Center for Lunar Origin and Evolution (CLOE)

1. Center for Lunar Origin and Evolution (CLOE) PI: William Bottke, Southwest Research Institute “Understanding the Formation and Bombardment History of the Moon”

2. Southwest Research Institute in Boulder

3. Meet the CLOE Team! Luke Dones Steve Mojzsis Hal Levison Robin Canup Amy Barr Clark Chapman William Bottke Stephanie Shipp Bill Ward Erik Hauri Jay Melosh David Nesvorny

4. CLOE Themes and Organization • PI: William Bottke • Deputy PI: Clark Chapman • Theme I Lead: Robin Canup • Theme II Lead: Clark Chapman • Theme III: Lead: Hal Levison • E/PO Lead: Stephanie Shipp

5. CLOE Organizational Chart • PI: William Bottke (SwRI) • Deputy PI: Clark Chapman (SwRI) • CLOE’s Executive Council (EC): Bottke, Canup, Levison, Chapman • Theme I. Lead: Robin Canup (SwRI) • Co-Is: Amy Barr, Bill Ward, Jay Melosh (U. Arizona), Erik Hauri (DTM) • Collaborators: Roger Phillips (SwRI). • Theme II: Lead: Clark Chapman (SwRI) • Co-Is: Steve Mojzsis (U. Colorado) • Collaborators: Herb Frey (GSFC), Barb Cohen (MSFC), Tim Swindle (U. Arizona), Dave Kring (LPI), Scott Anderson (SwRI) • Theme III: Lead: Hal Levison (SwRI) • Co-Is: Luke Dones (SwRI), David Nesvorny (SwRI) • Collaborators: Alessandro Morbidelli (Obs. Nice), David Vokrouhlicky (Charles U., Czech Republic), Dave O’Brien (PSI). • E/PO: Leader: Stephanie Shipp (LPI) • Co-I: Amy Barr (SwRI)

6. Why Should We Study the Moon? • We have a “Big Picture” problem: • The public has almost no idea why we should go back to the Moon from a science perspective. • Most planetary scientists have the same problem! “This is really cool” “Been there, done that!”

7. What Most People Do Not Consider • The Moon itself is fascinating, but it is also a “Rosetta Stone” for telling us about: • The unknown nature of the primordial Earth! • The critical last stages of planet formation throughout the solar system!

8. Science Concepts • Three fundamental scientific concepts have emerged from our exploration of the Moon to date: • Lunar origin by giant impact • The existence of an early lunar magma ocean, and • The potential of an impact cataclysm at 3.9 billion years ago. 2007 study by National Research Council.

9. Science Concepts • Three fundamental scientific concepts have emerged from our exploration of the Moon to date: • Lunar origin by giant impact • The existence of an early lunar magma ocean, and • The potential of an impact cataclysm at 3.9 billion years ago. 2007 study by National Research Council.

10. Theme 1: Formation of the Moon • Giant impact of Earth and Mars-sized protoplanet forms a disk of rocky/vapor material. • However, we still do not know whether such a disk can evolve into the Moon that we see today! Impactor Trajectory Early Earth Iron core vs. stony mantle Animation from Robin Canup

11. Theme 1: Formation of the Moon Objective:Determine the implications of Giant Impact hypothesis for the Moon’s physical and compositional state Approach: Self-consistent model of lunar origin, starting from an impact and ending with a fully-formed Moon Lead: Robin Canup (SwRI) Co-Is: Amy Barr (SwRI), Erik Hauri (Carnegie), Jay Melosh (Arizona), and William Ward (SwRI)

12. Simulating Moon-Forming Impacts Goal: Determine initial dynamical, thermodynamical, and compositional properties of impact-generated protolunar disk SPH/particle code: first 24-hours CTH/grid code: first week

13. Protolunar Disk Evolution Goals: Determine extent of Earth-Moon chemical mixing, volatile loss, rate & nature of Moon’s accumulation Two-part coupled model: Evolution of vapor-melt disk inside Roche limit + simulations of Moon’s accretion outside Roche limit

14. Initial Lunar State Goals: Determine extent of melting in the early Moon • Simulate the Moon’s thermal state as it forms, including impact heating and radiative cooling. • Estimate magma ocean depth and degree of metal & silicate equilibration

15. Science Concepts • Three fundamental scientific concepts have emerged from our exploration of the Moon to date: • Lunar origin by giant impact • The existence of an early lunar magma ocean, and • The potential of an impact cataclysm at 3.9 billion years ago. 2007 study by National Research Council.

16. Science Concepts • Three fundamental scientific concepts have emerged from our exploration of the Moon to date: • Lunar origin by giant impact • The existence of an early lunar magma ocean, and • The potential of an impact cataclysm at 3.9 billion years ago. 2007 study by National Research Council.

17. Science Motivation • Three fundamental scientific concepts have emerged from our exploration of the Moon to date: • Lunar origin by giant impact • The existence of an early lunar magma ocean, and • The potential of an impact cataclysm at 3.9 billion years ago. 2007 study by National Research Council.

18. What is Interesting About the Bombardment History of the Moon? Orientale Basin; Kaguya Mission

19. Ages of Lunar Samples • Most ancient lunar rocks cluster near ~3.8-3.9 Ga. • Ar-Ar-based ages of basins cluster near 3.9 Ga. All available Ar-Ar ages of highlands rocks as of 1973. Gaussians along bottom (of equal area) represent individual samples. Dark line (“ideogram”) is sum of those Gaussians. Data from Turner et al. (1973)

20. The Lunar Impact Rate • Lunar impact rate has been variable with time. Hartmann et al. (1981); Horz et al. (1991)

21. The Lunar Impact Rate • Lunar impact rate has been variable with time. • Crater production rates >100 times higher >3.8 billion years ago. Hartmann et al. (1981); Horz et al. (1991)

22. The Lunar Impact Rate • Lunar impact rate has been variable with time. • Crater production rates >100 times higher >3.8 Gy ago. • Relatively constant crater rate since ~3.2 Ga. Hartmann et al. (1981); Horz et al. (1991)

23. Lunar Late Heavy Bombardment • Were most large basins produced by a spike of impactors near ~ 3.9 Ga, creating a terminal cataclysm?

24. Lunar Late Heavy Bombardment • Or were most produced by a declining bombardment of leftover planetesimals from terrestrial planet formation?

25. Theme 3. Determining Lunar Impact Rates Lead: Hal Levison(SwRI) Co-Is: David Nesvorny (SwRI), Luke Dones (SwRI)

26. Post Accretion and the LHB: Part 1 • Sea of bodies: • Moon to Mars-sized bodies • Smaller planetesimals. • Some bodies pushed to high eccentricities & inclinations. • Here they live long enough to strike the Moon between 3.8-4.5 Ga. Location of Asteroid Belt Planetesimals Protoplanets

27. Post-Accretion and the LHB: Part 2 Comets • Old view. Gas giants/comets formed near present locations (5-30 AU) and reached current orbits ~4.5 Gy ago.

28. Post-Accretion and the LHB: Part 2 Comets • Old view. Gas giants/comets formed near present locations (5-30 AU) and reached current orbits ~4.5 Gy ago. Primordial disk of comets New view. Gas giants formed in more compact formation between 5 to ~20 AU. Massive comet population existed out to ~30 AU. Fernandez and Ip (1986); Malholtra (1995); Thommes et al. (1999; 2003)

29. Post-Accretion and the LHB: Part 2 Comets • Old view. Gas giants/comets formed near present locations (5-30 AU) and reached current orbits ~4.5 Gy ago. Primordial disk of comets • New view. Gas giants formed in more compact formation between 5 to ~20 AU. Massive comet population existed out to ~30 AU. • Best developed and most successful scenario of this is the Nice Model. Fernandez and Ip (1986); Malholtra (1995); Thommes et al. (1999; 2003) Tsiganis et al. (2005)

30. Destabilizing the Outer Solar System Tsiganis et al. (2005); Morbidelli et al. (2005); Gomes et al. (2005) Watch what happens after 850 My!

31. The Nice Model Jupiter/Saturn enter 1:2 mean motion resonance Tsiganis et al. (2005); Morbidelli et al. (2005); Gomes et al. (2005) • Gravitational interactions with massive disk of comets causes migration. In this simulation, at 850 My, Jupiter/Saturn enter 1:2 MMR. • This pushes Uranus and Neptune into comet disk.

32. Lunar Basin Formation Imbrium Basin Formation on Moon • Lunar basins may come from impacting comets/asteroids scattered by reorganization of solar system!

33. The Early Lunar Impact Rate For illustration purposes only! • Goal. Calculate the nature of the impact flux between 3.8-4.5 Ga. • Approach. New simulations that track how planetesimals evolved in the inner solar system prior to the Nice model event. Link work back to Theme 2.

34. Theme 2. Observational Constraints on the Bombardment History of the Moon • Objective. Find new “ground truth” to determine the lunar impact rate over its early (and late) history. Lead: Clark Chapman (SwRI) Co-I: Steve Mojzsis (U. Colorado)

35. Task 2.1 Bombardment Thermochronometry of Early Moon Earth, and Asteroids (Mojzsis) • Goal. Study datable massive heating events in ancient zircons and other minerals from the Earth, Moon, and asteroids to determine ancient impact rates on these objects. • Approach. Many ancient zircons (ZiSiO4) have overgrowths that record thermal pulses. Using secondary ion mass spectrometry (SIMS), we will date these events and provide new constraints on the timing, intensity, and duration of lunar bombardment. Trail et al. (2005)

36. Example: Hadean Zircons fromJack Hills, Australia • Core ages are generally 4.2 Ga, while overgrowths are at~3.95 Ga. Nothing is found in between. • Support for terminal cataclysm?

37. Task 2.2 Relative Lunar Cratering Chronology (Chapman) • Baldwin counted small craters (0.5 < D < 4 km) on/near lunar nearside craters to get their ages. • His method reproduces (within 20-30 My) the ages of two craters with known ages: • Copernicus (~800 My) • Tycho (~110 My) Baldwin (1985)

38. Lunar Impact Rates From Baldwin • Goal. Establish chronology of observable lunar geology using new crater counts. • Approach. Use Baldwin’s technique and latest lunar imagery to establish relative crater stratigraphy from present to LHB. • Absolute ages will come from Theme 3. Baldwin (1985)

39. Other Institute Objectives • Training • We will be hiring 4 postdocs and 3 graduate students. • Graduate seminar on the formation and evolution of the Moon • Based at the University of Colorado; joint Planetary/Geology departments • Origin of the Earth-Moon System II: Conference and Book • Conference designed to present new work on the Origin of the Moon • The conference will lead to a book published through Cambridge Univ. Press. • Many opportunities for joint efforts with the NLSI teams. • Solar System Bombardment Focus Group

40. CLOE E/PO Partnership with Summer Science Program, Inc. to inspire and educate future scientists • 72 high school students/ year • 6 week science experience observing and analyzing orbital elements of asteroids • 2-day CLOE science project integrated into experience • Students encouraged to present at LPSC/NLSI conference • Materials available for other institutions to replicate. Impact: 288 HS Students Lead: Stephanie Shipp (LPI). Co-I: Amy Barr (SwRI)

41. CLOE E/PO Library programstoengage young explorers in lunar science • A suite of hands-on activities for library learning environments • 90 children’s librarians prepared to bring lunar science into programs through 2-day workshops (CO and WY / ND and SD / ID, and MT) • Web-training of an existing nationwide network of 480 librarians • Continued support of network Impact: 10,800 children annually in 4 years

42. CLOE E/PO CLOE Web page designed by students to engage the general public in NLSI science • Denver School of Science and Technology high school students and faculty • High-school students learn about CLOE and NLSI science, scientists, and careers • Design and maintain a web page that engages the public • Traditional and new media Impact: Enhanced student and public engagement

43. Any Questions?

46. CLOE Team Members • PI: William Bottke; Deputy PI: Clark Chapman • CLOE’s Executive Council (EC): Bottke, Canup, Levison, Chapman • Theme I. Leader: Robin Canup • Co-Is: Amy Barr, Bill Ward, Jay Melosh (U. Arizona), Erik Hauri (DTM) • Collaborators: Roger Phillips (SwRI). • Theme II: Leader: Clark Chapman • Co-Is: Steve Mojzsis (U. Colorado) • Collaborators: Herb Frey (GSFC), Barb Cohen (MSFC), Tim Swindle (U. Arizona), Dave Kring (LPI), Scott Anderson (SwRI) • Theme III: Leader: Hal Levison • Co-Is: Luke Dones, David Nesvorny • Collaborators: Alessandro Morbidelli (Obs. Nice), David Vokrouhlicky (Charles U., Czech Republic), Dave O’Brien (PSI). • E/PO: Leader: Stephanie Shipp (LPI) • Co-I: Amy Barr (SwRI)

47. Task 3.1 The Post-Late Heavy Bombardment Era Background Main Belt Observed Families Parker et al. (2008) • Goal. Determine how specific asteroid breakup events have affected lunar impact flux. Use info to compute absolute lunar crater ages. • Approach. Model formation age and evolution of asteroid families. Determine nature of lunar impact spikes. Couple to Theme 2 work.

48. Example: Asteroids Drift into Resonances by the Yarkovsky Effect Koronis family • Observed • Model Bottke et al. (2001)

49. Education and Public Outreach (E/PO) • LPI’s “Explore!” library program • Afterschool programs in lunar science and exploration ste up through programs in partnership with state libraries across 6 western states. • Targeted toward unrepresented populations • Summer Science Program, Inc. • Develop next generation of lunar scientists in collaboration with established SSP program. • Work with gifted high school and provide challenging lunar science program. • Develop CLOE web portal with high school students Denver School for Science and Technology. Lead: Stephanie Shipp (LPI). Co-I: Amy Barr (SwRI)