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  1. Title Space Weathering on Main Belt Asteroids Robert Jedicke - Institute for Astronomy David Nesvorny - Southwest Research Institute

  2. Jedicke Nature Paper Jedicke et al. (2004) Nature 429 (6989), 275-277.

  3. Nesvorny Icarus Paper submitted to Icarus

  4. The S-Complex Conundrum The S-Complex Conundrum

  5. The S-Complex Conundrum The most numerous class of meteorites (Ordinary Chondrites) have spectra that do NOT match their presumed parent bodies in the asteroidal S-Complex.

  6. S/OC Spectra Comparison Mean S-Complex Spectrum vs. Mean OC Meteorite Spectra

  7. Meteorite Source Regions JFC MC 3:1 MC OB n6 Meteorite Source Regions

  8. S/C-Complex H<15 Semi-Major Axis Distribution n6 3:1 Real distribution of asteroids within S & C complexes

  9. Nu6 animation Meteorite Delivery from n 6 APHELION@ PERIHELION@ JUPITER VENUS MARS EARTH MARS EARTH VENUS

  10. Space Weathering? Space Weathering?

  11. Space Weathering A little understood process that reddens and darkens spectra while decreasing absorption band depths.

  12. Space Weathering Agents Space Weathering Agents * micro-meteoroid bombardment * solar irradiation * solar wind * cosmic rays

  13. Space Weathering Modifiers Modified by: * large impacts * rubble pile re-accumulation * regolith 'gardening'

  14. Space Weathering Evidence Evidence: * lunar rocks & soil * laboratory simulations (nanophase Fe production) * in-situ asteroid observations

  15. Gaspra True Colour Gaspra's True Colours

  16. Gaspra Enhanced Colour Old Surface Fresh Surface Gaspra's Enhanced Colours

  17. Ida Enhanced Colour Old Surface Fresh Surface Ida's Enhanced Colours

  18. Space Weathering in the Main Belt Space Weathering in the Main Belt Need asteroid: * age * colors * albedo

  19. The Data Collection Orbit ElementsAbsolute Magnitude SDSS Colors Proper Elements THISSTUDY IRAS Albedo FamilyMembership SMASS 1 & 2Spectra

  20. SDSS MOC Sloan Digital Sky Survey Moving Object Catalog

  21. SDSS Telescope (Image credit: Fermilab Visual Media Services) (Image credit: Fermilab Visual Media Services)

  22. SDSS Camera http://www.astro.princeton.edu/PBOOK/camera/camera.htm

  23. SDSS sin(I) vs. Semi-Major Axis (Colour) SDSS Asteroid Colours vs. sin(Inclination) & Semi-Major Axis ___________________________________________________ Notable SDSS discoveries: *the main belt *MB color gradation *asteroid families

  24. N43 SMASS vs. SDSS H-distn SMASS vs. SDSS

  25. N44 C-S-V SMASS SDSS Comparison SMASS vs. SDSS

  26. N45 PC2 vs. PC1 Type Comparison S X Separation of Asteroid Types in SDSS Colour Space C

  27. Asteroid Families Asteroid Families

  28. Remnants Asteroid families are the remnants of asteroid collisions.

  29. Remnants All the asteroids in a family were 'created' at the same time and are genetically related.

  30. Asteroid Family Identification Asteroid Family Identification

  31. Orbit Element Similarity Asteroid families are identified by their similarity in orbital elements.

  32. Osculating vs. Proper Elements Osculating Elements: Instantaneous 2-body orbit elements. Proper Elements: Long term 'average' orbit elements.

  33. 3D Proper Elements Proper Elements

  34. Hierarchical Clustering Method Distance Metric: d = n a [ 1.25 (Da/a)2 + 2 De2 + 2 (Dsin i)^2 ]1/2 Hierarchical Clustering Method: Family membership requires that all family members are connected by a chain, where each member is attached to its neighbour by less than a limiting distance.

  35. N46 Stalagtite Diagram Velocity Cutoff Stalagtite Diagram This axis is difficult to explain 

  36. N47 Family Velocity Cutoff Determination Velocity cutoff selection

  37. Koronis Family 20 m/s Cutoffs Koronis Family Velocity Cutoffs http://www.boulder.swri.edu/~davidn/family/family.html

  38. Koronis Family 50 m/s Cutoffs Koronis Family Velocity Cutoffs

  39. Koronis Family 100 m/s Cutoffs Koronis Family Velocity Cutoffs

  40. Family Proper e & sin(I) vs. semi-major axis Asteroid Families

  41. N48 Eccentricity vs. Semi-major Axis Family/Background FAMILIES BACKGROUND

  42. 3D Family Proper Element Blobs Asteroid Families

  43. Asteroid Family Dating Asteroid Family Dating

  44. 3 Techniques Dating Techniques: * SFD modelling * Yarkovsky spreading * Dynamical integration

  45. Yarkovsky Spreading Yarkovsky Spreading

  46. Adeona Family Spreading Carruba et al. (2003), Icarus 162, Issue 2, p. 308-327.

  47. N49 Yarkovsky Drift Yarkovsky Drift Dating

  48. Dynamical Integration Dynamical Integration

  49. Karin Cluster proper e & I vs. a Karin Members Isotropic ejectionat dV=15m/s withdifferent n and w The Karin Cluster Best ‘fit’ withcollision atperihelion Koronis Members Nesvorny et al., Science 417, 720-722

  50. Karin Cluster w & O vs. time The Karin Cluster Nesvorny et al., Science 417, 720-722