The Asteroids and the Early Solar System

Planetary formation What a Nice model Density Early Solar System KOALA Conclusion

The asteroids and the early Solar System

B. Carry European Space Agency

1/25 B. Carry, ESA, 2012-10-104 Planetary formation What a Nice model Density Early Solar System KOALA Conclusion Resume of planetary formation

Step-by-step a. Gas & dust cloud contracts b. Disk forms c. Rotation, accumulation @ center d. A star is born e. Accretion within the disk f. Planetary system

2/25 B. Carry, ESA, 2012-10-104 Planetary formation What a Nice model Density Early Solar System KOALA Conclusion Resume of planetary formation

Step-by-step a. Gas & dust cloud contracts b. Disk forms c. Rotation, accumulation @ center d. A star is born e. Accretion within the disk f. Planetary system

2/25 B. Carry, ESA, 2012-10-104 Planetary formation What a Nice model Density Early Solar System KOALA Conclusion Resume of planetary formation

Step-by-step a. Gas & dust cloud contracts b. Disk forms c. Rotation, accumulation @ center d. A star is born e. Accretion within the disk f. Planetary system

2/25 B. Carry, ESA, 2012-10-104 Planetary formation What a Nice model Density Early Solar System KOALA Conclusion Interest of asteroids 1. Large population ◦ 600 000 objects (several millions) ◦ Sample the whole Solar System [1–100 AU] ◦ Sample all the compositions [rocks → ices] 2. Primitive population ◦ Small objects [km] ◦ Internal energy ≈ null ◦ No endogenous activity

. Direct witnesses of the early Solar System

3/25 B. Carry, ESA, 2012-10-104 Planetary formation What a Nice model Density Early Solar System KOALA Conclusion The 1982’s view

1. Asteroid taxonomy • Reﬂectance • Albedo • 24 classes

2. Strong gradient in 1 AU • X : Iron cores • V,A : Crust & Mantle Bus-DeMeo Taxonomy Key • S : Melted silicates S-complex 1.5

S1 Sa Sq Sr Sv • C : Most primitive 0.45 2.45 • D,T : Comet nucleus ? C-complex BC Cb Cg Cgh Ch

X-complex

3. Paradigm from 1982 X Xc Xe Xk ◦ Survey of 800 asteroids End members ◦ Visible spectrometry DK L T I In-situ formation A OQ R V 4/25 B. Carry, ESA, 2012-10-104 http://smass.mit.edu/busdemeoclass.html Planetary formation What a Nice model Density Early Solar System KOALA Conclusion The 1982’s view

1. Asteroid taxonomy • Reﬂectance • Albedo • 24 classes

2. Strong gradient in 1 AU • X : Iron cores • V,A : Crust & Mantle Bus-DeMeo Taxonomy Key • S : Melted silicates S-complex Ordinary chondrites 1.5

S1 Sa Sq Sr Sv • C : Most primitive 0.45 2.45 • D,T : Comet nucleus ? C-complex Carbonaceous chondrites? BC? Cb Cg Cgh Ch

X-complex Nickel-iron - Stony iron - Entatites

3. Paradigm from 1982 X Xc Xe Xk ◦ Survey of 800 asteroids End members ◦ Visible spectrometry ??? ? DK L T In-situ formation I ??? ??? A OQ R V 4/25 B. Carry, ESA, 2012-10-104 http://smass.mit.edu/busdemeoclass.html Planetary formation What a Nice model Density Early Solar System KOALA Conclusion The 1982’s view

1. Asteroid taxonomy Relative fractions of classes • Reﬂectance • Albedo • 24 classes

2. Strong gradient in 1 AU • X : Iron cores • V,A : Crust & Mantle Adapted from Gradie and Tedesco, 1982 • S : Melted silicates • C : Most primitive • D,T : Comet nucleus ?

3. Paradigm from 1982 ◦ Survey of 800 asteroids ◦ Visible spectrometry I In-situ formation

4/25 B. Carry, ESA, 2012-10-104 Planetary formation What a Nice model Density Early Solar System KOALA Conclusion The 1982’s view

1. Asteroid taxonomy Relative fractions of classes • Reﬂectance • Albedo • 24 classes

2. Strong gradient in 1 AU • X : Iron cores • V,A : Crust & Mantle Adapted from Gradie and Tedesco, 1982 • S : Melted silicates • C : Most primitive • D,T : Comet nucleus ?

3. Paradigm from 1982 ◦ Survey of 800 asteroids ◦ Visible spectrometry I In-situ formation

4/25 B. Carry, ESA, 2012-10-104 Planetary formation What a Nice model Density Early Solar System KOALA Conclusion Some open questions

20 10 18 Nectaris (3.90 Gy) 10 Imbrium (3.85 Gy) Orientale (3.82 Gy?)

16 10

14 10 3.90 - 3.82 Gy 12 4.12 - 3.82 Gy 10 LHB Mass (g/year)

10 Apollo 17 Apollo 12 8 10 4.04.5 3.5 3.0 2.5 2.0 Age (109 years)

• Late Heavy Bombardment • • Planetary migration •

Excess cratering @ 3.8 Gy Hot Jupiters Thick disk for accretion Migration within disk Tiny fraction remains Solar System ?

5/25 B. Carry, ESA, 2012-10-104 Planetary formation What a Nice model Density Early Solar System KOALA Conclusion The Grand Tack & Nice model

A. Grand Tack – 100 kyr • Jupiter inward migration • Stopped by Saturn • Inner Solar System

B. The Nice Model – 700 Myr • Jupiter-Saturn interaction • Neptune pushed out • Outer Solar System

Overall result

Walsh et al. 2011 • Complete mixing • Removal of 99% mass

6/25 B. Carry, ESA, 2012-10-104 Planetary formation What a Nice model Density Early Solar System KOALA Conclusion The Grand Tack & Nice model

A. Grand Tack – 100 kyr • Jupiter inward migration • Stopped by Saturn • Inner Solar System

B. The Nice Model – 700 Myr • Jupiter-Saturn interaction • Neptune pushed out • Outer Solar System

Overall result • Complete mixing • Removal of 99% mass Gomes et al. 2005

6/25 B. Carry, ESA, 2012-10-104 Planetary formation What a Nice model Density Early Solar System KOALA Conclusion But... and the 1982’s view ?

Adapted from Gradie and Tedesco, 1982

In-situ formation ?

7/25 B. Carry, ESA, 2012-10-104 Planetary formation What a Nice model Density Early Solar System KOALA Conclusion But... and the 1982’s view ?

Adapted from Gradie and Tedesco, 1982

In-situ formation ?

Number instead of mass – Only largest asteroids

7/25 B. Carry, ESA, 2012-10-104 Planetary formation What a Nice model Density Early Solar System KOALA Conclusion The era of all-sky surveys

1. Number of discoveries sky-rocketed in 30 years • 10,000 in 1982 ... 600,000 in 2012 • Completeness vastly improved (2–5 km) I Dynamic models

2. Compositional information available for thousands of asteroids • SDSS : visible colours for 100,000 asteroids (vs 800) • WISE : albedo for 150,000 asteroids (vs 2000) I Large-scale taxonomy

3. Density is needed to convert numbers in mass • Limiting factor I How do we measure density ?

8/25 B. Carry, ESA, 2012-10-104 Planetary formation What a Nice model Density Early Solar System KOALA Conclusion The era of all-sky surveys

1. Number of discoveries sky-rocketed in 30 years • 10,000 in 1982 ... 600,000 in 2012 • Completeness vastly improved (2–5 km) I Dynamic models

2. Compositional information available for thousands of asteroids • SDSS : visible colours for 100,000 asteroids (vs 800) • WISE : albedo for 150,000 asteroids (vs 2000) I Large-scale taxonomy

3. Density is needed to convert numbers in mass • Limiting factor I How do we measure density ?

8/25 B. Carry, ESA, 2012-10-104 Planetary formation What a Nice model Density Early Solar System KOALA Conclusion The era of all-sky surveys

1. Number of discoveries sky-rocketed in 30 years • 10,000 in 1982 ... 600,000 in 2012 • Completeness vastly improved (2–5 km) I Dynamic models

2. Compositional information available for thousands of asteroids • SDSS : visible colours for 100,000 asteroids (vs 800) • WISE : albedo for 150,000 asteroids (vs 2000) I Large-scale taxonomy

3. Density is needed to convert numbers in mass • Limiting factor I How do we measure density ?

8/25 B. Carry, ESA, 2012-10-104 Planetary formation What a Nice model Density Early Solar System KOALA Conclusion How do we measure density ?

M ρ = V

9/25 B. Carry, ESA, 2012-10-104 Planetary formation What a Nice model Density Early Solar System KOALA Conclusion How do we measure density ?

M ρ = V

10/25 B. Carry, ESA, 2012-10-104 Planetary formation What a Nice model Density Early Solar System KOALA Conclusion Mass measurements 1. Flyby Gravitational interaction ◦ Asteroid - Probe ◦ Precise but rare

2. Satellites ◦ Asteroid - Satellite ◦ Precise and about common

3. Deﬂection ◦ Asteroid - Asteroid ◦ Low precision but common

4. Ephemeris ◦ Asteroid - Everything ◦ Low precision but common

11/25 B. Carry, ESA, 2012-10-104 Planetary formation What a Nice model Density Early Solar System KOALA Conclusion Mass measurements 1. Flyby Gravitational interaction ◦ Asteroid - Probe ◦ Precise but rare

2. Satellites ◦ Asteroid - Satellite ◦ Precise and about common

3. Deﬂection ◦ Asteroid - Asteroid ◦ Low precision but common

4. Ephemeris ◦ Asteroid - Everything ◦ Low precision but common

11/25 B. Carry, ESA, 2012-10-104 Planetary formation What a Nice model Density Early Solar System KOALA Conclusion How do we measure density ?

M ρ = V

12/25 B. Carry, ESA, 2012-10-104 Planetary formation What a Nice model Density Early Solar System KOALA Conclusion Volume measurements

M ρ = V

• Masses : 287

• Diameters : ◦ IRAS : 2228 ◦ AKARI : 10 000 ◦ WISE : 150 000 ◦ Gaia : 10 000

13/25 B. Carry, ESA, 2012-10-104 Planetary formation What a Nice model Density Early Solar System KOALA Conclusion Volume measurements

s M δρ δM2 δV 2 ρ = = + V ρ M V s δM2 δR2 • Masses : 287 = + 9 M R • Diameters : ◦ IRAS : 2228 ◦ AKARI : 10 000 ◦ WISE : 150 000 ◦ Gaia : 10 000

13/25 B. Carry, ESA, 2012-10-104 Planetary formation What a Nice model Density Early Solar System KOALA Conclusion Volume measurements

s M δρ δM2 δV 2 ρ = = + V ρ M V s δM2 δR2 • Masses : 287 = + 9 M R • Diameters : ◦ IRAS : 2228 ◦ AKARI : 10 000 The Volume ◦ WISE : 150 000 is (easily) the ◦ Gaia : 10 000 Limiting Factor

13/25 B. Carry, ESA, 2012-10-104 Planetary formation What a Nice model Density Early Solar System KOALA Conclusion Summary of accuracy

14/25 B. Carry, ESA, 2012-10-104 Planetary formation What a Nice model Density Early Solar System KOALA Conclusion Summary of accuracy

14/25 B. Carry, ESA, 2012-10-104 Planetary formation What a Nice model Density Early Solar System KOALA Conclusion Current knowledge on density

Carry 2012 15/25 B. Carry, ESA, 2012-10-104 Planetary formation What a Nice model Density Early Solar System KOALA Conclusion Compositional distribution

Adapted from Gradie and Tedesco, 1982

16/25 B. Carry, ESA, 2012-10-104 Planetary formation What a Nice model Density Early Solar System KOALA Conclusion Compositional distribution revised

DeMeo & Carry Composition distribution revisited is radically diﬀerent ! • Almost complete mix everywhere • Absence of mixing in Hilda & Trojan

I Evidences for Grand Tack and Nice models 17/25 B. Carry, ESA, 2012-10-104 Planetary formation What a Nice model Density Early Solar System KOALA Conclusion Open questions

Bus-DeMeo Taxonomy Key

S-complex Ordinary chondrites 1.5 • Meteorite & asteroid spectroscopy

S1 Sa Sq Sr Sv 0.45 2.45 C-complex Carbonaceous chondrites? I Now based on 0.5–2.5 µm BC? Cb Cg Cgh Ch I Wider spectral range : 3–5 & 5–40 µm X-complex Nickel-iron - Stony iron - Entatites X Xc Xe Xk I Albedo & thermal inertia End members ??? ? DK L T

??? ??? A OQ R V • More asteroid analogs http://smass.mit.edu/busdemeoclass.html

I Laboratory experiments No interpretation for 50% I Recovery campaigns

• Density determinations

I Binary systems (now ∼50/200) I Accurate volume determination Albedo biased

18/25 B. Carry, ESA, 2012-10-104 Planetary formation What a Nice model Density Early Solar System KOALA Conclusion Accurate volume determination

1. Direct measurements • WYSIWYG 6= model-dependent I Disk-resolved imaging I Stellar occultations

2. Realistic 3-D shape • Assumptions ⇒ biases • Concavity ⇔ Volume I Lightcurves (dense & sparse)

3. Geometry completeness • Extensive approach I Mid-IR radiometry I Interferometry I Radar echoes

19/25 B. Carry, ESA, 2012-10-104 Planetary formation What a Nice model Density Early Solar System KOALA Conclusion Accurate volume determination

1. Direct measurements • WYSIWYG 6= model-dependent I Disk-resolved imaging I Stellar occultations

2. Realistic 3-D shape • Assumptions ⇒ biases • Concavity ⇔ Volume I Lightcurves (dense & sparse)

3. Geometry completeness • Extensive approach I Mid-IR radiometry I Interferometry I Radar echoes

19/25 B. Carry, ESA, 2012-10-104 Planetary formation What a Nice model Density Early Solar System KOALA Conclusion Accurate volume determination

1. Direct measurements • WYSIWYG 6= model-dependent I Disk-resolved imaging I Stellar occultations

2. Realistic 3-D shape • Assumptions ⇒ biases • Concavity ⇔ Volume I Lightcurves (dense & sparse)

3. Geometry completeness • Extensive approach I Mid-IR radiometry I Interferometry I Radar echoes

19/25 B. Carry, ESA, 2012-10-104 Planetary formation What a Nice model Density Early Solar System KOALA Conclusion The concept of KOALA

20/25 B. Carry, ESA, 2012-10-104 Planetary formation What a Nice model Density Early Solar System KOALA Conclusion The concept of KOALA

20/25 B. Carry, ESA, 2012-10-104 Planetary formation What a Nice model Density Early Solar System KOALA Conclusion Accuracy of KOALA

Pre-ﬂyby model vs. Rosetta Accuracy KOALA Shape : 2 km RMS Diameter ∼ 2% Carry et al. 2010 Carry et al. 2012 Volume ≤ 15%

21/25 B. Carry, ESA, 2012-10-104 Planetary formation What a Nice model Density Early Solar System KOALA Conclusion Accuracy of KOALA

22/25 B. Carry, ESA, 2012-10-104 Planetary formation What a Nice model Density Early Solar System KOALA Conclusion On-going research...

1. Lightcurves & Stellar occultations

I Interactions with amateur community I Now 200 convex shape models available I Size determination for 25%

2. Disk-resolved imaging

I AO camera on VLT, Keck, Gemini I KOALA shape modeling I Working on ∼30 objects

3. Adding data modes in KOALA • Mid-infrared (thermal) radiometry • Interferometry fringes • Radar echoes I Getting ready for massive inputs

23/25 B. Carry, ESA, 2012-10-104 Planetary formation What a Nice model Density Early Solar System KOALA Conclusion On-going research...

1. Lightcurves & Stellar occultations

I Interactions with amateur community I Now 200 convex shape models available I Size determination for 25%

2. Disk-resolved imaging

I AO camera on VLT, Keck, Gemini I KOALA shape modeling I Working on ∼30 objects

3. Adding data modes in KOALA • Mid-infrared (thermal) radiometry • Interferometry fringes • Radar echoes I Getting ready for massive inputs

23/25 B. Carry, ESA, 2012-10-104 Planetary formation What a Nice model Density Early Solar System KOALA Conclusion ... up to 2020

• Spin • Shape & Size 5 4 5 I 10 objects I 10 – 10 objects

I Accretion epoch I Size-freq. distribution

I YORP, Yarkovsky (non G~) I Dynamics & Collisions

• Surface properties • Density 4 5 2 3 I 10 – 10 objects I 10 –10 objects

I Albedo, reﬂectance I Composition

I Link with meteorites I Internal structure

24/25 B. Carry, ESA, 2012-10-104 Planetary formation What a Nice model Density Early Solar System KOALA Conclusion Summary

• Asteroids are remnants from the early Solar System

I Distribution of composition → initial conditions I Evidences for planetary migration like many exoplanets

• Asteroid composition remains elusive in many cases

I Half of the classiﬁcation lacks compositional interpretation I Still a lot of observational constraints needed

• Surface and physical properties mostly unknown

I Albedo, thermal inertia, density → Composition I Period, spin, shape → YORP & Yarkovsky

25/25 B. Carry, ESA, 2012-10-104