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Future Ground-based Solar System
Research Synergies with Space Probes and Space
Telescopes Portoferraio, Isola d'Elba, Livorno
(Italy), September 8-12, 2008 The chemical
diversity of comets synergies between space
exploration and ground-based radio
observations J. Crovisier, N. Biver D.
Bockelée-Morvan, P. Colom LESIA, Observatoire de
Paris J. Boissier IRAM, Saint Martin
d'Hères D.C. Lis CalTech, Pasadena
Allain Manesson Mallet, 1683, Description de
l'Univers
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Fundamental questions on comets What are comets
? What is their composition ? How do they work
? What is their role in the Solar System ? How
did they form ? How did they evolve ? What is
their relationship with other small bodies ? Is
there a relation between their orbits and their
chemical composition ?
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Dynamical families of comets (from Levison,
1997)? T Tisserand? parameter
Kuiper-belt comets
Oort-cloud comets
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Earth-based observations figure of
merit QH2O / ? roughly proportional to signal
Crovisier et al. 2008, PSS, in press
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number of molecules detected by
radio spectroscopy as a function of the figure
of merit QH2O / ?
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The water production rate of comets provides a
standard for monitoring cometary activity and a
reference for relative abundances in nucleus ices
direct measurement 557 GHz line of H2O 12 comets
with Odin in 2001-2006 also SWAS Herschel is
next
indirect measurement 18-cm lines of OH at Nançay
40 comets since 2000
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Radio spectroscopy
IRAM
CSO
HCN, CH3OH, H2CO, CO, HNC, H2S, CS (molecules
observed in more than 10 comets)? rare species
and isotopes in a few comets
CSO
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The inventory of relative abundances of cometary
molecules
Bockelée-Morvan et al. 2005, in Comets II, (with
updates)?
cumulative histogram how many molecules remain
to be detected?
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73P/Schwassmann-Wachmann 3 Jupiter-family
comet May 2006 ? 0.08 UA a fragmented
comet similar compositions for fragments B and
C methanol depletion
Spitzer Space Telescope Reach Vaubaillon 2006
IR view Dello Russo et al. 2007, Nature, 448,
172
Radio view Biver et al. 2008, ACM
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The HNC molecule and the problem of its
origin variations of HNC/HCN with helio. distance
and among comets thermal degradation of organic
grains?
Lis et al. 2008, ApJ, 675, 931
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17P/Holmes Jupiter-family comet huge outburst on
24 October 2007 detected molecules OH, C,
CH3OH, H2CO, HCN, CH3CN, HC3N, H2S, SO, HNC,
CS isotopic ratios C, N, S in HCN, CS,
H2S C14N/C15N 16540 HC14N/HC15N
13926 14N/15N terrestre 270 Bockelée-Morvan
et al. 2008, ApJ, 679, L49
Biver et al. 2008, ACM2008
IRAM interferometer see talk by Boissier et al.
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Isotopic ratios in 17P/Holmes
Bockelée-Morvan et al. 2008, ApJ, 679, L49
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8P/Tuttle Halley-family comet January 2008 ?
0,25 UA detection of HCN, HNC, CH3OH, CS, H2S,
H2CO, CH3CN search for CO and rare species HNCO,
HCOOH, SO, HC3N, OCS Biver et al. 2008,
ACM2008 In complement first IR observations of
a comet with VLT/CRIRES studies of H2O, HCN,
CH4, C2H2, C2H6, CH3OH Bockelée-Morvan et al.
2008, ACM2008 poster by Jehin et al.
HNC
Biver et al. 2008, ACM2008
also IRAM interferometer see talk by Boissier et
al.
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Comets close to the Sun - difficult/impossible
to observe in the visible/IR or with
spacecraft (except coronagraphs)? - possible with
some radio telescopes rh lt 0.20 AU
gt solar elong. lt 11.5 allows investigation
of - gas velocity and temperature - specific
mechanisms (e.g. photolysis shielding)? -
high-temperature sublimation and search for
refractories IRAM observations C/2002 X5
(Kudo-F.) _at_ 0.21 AU C/2002 V1 (NEAT) _at_
0.11 AU C/2006 P1 (McNaught) _at_ 0.21 AU Biver et
al. 2008, ACM2008, and in preparation
rh 0.12 AU !!
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The chemical diversity ofcomets from radio
observations Our preceding study was based upon
20 comets. We now have more than 30 comets.
Biver et al. 2002, Earth Moon Planets, 90, 323
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Chemical composition vs dynamical classes no
obvious correlation
Crovisier et al. 2008, PSS, in press
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• Conclusions
• The cometary diversity can only be studied by
  large ground-based or Earth-orbit observing
  programmes. Space exploration accesses only a
  limited number of objects (short-period comets).
• Radio spectroscopy (as well as visible and IR
  spectroscopy) reveals a broad chemical diversity
  among comets.
• There is no obvious correlation between chemical
  diversity and the dynamical classes of comets.

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Prospects with new facilities...
Rosetta/MIRO
Herschel see talk by Lellouch
ALMA see talk by Biver
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the end
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H2O
para
ortho