A new vision of water in the Moon
Masahiro Kayama1, 2
1Department of Earth and Planetary Materials Science, Tohoku University
2Creative Interdisciplinary Research Division, Frontier Research Institute forInterdisciplinary Sciences, Tohoku University

Introduction – Giant impact –Proto-Earth

Melt ?
Wet EarthAccretion

Giant Impact
TheiaSolid?

Dry? or Wet?
Moon

High (Melt) ? or Low energetic (Solid) ?
≒ Wet ? or Dry ? Moon (≒ interior !!)Introduction – Water of the Moon –▪Surface = Dry, but…
SpacecraftMeteorite▪Interior = Wet? Dry?
Previously dry, but recently…
• Water-rich minerals• Wet simulation model

ApolloSampleCalculation

Water-richMoon !?

Introduction – Water: the key to Moon’s history –Dry ?

Wet ?

Problem !
Contribution to the history

Giant Impact

Differentiation

Deep Moonquake→ High or Low energetic ?

→ Overturn ? Melt ?

→ Heat ? Fluid (water) ?

Introduction – Water resource –If water is available in the Moon,

annual space budget is reduced bySpacecraft$121, 000, 000,0000

Mining (He3, Metal)

Drinking

EatingBreathing

The purpose of this study
Introducing our and previous studies of lunar water:
Surface to Subsurface▪ Water near the poles and in the subsurface▪ Solar wind-induced OH on the regolith soil
▪ OH in the old anorthosite crust

Shallow to Deep Mantle▪ OH in the shallow to deep mantle▪ OH and H2O in the shallow KREEP-rich mantle▪ Fluid in the low seismic velocity zone

With a discussion of the Moon’s history
With the future plans (Sample return, Seismic and Neutrino)Surface water – The Deep Impact Spacecraft –Sunshine et al. (2009)

Deep Impact ⇒Basemap

Albedo Temperature
>4 μm

Water
2.8 μmH2O orHydrous phase
OH/H2OOHNear Infrared (NIR) spectrometer detected the water bands• 2.8-3.1 μm: OH, H2O and hydrous phase
Bulk water content of the soil: 0.3 wt.% (Volatility: 0.5 wt.%)Surface water – LCROSS Spacecraft –⇐ LCROSS spacecraft

Colaprete et al. (2010)

Near Infrared (NIR) spectrometer found the water bands• 2.2, 1.9, 1.4 μm: OH, H2O and Ice in the surface (~0.7 m depth)• Mainly Asteroid/Comet, Slightly Solar Wind origins

155 ± 12 kg = 5.6 ± 2.9 wt.% OH & H2O near the South Pole

Surface water – Apollo samples –Hydroxyl in the regolith agglutinate

Liu et al. (2010)

H implantation by the solar wind

Maximum 70 ppm
Water-rich regolith → Solar-wind induced hydroxyl
in the agglutination

Surface water – Apollo samples –Hydroxyl in the old lunar anorthosite crusts
Plagioclase:<1 ppb to <6.4 ppm

Olivine: <d.l.

⇩ Mantle: 11 ppm

Hui et al. (2010)

Subsurface water – Lunar meteorite –Hydroxyl/molecular water inlunar meteorite (Kayama et al. in submitted)

Bulk water content▪Spacecraft (the poles)
Lunar prospector: 0.1 wt.%?

Deep Impact: 0.3 wt.%
LCROSS: 5.6 wt.%

Chandrayaan-1: 80 ppm▪Lunar rocks (the PKT)
Basalt: <1 ppb?

Anorthosite: <1 ppb to• SiO2 (s) + 2H2O ↔ H4SiO4 (aq)(Moganite)(Water)>76 ppm>46 ppm(Silicic acid)

Sunlit surface: Fluid predicated moganite

Subsurface: Fluid can cold-trapped as water ice<6.4 ppm

Regolith: <70 ppm

Subsurface breccia: >46 ppm⇒ Most water-rich pole
Slight water from surface tosubsurface in the whole Moon

The purpose of this study
We will introduce our and previous studies of lunar water:
Surface to Subsurface▪ Water ice near the poles and in the subsurface▪ Solar wind-induced OH on the regolith soil
▪ OH in the old anorthosite crust

Shallow to Deep Mantle▪ OH in the shallow to deep mantle▪ OH and H2O in the shallow KREEP-rich mantle▪ Fluid in the low seismic velocity zone

With a discussion of the Moon’s history
With the future plans (Sample return, Seismic and Neutrino)Traces of water in the mantle
Procellarum Basin
MareMare Basin
0 km• Basaltic magma
SIMS & FTIRApatitePlagioclase (+EPMA)

Magma chamber
30 km• Gabbro (Mg-suite)
Olv, Pyx, Plg → SIMS & FTIR

Partial Melting• MeltMelt inclusion (Olivine-hosted)→ SIMS & FTIR

1100 km?
1740 km

SIMSFTIR

Water in the Mantle – Apollo samples –Lunar apatite with abundant volatilities

Boyce et al. (2010)▪ Apatite in KREEP-rich basalt▪ No correlation of H with Cl-S
▪ Assuming partition coefficient, melting rate,
NAMs %, degassing degree of the Earth
Apatite: up to 4000 ppm OH
Mantle: 6-30 ppm Water

Water in the Mantle – Apollo samples –High Pre-Eruptive Water-rich Melt Inclusions

Hauri et al. (2011)

Melt inclusion in olivine of High-Ti volcanic glass bead
10 μm

H2O (ppm)

H2O (ppm)▪ Olivine-hosted melt inclusions without magmatic degassing▪ Abundant volatilities (H, F, S, Cl) similar to MORB
Mantle: 79-409 ppm Water*Assuming partition coefficient, melting rate of the Earth*Degassing degree: 0 % (95-99 % for Apatite)

Water in the Mantle – Lunar meteorite –Water-rich gabbro and wet upper mantle beneath the PKT
lunar meteorite (Kayama et al. in submitted)
Olivine Hill
Reflectance

OH: 2.8-3.0 μm=3333-3550 cm–1

Bullialdus

Theophilus
2400

2700

3000

Wavelength (nm)MineralMode (vol.%)

Olivine51.0

238

Clinopyroxene

41.1

198

Plagioclase

7.1

85

Others

0.80Content (ppm)

Bulk content（ppm）
Mantle: >210 ± 88 ⇐ no assumptions▪Melt inclusion▪Olivine▪Clinopyroxene⇒ SIMS analysis

Wet Mantle
Geophysical constraints on water content of the mantle▪ Layered water distribution of the lunar magma ocean▪ Water estimation of the Mantle by Electric conductivity and Tidal Q*Olv & Opx, <4.5 GPa, Low/High f, rQ=0.3-0.6
Water content of the Mantle: 0.1-0.01 wt.%
Quicker accretion of the fragment than cooling after Giant Impact

Dry Mantle
Dry Mantle based on chlorine isotope

Sharp et al. (2010)▪ Chlorine isotope of the Apollo basalt, volcanic glass and apatite▪ δ37Cl in Lunar rocks: -1-+24 ‰ *in Earth’s rocks: 0-1.6 ‰▪ Inferred mantle water content: <10 ppb H, based on δ37Cl
Mostly Dry, but rarely Wet Mantle view?

Dry Mantle
High energetic Giant Impact model

Wang and Jocobsen (2016)▪ Water-heterogeneous view of the Mantle, but…
▪ Overall Wet? (11-409 ppm) or Dry? (<1-10 ppb)
▪ Close relationship with the Giant Impact model !!

In the future plan
Seismic tomography

Mantle overturnGiant impact
Melt?

Solid?

Interpreted by a comparison of water distribution of theMoon’s with thermal gradient
Seismology

Neutrino Geophysics

Thank you for your attention !!