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Slide1: 

Testing the Giant Impact Hypothesis Harrison H. Schmitt University of Wisconsin-Madison GSA 2005

Slide2: 

Fundamental Lunar Science Question: What is the Connection?

Slide3: 

If Science Were Your Only Objective: Where Would You Send Me?????

Lunar Origin Standard Hypothesis: 

Lunar Origin Standard Hypothesis Giant Impact at ~4.55 B.Y. by Mars-sized Asteroid High Angular Momentum of Earth-Moon System Computer Modeling Provides Plausible Dynamics for Giant Impact Origin Most of Lunar Material and Geochemical “Anomalies” Provided by Impactor I.E., Impact Assisted Capture of Impactor Ejected Material’s Temperature raised to Several Thousands of Degrees

Challenges for Giant Impact Hypothesis - 1: 

Challenges for Giant Impact Hypothesis - 1 Undifferentiated, Primordial Components in Lower Mantle Volatile Element Concentrations in non-glass components of Apollo 17 Orange and Apollo 15 Green Volcanic Glass >>Mare Basalts (Meyer, Et Al, 1989) Primitive Lead in Orange Volcanic Glass (Nunes, Et Al 1974) Chondritic Tungsten in Orange Volcanic Glass (Lee, Et Al 1997) Distinctive Au/Ir and Zr/Y in Orange Volcanic Glass (Neal, 2000) Seismic and Trace Element Data Suggests Increased Aluminum As Garnet Below 500km (Hahn, 2000; Neal, 2001) Least Some of the Orange and Green Volcanic Glasses Initial Melt Apparently Formed With Garnet Present (Neal, 2001) Indicates Lower Mantle Has Not Melted (Goins, Et Al, 1981; Neal, 2001)

Challenges for Giant Impact Hypothesis - 2: 

Challenges for Giant Impact Hypothesis - 2 Hf/W Systematics Indicate Earth and Moon Core Forming Material Separated at ~30 M.Y. Whereas the Moon’s Core Dynamo Did Not Appear Until ~3.9 B.Y. Suggests Metallic Core Formation Delayed to ~3.9 B.Y. Cool, Largely Silicate Proto-core in the Way of Migrating Fe-rich Liquid? Lunar FeO and Hf/W Indicates Small Earth Mantle Component, If Any (Taylor/Esat, 1996; Jones/palme, 2000) However…….87Sr/86Sr Suggests Large Earth Mantle Component (Carson and Lugmair, 2000)

Origin of the MoonCapture Alternative to Giant Impact Hypothesis: 

Origin of the Moon Capture Alternative to Giant Impact Hypothesis Capture Hypothesis: The Moon and the Earth Formed As Independent Planets in the Same Part of the Solar System Moon Captured by the Earth Prior to at Least 2.5 Billion Years Ago, the Age of the Oldest Known Evidence of Tidal Interaction. Same Oxygen Isotope Feeding Zone of ~1 AU±0.5 Possibly at Sun-Earth Libration Point Additional Lunar Devolatilization Relative to the Earth by Impact Effects During Formation of the Magma Ocean Extremely High Temperatures at Each Point of Impact in <1/6th Gravity Field

Origin of the MoonProblems for Capture Hypothesis: 

Origin of the Moon Problems for Capture Hypothesis No Modern Modeling Studies to Support Capture: Considered Very Low Physical Probability Capture, However, Is a Relatively Common Phenomenon in the Solar System (Mars, Asteroids, Giant Planet Moons, Kuiper Belt. No Significant Modeling Effort Since 1972 Accounting for the High Angular Momentum of Earth-moon System Potential Dynamics of Capture or Cumulative Effect of Post-capture Accretion Accounting for Out-of-ecliptic Orbit and Non-parallel Rotational Axis Cumulative Effect of Post-capture Impactors ?

Slide9: 

My Suggestion For Science Mission: Southwestern Rim of Serenitatis (SCULPICCIUS GALLES REGION) AS17-153-23564

Slide10: 

APPARENT COLLAPSE CRATER WITH OBSERVED RED, ORANGE AND BLACK LAYERS BENEATH RIM (Visually observed by the presenter from orbit and on the prime film.) AS17-149-22882

Slide11: 

SHORTY CRATER NORTH WALL OF CRATER WEST WALL OF CRATER SCULPICCIUS GALLES REGION SW EDGE SERENITATIS BASIN 50µ 30M 5KM PYROCLASTIC GLASS DEPOSITS TAURUS LITTROW 25KM PYROCLASTICS LOW-TI MARE BASALT NASA PHOTOS

Slide12: 

SHORTY CRATER ORANGE “SOIL” (PYROCLASTIC GLASS) ~20CM FRACTURED BASALT BOULDER CRATER RIM LIGHT-GRAY OUTER WALL MATERIAL REDDISH ZONE ORANGE INNER ZONE COLOR REFERENCE 70CM CORE UPPER 20CM ORANGE LOWER 50 CM BLACK © HARRISON H. SCHMITT UNIVERSITY OF WISCONSIN-MADISON NASA PHOTO YELLOWISH OUTER ZONE

Slide13: 

RETURN TO THE MOON HARRISON H. SCHMITT A PRAXIS-SPRINGER BOOK 2005 NASA PHOTO