Odin Astronomy WorkshopParis — 16-17 March 2007
Water in comets:Odin observations in a historical perspective
Jacques Crovisierand 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 spectrumobserved visually by
G. B. DonatiC/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)
cellule àétincelles
comète
spectroscopeéchantillonde gaz
lunetteWilliam Huggins(1824—1910)
Huggins, 1868, Phil. Trans. 158, 529(adapted by Schellen)
Sun
Carbon (olive oil)
Carbon (ethane)
C/1868 L1 (Winnecke)
5D/Brorsen
Spark spectrum
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 (Hale-Bopp)…• 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 ratesof water and other
species withheliocentric distance:
clues to the sublimation mechanisms
Biver et al. 2002Earth Moon Planets, 90, 5
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)
Water as the mainvolatile species
Remote sensing studies of comets
X AX 15
Crovisier, 2005, Int. Comets Quart., 27, 3
The need for a reliable excitation/tranfer model
Escape probability methodvs
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 waterpossible 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 moleculesas a function of temperature
Recent resultsC/2001 Q4 (NEAT) methane Tspin = 33±3 K Kawakita et al. 2005, ApJ 623, L49
C/1999 S4 (LINEAR) water Tspin > 30 K Dello Russo et al. 2005, ApJ 621, 537
C/1999 H1 (Lee) water Tspin ≈ 30 K idem
C/2001 A2 (LINEAR) water Tspin = 23±4 K idem
Why are all these temperatures similar?What is their signification?
Table from Kawakita et al. 2004, ApJ 601, 1152
Ortho-to-Para ratiosand spin temperatures
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 chemistryin the Solar System
A GT-KP planetary program proposed for HerschelP. 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 2010Q[H2O] = 1.2 1028 s-1 = 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)
C/2002 T7 (LINEAR)
H2O 557 GHz
Solar elongation constraint for various observatories:
Reminder for future instruments:
The solar elongation constraint is a strong penalty for
cometary observations!!
C/2006 P1(McNaught)
thank you foryour attention