Results from the Lunar Reconnaissance Orbiter (LRO)

Amanda R. Hendrix Planetary Science Institute

The Moon: From Labs to Towns El Escorial 5 July 2016 topics • The LRO mission & some results • Results from UV Moon studies (including LRO) – Space weathering effects – Hydration • Future US missions – Lunar Flashlight – Lunar Resource Prospector – LunaH-Map Lunar Reconnaissance Orbiter (LRO) (2009) • The ﬁrst US mission to the Moon in over ten years • Camera is LROC – mapping the entire surface of the Moon at unprecedented resolutions (~0.5 m/pixel) Aristarchus Crater

1 kilometer WAC 689, 566, 321 nm RGB Boulders on floor of Aristarchus crater shed from central peak waiting for astronauts to sample!

Arrowed rock is 35 meters wide 670 m diameter crater: whole mosaic width is 10,000 pixels, stretched to preserve ejecta detail

Shadow or secondary ejecta?

464 meters wide Crater interior, 500 m wide Hevelius Formation (NW of Orientale)

WAC Global Mosaic 1/4 resolution (400 m/p) 17 km diameter

WAC Global Full Res 100 m/p Apollo 11 landing site

Apollo 12 landing site Luna 24 (rela&vely) recent lunar volcanism Irregular mare patches <~100 My Based on crater coun&ng studies

Braden et al. (2014) This area, near the crater Maskelyne (4.330°N, 33.750°E), is one of many newly discovered young volcanic deposits on the Moon. Called irregular mare patches, these areas are thought to be remnants of small basal&c erup&ons that occurred much later than the commonly accepted end of lunar volcanism, 1 to 1.5 billion years ago.

Water on the Moon

• Lunar samples (from Apollo & Soviet missions) hinted at

small amounts of H2O … but not widely believed! • Now we have multiple lines of evidence for lunar hydration – Especially in the permanently shadowed regions How could there be water at the lunar poles?

• The Sun never rises more than a few degrees above the polar horizon so the crater ﬂoors are in permanent shadow .

• The crater ﬂoors are very cold w/ temperatures ~25-30K (-405-415° F), so water molecules move very slowly and are trapped for billions of years.

Lunar north pole Temperature map (north pole) Evidence for Water at the Poles

Clementine Lunar Prospector (1994) (1999) Bistatic radar Neutron spectrometer LCROSS: impact into a polar PSR to look for

H2O in plume Water, water everywhere! Observations from the Moon Mineralogical Mapper (M3), Cassini and EPOXI showed wide spread evidence for hydroxyl (OH) and water

This map is made from INFRARED measurements

Clark et al. 2010 Blue, cyan, magenta and pink areas = adsorbed water and/or hydroxyl Red, green, yellow and orange = little to no water or hydroxyl Where could water come from?

Comets and Asteroids Solar Wind

Some of the H2O is likely present in the Moon inherently UV wavelength ranges

Lyman-alpha = 1216 Å = 121.6 nm

ISO report, 2007 Early UV Moon observations

• Wood, 1910; 316-326 nm

1910 Early UV Moon observations

• Wood, 1912; 316-326 nm

1910 Early UV Moon observations

• Wright, 1929; 360 nm Apollo 17 UVS (1972)

1180-1680 Å

Atmosphere: Provided upper limits on H, O, C, N, Kr, Xe,

H2, CO (Feldman & Morrison, 1991)

147 nm

Apollo 17 spectral reversal: mare regions are ~5% brighter than highlands at 147 nm

Lucke et al. 1976 Apollo 17 UVS spectrum compared to a SOLSTICE solar spectrum (red line). There is good agreement in spectral shape for λ>~140 nm. UV observations from the Moon • Apollo 16 – the Far Ultraviolet Camera/ Spectrograph (UVC)

• Primary objective: determine the location and extent of gaseous material (principally hydrogen) in preselected regions of the celestial sphere. • Camera capability included acquisition of direct imagery and spectroscopy of the same target. UV observations from the Moon UV observations from the Moon

International Ultraviolet ExpIorer (IUE)

Hopkins Ultraviolet Telescope (HUT) (Henry et al., 1995)

Apollo 17 UVS

0° HUT ca. 1995

Galileo Lunar Flybys, 1990, 1992 from Hendrix, 1996 Lunar MUV spectra

Sample Galileo UVS lunar measurements Consistent with Apollo 17

Hendrix 1996 Cassini UVIS

The Cassini UVIS made a single observation of the Moon during the Earth-Moon flyby on August 18, 1999.

~110-196 nm spectral range.

Spatial pixels on the Moon for the first time

The observation was designed such that the UVIS slit was oriented along the equator of the Moon and pointed at a fixed RA/Dec; the Moon moved along the length of the UVIS slit. As the Moon moved through the UVIS slit, signal was recorded first from the illuminated half of the disk, then the night-side. Still more UV observations of the Moon …

• Rocket experiments • HST/STIS • UIT • NOZOMI • SSBUV • EUVE • GOME • SOLSTICE • Rosetta Alice • LADEE • LCROSS • SNOE (Student Nitric Oxide Explorer) • And more! • Several have resulted in solar phase curves, useful for understanding photometric characteristics LAMP: LRO LAMP FUV Spectrograph Lyman alpha mapping project Mass: 6.08 kg Power: 4.8 W λ Range: 57-196 nm FOV: 0.3º×6.0º Filled-Slit λ Range: <4 nm LAMP atmosphere measurements

• LAMP has provided stricter upper limits on the Apollo 17 UVS-measured species (Cook et al., 2013) • Detected helium (Stern et al., 2012) Variations in Lunar Helium – correlated with solar wind (Feldman et al, 2012)

– A clear decrease is observed during passages into the Earth’s magnetotail – Models show correlations with thermal release from the dayside surface (red points);

Monte Carlo model by Dana Hurley assumes a constant solar wind alpha flux of 1.2 x 107 cm2 s1 PSR Water Frost – LAMP measurements (Gladstone et al., 2012)

Water Frost Abundance 2.0% 1.0% 0.8% 0.3% The strong UV absorption by H2O

wow!

The strong UV absorption means this is a very sensitive detector of H2O ice Water spectral signature in FUV (thermal emission is not an issue) LAMPS’s dayside measurements of hydration

intimate mixture models

164-173 nm Spectral slopes: 175-190 nm

morning afternoon

-no diurnal variation Spectral slopes: 164-173 nm

Dawn Noon Dusk Less Hydration More Hydration Less Hydration More

After Hendrix et al., JGR, 2012…. here using data from Oct 2009-Dec 2012

To determine slopes, we correct reflectance using µ0/(µ+µ0) then measure slope of a straight line fit to 164-173 nm region Spectral slopes: 164-173 nm

Dawn Noon Dusk Relatively red slopes = hydration at colder places

Blue slopes = no water near mid-day Less Hydration More Hydration Less Hydration More

After Hendrix et al., JGR, 2012…. here using data from Oct 2009-Dec 2012

To determine slopes, we correct reflectance using µ0/(µ+µ0) then measure slope of a straight line fit to 164-173 nm region Hendrix et al. (2012) current (thru June 2011) (thru July 2013) Back to the topic of why the Apollo 17 UVS and HUT spectra were different …

Apollo 17 UVS

HUT

Terrain type differences

Compositional differences due to time of day/observational geometry LAMP – dayside observations

Composition • Opaques: Maria are bluer than highlands

• The presence of H2O at certain locations/times of day affects spectral slope in 164-173 nm region

Weathering • All regions are somewhat blue in the FUV • Less-weathered regions are redder (or less blue) in the FUV

Western Equatorial Hemisphere WAC Map matched to LAMP res.

61 LAMP Ly-α: Spectral Reversal

62 Why is there a spectral reversal? • Mare material have higher index of refraction relative to highlands material • At shorter wavelengths, surface scattering dominates over volume scattering so that reflectance is directly related to the index of refraction

volume scattering ~ exp (-αD ), where α= 4πk /λ

surface scattering ~ [(n -1)2+k2]/[(n+1)2+k2 • However, the correlation between visibly bright and UV-dark lunar regions as is imperfect, and UV spectra may therefore contain more information than what is known from visible spectra (Henry et al. 1976). UV Effects of Space Weathering

• Wagner et al. (1987) pointed out that lunar soils exhibit the spectral reversal - while powdered lunar rocks do not – This links the spectral reversal to space weathering • The UV is an ideal region in which to study space weathering effects – UV radiation is less penetrating than visible radiation. So we’re sensing • the uppermost layers of regolith • the weather-induced rims of grains (e.g. Keller et al., 2000) VNIR: weathered soils are darker, redder Lunar samples

Thick: soils

Thin: rocks

LUNAR SAMPLES Data from Wagner et al. (1987) Hendrix & Vilas (2006) VNIR: weathered soils are darker, redder Lunar samples

Thick: soils

Thin: rocks • UV: weathered soils are bluer, relatively bright • Note that rocks have steeper UV slopes • Note the FUV upturn in the soils – similar to how the moon itself behaves

LUNAR SAMPLES The UV dropoff degrades in response to weathering - From Wagner et al. (1987) consistent with the nanophase iron idea. Slope-slope plot: lunar samples

Lunar soils more weathered Lunar rocks less weathered VNIR slope (550-1640 nm) slope VNIR

NUV slope (300-400 nm) Hendrix & Vilas 2006 Hapke, 2001 Hapke, 2001 UV effects of space weathering

• So what we’re likely seeing in response to weathering in the UV is a “weathering away” of the UV absorption that is typical of silicates

Hendrix and Vilas, 2006

Swirls: Reiner Gamma

Denevi et al. (2014) have demonstrated that swirls LROC WAC: Vis, left; UV, right exhibit steep 321/416 nm ratios – consistent with a lack of weathering.

Swirls: redder than surrounding terrain, consistent with low amounts of space weathering

Reiner Gamma

Hendrix et al. (2016) Swirls: redder than surrounding terrain, consistent with low amounts of space

1" 2" weathering

4" Gerasimovich

3" 1"

Hendrix et al. (2016) The far-UV swirl is redder than surrounding terrain

9°N

LAMP: ratio image 5°N Hendrix et al., 2016 Garrick-Bethell et al., 2011 299°E 304°E Summary & Conclusions • The UV wavelength range is a useful and interesting region in which to study the surface of the Moon

– Sense presence of H2O (and other volatiles) – Study weathering effects • Important applications at other airless bodies – e.g. icy moons, primitive bodies Future NASA missions Lunar Flashlight

Looking for surface ice deposits and identifying favorable locations for in-situ utilization in lunar south pole cold traps

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0.45$ ice$ 0.5wt%$ 0.4$ 1.0wt%$

Reﬂectance( 2.0wt%$ Mission Approach 0.35$ 5.0wt%$

0.3$ 10wt%$ • JPL-MSFC Team 20wt%$ 0.25$ 40wt%$ 80wt%$ • 6U spacecraft, 14 kg 0.2$ regolith$ 0.5$ 1$ 1.5$ 2$ 2.5$ • Launch on SLS EM-1 in 2018 Wavelength((microns)( • Chemical propulsion system Measurement Approach • 1-2 micron spectrometer • Active multiband • Elliptical orbit (20-9,000 km, reflectrometry using lasers in 12 hr period) 4 near-IR water bands to • Science phase: ~10min illuminate 1 km spots on the passes, 60 orbits lunar surface 81 Resource Prospector (RP) Overview

Mission: • Characterize the nature and distribution of water/volatiles in lunar polar sub-surface materials • Demonstrate ISRU processing of lunar regolith

2 kilometers 100-m radius landing ellipse

Project Timeline: RP Specs: ü FY13: Pre-Phase A: MCR (Pre-Formulation) Mission Life: 6-14 earth days (extended missions being studied) ü FY14: Phase A (Formulation) Rover + Payload Mass: 300 kg ü FY15: Phase A (Demonstration: RP15) Total system wet mass (on LV): 5000 kg • FY16: Phase A (Risk Reduction) Rover Dimensions: 1.4m x 1.4m x 2m • FY17: Phase B: SRR/MDR Rover Power (nom): 300W • FY18: PDR (Implementation) Customer: HEOMD/AES • FY19: CDR (Critical design) Cost: ~$250M (excl LV) • FY20: I&T Mission Class: D-Cat3 • FY21: RP launch Launch Vehicle: Falcon 9 v1.1

ColapreteTitle_Design Editor No ITAR/EAR export materials herein 10/21/2015 82 Determining ‘Operationally Useful’ Deposits

We know that water (and other H-bearing compounds) is there, but not at the scales of utilization Need to assess the extent of the resource ‘ore body’ Local Regions (100s to 1000s of meters) Vertical Profiles Distribution and Form

An ‘Operationally Useful’ Resource Depends on What is needed, How much is needed, and How often it is needed Potential Lunar Resource Needs*

§ 1,000 kg oxygen (O2) per year for life support backup (crew of 4) § 3,000 kg of O2 per lunar ascent module launch from surface to L1/L2 § 16,000 kg of O2 per reusable lunar lander ascent/descent vehicle to L1/L2 (fuel from Earth) § 30,000 kg of O2/Hydrogen (H2) per reusable lunar lander to L1/L2 (no Earth fuel needed) *Note: ISRU production numbers are only 1st order estimates for 4000 kg payload to/from lunar surface

ColapreteTitle_Design Editor No ITAR/EAR export materials herein 10/21/2015 83 Provide Data on How to Work in Polar Regions

Roving • Traversing in soft soil; Slippage or Burial • Sharp thermal gradients across rover and variable thermal interface with surface

Navigation • Performance of passive imaging for hazard detection and localization • Performance of active illumination (ﬂood lighting and laser projection) • Positive and negative obstacles (size, shape, distribution, composition) • Hazard / obstacle distributions at scales of ~10 cm Drilling • Understand rover/drill interactions on under lunar loading and slopes • Force on bit; Slip/unintended motion • Stances during drilling / stuck drill and options for stuck drill recovery • Unknown near-surface regolith compaction proﬁle / pre-load requirements

Planning and Operations • “Real-time” operations with 10-30 sec DTE latency • Chasing the sun and comm vs designing missions to survive extended LOS or lunar night • Uncertainties in DTMs and impact on planning

ColapreteTitle_Design Editor No ITAR/EAR export materials herein 10/21/2015 84 Resource Prospector – The Tool Box

Mobility Prospecting Processing & Analysis Rover Neutron Spectrometer System • Mobility system

• Cameras (NSS) • Surface interaction • Water-equivalent hydrogen > 0.5 Oxygen & Volatile Extraction wt% down to 1 meter depth Node (OVEN) NIR Volatiles Spectrometer • Volatile Content/Oxygen System (NIRVSS) Extraction by warming • Total sample mass • Surface H2O/OH identification

• Near-subsurface sample characterization Lunar Advanced Volatile • Drill site imaging Analysis (LAVA) • Drill site temperatures • Analytical volatile identification and quantification in delivered sample with GC/MS • Measure water content of regolith at 0.5% (weight) or Sampling greater • Characterize volatiles of Drill interest below 70 AMU • Subsurface sample acquisition • Auger for fast subsurface assay • Sample transfer for detailed subsurface assay

ColapreteTitle_Design Editor No ITAR/EAR export materials herein 10/21/2015 85 Thank you! Interested in the Moon?

• Check out: – LROC site • lroc.sese.asu.edu – LPOD (lunar photo of the day) • lpod.wikispaces.com