Lunar Polar Missions: Science and Instrumentation

1. Lunar Polar Missions: Science and Instrumentation Dr. Barbara Cohen VP40, Lunar Precursor Robotics Program MSFC Barbara.A.Cohen@nasa.gov

3. highlands feldspathic mare/maria basaltic Impact basins Aitken crater South Pole - Aitken Basin Impact craters South Pole Near side Far side

4. The Moon is a terrestrial planet • The Moon today presents a record of geologic processes of early planetary evolution: • Interior retains a record of the initial stages of planetary evolution • Crust has never been altered by plate tectonics (Earth) planetwide volcanism (Venus), or wind and water (Mars & Earth) • Surface exposed to billions of years of volatile input • The Moon holds a unique place in the evolution of rocky worlds - many fundamental concepts of planetary evolution were developed using the Moon • The Moon is ancient and preserves an early history • The Moon and Earth are related and formed from a common reservoir • Moon rocks originated through high-temperature processes with no involvement with water or organics

5. Lunar framework: Giant impact • Mars-sized body slammed into the proto-Earth at 4.56 Ga • Moon formed out of crust/upper mantle component - lack of metal • Moon material was hot - lack of volatile elements • Moon/Earth have shared angular momentum & oxygen isotopes

6. Lunar framework: Magma ocean • Differentiation via igneous processes • Basaltic volcanism via mantle density overturn • Incompatible elements in KREEP layer • Redistribution by impact processes

7. Lunar framework: Crater history • The Moon is the only place where the link is forged between radiometric ages of rocks and relative ages by crater counting • Crater record of the Moon reflects the flux of impactors in the inner solar system • Bombardment history of the Moon is magnified on the Earth

8. Lunar framework: Volatile record • Lunar plasma environment, atmosphere, regolith and polar regions in permanent shade constitute a single system in dynamic flux that links the interior of the Moon with the space environment and the volatile history of the solar system

9. Priorities for lunar science • Test the cataclysm hypothesis by determining the spacing in time of the creation of the lunar basins. • Anchor the early Earth-Moon impact flux curve by determining the age of the oldest lunar basin (South Pole-Aitken Basin). • Establish a precise absolute chronology. • Determine the compositional state (elemental, isotopic, mineralogic) and compositional distribution (lateral and depth) of the volatile component in lunar polar regions. • Determine the lateral extent and composition of the primary feldspathic crust, KREEP layer, and other products of planetary differentiation. • Determine the thickness of the lunar crust (upper and lower) and characterize its lateral variability on regional and global scales. • Characterize the chemical/physical stratification in the mantle, particularly the nature of the putative 500-km discontinuity and the composition of the lower mantle. • Determine the global density, composition, and time variability of the fragile lunar atmosphere before it is perturbed by further human activity. • Determine the size, composition, and state (solid/liquid) of the core of the Moon. • Inventory the variety, age, distribution, and origin of lunar rock types. • Determine the size, charge, and spatial distribution of electrostatically transported dust grains and assess their likely effects on lunar exploration and lunar-based astronomy.

10. Robotic lunar exploration objectives • Global mapping of the lunar surface • Identify optimal landing site(s) on the Moon for robotic and human explorers • Find and characterize resources that make exploration affordable and sustainable • Locate and characterize lunar volatiles • Characterize sunlight and surface environment of poles • Field test new equipment, technologies and approaches (e.g., dust and radiation mitigation) • Support demonstration, validation, and establishment of heritage of systems for use on human missions • Determine how life will adapt to space environments • Emplace infrastructure to support human exploration • Gain operational experience in lunar environments • Provide opportunities for industry, educational and international partners

11. The “dark side” and eternal light

12. Permanent sunlight and shadow • Because of solar inclination angle, topography is important at the poles • Some polar high points are in near-permanent sunlight • Some polar crater floors are in permanent shadow - cold traps!

13. Polar volatiles • Lunar Prospector - orbiter in 1990’s • Carried a Neutron Spectrometer to measure H - but LP NS pixels are large (> 40 km) • LP data indicate polar H content of ~150-200 ppm • H could be from solar wind (uniform distribution over light & dark areas) • H could be as OH- or H2O from comet and asteroid input cold-trapped in permanent shadow (heterogeneous distribution only in dark areas) • Mission data that can help: • Measure H content of illuminated regolith: • If H content ~ 150 ppm, then H is of solar wind origin and uniformly distributed • If H content << 150 ppm, then H is probably segregated and concentrated in cold traps • Explore shadowed areas to determine the form, distribution, and useability of H and other volatiles such as CO2, organic, etc.

14. Neutron signature

15. Radar signature

16. Notational site - Shackleton Permanently dark crater South Pole (Approx.) To Earth Landing Zone Shackleton Rim Candidate site 5 km 0

17. Possible mission elements • Surface Morphology / Lighting • Mast-mounted stereo imaging system OR alternative in dark regions such as radar / lidar / UV / enhanced vis-IR • Regional subsurface structure • Seismic using an active source (lander) and passive distributed receivers • Several mining techniques could help in this area but as yet are not fully described • Regolith H (and other volatiles) nature and content • Drill/penetrometers (need to penetrate below ~10 cm desiccated layer; from LP neutron data) • Mass Specrometer (MS) system to measure volatile species, concentration, and isotopic ratios • Sample handling system to get sample to instruments OR instrument to sample • Neutron Signature • Neutron spectrometer (ground truth orbital data) • Geotechnical Properties • Drill / arm to measure properties in situ with exchangeable end-effectors • Remote sensing of Elemental and Mineralogy • X-ray techniques (APXS from MER, Raman spectroscopy, X-ray Fluorescence XRF, etc.)

18. Some possible instruments

19. Current missions: LRO/LCROSS

20. Proposed penetrometer missions • JAXA mission Lunar-A (now cancelled) • http://www.isas.jaxa.jp/e/enterp/missions/lunar-a/index.shtml • Two penetrometers, payload mass on each ~10 kg? • Two-component seismometer • Heat-flow probe • Tiltmeter and accelerometer • UK Penetrometer studies and proposals • http://www.mssl.ucl.ac.uk/planetary/missions/Micro_Penetrators.php • Penetrometer payload, Total Mass ~2Kg • Accelerometer & tiltmeter • Seismometers • Thermal • Geochemistry • Options: mineralogy camera, radiation monitor, magnetometer