Chapter 13 – History in the Dust – Contents

History in the Dust

This chapter chronicles the technical analyses and interpretations, both geochemical and geological, by Dr. Harrison H. Schmitt of the observations and samples from the surface of Taurus-Littrow obtained during the three days he spent on the Moon in December, 1972 as a member of the Apollo 17 crew.

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Table of Contents

The Regolith of Taurus-Littrow: Strata, Source Craters, Ages and Implications

Preface

Major Findings

Summary of the 13 major findings resulting from the synthesis of data related to the observations and samples of regolith in the valley of Taurus-Littrow.

1.0 Introduction

General review of the sources of data related to this synthesis.

1.1 General Nature of Lunar Regolith

2.0 Error Limits Related to Taurus-Littrow Data Synthesis

3.0 Apollo 17 Deep Drill Core

Definition and analysis of the 11 regolith ejecta zones (strata) in the 2.85 m long deep drill core and their source impact craters based on half-cm log of the core and ejecta zone lithologies.

3.1 Introduction

3.2 Deep Drill Core Maturity Indices and Regolith Ejecta Zones

3.2.1 Agglutinate Formation in Relation to Is/FeO Maturity Index

3.3 Regolith Transport After Large Impacts in Lunar Gravity and Vacuum

3.4 Source Craters for Regolith Ejecta in Deep Drill Core

3.4.1 Lara Crater as Possible Source Crater

3.4.2 Possible Source Craters on the Massifs

3.4.3 Reach of Each Source Crater’s Regolith Ejecta

3.4.4 Summary

4.0 Process Sequence that Forms Inter-Crater Regolith

Details on the processes that formed the Taurus-Littrow regolith, including partial reset of Is/FeO values by impact shock and heat, as represented in the deep drill core and other Taurus-Littrow regolith samples.

4.1 Introduction

4.2 Impact Shock Partial Resets of Is/FeO Values

4.3 Summary of Detailed Is/FeO Log of Apollo 17 Deep Drill Core

5.0 Petrography and Composition of Deep Drill Core Regolith Zones

Detailed compositional modeling of the regolith ejecta zones in the deep drill core in relation to the geological context and nature of regolith at the site of a zone’s source crater.

5.1 Introduction

5.2 Compositional Modeling of Source Regolith for Deep Drill Core Regolith Ejecta Zones

6.0 ΔIs/FeO-Based Ages of Source Crater Impacts and Zone Deposition

Calculation of ∆Is/FeO / Myr values for alpha+beta and solar proton additions to regolith Is/FeO and preliminary ∆Is/FeO-based exposure age dating of the source craters related to each regolith ejecta zone in the deep drill core, including an analysis of related nitrogen isotopic fractionation data.

6.1 Introduction

6.2 Nitrogen Isotopic Ratios in the Deep Drill Core

6.2.1 Introduction

6.2.2 Detailed Relationships Between ∆Is/FeO and δ15N‰ in the Deep Drill Core

6.2.3 Second Change in the Energy of the Solar Wind Late in Lunar History

6.3 Solar Proton and Uranium+Thorium Alpha+Beta Decay Particles Contributions to ∆Is/FeO / Myr

6.3.1 Introduction

6.3.2 Alpha+Beta-only ∆Is/FeO / Myr

6.3.3 Solar Proton-only ∆Is/FeO / Myr

6.3.4 Regolith Particle Patinas Possible Role in Attenuation of Proton-only ∆Is/FeO

6.4 ∆Is/FeO Derived Exposure and Deposition Ages for Deep Drill Core Zones

6.4.1 Introduction

6.4.2 Evaluation of Deep Drill Core Cosmic Ray Exposure Ages

6.4.3 Potential Fractionation of Light Isotopes of Noble Gas Spallation Products during Regolith Maturation

6.4.4 Depth Corrections for Post-Burial Additions to Apparent Cosmic Ray Exposure Ages

7.0 Ilmenite and Volcanic Ash Attenuation of Nano-Phase Iron Formation During Regolith Maturation

Final ∆Is/FeO-based exposure age dating of the source craters related to each regolith ejecta zone in the deep drill core, as adjusted for Is/FeO attenuation by volcanic glass and ilmenite.

7.1 Introduction

7.2 Ilmenite Attenuation of Nano-Phase Iron Formation

7.3 Pyroclastic Ash Attenuation of Nano-Phase Iron Formation and Corrected Deep Drill Core Ages

8.0 Comparison of Deep Drill Core Zone, Is/FeO-based Exposure Ages with Integrated Cosmic Ray Exposure Ages

Analysis of the contrast between ∆Is/FeO-based exposure ages and cosmic ray exposure values.

9.0 Rate of Impact Is/FeO Resets Recorded in Deep Drill Core and Apollo 17 Neutron Probe Stratigraphic Interpretation of Deep Drill Core

9.1 Rate of Impact Is/FeO Resets

9.2 Apollo 17 Neutron Probe Stratigraphic Interpretation of Deep Drill Core

10.0 Geology and Maturation of Orange+Black Ash at Shorty Crater

Detailed synthesis of observations and data related to the orange+black ash at Shorty Crater, in particular, as related to the core 74001/2 from this nearly pristine pyroclastic ash deposit.

10.1 Geological Context of the Orange+Black Ash Deposit

10.2 Regolith Development on Ash Deposits

10.3 Deposition Ages of Orange+Black Ash Deposit

10.4 Pyroclastic Record of the Decline of the Ancient Lunar Magnetic Field

10.5 Primordial δ15N‰ for the Moon

10.6 Very Low Titanium (VLT) Ash Eruptions

11.0 Light Gray Regolith

Geology and implications of the light gray regolith ejecta deposit that protected the orange+black ash in situ for ~3.5 billion years.

11.1 Introduction

11.2 Inconsistency Between Cosmic Ray Ages and Is/FeO Values

12.0 Lunar History in Nitrogen Isotopic Data from Shorty Crater Pyroclastic Ash and Light Gray Regolith

13.0 Solar and Lunar History in Regolith and Regolith Breccias at Van Serg Crater

13.1 Introduction

13.2 Regolith Ejecta Sequence at Van Serg Crater and its Correlation with Deep Drill Core Zones

13.3 Deposition Age Estimates for Regoiith Ejecta Zones Sampled at Van Serg Crater

13.4 Solar History in Nitrogen Isotopes at Van Serg Crater

14.0 Nitrogen Isotopes Implications Relative to Solar History

Implications of variations in the values of δ15N‰ (14N/15N ratio) as related to the composition of the solar wind over time.

15.0 Source Crater Ages Versus Diameter to Depth Ratios

16.0 Average Frequency of Large, Proton-Only Increases in ∆Is/FeO In the Half-Cm Record of the Deep Drill Core

17.0 Geology of the Light Mantle Avalanche Deposits

Analysis of the geology and ages of three South Massif avalanche deposits that make up the light mantle unit in Taurus-Littrow.

17.1 Introduction

17.2 General Relationships

17.3 Light Mantle Avalanche Dynamics

17.4 Deposition Age of the Young Light Mantle

17.5 Stratigraphy of Light Mantles in Core 73001/2

17.6 Stratigraphic Data in Core 73001/2

17.7 Deposition Age of the Old Light Mantle

17.8 Age of the Ancient Light Mantle Avalanche

17.9 Summary of the Detailed Is/FeO Log of Double Drive Tube Core 73001/2

17.10 Regolith Accumulation on the South Massif Slope

17.11 Basaltic Regolith and Pyroclastic Ash Ejecta Deposition on the South Massif Slope

17.12 Relationships of Station 3 Trench Samples to Core 73001/2

17.13 Lee-Lincoln Thrust Fault Activity Triggers for Light Mantle Avalanches

18.0 Thermo-luminescence of Taurus-Littrow Regolith

Geological interpretations of thermo-luminescence values in Station 6 regolith and the deep drill core.

18.1 Introduction

18.2 Continuously Shaded Regolith Sample 76240

18.3 Periodically Shaded Regolith Samples 72220 and 72320

18.4 Buried Zones in the Deep Drill Core

19.0 Regolith Core 76001 from North Massif Station 6

Geological history of North Massif slope regolith.

19.1 Introduction

19.2 Petrographic, Petrological and Maturation Variables in Core 76001

19.3 Exposure Age Considerations Related to Core 76001

20.0 Orange+Black and VLT Ash Distribution in North Massif Slope Regolith

21.0 Boulder Tracks in Massif Regolith

21.1 Introduction

21.2 Longevity of Massif Boulder Tracks

22.0 Age of Imbrium Basin-Forming Impact Between 3.850 and 3.795 Ga

23.0 Dark Mantle Dilution of Light Mantle Regolith

24.0 ∆Is/FeO / Myr Considerations Related to Station 1 Samples

25.0 Lithoclastic Debris Erupted Prior to Basalt Eruption

Evidence for pre-mare basalt eruption of lithoclastic debris due to release of volatiles as heat accumulation in the upper mantle approached partial melting.

25.1 Introduction

25.2 Presence of Lithoclastic Debris in North Massif Slope Regolith

25.3 Summary

26.0 Volatile Concentrations in Bulk Regolith vs. Regolith Breccias

27.0 Symplectites in Dunite 72415 and Troctolite 76535

Pressure release origin for symplectites, as evidence for a Procellarum basin-forming impact at ~4.35 Ga.

27.1 Introduction

27.2 Lunar Symplectite Petrogenesis

27.3 Norwegian Basal Gneiss Region Symplectite Analogs

27.4 Procellarum Basin-forming Impact

27.5 Summary

28.0 Fractional Crystallization of Station 1 Ilmenite Basalt