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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

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title

Title

Space Weathering on Main Belt Asteroids

Robert Jedicke - Institute for Astronomy

David Nesvorny - Southwest Research Institute

jedicke nature paper
Jedicke Nature Paper

Jedicke et al. (2004)

Nature 429 (6989), 275-277.

nesvorny icarus paper
Nesvorny Icarus Paper

submitted to Icarus

the s complex conundrum
The S-Complex Conundrum

The S-Complex Conundrum

the s complex conundrum5
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
S/OC Spectra Comparison

Mean

S-Complex

Spectrum

vs.

Mean

OC Meteorite

Spectra

meteorite source regions
Meteorite Source Regions

JFC

MC

3:1

MC

OB

n6

Meteorite Source Regions

s c complex h 15 semi major axis distribution
S/C-Complex H<15 Semi-Major Axis Distribution

n6

3:1

Real

distribution

of asteroids

within S & C

complexes

nu6 animation
Nu6 animation

Meteorite Delivery from

n

6

APHELION@

PERIHELION@

JUPITER

VENUS

MARS

EARTH

MARS

EARTH

VENUS

space weathering
Space Weathering?

Space Weathering?

space weathering11
Space Weathering

A little understood process

that reddens and darkens

spectra while decreasing

absorption band depths.

space weathering agents
Space Weathering Agents

Space Weathering Agents

* micro-meteoroid bombardment

* solar irradiation

* solar wind

* cosmic rays

space weathering modifiers
Space Weathering Modifiers

Modified by:

* large impacts

* rubble pile re-accumulation

* regolith 'gardening'

space weathering evidence
Space Weathering Evidence

Evidence:

* lunar rocks & soil

* laboratory simulations

(nanophase Fe production)

* in-situ asteroid observations

gaspra true colour
Gaspra True Colour

Gaspra's True Colours

gaspra enhanced colour
Gaspra Enhanced Colour

Old Surface

Fresh Surface

Gaspra's Enhanced Colours

ida enhanced colour
Ida Enhanced Colour

Old Surface

Fresh Surface

Ida's Enhanced Colours

space weathering in the main belt
Space Weathering in the Main Belt

Space Weathering in the Main Belt

Need asteroid:

* age

* colors

* albedo

the data collection
The Data Collection

Orbit ElementsAbsolute Magnitude

SDSS Colors

Proper

Elements

THISSTUDY

IRAS Albedo

FamilyMembership

SMASS 1 & 2Spectra

sdss moc
SDSS MOC

Sloan Digital Sky Survey

Moving Object Catalog

sdss telescope
SDSS Telescope

(Image credit: Fermilab Visual Media Services)

(Image credit: Fermilab Visual Media Services)

sdss camera
SDSS Camera

http://www.astro.princeton.edu/PBOOK/camera/camera.htm

sdss sin i vs semi major axis colour
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

n45 pc2 vs pc1 type comparison
N45 PC2 vs. PC1 Type Comparison

S

X

Separation

of Asteroid

Types in

SDSS

Colour

Space

C

asteroid families
Asteroid Families

Asteroid Families

remnants
Remnants

Asteroid families are

the remnants of

asteroid collisions.

remnants29
Remnants

All the asteroids

in a family were

'created' at the

same time and are

genetically related.

asteroid family identification
Asteroid Family Identification

Asteroid Family Identification

orbit element similarity
Orbit Element Similarity

Asteroid families

are identified

by their similarity

in orbital elements.

osculating vs proper elements
Osculating vs. Proper Elements

Osculating Elements:

Instantaneous 2-body orbit elements.

Proper Elements:

Long term 'average' orbit elements.

3d proper elements
3D Proper Elements

Proper

Elements

hierarchical clustering method
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
N46 Stalagtite Diagram

Velocity Cutoff Stalagtite Diagram

This axis is difficult to explain 

koronis family 20 m s cutoffs
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 50 m/s Cutoffs

Koronis Family Velocity Cutoffs

koronis family 100 m s cutoffs
Koronis Family 100 m/s Cutoffs

Koronis Family Velocity Cutoffs

asteroid family dating
Asteroid Family Dating

Asteroid Family Dating

3 techniques
3 Techniques

Dating Techniques:

* SFD modelling

* Yarkovsky spreading

* Dynamical integration

yarkovsky spreading
Yarkovsky Spreading

Yarkovsky Spreading

adeona family spreading
Adeona Family Spreading

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

n49 yarkovsky drift
N49 Yarkovsky Drift

Yarkovsky Drift Dating

dynamical integration
Dynamical Integration

Dynamical Integration

karin cluster proper e i vs a
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
Karin Cluster w & O vs. time

The

Karin

Cluster

Nesvorny et al., Science 417, 720-722

principal component colors
Principal Component Colors

Principal Component Colours

principal component definition
Principal Component Definition

Principal Components:

Linear combination

of colours that

maximizes variation.

SDSS u, g, r, i, z

n50 pc2 vs pc1 background family members
N50 PC2 vs. PC1 Background & Family Members

Background & Family Member's

Color-Color Distribution

n51 family pc2 vs pc1
N51 Family PC2 vs. PC1

X

S

Family's Mean

Color-Color

Distribution

C

n52 average slope vs pc1
N52 Average Slope vs. PC1

Average

Spectral

Slope vs. PC1

space weathering rate
Space Weathering Rate

Space Weathering Rate

Asteroid Family Dating

s complex pc1 vs age
S-Complex PC1 vs. Age

S-Complex

Mean Family

PC1 vs. Age

space weathering equation
Space Weathering Equation

Assuming a constant flux of a‘Space Weathering agent’:

PC1(t) = PC1(0) + DPC1[1-exp(-t/t)]

Generalized to:

PC1(t) = PC1(0) + DPC1[1-exp(-t/t)a]

With:

PC1(0) =0.32±0.01

t = (25±5)109

DPC1=1.0±0.1

a=0.50±0.05

n53 pc1 vs age s c complex
N53 PC1 vs Age S & C Complex

S- & C-Complex Mean Family PC1 vs. Age

FIRST RATE MEASUREMENT!

n54 koronis karin comparison
N54 Koronis Karin Comparison

But Karin is a

member of the

Koronis family!?

Koronis

& Family

vs. Karin

n55 themis veritas comparison
N55 Themis Veritas Comparison

Themis

& Family

vs. Veritas

s c oc pc1 comparison
S/C/OC PC1 Comparison

S & C Complex

PC1 Distribution

with average OC

meteorite colors

other space weathering effects
Other Space Weathering Effects?

Other

Space Weathering

Effects?

albedo vs age
Albedo vs. Age

SIMPS

Albedo

vs.

Age

2mass colors vs age
2MASS Colors vs. Age

2MASS IR

band ratios

and colors

VERSUS

Family Age

future work
Future Work…

Future Work...

space weathering rate sensitivity
Space Weathering Rate sensitivity

Space weathering rate

is sensitive to colours

for youngest families.

spectroscopic campaign
Spectroscopic Campaign

Spectroscopic observing

campaign for small MB

asteroids in young families.

pc1 s c family background
PC1 S/C Family/Background

Different

Family

vs.

Background

ratio in

S/C Complexes

thank you
Thank-you

THE END

THANKS!