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