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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
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
07/06/06
How we see comet s now
07/06/06
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
07/06/06
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
07/06/06
The f amily t r ee f or comet s pr oposed by Levison (1997)
07/06/06
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?
07/06/06
Remote sensing studies of comets
07/06/06
Space exploration of comets
07/06/06
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
07/06/06
Chemicalspecies and their
sublimationtemperatures
07/06/06
The « snow lines » for various volatiles
07/06/06
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
07/06/06
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
07/06/06
The diversity of comets from narrow band photometry
A Hear n et al., 1995, Icarus, 118, 223
07/06/06
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
07/06/06
The view from the infrared
access to hydrocarbons
07/06/06
C/1999 (Lee) & C/1999 S4 (LINEAR)Keck telescope - Mumma et al. 2001, Science, 292, 1334
CH3OH C2H6 #CH4 OH §
unident. ?
Infrared spectra
07/06/06
07/06/06
The view from the radio
access to minor species
07/06/06
Radio spectra:search for minor species
07/06/06
07/06/06
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
07/06/06
Spin temperatures
07/06/06
No obvious explanationfor the spin temperatures
of cometary molecules
07/06/06
The D/H ratio in comets and in the Solar System
07/06/06
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)
07/06/06
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 ?
07/06/06
07/06/06
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
07/06/06
The cycle of dust in the Universe
07/06/06
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)
07/06/06
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]
07/06/06
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.
07/06/06
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.
07/06/06
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