Space Weathering on Main Belt Asteroids

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Title
Space Weathering on Main Belt Asteroids
Robert Jedicke - Institute for Astronomy David
Nesvorny - Southwest Research Institute
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Jedicke Nature Paper
Jedicke et al. (2004) Nature 429 (6989), 275-277.
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Nesvorny Icarus Paper
submitted to Icarus
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The S-Complex Conundrum
The S-Complex Conundrum
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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.
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S/OC Spectra Comparison
Mean S-Complex Spectrum vs. Mean OC
Meteorite Spectra
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Meteorite Source Regions
Meteorite Source Regions
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S/C-Complex Hlt15 Semi-Major Axis Distribution
Real distribution of asteroids within S
C complexes
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Nu6 animation
Meteorite Delivery from
n
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APHELION_at_
PERIHELION_at_
JUPITER
VENUS
MARS
EARTH
MARS
EARTH
VENUS
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Space Weathering?
Space Weathering?
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Space Weathering
A little understood process that reddens and
darkens spectra while decreasing absorption band
depths.
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Space Weathering Agents
Space Weathering Agents
micro-meteoroid bombardment solar
irradiation solar wind cosmic rays
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Space Weathering Modifiers
Modified by
large impacts rubble pile re-accumulation
regolith 'gardening'
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Space Weathering Evidence
Evidence
lunar rocks soil laboratory simulations
(nanophase Fe production) in-situ asteroid
observations
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Gaspra True Colour
Gaspra's True Colours
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Gaspra Enhanced Colour
Gaspra's Enhanced Colours
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Ida Enhanced Colour
Ida's Enhanced Colours
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Space Weathering in the Main Belt
Space Weathering in the Main Belt
Need asteroid
age
colors
albedo
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The Data Collection
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SDSS MOC
Sloan Digital Sky Survey Moving Object Catalog
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SDSS Telescope
(Image credit Fermilab Visual Media Services)
(Image credit Fermilab Visual Media Services)
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SDSS Camera
http//www.astro.princeton.edu/PBOOK/camera/camera
.htm
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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
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N43 SMASS vs. SDSS H-distn
SMASS vs. SDSS
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N44 C-S-V SMASS SDSS Comparison
SMASS vs. SDSS
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N45 PC2 vs. PC1 Type Comparison
S
X
Separation of Asteroid Types in SDSS Colour Space
C
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Asteroid Families
Asteroid Families
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Remnants
Asteroid families are the remnants of asteroid
collisions.
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Remnants
All the asteroids in a family were 'created' at
the same time and are genetically related.
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Asteroid Family Identification
Asteroid Family Identification
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Orbit Element Similarity
Asteroid families are identified by their
similarity in orbital elements.
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Osculating vs. Proper Elements
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3D Proper Elements
Proper Elements
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Hierarchical Clustering Method
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.
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N46 Stalagtite Diagram
Velocity Cutoff Stalagtite Diagram
This axis is difficult to explain ?
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N47 Family Velocity Cutoff Determination
Velocity cutoff selection
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Koronis Family 20 m/s Cutoffs
Koronis Family Velocity Cutoffs
http//www.boulder.swri.edu/davidn/family/family.
html
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Koronis Family 50 m/s Cutoffs
Koronis Family Velocity Cutoffs
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Koronis Family 100 m/s Cutoffs
Koronis Family Velocity Cutoffs
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Family Proper e sin(I) vs. semi-major axis
Asteroid Families
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N48 Eccentricity vs. Semi-major Axis
Family/Background
FAMILIES
BACKGROUND
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3D Family Proper Element Blobs
Asteroid Families
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Asteroid Family Dating
Asteroid Family Dating
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3 Techniques
Dating Techniques
SFD modelling Yarkovsky spreading Dynamical
integration
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Yarkovsky Spreading
Yarkovsky Spreading
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Adeona Family Spreading
Carruba et al. (2003), Icarus 162, Issue 2, p.
308-327.
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N49 Yarkovsky Drift
Yarkovsky Drift Dating
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Dynamical Integration
Dynamical Integration
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Karin Cluster proper e I vs. a
Karin Members
Isotropic ejectionat dV15m/s withdifferent n
and w
The Karin Cluster
Best fit withcollision atperihelion
Koronis Members
Nesvorny et al., Science 417, 720-722
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Karin Cluster w O vs. time
The Karin Cluster
Nesvorny et al., Science 417, 720-722
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Principal Component Colors
Principal Component Colours
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Principal Component Definition
SDSS u, g, r, i, z
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N50 PC2 vs. PC1 Background Family Members
Background Family Member's Color-Color
Distribution
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N51 Family PC2 vs. PC1
X
S
Family's Mean Color-Color Distribution
C
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N52 Average Slope vs. PC1
Average Spectral Slope vs. PC1
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Space Weathering Rate
Space Weathering Rate
Asteroid Family Dating
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S-Complex PC1 vs. Age
S-Complex Mean Family PC1 vs. Age
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Space Weathering Equation
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N53 PC1 vs Age S C Complex
S- C-Complex Mean Family PC1 vs. Age
FIRST RATE MEASUREMENT!
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N54 Koronis Karin Comparison
Koronis Family vs. Karin
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N55 Themis Veritas Comparison
Themis Family vs. Veritas
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S/C/OC PC1 Comparison
S C Complex PC1 Distribution with average
OC meteorite colors
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Other Space Weathering Effects?
Other Space Weathering Effects?
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Albedo vs. Age
SIMPS Albedo vs. Age
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PC1 vs. Absolute Magnitude
DIAMETER
PC1 vs. H
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2MASS Colors vs. Age
2MASS IR band ratios and colors VERSUS Family Age
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Future Work
Future Work...
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Space Weathering Rate sensitivity
Space weathering rate is sensitive to colours for
youngest families.
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Spectroscopic Campaign
Spectroscopic observing campaign for small
MB asteroids in young families.
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PC1 S/C Family/Background
Different Family vs. Background ratio in S/C
Complexes
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Thank-you
THE END
THANKS!