Title Space Weathering on Main Belt Asteroids Robert Jedicke - Institute for Astronomy David Nesvorny - Southwest Research Institute
Jedicke Nature Paper Jedicke et al. (2004) Nature 429 (6989), 275-277.
Nesvorny Icarus Paper submitted to Icarus
The S-Complex Conundrum The S-Complex Conundrum
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.
S/OC Spectra Comparison Mean S-Complex Spectrum vs. Mean OC Meteorite Spectra
Meteorite Source Regions JFC MC 3:1 MC OB n6 Meteorite Source Regions
S/C-Complex H<15 Semi-Major Axis Distribution n6 3:1 Real distribution of asteroids within S & C complexes
Nu6 animation Meteorite Delivery from n 6 APHELION@ PERIHELION@ JUPITER VENUS MARS EARTH MARS EARTH VENUS
Space Weathering? Space Weathering?
Space Weathering A little understood process that reddens and darkens spectra while decreasing absorption band depths.
Space Weathering Agents Space Weathering Agents * micro-meteoroid bombardment * solar irradiation * solar wind * cosmic rays
Space Weathering Modifiers Modified by: * large impacts * rubble pile re-accumulation * regolith 'gardening'
Space Weathering Evidence Evidence: * lunar rocks & soil * laboratory simulations (nanophase Fe production) * in-situ asteroid observations
Gaspra True Colour Gaspra's True Colours
Gaspra Enhanced Colour Old Surface Fresh Surface Gaspra's Enhanced Colours
Ida Enhanced Colour Old Surface Fresh Surface Ida's Enhanced Colours
Space Weathering in the Main Belt Space Weathering in the Main Belt Need asteroid: * age * colors * albedo
The Data Collection Orbit ElementsAbsolute Magnitude SDSS Colors Proper Elements THISSTUDY IRAS Albedo FamilyMembership SMASS 1 & 2Spectra
SDSS MOC Sloan Digital Sky Survey Moving Object Catalog
SDSS Telescope (Image credit: Fermilab Visual Media Services) (Image credit: Fermilab Visual Media Services)
SDSS Camera http://www.astro.princeton.edu/PBOOK/camera/camera.htm
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
N43 SMASS vs. SDSS H-distn SMASS vs. SDSS
N44 C-S-V SMASS SDSS Comparison SMASS vs. SDSS
N45 PC2 vs. PC1 Type Comparison S X Separation of Asteroid Types in SDSS Colour Space C
Asteroid Families Asteroid Families
Remnants Asteroid families are the remnants of asteroid collisions.
Remnants All the asteroids in a family were 'created' at the same time and are genetically related.
Asteroid Family Identification Asteroid Family Identification
Orbit Element Similarity Asteroid families are identified by their similarity in orbital elements.
Osculating vs. Proper Elements Osculating Elements: Instantaneous 2-body orbit elements. Proper Elements: Long term 'average' orbit elements.
3D Proper Elements Proper Elements
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.
N46 Stalagtite Diagram Velocity Cutoff Stalagtite Diagram This axis is difficult to explain
N47 Family Velocity Cutoff Determination Velocity cutoff selection
Koronis Family 20 m/s Cutoffs Koronis Family Velocity Cutoffs http://www.boulder.swri.edu/~davidn/family/family.html
Koronis Family 50 m/s Cutoffs Koronis Family Velocity Cutoffs
Koronis Family 100 m/s Cutoffs Koronis Family Velocity Cutoffs
Family Proper e & sin(I) vs. semi-major axis Asteroid Families
N48 Eccentricity vs. Semi-major Axis Family/Background FAMILIES BACKGROUND
3D Family Proper Element Blobs Asteroid Families
Asteroid Family Dating Asteroid Family Dating
3 Techniques Dating Techniques: * SFD modelling * Yarkovsky spreading * Dynamical integration
Yarkovsky Spreading Yarkovsky Spreading
Adeona Family Spreading Carruba et al. (2003), Icarus 162, Issue 2, p. 308-327.
N49 Yarkovsky Drift Yarkovsky Drift Dating
Dynamical Integration Dynamical Integration
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
Karin Cluster w & O vs. time The Karin Cluster Nesvorny et al., Science 417, 720-722