). Dr. Cloutis, along with his collaborators, will be spectrally characterizing these samples by reflectance spectroscopy from the ultraviolet to the infrared (0.2-16 microns) and generating mineral separates to characterize the major phases (olivine, plagioclase feldspar, pyroxene, oxides). The goal is to determine the spectral properties of pristine lunar samples, particularly in the ultraviolet, where even trace amounts of ferric iron (expected to be absent in the pristine samples, but which may form during even short exposures to the terrestrial environment) can affect the ultraviolet spectral properties.

intxt-shock-nanoIronLunar samples and soil have distinctive magnetic properties linked to the presence of free FeNi metal, FeSi and nanophase iron. The nanophase iron is a major darkening agent in agglutinates, a product of space weathering due in part to micrometeoroid bombardment. Magnetic measurements offer a means of quantifying the presence and effective grain size of metal in lunar soils and can be used as an index of shock metamorphism in lunar samples and meteorites as effective metal grain size increases with shock state. The spectral properties of mafic minerals mixed with nanophase iron this summer will also be studied by Dr. Cloutis and colleagues.

Finally, several CLRN members are working on the Mistastin Lake impact structure, Labrador. The target rock is largely plagioclase feldspar, and hence provides an excellent terrestrial analogue for the effects of impact on the lunar surface.

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CLRN researchers are also working to address the dynamics of ejected lunar dust. Our goal is to examine in detail the delivery of lunar dust from impacts of all sizes between the Moon and Earth. Numerical integration of the equations of motion, coupled with an ejection model and treatment of Lorentz forces is to be included. This will address the issue of ocean sediment He3 flux variations and if these could be due largely to lunar impacts alone. Furthermore, because the Moon is airless, material is easily ejected, but material on sub-orbital ballistic trajectories is also free to disperse across the surface. This results in secondary and possibly tertiary craters. Ongoing investigations include the effects of lunar impact flashes in terms of their ejecta. Although the impactors are relatively small, they could excavate a considerable amount of material that could form a short-lived dust plume as it disperses across the surface. This is of interest from a safety point of view in terms of the possibility of human lunar exploration.

A major part of the CLRN’s work includes the development of an instrument suite for a landed dust characterization mission, building upon Canadian expertise in Lidar systems (e.g., NASA Phoenix mission) and astromaterials. This mission will be directly complementary to the proposed orbital Lunar Atmosphere and Dust Environment Explorer (LADEE) mission, currently in development by NASA. It is our hope that, through the NLSI, CLRN members will establish links with U.S. colleagues involved in the LADEE mission and so develop opportunities for Canadian involvement in a landed dust mission.