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Iron and nickel atoms in cometary atmospheres even far from the Sun

Abstract

In comets, iron and nickel are found in refractory dust particles or in metallic and sulfide grains1. So far, no iron- or nickel-bearing molecules have been observed in the gaseous coma of comets2. Iron and a few other heavy atoms, such as copper and cobalt, have been observed only in two exceptional objects: the Great Comet of 18823 and, almost a century later, C/1965 S1 (Ikeya–Seki)4,5,6,7,8,9. These sungrazing comets approached the Sun so closely that refractory materials sublimated, and their relative abundance of nickel to iron was similar to that of the Sun and meteorites7. More recently, the presence of iron vapour was inferred from the properties of a faint tail in comet C/2006 P1 (McNaught) at perihelion10, but neither iron nor nickel was reported in the gaseous coma of comet 67P/Churyumov–Gerasimenko by the in situ Rosetta mission11. Here we report that neutral Fe i and Ni i emission lines are ubiquitous in cometary atmospheres, even far from the Sun, as revealed by high-resolution ultraviolet–optical spectra of a large sample of comets of various compositions and dynamical origins. The abundances of both species appear to be of the same order of magnitude, contrasting the typical Solar System abundance ratio.

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Fig. 1: Example of Fe i and Ni i lines in comet 103P/Hartley 2.
Fig. 2: Ni/Fe abundance ratios from the multilevel model versus heliocentric distance.

Data availability

The datasets analysed during the current study are available at the ESO Science Archive Facility at http://archive.eso.org/eso/eso_archive_main.html, under programme numbers 073.C-0525, 075.C- 0355(A), 080.C-0615, 086.C-0958, 087.C-0929, 270.C-5043, 274.C-5015, 2100.C-5035(A), 280.C-5053 and 2101.C-5051.

References

  1. Zolensky, M. E. et al. Mineralogy and petrology of comet 81P/Wild 2 nucleus samples. Science 314, 1735–1739 (2006).

    ADS  CAS  PubMed  Google Scholar 

  2. Bockelée-Morvan, D. & Biver, N. The composition of cometary ices. Philos. Trans. R. Soc. Lond. A 375, 20160252 (2017).

    ADS  Google Scholar 

  3. Copeland, R. & Lohse, J. G. in Copernicus: an International Journal of Astronomy Vol. 2, 225–244 (1882).

  4. Arpigny, C. in Liege International Astrophysical Colloquia Vol. 22 (eds Boury, A. et al.) 189–197 (1979).

  5. Combi, M. R., DiSanti, M. A. & Fink, U. The spatial distribution of gaseous atomic sodium in the comae of comets: evidence for direct nucleus and extended plasma sources. Icarus 130, 336–354 (1997).

    ADS  CAS  Google Scholar 

  6. Dufay, J., Swings, P. & Fehrenbach, Ch. Spectrographic observations of comet Ikeya-Seki (1965f). Astrophys. J. 142, 1698 (1965).

    ADS  CAS  Google Scholar 

  7. Preston, G. W. The spectrum of Ikeya-Seki (1965f). Astrophys. J. 147, 718–742 (1967).

    ADS  CAS  Google Scholar 

  8. Slaughter, C. D. The emission spectrum of comet Ikeya-Seki 1965-f at perihelion passage. Astron. J. 74, 929 (1969).

    ADS  Google Scholar 

  9. Thackeray, A. D., Feast, M. W. & Warner, B. Daytime spectra of comet Ikeya-Seki near perihelion. Astrophys. J. 143, 276 (1966).

    ADS  CAS  Google Scholar 

  10. Fulle, M. et al. Discovery of the atomic iron tail of comet McNaught using the heliospheric imager on STEREO. Astrophys. J. Lett. 661, L93–L96 (2007).

    ADS  CAS  Google Scholar 

  11. Altwegg, K. & ROSINA Team. Chemical highlights from the Rosetta mission. In Proceedings of the International Astronomical Union Vol. 13, 153–162 (IAU, 2017).

  12. Arpigny, C. et al. Anomalous nitrogen isotope ratio in comets. Science 301, 1522–1524 (2003).

    ADS  PubMed  Google Scholar 

  13. Guzik, P. & Drahus, M. Gaseous atomic nickel in the coma of interstellar comet 2I/Borisov. Nature https://doi.org/10.1038/s41586-021-03485-4 (2021).

  14. Arpigny, C. On the nature of comets. In Proceedings of the Robert A. Welch Foundation Conferences on Chemical Research XXI, Cosmochemistry (ed. Mulligan, W. O.) 9 (1978).

  15. Cochran, A. L. & Schleicher, D. G. Observational constraints on the lifetime of cometary H2O. Icarus 105, 235–253 (1993).

    ADS  CAS  Google Scholar 

  16. Biver, N. et al. Long-term monitoring of the outgassing and composition of comet 67P/Churyumov–Gerasimenko with the Rosetta/MIRO instrument. Astron. Astrophys. 630, A19 (2019).

    CAS  Google Scholar 

  17. Womack, M., Sarid, G. & Wierzchos, K. CO in distantly active comets. Publ. Astron. Soc. Pacif. 129, 031001 (2017).

    ADS  Google Scholar 

  18. Lodders, K. Solar elemental abundances. In Oxford Research Encyclopedia of Planetary Science https://doi.org/10.1093/acrefore/9780190647926.013.145 (2020).

  19. Larimer, J. W. & Anders, E. Chemical fractionations in meteorites – III. Major element fractionations in chondrites. Geochim. Cosmochim. Acta 34, 367–387 (1970).

    ADS  CAS  Google Scholar 

  20. Grossman, L. & Larimer, J. W. Early chemical history of the solar system. Rev. Geophys. Space Phys. 12, 71–101 (1974).

    ADS  CAS  Google Scholar 

  21. Lewis, J. S. Physics and Chemistry of the Solar System 2nd edn (Academic Press, 2004).

  22. Berger, E. L., Zega, T. J., Keller, L. P. & Lauretta, D. S. Evidence for aqueous activity on comet 81P/Wild 2 from sulfide mineral assemblages in Stardust samples and CI chondrites. Geochim. Cosmochim. Acta 75, 3501–3513 (2011).

    ADS  CAS  Google Scholar 

  23. Bradley, J. P. Chemically anomalous, preaccretionally irradiated grains in interplanetary dust from comets. Science 265, 925–929 (1994).

    ADS  CAS  PubMed  Google Scholar 

  24. Ishii, H. A. et al. Comparison of comet 81P/Wild 2 dust with interplanetary dust from comets. Science 319, 447 (2008).

    ADS  CAS  PubMed  Google Scholar 

  25. Bockelée-Morvan, D. et al. Comet 67P outbursts and quiescent coma at 1.3 au from the Sun: dust properties from Rosetta/VIRTIS-H observations. Mon. Not. R. Astron. Soc. 469, S443–S458 (2017).

    Google Scholar 

  26. Hensley, B. S. & Draine, B. T. Thermodynamics and charging of interstellar iron nanoparticles. Astrophys. J. 834, 134 (2017).

    ADS  Google Scholar 

  27. Ip, W.-H. & Jorda, L. Can the sodium tail of Comet Hale–Bopp have a dust-impact origin? Astrophys. J. 496, L47–L49 (1998).

    ADS  CAS  Google Scholar 

  28. Wurz, P. et al. Solar wind sputtering of dust on the surface of 67P/Churyumov–Gerasimenko. Astron. Astrophys. 583, A22 (2015).

    Google Scholar 

  29. Bloch, M. R. & Wirth, H. L. Abiotic organic synthesis in space. Naturwissenschaften 67, 562–564 (1980).

    ADS  CAS  Google Scholar 

  30. Klotz, A. et al. Possible contribution of organometallic species in the solar system ices. Reactivity and spectroscopy. Planet. Space Sci. 44, 957–965 (1996).

    ADS  CAS  Google Scholar 

  31. Huebner, W. F. Dust from cometary nuclei. Astron. Astrophys. 5, 286–297 (1970).

    ADS  CAS  Google Scholar 

  32. Tarakeshwar, P., Buseck, P. R. & Timmes, F. X. On the structure, magnetic properties, and infrared spectra of iron pseudocarbynes in the interstellar medium. Astrophys. J. 879, 2 (2019).

    ADS  CAS  Google Scholar 

  33. Smith, K. E., House, C. H., Arevalo, R. D., Dworkin, J. P. & Callahan, M. P. Organometallic compounds as carriers of extraterrestrial cyanide in primitive meteorites. Nat. Commun. 10, 2777 (2019).

    ADS  PubMed  PubMed Central  Google Scholar 

  34. Prialnik, D., Benkhoff, J. & Podolak, M. in Comets II (eds Festou et al.) 359–387 (Univ. of Arizona Press, 2004).

  35. Levison, H. F. Comet taxonomy. In Completing the Inventory of the Solar System Vol. 107 (eds. Rettig, T. W. & Hahn, J. M.) 173–191 (ASP, 1996).

  36. A’Hearn, M. F., Schleicher, D. G., Millis, R. L., Feldman, P. D. & Thompson, D. T. Comet Bowell 1980b. Astron. J. 89, 579–591 (1984).

    ADS  Google Scholar 

  37. Schleicher, D. G. The fluorescence efficiencies of the CN violet bands in comets. Astron. J. 140, 973–984 (2010).

    ADS  CAS  Google Scholar 

  38. Schleicher, D. G. & A’Hearn, M. F. The fluorescence of cometary OH. Astrophys. J. 331, 1058 (1988).

    ADS  CAS  Google Scholar 

  39. Bhardwaj, A. & Raghuram, S. A coupled chemistry-emission model for atomic oxygen green and red-doublet emissions in the comet C/1996 B2 Hyakutake. Astrophys. J. 748, 13 (2012).

    ADS  Google Scholar 

  40. Raghuram, S. et al. A physico-chemical model to study the ion density distribution in the inner coma of comet C/2016 R2(Pan-STARRS). Mon. Not. R. Astron. Soc. 501, 4035–4052 (2021).

  41. Weaver, H., Feldman, P., A’Hearn, M., Dello Russo, N. & Stern, A. Comet 103P/Hartley. IAU Circ. 9183, 1 (2010).

    ADS  Google Scholar 

  42. Roth, N. X. et al. Probing the evolutionary history of comets: an investigation of the hypervolatiles CO, CH4, and C2H6 in the Jupiter-family Comet 21P/Giacobini–Zinner. Astron. J. 159, 42 (2020).

    ADS  CAS  Google Scholar 

  43. DiSanti, M. A. et al. Depleted carbon monoxide in fragment C of the Jupiter-family comet 73P/Schwassmann–Wachmann 3. Astrophys. J. Lett. 661, L101–L104 (2007).

    ADS  CAS  Google Scholar 

  44. Böhnhardt, H. et al. The unusual volatile composition of the Halley-type comet 8P/Tuttle: addressing the existence of an inner Oort cloud. Astrophys. J. Lett. 683, L71 (2008).

    ADS  Google Scholar 

  45. Lupu, R. E., Feldman, P. D., Weaver, H. A. & Tozzi, G.-P. The fourth positive system of carbon monoxide in the Hubble Space Telescope spectra of comets. Astrophys. J. 670, 1473–1484 (2007).

    ADS  CAS  Google Scholar 

  46. DiSanti, M. A. et al. Detection of formaldehyde emission in comet C/2002 T7 (LINEAR) at infrared wavelengths: line-by-line validation of modeled fluorescent intensities. Astrophys. J. 650, 470–483 (2006).

    ADS  CAS  Google Scholar 

  47. Paganini, L. et al. Observations of comet C/2009 P1 (Garradd) at 2.4 and 2.0 AU before perihelion. In Asteroids, Comets, Meteors 2012 Vol. 1667, 6331 (Lunar Planetary Institute, 2012).

  48. Paganini, L. et al. The unexpectedly bright comet C/2012 F6 (Lemmon) unveiled at near-infrared wavelengths. Astron. J. 147, 15 (2013).

    ADS  Google Scholar 

  49. Biver, N. et al. The extraordinary composition of the blue comet C/2016 R2 (PanSTARRS). Astron. Astrophys. 619, A127 (2018).

    CAS  Google Scholar 

  50. Wierzchos, K. & Womack, M. C/2016 R2 (PANSTARRS): a comet rich in CO and depleted in HCN. Astron. J. 156, 34 (2018).

    ADS  Google Scholar 

  51. Faggi, S., Mumma, M. J., Villanueva, G. L., Paganini, L. & Lippi, M. Quantifying the evolution of molecular production rates of comet 21P/Giacobini–Zinner with iSHELL/NASA-IRTF. Astron. J. 158, 254 (2019).

    ADS  CAS  Google Scholar 

  52. de Val-Borro, M. et al. A survey of volatile species in Oort cloud comets C/2001 Q4 (NEAT) and C/2002 T7 (LINEAR) at millimeter wavelengths. Astron. Astrophys. 559, A48 (2013).

    Google Scholar 

  53. Yamamoto, T., Nakagawa, N. & Fukui, Y. The chemical composition and thermal history of the ice of a cometary nucleus. Astron. Astrophys. 122, 171–176 (1983).

    ADS  CAS  Google Scholar 

  54. Yamamoto, T. Formation environment of cometary nuclei in the primordial solar nebula. Astron. Astrophys. 142, 31–36 (1985).

    ADS  CAS  Google Scholar 

  55. Gilbert, A. G. & Sulzmann, K. G. P. The vapor pressure of iron pentacarbonyl. J. Electrochem. Soc. 121, 832 (1974).

    ADS  CAS  Google Scholar 

  56. Stull, D. R. Vapor pressure of pure substances. Organic and inorganic compounds. Ind. Eng. Chem. 39, 517–540 (1947).

    CAS  Google Scholar 

  57. Delsemme, A. H. Chemical composition of cometary nuclei. In IAU Colloq. 61: Comet Discoveries, Statistics, and Observational Selection (ed. Wilkening, L. L.) 85–130 (IAU, 1982).

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Acknowledgements

We thank P. van Hoof for discussions on the iron atomic data and their uncertainties. We thank R. Hewins and R. Warin for discussions about various Fe- and Ni-rich compounds in meteorites. We thank C. Arpigny, D. Bockelée-Morvan, A. Decock, C. Opitom, H. Rauer, P. Rousselot and B. Yang for leading some UVES proposals, and the ESO staff for service mode observations. J.M., D.H. and E.J. are Honorary Research Director, Research Director and Senior Research Associate at the Fonds de la Recherche Scientifique (F.R.S-FNRS), respectively.

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J.M. analysed the spectra and the coma profiles and wrote the main text. D.H. contributed to the proposals and observations, reduced and calibrated the spectra, built the fluorescence model, computed the carbonyl sublimation properties and wrote the Supplementary Information. E.J. led the UVES proposals and made most of the observations. All authors contributed to the discussion and the final text.

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Correspondence to J. Manfroid.

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Peer review information Nature thanks Dennis Bodewits and Ryan Fortenberry for their contribution to the peer review of this work.

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Extended data figures and tables

Extended Data Fig. 1 Examples of UVES comet spectra.

Comet spectra obtained with the UVES spectrograph at ESO VLT, showing many Fe i and Ni i lines in the selected wavelength region (3,425–3,530 Å). a, Spectrum of the water-poor and CO-rich long-period comet C/2016 R2 (PanSTARRS) at 3 au. b, Spectrum of the Jupiter-family comet 88P/Howell at 1.4 au. c, Spectrum of the new comet C/2002 T7 (LINEAR) at 0.68 au, with lines from the OH(1-2) band. d, Spectrum of the long-period comet C/2020 X5 (Kudo−Fujikawa). Fe i and Ni i lines are indicated by red and blue marks, respectively.

Extended Data Fig. 2 Comparisons of Fe i, Ni i and dust production rates.

ad, The production rates of Fe i and Ni i are compared to Afρ (which is the product of the reflectivity of the grains, their filling factor and the radius of the coma; used as a proxy for the dust production rate) and to the production rates of OH, CN and CO2+, as determined from our spectra. ef, The production rates of Fe i and Ni i are compared to those of H2O and CO measured in various previous studies for comets 8P, 9P, 21P, 73P, 103P, C/2000 WM1, C/2001 Q4, C/2002 T7, C/2009 P1, C/2012 F6 and C/2016 R2 at about the same epochs as our observations41,42,43,44,45,46,47,48,49,50,51,52. The various cometary types are colour-coded according to their dynamical classification (see Extended Data Table 1). The OH and H2O values relative to comet C/2016 R2 are upper limits. The Pearson correlation coefficients calculated without (with) the C/2016 R2 data are ρOH = 0.844 (0.531), ρAfρ = 0.644 (0.616), ρCN = 0.892 (0.518), \({\rho }_{{{{\rm{CO}}}_{2}}^{+}}\) = 0.755 (0.804), \({\rho }_{{{\rm{H}}}_{2}{\rm{O}}}\) = 0.849 (0.627) and ρCO = 0.752 (0.770).

Extended Data Fig. 3 Iron and nickel carbonyl sublimation properties.

a, Sublimation rates (Z; in molecules cm−2 s−1) of Fe and Ni carbonyls as a function of temperature, compared to those of the main ices in comets. The carbonyl rates are intermediate between those of H2O and CO2. b, The ratio of the sublimation rate of Ni(CO)4 over that of Fe(CO)5 shows that the former is considerably higher than the latter. These quantities were computed as follows. As in refs. 53,54, we estimate the condensation or sublimation temperature Ts of these compounds by solving the equation fxnkTs = Pv,x(Ts) where fx is the relative abundance of species x, n is the number density of the gas, k is the Boltzmann constant, and Pv,x is the vapour pressure, given by the relation log[Pv,x(T)] = −(A/T) + B. The constants A and B for Fe(CO)5 and Ni(CO)4 are obtained from refs. 55,56: A = 2,097 K and B = 11.62 for Fe(CO)5, A = 1,534 K and B = 10.87 for Ni(CO)4, with Pv,x in dyn cm−2. We consider relative abundances fx of 10−3–10−5 × fx(H2O) for both Fe(CO)5 and Ni(CO)4, and we adopt n = 1013 cm−3 as in ref. 54. The resulting sublimation temperatures of the iron and nickel carbonyls (97–108 K and 74–82 K, respectively, depending on fx) are between the sublimation temperatures of H2O and CO2 (152 K and 72 K), whereas CO sublimates at 25 K (ref. 54). The sublimation rate (in molecules cm−2 s−1) from the surface of a pure ice into vacuum can be expressed as57: Zx(T= Pv,x(T)(2πmxkT)−1/2, where T is the ice temperature and mx the mass of species x.

Extended Data Table 1 Conditions of comet observations with UVES at ESO VLT
Extended Data Table 2 Ni/Fe abundance ratios from the three-level and multilevel models
Extended Data Table 3 Production rates of molecules and dust

Supplementary information

Supplementary Information

This file contains details regarding the FeI and NiI fluorescence models and abundance measurements, Supplementary Figures 1–6 and Supplementary References.

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Manfroid, J., Hutsemékers, D. & Jehin, E. Iron and nickel atoms in cometary atmospheres even far from the Sun. Nature 593, 372–374 (2021). https://doi.org/10.1038/s41586-021-03435-0

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