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Odin Astronomy Workshop
Paris — 16-17 March 2007
Water in comets:
Odin observations in a
historical perspective
Jacques Crovisier
and the Meudon comet group
Observatoire de Paris
Important steps in cometary science:
I — historic milestones
• 1819 — Arago observes polarisation of C/1819 N1:
evidence for reflected sunlight.
• 1864 — Donati observes emission bands in C/1864 N1
(Tempel): evidence for fluorescence.
• 1868 — Huggins compares the spectrum of C/1868 L1
(Winnecke) with laboratory spectra.
• 1930—1940 — Wurm & Swings postulate that cometary
radicals come from parent molecules (water…).
• ca 1950 — Whipple and the dirty snow ball model.
First cometary spectrum
observed visually by
G. B. Donati
C/1864 N1 (Tempel)
Donati, 1864, Astron. Nachr., 62, 375
Giovanni Donati
(1826—1873}
C/2001 A2 (LINEAR)
réseau + caméra CCD
© C. Buil
1868 : first identification
of cometary emission bands
by Huggins (1824—1910)
comète
cellule à
étincelles
lunette
échantillon
de gaz
William Huggins
(1824—1910)
spectroscope
Sun
Carbon (olive oil)
Carbon (ethane)
C/1868 L1 (Winnecke)
5D/Brorsen
Spark spectrum
Huggins, 1868, Phil. Trans. 158, 529
(adapted by Schellen)
Important steps in cometary science:
II — modern techniques
• ca 1970 — Space observations of H, OH.
• 1973 — Observations of OH in C/1973 E1 (Kohoutek) with
the Nançay radio telescope.
• 1985—1986 — IR observations of water in 1P/Halley.
• 1996 — ISO observations of water in C/1985 O1 (HaleBopp)…
• 1999 — SWAS observation of water in C/1999 H1 (Lee).
Then comes Odin…
Odin ISO : water bands
Crovisier et al. Science, 1997
First observations of rotational lines of water in comets
ISO :
C/1995 O1 (Hale-Bopp)
SWAS :
C/1999 H1 (Lee)
Biver et al., 2007, PASS, in press
Why study cometary water?
The motor of cometary activity:
# sublimation
# thermodynamical processes
Contributions to planetary atmospheres
The « snow lines » for various volatiles
The evolution of
the production rates
of water and other
species with
heliocentric distance:
clues to the
sublimation mechanisms
Biver et al. 2002
Earth Moon Planets, 90, 5
Water as the main
volatile species
Molecules from
cometary ices:
The inventory of
relative abundances
Bockelée-Morvan et al.
2005, in Comets II,
Festou et al. edts,
Univ. Arizona Press
(with updates)
Remote sensing studies of comets
X 15
XA
Crovisier, 2005, Int. Comets Quart., 27, 3
The need for a reliable excitation/tranfer model
Escape probability method
vs
Monte Carlo simulations
==> presentation by Vladimir Zakharov
Achievements of Odin
from cometary observations
• check of Odin pointing
• monitoring of water production
• support to space missions (Deep Space 1, Deep Impact)
• kinematics of water from line shapes
• constraints to cometary models from maps
• first observation of H218O — 18O/16O ratio
• observations of ammonia
Open issues on cometary water
possible clues to the origins
• Isotopic ratios:
• D/H ratio
not studied with ODIN
• 18O/16O
==> see presentation by Nicolas Biver
• The ortho-to-para ratio and spin temperature:
not studied with Odin
The D/H ratio in the Solar System
Ortho-to-para ratios of cometary molecules
as a function of temperature
Ortho-to-Para ratios
and spin temperatures
Table from Kawakita et al. 2004, ApJ 601, 1152
C/2001
C/1999
C/1999
C/2001
Q4
S4
H1
A2
(NEAT)
(LINEAR)
(Lee)
(LINEAR)
methane
water
water
water
Recent
Tspin
Tspin
Tspin
Tspin
results
= 33±3 K
> 30 K
≈ 30 K
= 23±4 K
Kawakita et al. 2005, ApJ 623, L49
Dello Russo et al. 2005, ApJ 621, 537
idem
idem
Why are all these temperatures similar?
What is their signification?
Prospective
More comets with Odin?
• Odin is still alive
• TOO comets
• 8P/Tuttle next winter:
•Q[H2O] = 3.E28 s-1
•Delta = 0.25 AU
Water and related chemistry
in the Solar System
A GT-KP planetary program proposed for Herschel
P. Hartogh, E. Lellouch, J. Crovisier et al.
 Mars
 Outer planets
 Comets
Comets for Herschel GT-KP
144P/Kushida
January 2009
Q[H2O] = 0.8 1028 s-1
22P/Kopff
May 2009
Q[H2O] = 2.5 1028 s-1
81P/Wild 2
February 2010 the Stardust comet
Q[H2O] = 1.3 1028 s-1
29P/Schwassmann-Wachmann 1
Search for H2O
103P/Hartley 2 October 2010
Q[H2O] = 1.2 1028 s-1 D = 0.12 AU
TOO comet
Q[H2O] > 1029 s-1
MIRO:
the Microwave Instrument
for the Rosetta Orbiter
Gulkis et al., 2007, SSR (in press)
H2O 557 GHz
C/2002 T7 (LINEAR)
Reminder for future instruments:
The solar elongation constraint is
a strong penalty for cometary
observations!!
Solar elongation constraint for various observatories:
C/2006 P1
(McNaught)
thank you for
your attention