Advertisement

Infrared Spectroscopy of Cometary Parent Molecules

  • H. A. Weaver
  • H. P. Larson
  • M. J. Mumma
Chapter
Part of the Astrophysics and Space Science Library book series (ASSL, volume 167)

Abstract

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.

Keywords

Parent Molecule Solar Flux Cometary Nucleus Fundamental Band Water Production Rate 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

Preview

Unable to display preview. Download preview PDF.

Unable to display preview. Download preview PDF.

References

  1. A’Hearn, M.F., and Feldman, P.D. (1982) ‘Carbon in comet Bradfield (1979l)’, Ap. J. Lett., 242, L187–L190.CrossRefGoogle Scholar
  2. Allen, M., et al. (1987) ‘Evidence for methane and ammonia in the coma of comet P/Halley’, Astron. Ap., 187, 502–512.ADSGoogle Scholar
  3. Altenhoff, W.J., et al. (1983) ‘Radio observations of comet 1983d’, Astron. Ap., 125, L19–L22.ADSGoogle Scholar
  4. 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.ADSCrossRefGoogle Scholar
  5. Bockelée-Morvan, D. (1987) ‘A model for the excitation of water in comets’, Astron. Ap., 181, 169–181.ADSGoogle Scholar
  6. Bockelée-Movan, D., and Crovisier, J. (1987a) ‘The role of water in the thermal balance of the coma’, in E.J. Rolfe and B. Battrick (eds.), Symposium on the diversity and similarity of comets, ESA SP-278, 235–240.Google Scholar
  7. 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.ADSGoogle Scholar
  8. 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.ADSCrossRefGoogle Scholar
  9. Chin, G., and Weaver, H.A. (1984) ‘Vibrational and rotational excitation of CO in comets: nonequilibrium calculations’, Ap. J., 285, 858–869.ADSCrossRefGoogle Scholar
  10. Combes, M., et al. (1988) ‘The 2.5–12 µm spectrum of comet Halley from the IKS-VEGA experiment’, Icarus, 76, 404–436.ADSCrossRefGoogle Scholar
  11. Crovisier, J. (1984) ‘The water molecule in comets: fluorescence mechanisms and thermodynamics of the inner coma’, Astron. Ap., 130, 361–372.ADSGoogle Scholar
  12. Crovisier, J. (1987) ‘Rotational and vibrational synthetic spectra of linear parent molecules in comets’, Astron. Ap. Suppl. Ser., 68, 223–258.ADSGoogle Scholar
  13. Crovisier, J. (1989) ‘The photodissociation of water in cometary atmospheres’, Astron. Ap., 213, 459–464.ADSGoogle Scholar
  14. Crovisier, J. (1990) ‘Infrared cometary spectroscopy’, in 22nd ESLAB symposium on infrared spectroscopy in astronomy, ESA SP-290, in press.Google Scholar
  15. Crovisier, J., and Encrenaz, Th. (1983) ‘Infrared fluorescence of molecules in comets: the general synthetic spectrum’, Astron. Ap., 126, 170–182.ADSGoogle Scholar
  16. 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.ADSGoogle Scholar
  17. Despois, D., et al. (1986) ‘Observations of hydrogen cyanide in comet Halley’, Astron. Ap., 160, L11–L12.ADSGoogle Scholar
  18. Drapatz, S., Larson, H.P., and Davis, D.S. (1987) ‘Search for methane in comet P/Halley’, Astron. Ap., 187, 497–501.ADSGoogle Scholar
  19. 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.ADSCrossRefGoogle Scholar
  20. Feldman, P.D., and Brune, W.U. (1977) ‘Carbon production in comet West 1975n’, Ap. J. Lett., 209, L45–L48.ADSCrossRefGoogle Scholar
  21. 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.ADSGoogle Scholar
  22. Hu, H-Y., and Larson, H.P. (1990) ‘The photochemical lifetime of H2O in cometary comae’, preprint.Google Scholar
  23. 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.ADSCrossRefGoogle Scholar
  24. Kawara, K., Gregory, B., Yamamoto, T., and Shibai, H. (1988) ‘Infrared spectroscopic observation of methane in comet Halley’, Astron. Ap., 207, 174–181.ADSGoogle Scholar
  25. Labs, D., and Neckel, H. (1968) ‘The radiation of the solar photosphere from 2000 Å to 100 µ’, Zs. Ap., 69, 1–73.ADSGoogle Scholar
  26. Larson, H.P., Mumma, M.J., Weaver, H.A., and Davis, D.S. (1986) ‘Velocity-resolved observations of water in comet Halley’, Ap. J. Lett., 309, L95–L99.ADSCrossRefGoogle Scholar
  27. 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.ADSGoogle Scholar
  28. 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.ADSCrossRefGoogle Scholar
  29. Larson, H.P., Hu, H-Y., Mumma, M.J., and Weaver, H.A. (1990) ‘Outbursts of H20 in comet P/Halley’, Icarus, in press.Google Scholar
  30. 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.ADSGoogle Scholar
  31. Millis, R.L., and Schleicher, D.G. (1986) ‘Rotational period of comet Halley’, Nature, 324, 646–649.ADSCrossRefGoogle Scholar
  32. Moroz, V.I., et al. (1987) ‘Detection of parent molecules in comet P/Halley from the IKS-VEGA experiment’, Astron. Ap., 187, 513–518.ADSGoogle Scholar
  33. Mumma, M.J. (1982) ‘Speculations on the infrared spectra of comets’, in M.J. Mumma, K. Fox, and J. Hornstein (eds.), Vibrational-rotational spectroscopy for planetary atmospheres, NASA CP-2223, v. II, 717–744.Google Scholar
  34. Mumma, M.J., Kostiuk, T., and Weaver, H.A. (1984) ‘Limits on the production of NH3 in comet IRAS-Araki-Alcock’, BAAS, 16, 638.ADSGoogle Scholar
  35. 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.ADSCrossRefGoogle Scholar
  36. 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.ADSGoogle Scholar
  37. Mumma, M., Blass, W., Weaver, H., and Larson, H. (1988) ‘Measurements of the orthopara ratio and nuclear spin temperature of water in comets Halley and Wilson (1986l) and implications for their origin and evolution’, in H.A. Weaver, F. Paresce and L. Danly (eds.), Poster Book from the STScI workshop on the Formation and Evolution of Planetary Systems, pp. 157–168.Google Scholar
  38. Mumma, M.J., and Reuter, D. (1989) ‘On the identification of formaldehyde in Halley’s comet’, Ap. J., in press.Google Scholar
  39. Ney, E.P. (1974) ‘Multiband photometry of comets Kohoutek, Bennett, Bradfield, and Encke’, Icarus, 23, 551–560.ADSCrossRefGoogle Scholar
  40. Oishi, M., et al. (1978) ‘Infrared observations of comet West (1975n). I. Observational results’, Publ. Astron. Soc. Japan, 30, 149–159.ADSGoogle Scholar
  41. Roettger, E.E., Feldman, P.D., A’Hearn, M.F., Fes M.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.ADSCrossRefGoogle Scholar
  42. 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.ADSGoogle Scholar
  43. Snyder, L.E., Palmer, P., and De Pater, I. (1989) ‘Radio detection of formaldehyde emission from comet Halley’, Astron. J., 97, 246–253.ADSCrossRefGoogle Scholar
  44. Weaver, H.A., and Mumma, M.J. (1984) ‘Infrared molecular emissions from comets’, Ap. J., 276, 782–797.ADSCrossRefGoogle Scholar
  45. Erratum: (1984) Ap. J., 285, 872–873.CrossRefGoogle Scholar
  46. Weaver, H.A., Mumma, M.J., Larson, H.P., and Davis, D.S. (1986) ‘Post-Perihelion observations of water in comet Halley’, Nature, 324, 441–444.ADSCrossRefGoogle Scholar
  47. Weaver, H.A., Mumma, H.A., and Larson, H.P. (1987) ‘Infrared investigation of water in comet P/Halley’, Astron. Ap., 187, 411–418.ADSGoogle Scholar
  48. Wyckoff, S., Tegler, S., and Engel, L. (1990) ‘The ammonia abundance in four comets’, Ap. J., submitted.Google Scholar
  49. Yamamoto, T. (1982) ‘Evaluation of infrared line emission from constituent molecules of cometary nuclei’, Astron. Ap., 109, 326–330.ADSGoogle Scholar

Copyright information

© Springer Science+Business Media Dordrecht 1991

Authors and Affiliations

  • H. A. Weaver
    • 1
  • H. P. Larson
    • 2
  • M. J. Mumma
    • 3
  1. 1.Space Telescope Science InstituteBaltimoreUSA
  2. 2.Department of Planetary SciencesUniversity of ArizonaTucsonUSA
  3. 3.Planetary Systems BranchNASA Goddard Space Flight CenterGreenbeltUSA

Personalised recommendations