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GRAIL: Exploring the Moon from Crust to Core

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GRAIL: Exploring the Moon from Crust to Core LIVE INTERACTIVE LEARNING @ YOUR DESKTOP GRAIL: Exploring the Moon from Crust to Core Presented by: Dr. Sami Asmar and Don Boonstra June 2, 2011 Exploring the Lunar Interior Structure Crust To Core Via GRAIL Gravitational Field Measurements June 2011 Copyright 2011 California Institute of Technology Government sponsorship acknowledged Presenter: Sami Asmar Co-Investigator & GRAIL Deputy Project Scientist Jet Propulsion Laboratory California Institute of Technology The Earth/Moon System • Moon’s mean radius: 1737 km • Ratio of Moon/Earth radii 1/3.67 • Mass ratio of Moon/Earth is 1/81.301 • Mean density of the Moon is 3.35 times the density of water • Saturn floats in water! • Moon’s highest point above mean: +11 km • Moon’s lowest point below mean: -9 km • Moon’s surface area is 3.79x107 km2 • Asia’s surface area: 4.46x107 km2 • Africa: 3.02x107 km2 • Moon’s age ~4.5 billion years What if the Moon Did Not Exist? Contribute your thinking in the Chat What if the Moon Did Not Exist • The day would be eight hours long • The winds would be much stronger • Life, if any, might have a different biology • No honeymoons! • No lunatics! • Darker nights • No lunar calendar • No lecture today The Moon is moving away (3.8 cm per year) Great coincidence for perfect solar eclipses How did Earth get Its Moon? A. They formed together in this orbit (accretion) B. Earth captured the moon C.There was a giant impact The giant impact and the origin of the Moon Notional view of the lunar interior Wieczorek et al. [2006] Measurement Technique: Differential One-Way Ranging 2 1 4 3 x x x Let’s pause for questions from the audience Gravity and topography geochemistry petrology geology gravity -300 +300 mGal crustal density crustal thickness geophysical model elastic thickness load density surface-subsurface load ratio phase relationship of loads topography internal structure & thermal evolution -9 +10 km Comparing Gravity & Topography Admittance & coherence Surface load SELENE GRAIL Lithospheric crust, ρc Lithospheric mantle, ρm Subsurface load, Kaguya offset in phase Loading model predicts admittance and correlation spectra, which depend upon: GRAIL crustal density mantle density crustal thickness elastic thickness Kaguya magnitude of surface and subsurface loads phase relationship of loads Let’s pause for questions from the audience Thermal evolution: heat sources and sinks External Internal Heating Heating z Impacts z Radioactivity Cooling Cooling z Convection z Radiation Reconstruct source/sink contributions throughout geologic time Deep interior: Structure and state Apollo 11 retro-reflector • GRAIL gravity gives shape model (polar and equatorial flattening) • Lunar laser ranging gives physical librations • Since Apollo era • Combining the two allows us to deduce the existence of a lunar core inner core McDonald Observatory, Texas Ranging to the Moon If we had a good gravity field for the Moon, we could learn a lot. How do we get one? • Isaac Newton: Motion of satellite around a planet is largely due to the gravity field • Tracking the motion of a satellite is a good way to measure the gravity field • Since the Moon always keeps the same face toward the Earth, we cannot track a satellite on the farside directly from the Earth • But we can track one satellite with another satellite • This technique was pioneered with the GRACE mission around the Earth in 2002 • GRAIL is the GRACE concept carried to the moon x Solar Radiation Pressure to <0.001 mGal x Spacecraft IR Radiation x Lunar albedo & Lunar IR Project Overview Mission: Institutions: • Twin spacecraft launched on a ▪ MIT: Delta 2920H-10 ▪ Principal Investigator & Deputy • Launch in Sep. 2011 ▪ Science analysis & interpretation • Short duration of 9-months ▪ JPL: • 82 day mapping mission ▪ Project management, system • Low altitude, polar orbit engineering, mission assurance, mission operations, payload • Single payload mission development, science simulations • Imaging for education program & modeling, data processing Measurements: ▪ Contract with Lockheed Martin for spacecraft system ▪ Ka-band ranging measures relative velocity of the centers ▪ LM: of mass of two spacecraft ▪ Spacecraft development & flight ▪ Links to Deep Space Network for operations navigation, absolute position, and timing calibration ▪ GSFC: ▪ Data processing & analysis ▪ Sally Ride Science: ▪ Education & outreach cameras GRAIL Concept X-band Radio Science Beacon S-band link Telecom/Nav S-band Timing Code Ka-band ranging Let’s pause for questions from the audience Education Resources http://solarsystem.nasa.gov/yss How Long is a Year? A. About 3 Earth Months B. About 12 Earth months C.About 23 Earth months D.About 164.79 Earth years E. All of the above Education Resources Education Resources Education Resources Education Resources Eyes on Earth 3-D http://climate.nasa.gov/Eyes/ Thank you to the sponsor of tonight's Web Seminar: This web seminar contains information about programs, products, and services offered by third parties, as well as links to third-party websites. The presence of a listing or such information does not constitute an endorsement by NSTA of a particular company or organization, or its programs, products, or services. http://learningcenter.nsta.org http://www.elluminate.com National Science Teachers Association Dr. Francis Q. Eberle, Executive Director Zipporah Miller, Associate Executive Director Conferences and Programs Al Byers, Assistant Executive Director e-Learning NSTA Web Seminars Paul Tingler, Director Jeff Layman, Technical Coordinator LIVE INTERACTIVE LEARNING @ YOUR DESKTOP.
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