GRAIL: Exploring the Moon from Crust to Core

Transcription

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

2 Exploring the Lunar Interior Structure Crust To Core Via GRAIL Gravitational Field Measurements June 2011 Copyright 2011 California Institute of Technology Government sponsorship acknowledged

3 Presenter: Sami Asmar Co-Investigator & GRAIL Deputy Project Scientist Jet Propulsion Laboratory California Institute of Technology

4 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

5 What if the Moon Did Not Exist? Contribute your thinking in the Chat

6 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

7 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

8 The giant impact and the origin of the Moon

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

10 Measurement Technique: Differential One-Way Ranging

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14 Let s pause for questions from the audience

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

16 Comparing Gravity & Topography Admittance & coherence Surface load SELENE GRAIL Lithospheric crust, ρc Lithospheric mantle, ρm Subsurface load, offset in phase 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 Kaguya Kaguya GRAIL

17 Let s pause for questions from the audience

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

19 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

20 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

21 x Solar Radiation Pressure to <0.001 mgal

22 x Spacecraft IR Radiation

23 x Lunar albedo & Lunar IR

24 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: GSFC: Spacecraft development & flight operations Data processing & analysis Sally Ride Science: Education & outreach cameras

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

26 Let s pause for questions from the audience

27 Education Resources

28 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

29 Education Resources

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33 Eyes on Earth 3-D

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35 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.

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38 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 YOUR DESKTOP