Hostname: page-component-78c5997874-ndw9j Total loading time: 0 Render date: 2024-11-05T21:25:13.773Z Has data issue: false hasContentIssue false
  • English
  • Français

Infrared Spectroscopy of Cometary Parent Molecules

Published online by Cambridge University Press:  12 April 2016

H. A. Weaver ,
M. J. Mumma  and
H. P. Larson
H. A. Weaver
Affiliation:
Space Telescope Science, Institute 3700 San Martin Drive Baltimore, MD 21218, USA
M. J. Mumma
Affiliation:
Planetary Systems Branch NASA Goddard Space Flight Center Greenbelt, MD 20771, USA
H. P. Larson
Affiliation:
Department of Planetary Sciences, University of Arizona Tucson, AZ 85721, USA

Abstract

Core share and HTML view are not available for this content. However, as you have access to this content, a full PDF is available via the ‘Save PDF’ action button.

Most cometary parent molecules do not strongly fluoresce at ultraviolet and visible wavelengths, and some do not possess permanent electric dipole moments, preventing their study in the radio region as well. However, many of these molecules have strong ro-vibrational transitions in the near infrared (λ ∼ 2 – 5 μm). Since the solar flux at these wavelengths is quite strong, parent molecules in cometary comae can be probed directly via fluorescence in these infrared transitions. The feasibility of this approach was convincingly demonstrated by the detection of H2O in comet Halley (1986 III) from the Kuiper Airborne Observatory and by the detection of H2O, CO2, and H2CO using an infrared spectrometer (IKS) on VEGA. Tentative detections of near infrared lines of CH4 were also reported during ground-based and airborne observations of comets Halley and Wilson (1987 VII). High resolution spectroscopy of the infrared water transitions has yielded a wealth of new information on cometary physics: the absolute line intensities and spatial brightness profiles are used to determine water production rates and lifetimes, the relative line intensities probe the kinetic temperature profile in the coma, the line widths and line positions shed light on coma outflow dynamics, and the temporal variability in the lines provides information on the structure of the nucleus. These observations also allow the determination of the water ortho-to-para ratio, which may provide fundamental insight into the origin and/or evolutionary history of cometary nuclei. Similar observations of other molecules (those mentioned above plus others) will provide important complementary data and will also allow us to compile a volatile inventory for cometary nuclei, but such observations are extremely difficult due to the low abundances of these molecules (≤10% relative to water) and the limitations of present infrared facilities. Recent advances in infrared instrumentation promise to extend sensitivities for parent molecule searches to relative abundances well below 1%, especially if cooled, Earth-orbiting facilities are available.

Type
Section I: Observing Techniques and Interpretation
Information
International Astronomical Union Colloquium , Volume 116 , Issue 1: Comets in the Post-Halley Era , 1989 , pp. 93 - 106
Copyright
Copyright © Kluwer 1991

References

A’Hearn, M.F., and Feldman, P.D. (1982) ‘Carbon in comet Bradfield (1979l)’, Ap. J. Lett., 242, L187–L190.CrossRefGoogle Scholar
Allen, M., et al. (1987) ‘Evidence for methane and ammonia in the coma of comet P/Halley’, Astron. Ap., 187, 502–512.Google ScholarPubMed
AltenhofF, W.J., et al. (1983) ‘Radio observations of comet 1983d’, Astron. Ap., 125, L19–L22.Google Scholar
Baas, F., Geballe, T.R., and Walther, D.M. (1986) ‘Spectroscopy of the 3.4 micron emission feature in comet Halley’, Ap. J. Lett., 311, L97–L101.CrossRefGoogle Scholar
Bockelée-Morvan, D. (1987) ‘A model for the excitation of water in comets’, Astron. Ap., 181, 169–181.Google Scholar
Bockelée-Movan, D., and Crovisier, J. (1987a) ‘The role of water in the thermal balance of the coma’, in Rolfe, E.J. and Battrick, B. (eds.), Symposium on the diversity and simi larity of comets, ESA SP-278, 235–240.Google Scholar
Bockelée-Morvan, D., and Crovisier, J. (1987b) ‘The 2.7 μm water band of comet P/Halley: interpretation of observations by an excitation model’, Astron. Ap., 187, 425–430.Google Scholar
Brooke, T.Y., Knacke, R.F., Owen, T.C., and Tokunaga, A.T., (1989) ‘Spectroscopy of emission features near 3 μm in comet Wilson (1986l)’, Ap. J., 336, 971–978.CrossRefGoogle Scholar
Chin, G., and Weaver, H.A. (1984) ‘Vibrational and rotational excitation of CO in comets: nonequilibrium calculations’, Ap. J., 285, 858–869.CrossRefGoogle Scholar
Combes, M., et al. (1988) ‘The 2.5-12 μm spectrum of comet Halley from the IKS-VEGA experiment’, Icarus, 76, 404–436.CrossRefGoogle Scholar
Crovisier, J. (1984) ‘The water molecule in comets: fluorescence mechanisms and thermo dynamics of the inner coma’, Astron. Ap., 130, 361–372.Google Scholar
Crovisier, J. (1987) ‘Rotational and vibrational synthetic spectra of linear parent molecules in comets’, Astron. Ap. Suppl. Ser., 68, 223–258.Google Scholar
Crovisier, J. (1989) ‘The photodissociation of water in cometary atmospheres’, Astron. Ap., 213, 459–464.Google Scholar
Crovisier, J. (1990) ‘Infrared cometary spectroscopy’, in 22nd ESLAB symposium on in frared spectroscopy in astronomy, ESA SP-290, in press.Google Scholar
Crovisier, J., and Encrenaz, Th. (1983) ‘Infrared fluorescence of molecules in comets: the general synthetic spectrum’, Astron. Ap., 126, 170–182.Google Scholar
Danks, A.C., Encrenaz, T., Bouchet, P., Le Bertre, T., and Chalabaev, A. (1987) ‘The spectrum of comet P/Halley from 3.0 to 4.0 μm’, Astron. Ap., 184, 329–332.Google Scholar
Despois, D., et al. (1986) ‘Observations of hydrogen cyanide in comet Halley’, Astron. Ap., 160, L11–L12.Google Scholar
Drapatz, S., Larson, H.P., and Davis, D.S. (1987) ‘Search for methane in comet P/Halley’, Astron. Ap., 187, 497–501.Google Scholar
Encrenaz, Th., Crovisier, J., Combes, M., and Crifo, J.F. (1982) ‘A theoretical study of comet Halley’s spectrum in the infrared range’, Icarus, 51, 660–664.CrossRefGoogle Scholar
Feldman, P.D., and Brune, W.H. (1977) ‘Carbon production in comet West 1975n’, Ap. J. Lett., 209, L45–L48.CrossRefGoogle Scholar
Feldman, P.D., et al. (1987) ‘IUE observations of P/Halley: evolution of the ultraviolet spectrum between September 1985 and July 1986’, Astron. Ap., 187, 325–328.Google Scholar
Hu, H-Y., and Larson, H.P. (1990) ‘The photochemical lifetime of H2O in cometary comae’, preprint.Google Scholar
Johnson, J.R., Fink, U., and Larson, H.P. (1983) ‘The 0.9-2.5 micron spectrum of comet West (1976 VI)’, Ap. J., 270, 769–777.CrossRefGoogle Scholar
Kawara, K., Gregory, B., Yamamoto, T., and Shibai, H. (1988) ‘Infrared spectroscopie observation of methane in comet Halley’, Astron. Ap., 207, 174–181.Google Scholar
Labs, D., and Neckel, H. (1968) ‘The radiation of the solar photosphere from 2000 À to 100 μ’, Zs. Ap., 69, 1–73.Google Scholar
Larson, H.P., Mumrna, M.J., Weaver, H.A., and Davis, D.S. (1986) ‘Velocity-resolved ob servations of water in comet Halley’, Ap. J. Lett., 309, L95–L99.CrossRefGoogle Scholar
Larson, H.P., Mumma, M.J., and Weaver, H.A. (1987) ‘Kinematic properties of the neutral gas outflow from comet P/Halley’, Astron. Ap., 187, 391–397.Google Scholar
Larson, H.P., Weaver, H.A., Mumma, M.J., and Drapatz, S. (1988) ‘Airborne infrared spectroscopy of comet Wilson (1986l) and comparisons with comet Halley’, Ap. J., 338, 1106–1114.CrossRefGoogle Scholar
Larson, H.P., Hu, H-Y., Mumma, M.J., and Weaver, H.A. (1990) ‘Outbursts of H2O in comet P/Halley’, Icarus, in press.CrossRefGoogle Scholar
McFadden, L.A., A’Hearn, M.F., Feldman, P.D., Roettger, E.E., Edsall, D.M., and Butter-worth, P.S. (1987) ‘Activity of comet P/Halley on March 23-25, 1986: IUE observations’, Astron. Ap., 187, 333–338.Google Scholar
Millis, R.L., and Schleicher, D.G. (1986) ‘Rotational period of comet Halley’, Nature, 324, 646–649.CrossRefGoogle Scholar
Moroz, V.l., et al. (1987) ‘Detection of parent molecules in comet P/Halley from the IKS-VEGA experiment’, Astron. Ap., 187, 513–518.Google Scholar
Mumma, M.J. (1982) ‘Speculations on the infrared spectra of comets’, in Mumma, M.J., Fox, K., and Hornstein, J. (eds.), Vibrational-rotational spectroscopy for planetary atmo spheres, NASA CP-2223, v. II, 717–744.Google Scholar
Mumma, M.J., Kostiuk, T., and Weaver, H.A. (1984) ‘Limits on the production of NH3 in comet IRAS-Araki-Alcock’, BAAS, 16, 638.Google Scholar
Mumma, M.J., Weaver, H.A., Larson, H.P., Davis, D.S., and Williams, M. (1986) ‘Detection of water vapor in Halley’s comet’, Science, 232, 1523–1528.CrossRefGoogle ScholarPubMed
Mumma, M.J., Weaver, H.A., and Larson, H.P. (1987) ‘The ortho-para ratio of water vapor in comet P/Halley’, Astron. Ap., 187, 419–424.Google Scholar
Mumma, M., Blass, W., Weaver, H., and Larson, H. (1988) ‘Measurements of the ortho-para ratio and nuclear spin temperature of water in comets Halley and Wilson (1986l) and implications for their origin and evolution’, in Weaver, H.A., Paresce, F. and Danly, L. (eds.), Poster Book from the STScI workshop on the Formation and Evolution of Planetary Systems, pp. 157–168.Google Scholar
Mumma, M.J., and Reuter, D. (1989) ‘On the identification of formaldehyde in Halley’s comet’, Ap. J., in press.CrossRefGoogle Scholar
Ney, E.P. (1974) ‘Multiband photometry of comets Kohoutek, Bennett, Bradfield, and Encke’, Icarus, 23, 551–560.CrossRefGoogle Scholar
Oishi, M., et al. (1978) ‘Infrared observations of comet West (1975n). I. Observational results’, Publ. Astron. Soc. Japan, 30, 149–159.Google Scholar
Roettger, E.E., Feldman, P.D., A’IIearn, M.F., FesM., C., McFadden, L.A., and Gilmozzi, R. (1989) ‘IUE observations of the evolution of comet Wilson (1986l): comparison with P/Halley’, Icarus, 80, 303–314.CrossRefGoogle Scholar
Schloerb, F.P., Kinzel, W.M., Swade, D.A., and Irvine, W.M. (1987) ‘Observations of HCN in comet P/Halley’, Astron. Ap., 187, 475–480.Google ScholarPubMed
Snyder, L.E., Palmer, P., and De Pater, I. (1989) ‘Radio detection of formaldehyde emission from comet Halley’, Astron. J., 97, 246–253.CrossRefGoogle Scholar
Weaver, H.A., and Mumma, M.J. (1984) ‘Infrared molecular emissions from comets’, Ap. J., 276, 782–797.CrossRefGoogle Scholar
Erratum, : (1984) Ap. J., 285, 872–873.Google Scholar
Weaver, H.A., Mumma, M.J., Larson, H.P., and Davis, D.S. (1986) ‘Post-Perihelion obser vations of water in comet Halley’, Nature, 324, 441–444.CrossRefGoogle Scholar
Weaver, H.A., Mumma, H.A., and Larson, H.P. (1987) ‘Infrared investigation of water in comet P/Halley’, Astron. Ap., 187, 411–418.Google Scholar
Wyckoff, S., Tegler, S., and Engel, L. (1990) ‘The ammonia abundance in four comets’, Ap. J., submitted.Google Scholar
Yamamoto, T. (1982) ‘Evaluation of infrared line emission from constituent molecules of cometary nuclei’, Astron. Ap., 109, 326–330.Google Scholar