Abstract
Exobiology is not only the study of the origin, distribution and evolution of life in the universe, but also of structures — including at the molecular level, and processes — including organic chemical transformations — related to life. In that respect, with its dense nitrogen atmosphere, which includes a noticeable fraction of methane, and the many organic compounds which are present in the gas and aerosols phases, Titan appears to be a planetary object of prime interest for exobiology in the Solar system, allowing the study of chemical organic evolution in a planetary environment over a long time scale. We describe here some aspects of this extraterrestrial organic chemistry which involves many physical and chemical couplings in the different parts of what can be called ‘Titan's geofluid’ (gas phase, aerosol phases and surface solid and maybe liquid phases). The three complementary approaches which can be followed to study such chemistry of exobiological interest are considered. Those are experimental simulations in the laboratory, chemical and photochemical modeling and of course observation, using both remote sensing and in situ measurements, which is an essential approach. The Cassini-Huygens mission, that offers a unique opportunity to study in detail the many aspects of Titan's organic chemistry, is discussed and the many expected exobiological returns from the different instruments of the Cassini orbiter and the Huygens probe are considered.
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Afflalaye, A., Andrieux, D., Bénilan, Y., Bruston, P., Coll, P., Coscia, D., Gazeau, M.-C., Khlifi, M., Paillous, P., Sternberg, R., De Vanssay, E., Guillemin, J.-C., and Raulin, F.: 1995, 'Thermally Instable Polyynes and N-Organics of Planetological Interest: New Laboratory Data and Implications for their Detection by In Situ and Remote Sensing Techniques', Adv. Space Res. 15 (10), 5–11.
Badoz, J., Le Liboux, M., Nahoum, R., Israel, G., Raulin, F., and Torre, J.-P.: 1992, 'A sensitive cryogenic refractometer. Application to the refractive index determination of pure or mixed liquid methane, ethane and nitrogen', Rev. Sci. Instrum. 63 (5), 1–7.
Bossard, A., Mourey, D., and Raulin, F.: 1983, 'The escape of molecular hydrogen and the synthesis of organic nitriles in planetary atmospheres', Adv. Space Res. 3 (9), 39–43.
Capone, L. A., Dubach, J., Prasad, S. S., and Whitten, R. C.: 1983, Galactic cosmic rays and N2 dissociation on Titan', Icarus 55, 73–82.
Chyba, C.F., Thomas, P. J., Brookshaw, L., and Sagan, C.: 1990, 'Cometary delivery of organic molecules to the early Earth', Science 249, 366–373.
Clarke, D. W., and Ferris, J. P.: 1997, 'Titan haze: structure and properties of cyanoacetylene and cyanoacetylene-acetylene photopolymers', Icarus 127, 158–172.
Coll, P., Coscia, D., Gazeau, M.-C., De Vanssay, E., Guillemin, J.-C., and Raulin, F.: 1995, 'Organic chemistry in Titan's atmosphere: new data from laboratory simulations at low temperature', Adv. Space Res. 16 (2) 93–104.
Coll, P.: 1997, 'Modélisation expérimentale de l'atmosphère de Titan: production et caractérisations physico-chimiques d'analogues des aérosols et de la phase gazeuse enfin représentatifs',Thèse de Doctorat de l'Université Paris 12.
Coll, P., Coscia, D., Gazeau, M.-C., Guez, L., and Raulin, F.: 1997, 'New planetary atmosphere simulations: application to the organic aerosols of Titan', Adv. Space Res. 19 (7), 1113–1119.
Coll, P., Guillemin, J.C., Gazeau, M.-C., and Raulin, F.: 1999, 'Report and implications of the first observation of C4N2 in laboratory simulations of Titan's atmosphere', Planet. Space Sci., 47 (12), 1433–1440.
Combes, M., Vapillon, L., Gendron, E., Coustenis, A., Lai, O., Wittemberg, R., and Sirdey, R.: 1997, 'Spatially Resolved Images of Titan by Means of Adaptive Optics', Icarus 129, 482–497.
Coustenis, A., Salama, A., Lellouch, E., Encrenaz, Th., Bjoraker, G. L., Samuelson, R. E., De Graauw, Th., Feuchtgruber, F., and Kessler, M. F.: 1998, 'Evidence for water vapor in Titan's atmosphere from ISO/SWS data', Astron. Astrophys. 336, L85–L89.
Cruikshank, D. P., Roush, T. L., Owen, T. C., Geballe, T. R., De Bergh, C., Schmitt, B., Brown, R. H., Bartholomew, M. J.: 1993, 'Ices on the Surface of Triton', Science 261, 742–745.
Curtis, A.R.: 1979, 'An introduction to the facsimile Program', UK Atomic Energy Authority Harwell, AERE-R 9352.
Dermott, S. F., and Sagan, C.: 1995, 'Tidal effects of disconnected hydrocarbon seas on Titan', Nature 374, 238–240; and refs. included.
Dubouloz, N., Raulin, F., Lellouch, E., and Gautier, D.: 1989, 'Titan's hypothesized ocean properties: the influence of surface temperature and atmospheric composition uncertainties', Icarus 82, 81–96.
Frère, C.: 1989, 'Etude physico-chimique de l'atmosphère de l'aérosol et de l'océan de Titan', Thèse de Doctorat, Université Paris 12.
Frère, C., Raulin, F., Israel, G., and Cabane, C.: 1990, 'Microphysical Modeling of Titan's Aerosols: Application to the in Situ Analysis', Adv. Space Res. 10 (1), 159–163.
Gautier, D.: 1995, 'Titan's atmosphere composition: certainties and speculations', Adv. Space Res. 15 (3), 295–301.
Gautier, D.: 1997, 'The aeronomy of Titan', ESA-SP 1177, 199–209.
Gautier, D., and Raulin, F.: 1997, 'Chemical composition of Titan's atmosphere', ESA Special Publication SP 1177, 359–364.
Griffith, C.A., Owen, T., and Wagener, R.: 1991, 'Titan's surface and troposphere investigated with ground-based near-infrared observations', Icarus 93, 362–378.
Griffith, C.A.: 1993, 'Evidence for surface heterogeneity on Titan', Nature 364, 511–514.
Hunten, D. M., Tomasko, M. G., Flasar, F. M., Samuelson, R. E., Strobel, D. F., and Stevenson, D. J.: 1984, 'Titan', In Saturn, T. Gehrels & M.S. Matthews Eds., Univ. of Arizona Press, 671–759.
Khare, B. N., Sagan, C., Zumberge, J. E., Sklarew, D. S., and Nagy, B.: 1981, Organic solids produced by electrical discharge in reducing atmospheres: tholin molecular analysis', Icarus 48, 290–297.
Khare, B. N., Sagan, C., Thompson, W. R., Arakawa, E. T., Suits, F., Callcott, T. A., Williams, M. W., Shrader, S., Ogino, H., Willigham, T. O., and Nagy, B.: 1984, 'The organic aerosols of Titan', Adv. Space Res. 4 (12), 59–68.
Kasting, J.F.: 1997,'Warming early Earth and Mars', Science 276, 1213–1215.
Lara, L.M.: 1993, 'Estudio fotochimico de los componentes neutros de la atmosfera de Titan', Thesis Doctoral, Granada, Spain.
Lara, L.M., Lellouch, E., Lopez-Moreno, J. J., and Rodrigo, R.: 1996, 'Vertical distribution of Titans' atmospheric neutral constituents', J. Geophys. Res. 1001 (E10), 23261–23283.
Lellouch, E., Coustenis, A., Gautier, D., Raulin, F., Dubouloz, N., and Frere, C.: 'Titans Atmosphere and Hypothesized Ocean: a Reanalysis of the Voyager 1 Radio-Occultation and IRIS 7.7 µm data', Icarus 79, 328–349.
Lunine, J. I., Stevenson, D. J., and Yung, Y. L.:1983, 'Ethane ocean on Titan', Science 222, 1229–1230.
Lunine, J. I.: 1993, 'Does Titan have an ocean? A review of current understanding of Titan's surface', Rev. Geophys. 31 (2), 133–149.
Lunine, J. I.: 1997, 'Titan surface-atmosphere interactions', ESA SP-1177, 211–218.
McKay, C. P.: 1996, 'Elemental composition, solubility, and optical properties of Titan's organic haze', Planet.. Space Sci. 44 (8), 741–747.
Miller, S. L.: 1953, 'A production of aminoacids under possible primitive earth conditions' Science 117, 528–529.
Miller, S.L., and Orgel, L.: 1974, 'The origins of Life on the Earth', Prentice Hall, N. Jersey.
Molton, P.: 1974, 'Non-aqueous biosystems: the case for liquid ammonia as a solvent', J. British Interplanetary Soc. 27, 243–262.
Muhleman, D.O., Grossman, A. W., and Butler, B. J.: 1995, 'Radar investigation of Mars, Mercury and Titan', Ann. Rev. Earth and Planet. Sci. 23, 337–374.
Oro, J., and Cosmovici, C.B.: 1997, 'Comets and life on the primitive Earth', in Astronomical and Biochemical Origins and the Search for Life in the Universe, C.B. Cosmovici et al Eds., Editrice Compositori, Bologna, Italy, 97–120.
Owen, T., and Gautier, D.: 1989, 'Titan: some new results', Adv. Space Res. 9 (2), 73–78.
Owen, T. C., Roush, T. L., Cruikshank, D. P., Elliot, J. L., Young, L. A.., De Bergh, C., Schmitt, B., Geballe, T. R., Brown, R. H., Bartholomew, M. J.: 1993, 'Surface Ices and the Atmospheric Composition of Pluto', Science 261, 745–748.
Raulin, F., Mourey, D., and Toupance, G.: 1982, 'Organic syntheses from CH4-N2 atmospheres: implications for Titan', Origins of Life 12, 267–279.
Raulin, F.: 1987, 'Organic Chemistry in the Oceans of Titan', Adv. Space Res. 7 (5), 71–81.
Raulin, F.: 1990, 'Prebiotic Syntheses of Biologically Interesting Monomers in Aqueous Solutions: Facts and Constraints', J. British Interplan. Soc. 43, 39–45.
Raulin, F., Frere, C., Do, L., Khlifi, M., Paillous, P., and De Vanssay, E.: 1992, 'Organic chemistry on Titan versus terrestrial prebiotic chemistry: exobiological implications', ESA Special Publication SP 338, 149–160.
Raulin, F., Bruston, P., Paillous, P., and Sternberg, R.: 1995, 'The low temperature organic chemistry of Titan's geofluid', Adv. Space Res. 15 (3), 321–333.
Sagan, C., and Chyba, C.: 1997, 'The early faint sun paradox: organic shielding of ultraviolet-labile greenhouse gases', Science 276, 1217–1221.
Sagan, C., and Thompson, W. R.: 1984, 'Production and condensation of organic gases in the atmosphere of Titan',Icarus 59, 133–161.
Samuelson, R. E., Maguire, W. C., Hanel, R. A., Kunde, V. G., Jennings, D. E., Yung, Y. L., and Aikin, A. C.: 1983, 'CO2 on Titan', J. Geophys. Res. 88 (A11), 8709–8715.
Shock, E. L., McCollom, T., and Schulte, M. D.: 1995, 'Geochemical constraints on chemolithoautotrophic reactions in hydrothermal systems', Origins of Life and Evol. Biosphere 25, 141–159.
Smith, P. H., Lemmon, M. T., Lorenz, R. D., Sromovsky, L. A., Caldwell, J. J., and Allison, M. D.: 1996, 'Titan's surface revealed by HST Imaging', Icarus 119, 336–349.
Strobel, D.: 1982, 'Chemistry and evolution of Titan's atmosphere', Planet. Space Sci. 30, 839–848.
Thompson, W. R., Todd, H., Schwartz, J., Khare, B., and Sagan, C.: 1991, 'Plasma discharge in N2 + CH4 at low pressures: experimental results and applications to Titan', Icarus 90, 57–73.
Thompson, W. R., Zollweg, J. A., and Gabis, D. H.: 1992, 'Vapor-liquid equilibrium thermodynamics of N2 + CH4: model and Titan applications', Icarus 97, 187–199.
Toon, O., McKay, C. P., Courtin, R., and Ackerman, T.: 1988, 'Methane rain on Titan', Icarus 75, 255–284.
Toublanc, D.: 1992, 'Etude de la Physico-chimie de l'atmosphère de Titan', Thèse de Doctorat, Université Bordeaux.
Toublanc, D., Parisot, J.-P., Brillet, J., Gautier, D., Raulin, F., and Mckay, C. P.: 1995, 'Photochemical modeling of Titans atmosphere', Icarus 13, 2–26.
De Vanssay, E., Gazeau, M.-C., Guillemin, J.-C., and Raulin, F.: 1995, 'Experimental simulation of Titan's organic chemistry at low temperature', Planet. Space Sci. 43, 25–31.
Yung, Y.L., Allen, M., and Pinto, J. P.: 1984, 'Photochemistry of the atmosphere of Titan: comparison between model and observations', Astrophys. J. Suppl. Ser. 55, 465–506.
Yung, Y. L.: 1987, 'An update of nitrile photochemistry on Titan', Icarus 72, 468–472.
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Raulin, F., Owen, T. Organic Chemistry and Exobiology on Titan. Space Science Reviews 104, 377–394 (2002). https://doi.org/10.1023/A:1023636623006
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DOI: https://doi.org/10.1023/A:1023636623006