XVIIIèmes Rencontres de BloisPlanetary science: challenges and discoveries

28 May 2 J une 2006

Jacques CrovisierObservatoire de Paris

07/06/06

How comets were seen at the time of the castle of Blois (Renaissance) The comet of Ambroise Paré was in f act an aur or a

Peter CreutzerProspectus

1527

Pierre BoaistuauHistoires

prodigieuses1560

Ambroise ParéLes Monstres

1573

CamilleFlammarionAstronomie

Populaire1880

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How we see comet s now

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Asteroid belt

Main belt comets

Jupiter-Neptunesource zone

Oort cloud

Halley-family cometslong-period comets

Kuiper belt

Centaurs

Jupiter-familycomets

Nearly isotropiccomets

Dynamical evolution and comet families

Ecliptic comets

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XVIIIèmes Rencontres de BloisPlanetary science: challenges and discoveries

28 May 2 J une 2006

Jacques CrovisierObservatoire de Paris

07/06/06

Main belt comets

At the limit of the snow line

Sparse data: only 3 members

only imaging of dust coma

Hsieh & Jewitt, 2006, Science, 312, 561

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The f amily t r ee f or comet s pr oposed by Levison (1997)

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Fundamental question:

Oort-cloud comets formed in the Jupiter-Uranus region, were ejected to the Oort cloud, then coming back as nearly-isotropic comets.

Ecliptic comets were formed in the Kuiper belt beyond Neptune, then migrated to become Jupiter-family comets.

Does this difference of formation sites translates into differences of the physical and chemical properties of these two classes of comets?

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Remote sensing studies of comets

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Space exploration of comets

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Indicators of diversity

Dynamical indicators

Orbit, Tisserand parameter

Chemical indicators

from the visible: daughter species from the infrared: parent volatiles

from the radio: parent volatiles

Physical and other indicators

spin temperatures isotopic ratios

crystallinity of silicates nucleus density

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Chemicalspecies and their

sublimationtemperatures

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The « snow lines » for various volatiles

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Molecules from cometary ices:

The inventory ofrelative abundances

Bockelée-Morvan et al.2005, in Comets II,Festou et al. edts,Univ. Arizona Press

(with updates)

bar in red:variation from comet to comet

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The view from the visible with narrow band photometry

a study of 85 cometsA Hear n et al., 1995, Icarus, 118, 223

A clear-cut case? carbon-depleted cometsfrom the Jupiter family

Anomalous comets

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The diversity of comets from narrow band photometry

A Hear n et al., 1995, Icarus, 118, 223

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The diversity of comets from narrow band photometry:

Carbon-depleted comets

Filled symbols =Jupiter-family comets

Carbon-depleted comets

Adapt ed f r om A Hear n et al., 199507/06/06

Puzzling monsters: anomalous comets

CN, no C2

43P/Wolf-Harrington Fink, 1992,

Science, 257, 1926

NH2, no CN, no C2

C/1988 Y1 Yanaka Schleicher et al. 1993,

Icarus, 104, 157

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The view from the infrared

access to hydrocarbons

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C/1999 (Lee) & C/1999 S4 (LINEAR)Keck telescope - Mumma et al. 2001, Science, 292, 1334

CH3OH C2H6 #CH4 OH §

unident. ?

Infrared spectra

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The view from the radio

access to minor species

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Radio spectra:search for minor species

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Chemical diversity of comets(from radio observations)

Bockelée-Morvan & Crovisier 2002, EMP, 89, 53 Biver et al. 200507/06/06

Ortho-to-para ratios of cometary moleculesas a function of temperature

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Spin temperatures

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No obvious explanationfor the spin temperatures

of cometary molecules

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The D/H ratio in comets and in the Solar System

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Observations of HDO in comets

C/1996 B2 (Hyakutake)CSO

Bockelée-Morvan et al. 1998Icarus 133, 147

C/1995 O1 (Hale-Bopp)JCMT

Meier et al. 1998Science 279, 842

HDO is difficult to observe(a goal for Herschel and ALMA)

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The mystery of the 14N/15N ratioin cometary cyanides

HCN : 14N/15N ~ 300 (~ terrestrial)

C/1995 01 (Hale-Bopp)Jewitt et al. 1997, Science, 278, 90-93

CN : 14N/15N ~ 150C/1995 01 (Hale-Bopp), C/2000 WM1 (LINEAR), 122P/de Vico,153P/Ikeya-Zhang, C/2001 Q4 (NEAT), C/2003 K4 (LINEAR),

C/1999 S4 (LINEAR), 88P/Howell, 9P/Tempel 1Arpigny et al. 2003, Science, 301, 1522

Jehin et al. 2004, ApJ, 613, L61

Manfroid et al. 2005, A&A, 432, L5

Hutsemékers et al. 2005, A&A, 440, L21

Jehin et al. 2006, ApJ, 641, L154

Where is CN coming from ?

(semi) refractory organics ?

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The origin of crystalline silicates in comets

Are crystalline silicates also present in comets formed farther from the Sun?

Crystalline silicates are indeed identified in IR spectra of 103P/Hartley 2, 78P/Gehrels 2 and 9P/Tempel 1 (after Deep Impact).They are present in the dust of81 P/Wild 2 (Stardust).

It is more difficult to identify cr yst alline silicat es in J FCs

j ust because J FCs are more difficult to observe.

Olivine particle collected in 81P/Wild 2 by Stardust

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The cycle of dust in the Universe

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A controversial point: where is cometary CO

coming from?

Comet Hale-Bopp:A map of CO

with the IRAM interferometer(Henry, 2003, thesis)

The extension of the infrared CO lines

(DiSanti et al., 2001)

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The diversity of comet nuclei

Albedos ar e similar What about densit ies?07/06/06

Is pristine material from the internal nucleusdifferent from the outgassed material?

There is no such indication from the Deep Impact experimentor from observations of split comets

[C/1999 S4 (LINEAR), 73P/Schwassmann-Wachmann 3]

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Conclusions I :

There is evidence of a sub-class of carbon-depleted comets among JFCs How does this t ranslat e in abundances of parent volat iles?

Some JFCs may be depleted in CO and other hypervolatiles (hydrocarbons) this is not what is expected from their proposed site of formation.

Otherwise, Jupiter-family comets and Oort-cloud comets appear to be pretty much similar and both classes of comets appear to have a broad diversity of chemical composition.

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Conclusions I I :

Should we revise our ideas on the formation of comets?

However,

There may be interlopers in both classes of comets.

Chemical fractionation is certainly important.

We still lack data from Jupiter-family comets.

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