Odin Astronomy Workshop Paris — 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 — Donati observes emission bands in C/1864 N1 (Tempel): evidence for fluorescence — 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) cellule à étincelles comète spectroscope échantillon de gaz lunette William 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 — Observations of OH in C/1973 E1 (Kohoutek) with the Nançay radio telescope. 1985—1986 — IR observations of water in 1P/Halley — 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 rates of water and other species with heliocentric distance: clues to the sublimation mechanisms Biver et al Earth Moon Planets, 90, 5

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) Water as the main volatile 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 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 H 2 18 O — 18 O/ 16 O ratio observations of ammonia

Open issues on cometary water possible clues to the origins Isotopic ratios: D/H ratio not studied with ODIN 18 O/ 16 O ==> 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

Recent results C/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 ratios and 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 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[H 2 O] = s -1 22P/Kopff May 2009 Q[H 2 O] = s -1 81P/Wild 2 February 2010 the Stardust comet Q[H 2 O] = s -1 29P/Schwassmann-Wachmann 1 Search for H 2 O 103P/Hartley 2 October 2010 Q[H 2 O] = s -1  = 0.12 AU TOO comet Q[H 2 O] > s -1

MIRO: the Microwave Instrument for the Rosetta Orbiter Gulkis et al., 2007, SSR (in press) C/2002 T7 (LINEAR) H 2 O 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 for your attention