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Replacement and late formation of atmospheric N2 on undifferentiated Titan by impacts

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Abstract

Saturn’s moon Titan has attracted much attention because of its massive nitrogen atmosphere1, but the origin of this atmosphere is largely unknown. Massive secondary atmospheres on planets and satellites usually form only after a substantial differentiation of the body’s interior and chemical reactions during accretion2,3,4,5,6,7, yet Titan’s interior has been found to be incompletely differentiated8. Here we propose that Titan’s nitrogen atmosphere formed after accretion, by the conversion from ammonia that was already present on Titan during the period of late heavy bombardment about four billion years ago9. Our laser-gun experiments show that ammonia ice converts to N2 very efficiently during impacts. Numerical calculations based on our experimental results indicate that Titan would acquire sufficient N2 to sustain the current atmosphere and that most of the atmosphere present before the late heavy bombardment would have been replaced by impact-induced N2. Our scenario is capable of generating a N2-rich atmosphere with little primordial Ar on undifferentiated Titan. If this mechanism generated Titan’s atmosphere, its N2 was derived from a source in the solar nebula different from that for Earth, and the origins of N2 on Titan and Triton may be fundamentally different from the origin of N2 on Pluto.

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Figure 1: Efficiency of impact-induced N2 production from NH3–H2O ice for different NH3 content (red: 50%; blue: 10%).
Figure 2: Evolution of Titan’s N2 inventory during the LHB.
Figure 3: The concentration of NH3, nNH3, on Titan required to accumulate 1.5 bar of N2 for various surface temperatures.

References

  1. Lunine, J. I. & Atreya, S. K. The methane cycle on Titan. Nature Geosci. 1, 159–164 (2008).

    Article  Google Scholar 

  2. Atreya, S. K., Donahue, T. M. & Kuhn, W. R. Evolution of a nitrogen atmosphere on Titan. Science 201, 611–613 (1978).

    Article  Google Scholar 

  3. McKay, C. P., Scattergood, T. W., Pollack, J. B., Borucki, W. J. & van Ghyseghem, H. T. High-temperature shock formation of N2 and organics on primordial Titan. Nature 332, 520–522 (1988).

    Article  Google Scholar 

  4. Glein, C. R., Desch, S. J. & Shock, E. L. The absence of endogenic methane on Titan and its implications for the origin of atmospheric nitrogen. Icarus 204, 637–644 (2009).

    Article  Google Scholar 

  5. Abe, Y., Ohtani, E., Okuchi, T., Righter, M. & Drake, M. in Origin of the Earth and Moon (eds Canup, R. M. & Righter, K.) 413–433 (Univ. Arizona Press, 2000).

    Google Scholar 

  6. Kuramoto, K. & Matsui, T. Formation of a hot proto-atmosphere on the accreting giant icy satellite: Implications for the origin and evolution of Titan, Ganymede, and Callisto. J. Geophys. Res. 99, 21183–21200 (1994).

    Article  Google Scholar 

  7. Lunine, J. I., Choukroun, M., Stevenson, D. & Tobie, G. in Titan from Cassini–Huygens (eds Brown, R. H., Lebreton, J-P. & Waite, J. H.) 35–59 (Springer, 2009).

    Book  Google Scholar 

  8. Iess, L. et al. Gravity field, shape, and moment of inertia of Titan. Science 327, 1367–1369 (2010).

    Article  Google Scholar 

  9. Gomes, R., Levison, H. F., Tsiganis, K. & Morbidelli, A. Origin of the cataclysmic Late Heavy Bombardment period of the terrestrial planets. Nature 435, 466–469 (2005).

    Article  Google Scholar 

  10. Niemann, H. B. et al. The abundances of constituents of Titan’s atmosphere from the GCMS instrument on the Huygens probe. Nature 438, 779–784 (2005).

    Article  Google Scholar 

  11. Alibert, Y. & Mousis, O. Formation of Titan in Saturn’s subnebula: Constraints from Huygens probe measurements. Astronom. Astrophys. 465, 1051–1060 (2007).

    Article  Google Scholar 

  12. Hersant, F., Gautier, D., Tobie, G. & Lunine, J. I. Interpretation of the carbon abundance in Saturn measured by Cassini. Planet. Space Sci. 56, 1103–1111 (2008).

    Article  Google Scholar 

  13. Barr, A. C., Citron, R. I. & Canup, R. M. Origin of a partially differentiated Titan. Icarus 209, 858–862 (2010).

    Article  Google Scholar 

  14. Zahnle, K., Schenk, P. M. & Levison, H. F. Cratering rates in the outer solar system. Icarus 163, 263–289 (2003).

    Article  Google Scholar 

  15. Griffith, C. A. & Zahnle, K. Influx of cometary volatiles to planetary moons: the atmospheres of 1,000 possible Titans. J. Geophys. Res. 100, 16907–16922 (1995).

    Article  Google Scholar 

  16. Shuvalov, V. Atmospheric erosion induced by oblique impacts. Meteor. Planet. Sci. 44, 1095–1105 (2009).

    Article  Google Scholar 

  17. Lorentz, R. D., McKay, C. P. & Lunine, J. I. Analytical investigation of climate stability on Titan: sensitivity to volatile inventory. Planet. Space Sci. 47, 1503–1515 (1999).

    Article  Google Scholar 

  18. Waite, J. H. et al. Liquid water on Enceladus from observations of ammonia and 40Ar in the plume. Nature 460, 487–490 (2009).

    Article  Google Scholar 

  19. Bockelée-Morvan, D., Crovisier, J., Mumma, M. J. & Weaver, H. A. in Comets II (eds Festou, M. C., Keller, H. C. & Weaver, H. A.) 391–423 (Univ. Arizona Press, 2004).

    Google Scholar 

  20. Iro, N., Gautier, D., Hersant, F., Bockelée-Morvan, D. & Lunine, J. I. An interpretation of the nitrogen deficiency in comets. Icarus 161, 511–532 (2003).

    Article  Google Scholar 

  21. Cruikshank, D. P. et al. A spectroscopic study of the surfaces of Saturn’s large satellites: H2O ice, tholin, and minor constituents. Icarus 175, 268–283 (2005).

    Article  Google Scholar 

  22. McKinnon, W. B., Lunine, J. I. & Banfield, D. in Neptune and Triton (ed. Cruikshank, D. P.) 807–877 (Univ. Arizona Press, 1995).

    Google Scholar 

  23. Brown, M. E. & Calvin, W. M. Evidence for crystalline water and ammonia ices on Pluto’s satellite Charon. Science 287, 107–109 (2000).

    Article  Google Scholar 

  24. Penz, T., Lammer, H., Kulikov, Yu. N. & Biernat, H. K. The influence of solar particle and radiation environment on Titan’s atmosphere evolution. Adv. Space Res. 36, 241–250 (2005).

    Article  Google Scholar 

  25. Mandt, K. E. et al. Isotopic evolution of the major constituents of Titan’s atmosphere based on Cassini data. Planet. Space Sci. 57, 1917–1930 (2009).

    Article  Google Scholar 

  26. Marty, B. et al. Nitrogen isotopes in the recent solar wind from the analysis of Genesis targets: Evidence for large scale isotope heterogeneity in the early solar system. Geochim. Cosmochim. Acta 74, 340–355 (2010).

    Article  Google Scholar 

  27. Yurimoto, H. & Kuramoto, K. Molecular cloud origin for the oxygen isotope heterogeneity in the Solar System. Science 305, 1763–1766 (2004).

    Article  Google Scholar 

  28. Lyons, J. R. & Young, E. D. CO self-shielding as the origin of oxygen isotope anomalies in the early solar nebula. Nature 435, 317–320 (2005).

    Article  Google Scholar 

  29. Charnley, S. B. & Rodgers, S. D. The end of interstellar chemistry as the origin of nitrogen in comets and meteorites. Astrophys. J. 569, L133–L137 (2002).

    Article  Google Scholar 

  30. Lyons, J. R. et al. Timescales for the evolution of oxygen isotope compositions in the solar nebula. Geochim. Cosmochim. Acta 73, 4998–5017 (2010).

    Article  Google Scholar 

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Acknowledgements

This study was supported by Grant in Aid from the Japan Society for the Promotion of Science and the Mitsubishi Foundation. Y.S. thanks S. Fukuzaki for help with the experiments and K. Kuramoto, K. Hamano, M. Arakawa, S. Watanabe, V. Shuvalov, C. P. McKay, S. K. Atreya and D. F. Strobel for helpful discussions.

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Y.S. designed the ice target system for the experiments, performed the experiments, modelled Titan’s N2 inventory, and wrote the manuscript. H.G. performed the SPH simulations. T.K. designed the laser-gun system. All the authors discussed and contributed intellectually to the interpretation of the results.

Corresponding author

Correspondence to Yasuhito Sekine.

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The authors declare no competing financial interests.

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Sekine, Y., Genda, H., Sugita, S. et al. Replacement and late formation of atmospheric N2 on undifferentiated Titan by impacts. Nature Geosci 4, 359–362 (2011). https://doi.org/10.1038/ngeo1147

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