New Views of the Moon 2, Asia Workshop Report April 2018 Aizu University, Japan.

Transcription

1 New Views of the Moon 2, Asia Workshop Report April 2018 Aizu University, Japan. The New Views of the Moon 2 (NVM-2) Asia workshop was the third of three workshops ( designed to gather information for the next installment of the 2006 New Views of the Moon book published by the Mineralogical Society of America Review in Mineralogy and Geochemistry series. The first workshop was in the USA at the Lunar and Planetary Institute, Houston, in 2016 ( followed by NVM-2, Europe at the University of Münster, Germany, in 2017 ( newviews2017/). The goals of these workshops were to solicit input from the international lunar community on the advances in lunar science and exploration this century, and to have volunteers for chapter writing teams, as well as reviewers for the chapters when they are completed. The NVM-2, Asia workshop was held over 2.5 days at the excellent facilities of Aizu University with 57 people in attendance. Many thanks and much appreciation are extended to the Japan organizing committee of Hirode Demura, Makiko Ohtake, Hiroyuki Satoh, Yoshiaki Ishihara, and Junichi Haruyama. The theme of the workshop was looking to the future for lunar science and exploration. One poster and eight oral sessions comprised the meeting, with ample time for discussion in each oral session. The sessions were: Lunar Missions and Plans for Exploration Lunar Crust and Mantle Lunar Interior Lunar Craters, Impacts, and Surface Weathering Lunar Surface: Regolith, Volcanism & Dust Lunar Volatiles Future Mission Concepts New Views of the Moon 2: What s Next?

2 Lunar Missions and Plans for Exploration This session included talks from JAXA and NASA officials as well as talks on missions in development and those under study. JAXA is interested in pursuing lunar resources and how these potential reduce the cost of pace exploration. The Japanese lunar polar mission was described, with landing site selection being based on 5 criteria: presence of water, topography, direct communication with Earth, solar illumination, geology. JAXA is developing the rover and ISRO the lander. NASA described the Lunar Orbital Platform Gateway and noted that as originally proposed, lunar science is the area least served, indicating the gateway needs supplemental infrastructure. The HERACLES project involves an ESA-JAXA-developed lander, a reusable ESA launcher, with a rover from CSA. Samples would be collected and sent to the LOP-G to be returned to Earth by the astronauts when they visited. The Lunar-H Mapper cubesat mission to be launched on the SLS EM-1 to examine H deposits in PSRs with a neutron spectrometer. The footprint of the data product should be less than that of a large PSR so heterogeneity within the deposit can be investigated. Critical future lunar science missions include establishing a global lunar geophysical network, establishing an absolute crater chronology by targeting impact melt sample return from the oldest and youngest lunar craters. The young end of the crater count curve could also be constrained by in situ age dating of the youngest mare basalts (~1 Ga), although returning samples of these basalts would yield amore accurate age and allow detailed geochemical analyses and modeling of the young mantle source. More orbital data could be useful for understanding polar volatiles. - detection of surface water ice highly sensitive IR spectrometer and IR laser to give ppm detection, longer wavelength radar (L- and P-band). Scientists should provide better justification for polar regions because volatiles are present not just at the poles. Need to build science traceability matrix for polar and endogenous volatiles. Could we include a synthesis of the sample and RS datasets which ones are the best for different styles of operation and/or targets? Lunar Crust and Mantle Lunar meteorites (Dho-489) contain Mg-anorthosite (distinct from HMS) and the suggestion that anorthosites started forming earlier in the LMO crystallization was made. However, this requires a higher bulk Al2O3 content for the magma ocean. There is a new Fe map of the Moon using the Kaguya gamma-ray spectrometer article is in press in Icarus Naito et al. Hunting for the lunar mantle using mafic components identified from orbital data and although it depends on what we define as mantle, Sarah Crites showed where mantle could be with her mixing model.

3 XRD data of Apollo 17 soils were used as groundtruth for remote sensing data. Lunar granites/felsites have been dated using U-Pb (zircon), Ar-Ar, Rb-Sr, Sm- Nd, and K-Ca. The radiometric ages are all older than the crater count ages of silicic domes these domes aren t related to samples we have. In order to understand if lunar mantle is exposed on the surface of the Moon, we need to integrate diverse data sets to get the answer. Deconvolve compositions from Near-IR and compare with Diviner data. Can we identify mantle? Need to get the most out of RS data before sample return. We have mare basalts that samples the mantle but only from PKT. Nature of lunar crust is there an upper and lower crust? Still unclear. Mafic component imposed on PAN must come from mantle. Convergence of ages at ~4.3 Ga FAN, HMS, Mare source. Why? Jackson Crater (147 Ma old) to sample primitive Mg Anorthosite. Farside sample needed for calibration pf orbital RS data. Young basalt samples and SPA for young and old ages and mineralogy implications for mantle compositions. Silicic domes should be sampled. Lunar Interior Selene/Kaguya Lunar Radar Sounder (LRS). Buried regolith layers found by LRS on Selene. Correlation between CE-3 and LRS shown. GPR should be on Selene- R prospecting mission higher frequency 1-15 GHz. A global tectonics map was presented based upon LROC imagery and interpretations. 1:250,000 mapping on LRO WAC (100/pixel, uniform lighting geometry). Global map shows lack of structures around Crisium and Fecunditatis, and the interior of Procellarum. Usually associated with the edges of mare structures mapped! 4 major classification groups: flat floored, Scarps, V-shaped cross section, Catena (pits along their length). Vast majority of structures are V-shaped and are global. All others found predominantly in the nearside. Free core nutation (FCN) was discussed because there is no direct evidence of a liquid core. Need to use gravity measurements affected by the resonance of FCN. A gravimeter or laser interferometer anywhere on the lunar surface would be good to test FCN. Core super-cooling: Crystallization of fluid core creates density differences that generate magnetic field, but lower than the measured fields on old samples. Super-cooling of the fluid core could explain the observations only need a few 10s of Kelvin to achieve this. May be important for planetary cores, but gives very short time periods (10 5 years), but get factor of 10 increase in magnetic field. Combination of radar on the surface and from orbit would allow better understanding of the regolith and mega-regolith.

4 For understanding the lunar core, experiments with Fe alloys will be needed, and better connections with the metallurgy industry would be helpful. Surface gravimetry measurements over several lunar cycles would also be useful for examining if the outer core was liquid. Poster Session The data from SELENE multiband imager was used to derive new color polar mosaics of the Moon. A new crustal-component-enriched Bulk Silicate Moon composition was proposed based upon lunar meteorite data. The data support the addition of a crustal component enriched in Ba and Th to the cbsm from alkali-rich protobodies with chondritic refractory element ratios by heterogeneous accretion during impact. Particulate materials exhibit an inverse correlation of polarization and albedo. Data from eight lunar soils show such a correlation, but it is not linear. This is due to space weathering effects. The use of lunar lava tubes for human habitation should be the focus of future study. Lunar Craters, Impacts, and Surface Weathering Spin of the Moon can be investigated through long wave gravity and impacts can change the moment of inertia. Large impacts, like SPA, meant the Moon was spinning unstably after the impact, such that the farside would have faced Earth. The case for a classical terminal cataclysm is weak using lunar data, though meteorite data do show similar patterns. Many 3.9 Ga ages on the Moon are from Imbrium ejecta. Addressing these issues will require a combination of: o modeling of the composition of basin impact melt o petrology and geochemistry of samples to tie them to specific basins o detailed geochronology of multiple samples, ideally with multiple geochronologic systems o Such studies could be accomplished by landing and in situ dating, sample return to orbit, and/or sample return to Earth o Prime targets known at this time include the Crisium and Nectaris basins and the South Pole-Aitken (SPA) Basin Looking at differences before and after impacts on lunar surface, and at Cold Spots associated with fresh craters at the far UV wavelengths from LAMP. Unresolved question: Is LAMP seeing asymmetric space weathering of impact craters? Unresolved questions about Space Weathering and ways forward: o Does one process dominate (solar wind vs. micrometeorids) or are they both required (working together) to define space weathering? o Can laser experiments be translated to lunar surface weathering conditions? Can t get nanophase Fe with lasers. o Need hyperspectral imaging of the Moon expanded. o Need lab work: better ways to simulate impacts

5 How does space weathering affect the Christiensan Feature (CF)? More mature regolith has a longer CF than immature soil. Diviner CF shows clear effects of soil maturity. Lab studies shift CF to longer wavelengths. APL is studying different thermal gradients have on the CF. Effects likely tied to variations in the epiregolith thermal gradient. Next generation Diviner instrument needed. Space weathering in the far UV using Lyman Alpha shows nearside anomalies at 11.6 nm that are not swirls don t show up in radar or rock abundance, but do in CF. Discussion. In order to better understand Space Weathering, what are the missions/next steps that would help? Visit a swirl, high latitude regolith, understanding if micrometeoroid impacts alone can t make nanophase Fe. Specific places or samples that might address that? Swirl natural lab. Jackson crater. Look along a crater ray for SW rates. Lunar Surface: Regolith, Volcanism & Dust Different sensing techniques explore different regolith depths. Dividing the regolith up in vertical structure: Epiregolith: 0-2 cm (fairy castle, etc.); Shallow Regolith: 2-10 cm (cold spots); Deeper regolith >10 cm. Secondary impacts +primaries leads to much deeper and more rapid gardening of the regolith. Splotches are morphological lows and their size distribution and frequency = through reworking in 80,000 years to 2 cm. Cold spots = anomalous density features around new impacts. Very different physical features from splotches. Reworking down to 10 cm. Lot of mystery about what makes them and what destroys them. Secondary impacts dominate mixing in the upper meter. Radar X-band doesn t show the water ice signature that S-band does. Radar is important information on the locations, extents, and depths to individual flow units and deposits. Differences between S- and X-band observations of the same crater are also present, providing new insight into the size-distribution of radar scatters within ejecta. Outstanding questions remaining to be answered for pyroclastic deposits include: o Where are pyroclastic glasses found? Do all volcanic vents have o pyroclastic glasses? Do both large and small pyroclastic deposits contain volatile-bearing glasses? o Why don t pyroclastics at Sinus Aestuum have mapped water? o How do volatiles behave during an eruption? o How much water was present in source regions and how much variability is observed at different locations? o Are all pyroclastic deposit sites equal for communications to orbiters or Earth? o Are some sites more rugged than others (e.g., because of a high number and density of vents, impact craters, etc.)? o Are other potential resources nearby? Dust questions:

6 o Is adhesive force (gold s TDS photo NASA image AS Apollo 14 Preliminary Science Report) used in recent models? o Are measured differences of adhesion to horizontal & vertical used? Things for the future: Time for through mixing of regolith. Age of cold spots and what causes them and what makes them go away. Don t see cold spots around new craters <40 m. Instruments needed to get data to make progress: Infrared version of Shadow Cam, Laser spectrometer, hyper spectral imager, 6µm spectrometer to distinguish between molecular water and OH. Radar (L-band, sounder, meters-10s meters resolution). Selene radar was deeper than this. A polar orbiting LADEE. Magnetic field measurements. Global X-ray measurements. All orbiters going to Moon need to carry a com-relay capability. Robots for prospecting, e.g., pyroclastic deposits. Lunar Volatiles Despite all of the new data generated on endogenous lunar volatiles since the publication of New Views of the Moon, many important questions remain unanswered or only partially resolved. Advances could be made in the following ways: o Sample return from evolved crustal terranes (e.g., Compton-Belkovitch). o Continued research on volatiles in lunar samples for which little work has been reported, including high-ti basalts, high-al basalts, and Luna samples. o Any samples collected outside the PKT will be very important for determining whether there are differences in the volatile abundances between rocks within and outside the PKT. o Still unclear whether the H isotopic variations observed in lunar samples are being driven by fractionation processes, mixing of various reservoirs, or both. H isotopes were likely affected by secondary processes and mixing of multiple reservoirs, which preclude straightforward interpretations of the existing data. Combining solar wind H with Lunar Oxygen, a 2.5 cm thick layer around the Moon would form per billion years. Continuous supply of water to the Moon via solar wind, meteorites, and comets (Schorgofor and Taylor 2007). o Need: in situ water detection on and in polar regolith, isotopes to resolve origin of water, observatories combined landed stations (long lived) and orbiting asset (com relay as well as detection). Ground based observations or surface lunar water show latitudinal variations in surface H 2 O. Need targeted analyses of specific geologic features. Apatite in lunar meteorite NWA 2977 is water-poor, F-rich. Evidence for H 2 O is cryptic no pervasive post magmatic H 2 O-rich fluid. Internal versus surface water.

7 Internal new samples from different areas. Need experiments on H, H2, and H2O partitioning Future Mission Concepts Orbital mission data gathered since Apollo and Luna now allow targeted in situ and sample return missions to be developed: Analyzing the unopened Apollo samples will inform how to collect, return, and curate lunar volatile samples. Sample container design should learn from Apollo: (1) better, long lasting vacuum seals without the potential for indium contamination, (2) easier to use containers, (3) involve an overall general design that can be modified for specific samples, and (4) enable cryogenic cooling of samples to better preserve initial form of volatile compounds. Issues to be addressed: o Remote Analyses: Document and understand the lunar water cycle. Identify local source areas for Mg-suite crustal components. Characterize and distinguish properties of the lower crust from the lunar mantle and map their distribution. Identify-characterize-map potential localized resources. Provide iterative context analyses for landers and sample return. o In situ: Identify and map variations of diverse local geology and composition at lunar targets of interest. Characterize and confirm resources. Initiate geophysical stations to address crustal thickness variations, magnetics, heat flow, interior structure, shape and sharpness of crust-mantle boundary, etc. o Sample Return: Resolve planet-wide near-side/farside differences. Establish Solar System chronology by dating basin and crater events. Determine the composition and origin of the lower crust and mantle. Evaluate timing and diversity of secondary volcanism. APPROACH mission one penetrator with seismometer and heat flow. Three objectives understand the physical conditions of the lunar-forming giant impact, understand the thermal evolution of the Moon, undertand impact phenomena on the Moon. Seismometer 3 times as sensitive as Apollo at 1 Hz. Site in the center of PKT.

8 Rock Size Frequency distribution APPROACH landing site. Simulated the landing site rock abundance and how many times the penetrator would strike a rock ion that landing site. Simulation should 99% probability for success. Use radar data to get an idea of rocks at depth. Active seismic exploration package on the Moon. Target is shallow small seismometers and small source. Interested in ice deposits depth and thickness of ice layer. Deploy active-source and receivers on Lander and rover. Three seismic methods: 1) Surface wave analysis (most important for shallow ice deposits) estimate S- wave velocity in shallow formation ( 2 m). V S derived from surface wave is sensitive to the ice deposition. V S increases with ice deposition. 2) Seismic refraction source on lander and receiver on rover. Estimate P wave velocity to 100 m depth. Can integrate P and S wave velocities. 3) Seismic reflection method estimate P-wave velocity if we assume horizontally uniform structure. Use 9 m geophone array to estimate V P. Don t want to deploy the geophones on the Moon use a laser type receiver. New Views of the Moon 2: What s Next? Moon Diver (JPL development). Tethered rover to explore lava tubes. One lunar day but could survive the night if the surface lander could. Using Selene radar sounder to examine subsurface lava tubes. Looking at Mars as well as Moon. Using humanoid robot to explore lava tubes. Lava tube found in Marius Hills is close (~10 km) to the 1 Ga basalts (Rorus basalt) science and exploration suynergies? Lunar Samples won t be discussed explicitly in the NVM-2. Luna samples: JSC had 11 g and about half has been consumed. No big pieces left. 139 lunar meteorites (326 stones) kg total. Near surface, recently ejected. Somewhat limited availability. Antarctic meteorites ~40 in the 139 currently available. Science and engineering synergies. Samples-geophysics-context triad to get missions prioritized and put in context. It is essential to give engineers solid, quantitative requirements that don t change. Science needs to be involved at the beginning and requirements set early in the project. International Lunar Observatory Association proposes 4 Missions: ILO-1 to Malapert Mountain at the lunar south pole. This will be focused on central part of Milky Way. Possibly launched by India under discussion. ILO-X is a precursor Mission hopefully launching in Outreach is needed to report back to tax-payers about progress, especially with changing terminology. We need to be able to explain lunar science and exploration in plain language to general public. Steve Durst s Galaxy Forum is a good example of how to do this. EPO should be one of the research topics in lunar science. We need to undertake EPO as a public-private partnership or partnerships to raise money. Add an Appendix of EPO resources to NVM-2. JAXA Lunar and Planetary Exploration Data Analysis Group JLPEDA. Promotes scientific research, planning of space exploration, organization, facility

9 and strategic analysis of big datasets. Scientists and engineers represented. Working on polar regions and developing traverse maps. SLIM tech demo of pin-point landing. Discussion Points: Number of color plates $2,500/page. Several chapters refer to specific data products. The e-repository contains derived data products that can be used by the reader. This should be a first step for new user, next generation, general use and outreach efforts. BUT needs to link back to the original data set in the archive. This will be done. For EPO, which images would you need to use? Also for undergraduate teaching. Global maps should be in the same projection so they can be compared. Tectonics map would be a plate, but high-res in the e-repository. This cannot be everything to everyone we need to remember that. Standardize and choose a projection. Animations should be included. LRO Quickmap is also a resource that can be used. Community can suggest more maps for the community. GEOTIFF format. Color blind friendly? Can the PDF be color figures and the book = B&W? Need to check.