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Summary Slides

Summary Slides. Geo 50 – October 10, 2012 All Summaries Prior to the Midterm. The Moon: History of Exploration.  Telescopic Phase: Galileo  Photography: Mid-1800’s  Sputnik - 1957  Gagarin - 1961  Kennedy’s National Goal  Space Missions: The US-USSR Space Race

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Summary Slides

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  1. Summary Slides Geo 50 – October 10, 2012 All Summaries Prior to the Midterm

  2. The Moon: History of Exploration  Telescopic Phase: Galileo  Photography: Mid-1800’s  Sputnik - 1957  Gagarin - 1961  Kennedy’s National Goal  Space Missions: The US-USSR Space Race • 1959 Luna 3 (Farside) • 1964 Ranger 7, 8, 9 • 1966 Luna 9 (Soft Lander) • 1966 Surveyor I, III, V, VI, VII • 1966-1967 Lunar Orbiter I-V • 1969-1972 Apollo 11-17 • 1970-1976 Luna 16, 20, 24 • 1970 Lunakhod I, II, Zond spacecraft • 1990’s Galileo, Clementine, Lunar Prospector • 2000’s Japanese, US, Indian, Chinese missions  Future Plans • A lunar base? 1969

  3. The Moon - Characteristics and Surface Provinces

  4. The Interior of the Moon  Results • Less Natural Activity than Earth - ~10-20 quakes per year; <2 on Richter Scale - Energy expended ~0.1-10 lbs TNT; (10-7-10-10 of Earth) - Quakes occur at great depth - ~800-1000 km depth on the Moon - ~25 km depth on Earth - No correlation with surface features! - Occur coincident with lunar orbit cycles - Moonquakes are due to tides raised in the Moon by Earth and Sun - Seismic structure: - Revealed three major layers - Crust: 0-60 km; Vp < 6.5 km/sec - Mantle: 60-1400 km Vp ~8 km/sec - Small core? 1400-1700 km S-waves attenuated P-waves slower

  5. The Interior of the Moon  Implications • Layering Broadly Similar Between Earth and Moon - Layered interior: Chemical and mechanical • Important Differences: - Core: Small on the Moon 0.2 lunar radius versus 0.5 Earth radius - Lithosphere: Thick on the Moon 1000 km on the Moon versus 100 km on Earth What are implications for: Subsidence? Plate Tectonics? - Relationship of surface provinces.

  6. The Interior of the Moon  Results • Less Natural Activity than Earth - Mechanical layering - Present: Partially molten at ~800-1000 km Thick lithosphere!! - Past: What is the thermal evolution?? Area: 4π r2 Volume: 4/3π r3 - Positive gravity anomalies in mare - Mascons - Upper low velocity zone: Origin? - Role of impact cratering? - Megaregolith

  7. The Lithosphere of the Moon Impact Cratering Mechanics • Energy Partitioning and the Geological Effects Eh+ Ec + Epv + Ee + Es Heating Comminution Seismic Waves KE Reservoir of Kinetic Energy of Projectile (Velocity, Density, Size) Impact Plastic/Viscous Deformation Ejection of Material from Crater

  8. The Lithosphere of the Moon Lunar Craters and the Cratering Process • Sources of Information - Natural Earth craters - Explosion craters - Experimental impacts • Impact Cratering Mechanics - Stages in cratering events - Energy partitioning and the geological effects • The Lunar Cratering Record - Morphology of fresh craters - Multi-ringed impact basins • Summary - Impact Cratering as a Planetary Process

  9. The Lithosphere of the Moon  Summary - Impact Cratering as a Process • Major Source of Energy • Forms and Modifies Rock Material • Sculptures Planetary Surfaces • Major Degradational Process • Large-Scale Tectonic Process • Significant Process for Vertical and Lateral Mixing of Materials • Operates Over Very Short Time Periods, but Influence is Long- Lasting • Produces Thermal Anomalies • Significant in Planetary History (Density, Degradation, Flux) • Role on Planets with Atmospheres and impact on life (?)

  10. The Lithosphere of the Moon  Summary - Volcanism as a Process • 17% of Lunar Surface Covered With Mare Basalt • Mostly on the Nearside • Major Depositional Process • Large Number of Flow Units • Composition • Volcanism Active for Long Time • Thermal Evolution of the Interior • Ascent and Eruption Style • Eruption Rates

  11. Lunar Tectonics Summary • Moon is a one-plate planet. • Very quiet seismically. • Early period of heating and mild expansion. • Mare volcanism in basins, loading, flexure. • Later period of cooling and mild contraction. • Heat loss mechanism is conduction. • Tectonics: Vertical, loading and flexure, not lateral like Earth.

  12. Moon: Insights into the formative years of planetary history. • Ancient age of lunar crust. • Magma Ocean: Concept of wholesale melting. • Linkage of geological observations and accretionary theory. • Moon formed from impact of Mars-sized object into early Earth. • Lunar Interior: Crust, lithosphere and thermal evolution. • Differentiation, segregation instability and overturn. • The Moon as a “one-plate” planet in contrast to Earth. • Impact cratering is a fundamental geological process. • Cometary volatiles may accumulate near poles. • The Moon is a record of the first half of solar system history.

  13. The Lithosphere of Mercury  Impact Craters and Basins: • What is the influence of increased gravity? • Morphology: Looks like lunar farside - See craters from 100 m to 1000 km - Similar to the Moon but also different • Changes in crater morphology with increasing diameter - Interior of craters - Bowl-shaped <10 km - Transitional - Central peaks, flat floors, terraced walls - Interior terracing common: related to gravity? - Depth-diameter relationship - Exterior of craters - Secondary craters closer to the rim - Density of secondaries higher - Gravity keeps ejecta from travelling far • Basins - Peak rings at greater than 100 km - Earlier transition than on the Moon • Role of gravity and impact velocity • Conclusions

  14. The Lithosphere of Mercury Volcanic Activity and Igneous Processes: • Conclusions - Significant volcanic plains like lunar maria, but flood basalt mode and no albedo differences. - Different mineralogy? - Volcanism is very likely to have occurred in intercrater plains. Evidence is somewhat equivocal. - Could be basin ejecta - Could be flood lavas with no vents - Explosive volcanic activity: Evidence is seen (pits, pyroclastic deposits): relation to plains? - Crustal formation processes likely to be different: No anorthositic crust, higher crustal density. - Primary crust may blend with secondary crust!

  15. The Lithosphere of Mercury  Tectonism and Mountain Building: • No plate boundaries • No strike-slip and lateral offset • No major extension, graben - Some small graben in Caloris Basin • Some wrinkle ridges in plains • Major global scarps - Large scale, long - 100’s of km long, 1-2 km high - Globally distributed - Timing - After cratered terrain - Synchronous with smooth plains - Cause - Global compression - Cooling of lithosphere? - Solidification of core? • Summary - One-plate planet - A shrinking planet and global scale changes - Is this how plate tectonics starts?

  16. Mercury: Summary Planetary formational process led to the high metal/silica ratio in Mercury. • Geological history of Mercury: Moon-like but materials and processes differ: • Impact cratering • Volcanism: Very extensive, flood basalt style; intercrater plains likely volcanic. • Tectonism: Global and long-wavelength folding. Origin of plate tectonics? • Polar Processes: Ice in polar craters. Sources and preserved record. What are the radar reflective materials at the poles? Volatile species and their sources and sinks?: New discoveries on Hollows. Is Mercury still geologically active? Still an open question!

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