LIVE INTERACTIVE YOUR DESKTOP June 2, 2011 GRAIL: Exploring the Moon from Crust to Core Presented by: Dr. Sami Asmar and Don Boonstra

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/ 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 3.79x10 7 km 2 Asia’s surface area: 4.46x10 7 km 2 Africa: 3.02x10 7 km 2 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

Wieczorek et al. [2006] Notional view of the lunar interior

Measurement Technique: Differential One-Way Ranging

x

x

x

Let’s pause for questions from the audience

crustal density crustal thickness elastic thickness load density surface-subsurface load ratio phase relationship of loads gravity topography geophysical model internal structure & thermal evolution geochemistry petrology geology Gravity and topography mGal km

Comparing Gravity & Topography Admittance & coherence Loading model predicts admittance and correlation spectra, which depend upon:  crustal density  mantle density  crustal thickness  elastic thickness  magnitude of surface and subsurface loads  phase relationship of loads Lithospheric crust, ρ c Lithospheric mantle, ρ m Subsurface load, offset in phase Surface load SELENE Kaguya GRAIL Kaguya GRAIL

Let’s pause for questions from the audience

Thermal evolution: heat sources and sinks External Heating l Impacts Cooling l Radiation Internal Heating l Radioactivity Cooling l Convection Reconstruct source/sink contributions throughout geologic time

Deep interior: Structure and state inner core McDonald Observatory, Texas Ranging to the Moon 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

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: Twin spacecraft launched on a Delta 2920H-10 Launch in Sep Short duration of 9-months 82 day mapping mission Low altitude, polar orbit Single payload mission Imaging for education program Measurements: ▪Ka-band ranging measures relative velocity of the centers of mass of two spacecraft ▪Links to Deep Space Network for navigation, absolute position, and timing calibration Institutions: ▪MIT: ▪Principal Investigator & Deputy ▪Science analysis & interpretation ▪JPL: ▪Project management, system engineering, mission assurance, mission operations, payload development, science simulations & modeling, data processing ▪Contract with Lockheed Martin for spacecraft system ▪LM: ▪Spacecraft development & flight operations ▪GSFC: ▪Data processing & analysis ▪Sally Ride Science: ▪Education & outreach cameras

GRAIL Concept S-band link Telecom/Nav S-band Timing Code Ka-band ranging X-band Radio Science Beacon

Let’s pause for questions from the audience

Education Resources

How Long is a Year? A.About 3 Earth Months B.About 12 Earth months C.About 23 Earth months D.About Earth years E.All of the above

Education Resources

Eyes on Earth 3-D

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.

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 LIVE INTERACTIVE YOUR DESKTOP NSTA Web Seminars Paul Tingler, Director Jeff Layman, Technical Coordinator