JENNIFER HATCHELL – UNIVERSITY OF EXETER Cardiff Astrochemistry Jan 2004

NH3 in comets

with

Mike Bird (RAIUB)William Sherwood (MPIfR)Wilhelm Altenhoff (MPIfR)Floris van der Tak (MPIfR)Karl Menten (MPIfR)

Jennifer Hatchell (Exeter, ex-MPIfR)

JENNIFER HATCHELL – UNIVERSITY OF EXETER Cardiff Astrochemistry Jan 2004

Motivation

- NH3 along with CO2 and H2O is a constituent of cometary ices.-Nitrogen chemistry in early solar nebula poorly understood (N2, NH3 and N balance)- Spin temperature (from ortho/para ratio) implies formation temperature of ices

JENNIFER HATCHELL – UNIVERSITY OF EXETER Cardiff Astrochemistry Jan 2004

Radio observations

Photo: William Sherwood

JENNIFER HATCHELL – UNIVERSITY OF EXETER Cardiff Astrochemistry Jan 2004

Previous radio detectionsC/1983 D IRAS-Araki-Alcock (Altenhoff et al. 1983)C/1996 B2 Hyakutake (Palmer et al. 1996, Green Bank)C/1995 O1 Hale-Bopp (Butler et al. 2002, Green Bank)C/1995 O1 Hale-Bopp (Hirota et al. 1999, Nobeyama)C/1995 O1 Hale-Bopp (Bird et al. 1997, Effelsberg)

Direct detectionHalley (Allen et al. 1987; Meier et al. 1994, Giotto)

6%

0.3%

1.8%

1.0-1.8%

NH3 /H2O

0.1-2%

JENNIFER HATCHELL – UNIVERSITY OF EXETER Cardiff Astrochemistry Jan 2004

Optical detections of NH2 (daughter)

C/2002 T7 NH3 near 3 microns(Magee-Sauer et al. 2002)

C/1999 S4 LINEAR(Kawakita et al. 2001)C/1995 O1 Hale-Bopp &153P/Ikeya-Zhang(Kawakita et al. 2004)

Kawakita et al. 2002 reanalysisof earlier NH2 data

OPR 3.33Spin temp. 28K

Spin temp. 30K

NH3 /H2O = 0.5%

Infrared detections of NH3(lines often overlap with atmospheric absorptions)

NH3 /H2O = ???

JENNIFER HATCHELL – UNIVERSITY OF EXETER Cardiff Astrochemistry Jan 2004

Targets 2001,2002,2004

Images:

T.V

sosk

e, T.L

ovejo

y, S.K

im, and

M.Jäger/

G.R

hem

an

C/2001 A2 (NEAT) C/2002 C1 (Ikeya-Zhang) (153P)

C/2001 Q4 (NEAT) C/2002 T7 (LINEAR)

2001 2002

2004

JENNIFER HATCHELL – UNIVERSITY OF EXETER Cardiff Astrochemistry Jan 2004

OH 1665/1667 MHz

JENNIFER HATCHELL – UNIVERSITY OF EXETER Cardiff Astrochemistry Jan 2004

NH

3 2

4 G

Hz

JENNIFER HATCHELL – UNIVERSITY OF EXETER Cardiff Astrochemistry Jan 2004

NH

3 2

4 G

Hz

NH3 /H2O <=

0.5%

JENNIFER HATCHELL – UNIVERSITY OF EXETER Cardiff Astrochemistry Jan 2004

JENNIFER HATCHELL – UNIVERSITY OF EXETER Cardiff Astrochemistry Jan 2004

Conclusions

NH3 / H2O variable, 0.3-1.5% NH3 / H2O <= 0.5% in many comets: Halley and Hale-Bopp may have been exceptionalConsistency between radio / optically derived ratios

JENNIFER HATCHELL – UNIVERSITY OF EXETER Cardiff Astrochemistry Jan 2004

Upcoming comet missions

Deep Impact (NASA)9P/Tempel 1launch date Jan 12 2005Impactor + cameras July 4 2005

Rosetta (ESA)67 P/Churyumov-

Gerasimenko launched 2 March 2004

Lander 2014Rosetta

Philae (lander)