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Haze evolution in temperate exoplanet atmospheres through surface energy measurements

Abstract

Photochemical hazes are important opacity sources in temperate exoplanet atmospheres, hindering current observations from characterizing exoplanet atmospheric compositions. The haziness of an atmosphere is determined by the balance between haze production and removal. However, the material-dependent removal physics of the haze particles are currently unknown under exoplanetary conditions. Here we provide experimentally measured surface energies for a grid of temperate exoplanet hazes to characterize haze removal in exoplanetary atmospheres. We found large variations of surface energies for hazes produced under different energy sources, atmospheric compositions and temperatures. The surface energies of the hazes were found to be the lowest around 400 K for the cold plasma samples, leading to the lowest removal rates. We show a suggestive correlation between haze surface energy and atmospheric haziness with planetary equilibrium temperature. We hypothesize that habitable-zone exoplanets could be less hazy, as they would possess high-surface-energy hazes that can be removed efficiently.

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Fig. 1: Experimental set-up for exoplanet haze production and surface energy measurement.
Fig. 2: Summary of the derived surface energies for the cold plasma and UV exoplanet haze samples.
Fig. 3: Summary of the measured mean contact angles between water and the haze samples using circle fitting results.
Fig. 4: Summary of derived mean refractive indices at visible wavelengths for the haze samples.
Fig. 5: Haze production and removal schematics for low-surface-energy and high-surface-energy hazes.
Fig. 6: Exoplanet atmosphere haziness and properties of exoplanet haze samples as a function of temperature.

Data availability

Source data are provided with this paper. The original sessile drop contact angle image files and the processed contact angle and surface energy data files can be found in the repository at https://doi.org/10.7291/D1BM2P. The original data for Fig. 6 can be found in refs. 5,6,7,8,44,45,46,47,48,65.

References

  1. Zhang, X., Strobel, D. F. & Imanaka, H. Haze heats Pluto’s atmosphere yet explains its cold temperature. Nature 551, 352–355 (2017).

    Article  ADS  Google Scholar 

  2. Hörst, S. M. et al. Haze production rates in super-Earth and mini-Neptune atmosphere experiments. Nat. Astron. 2, 303–306 (2018).

    Article  ADS  Google Scholar 

  3. Arney, G. et al. The pale orange dot: the spectrum and habitability of hazy Archean Earth. Astrobiology 16, 873–899 (2016).

    Article  ADS  Google Scholar 

  4. Gao, P. et al. Aerosol composition of hot giant exoplanets dominated by silicates and hydrocarbon hazes. Nat. Astron. 4, 951–956 (2020).

    Article  ADS  Google Scholar 

  5. Knutson, H. A., Benneke, B., Deming, D. & Homeier, D. A featureless transmission spectrum for the Neptune-mass exoplanet GJ 436b. Nature 505, 66–68 (2014).

    Article  ADS  Google Scholar 

  6. Knutson, H. A. et al. Hubble Space Telescope near-IR transmission spectroscopy of the super-Earth HD 97658b. Astrophys. J. 794, 155 (2014).

    Article  ADS  Google Scholar 

  7. Kreidberg, L. et al. Clouds in the atmosphere of the super-Earth exoplanet GJ 1214b. Nature 505, 69–72 (2014).

    Article  ADS  Google Scholar 

  8. Libby-Roberts, J. E. et al. The featureless transmission spectra of two super-puff planets. Astrophys. J. 159, 57 (2020).

    Google Scholar 

  9. Jacobson, M. C., Hansson, H.-C., Noone, K. J. & Charlson, R. J. Organic atmospheric aerosols: review and state of the science. Rev. Geophys. 38, 267–294 (2000).

    Article  ADS  Google Scholar 

  10. Bender, F. A.-M. Aerosol forcing: still uncertain, still relevant. AGU Adv. 1, e2019AV000128 (2020).

  11. Trainer, M. G. et al. Organic haze on Titan and the early Earth. Proc. Natl Acad. Sci. USA 103, 18035–18042 (2006).

    Article  ADS  Google Scholar 

  12. He, C. et al. Laboratory simulations of haze formation in the atmospheres of super-Earths and mini-Neptunes: particle color and size distribution. Astrophys. J. 856, L3 (2018).

    Article  ADS  Google Scholar 

  13. He, C. et al. Photochemical haze formation in the atmospheres of super-Earths and mini-Neptunes. Astron. J. 156, 38 (2018).

    Article  ADS  Google Scholar 

  14. He, C. et al. Sulfur-driven haze formation in warm CO2-rich exoplanet atmospheres. Nat. Astron. 4, 986–993 (2020).

    Article  ADS  Google Scholar 

  15. He, C. et al. Haze formation in warm H2-rich exoplanet atmospheres. Planet. Sci. J. 1, 51 (2020).

    Article  Google Scholar 

  16. Seinfeld, J. H. & Pandis, S. N. Atmospheric Chemistry and Physics: From Air Pollution to Climate Change 2nd edn (Wiley, 2006).

  17. Kanakidou, M. et al. Organic aerosol and global climate modelling: a review. Atmos. Chem. Phys. 5, 1053–1123 (2005).

    Article  ADS  Google Scholar 

  18. Israelachvili, J. N. Intermolecular and Surface Forces 3rd edn (Academic Press, 2011).

  19. Tavana, H., Petong, N., Hennig, A., Grundke, K. & Neumann, A. W. Contact angles and coating film thickness. J. Adhes. 81, 29–39 (2005).

    Article  Google Scholar 

  20. He, C. et al. Gas phase chemistry of cool exoplanet atmospheres: insight from laboratory simulations. ACS Earth Space Chem. 3, 39–50 (2019).

    Article  Google Scholar 

  21. Moran, S. E. et al. Chemistry of temperate super-Earth and mini-Neptune atmospheric hazes from laboratory experiments. Planet. Sci. J. 1, 17 (2020).

    Article  Google Scholar 

  22. Vuitton, V. et al. H2SO4 and organosulfur compounds in laboratory analogue aerosols of warm high-metallicity exoplanet atmospheres. Planet. Sci. J. 2, 2 (2021).

    Article  Google Scholar 

  23. He, C. et al. Carbon monoxide affecting planetary atmospheric chemistry. Astrophys. J. 841, L31 (2017).

    Article  ADS  Google Scholar 

  24. Moses, J. I. et al. Compositional diversity in the atmospheres of hot Neptunes, with application to GJ 436b. Astrophys. J. 777, 34 (2013).

    Article  ADS  Google Scholar 

  25. Yu, X. et al. Surface energy of the Titan aerosol analog ‘tholin’. Astrophys. J. 905, 88 (2020).

    Article  ADS  Google Scholar 

  26. Slinn, W. G. N. et al. Some aspects of the transfer of atmospheric trace constituents past the air-sea interface. Atmos. Environ. 12, 2055–2087 (1978).

    Article  ADS  Google Scholar 

  27. Emerson, E. W. et al. Revisiting particle dry deposition and its role in radiative effect estimates. Proc. Natl Acad. Sci. USA 117, 26076–26082 (2020).

    Article  ADS  Google Scholar 

  28. Marlow, W. H. Size effects in aerosol particle interactions: the van der Waals potential and collision rates. Surf. Sci. 106, 529–537 (1981).

    Article  ADS  Google Scholar 

  29. Monti, J. M., McGuiggan, P. M. & Robbins, M. O. Effect of roughness and elasticity on interactions between charged colloidal spheres. Langmuir 35, 15948–15959 (2019).

    Article  Google Scholar 

  30. Hörst, S. M. et al. Laboratory investigations of Titan haze formation: in situ measurement of gas and particle composition. Icarus 301, 136–151 (2018).

    Article  ADS  Google Scholar 

  31. Trainer, M. G., Jimenez, J. L., Yung, Y. L., Toon, O. B. & Tolbert, M. A. Nitrogen incorporation in CH4-N2 photochemical aerosol produced by far ultraviolet irradiation. Astrobiology 12, 315–326 (2012).

    Article  ADS  Google Scholar 

  32. Köhler, H. The nucleus in and the growth of hygroscopic droplets. Trans. Faraday Soc. 32, 1152–1161 (1936).

    Article  Google Scholar 

  33. Fletcher, N. H. The Physics of Rainclouds (Cambridge Univ. Press, 1962).

  34. Gorbunov, B. & Hamilton, R. Water nucleation on aerosol particles containing both soluble and insoluble substances. J. Aerosol Sci. 28, 239–248 (1997).

    Article  ADS  Google Scholar 

  35. Raymond, T. M. & Pandis, S. N. Cloud activation of single-component organic aerosol particles. J. Geophys. Res. Atmos. 107, 4787 (2002).

    Article  ADS  Google Scholar 

  36. Wenzel, R. N. Resistance of solid surfaces to wetting by water. Ind. Eng. Chem. 28, 988–994 (1936).

    Article  Google Scholar 

  37. Hay, K. M., Dragila, M. I. & Liburdy, J. Theoretical model for the wetting of a rough surface. J. Colloid Interface Sci. 325, 472–477 (2008).

    Article  ADS  Google Scholar 

  38. Nishino, T., Meguro, M., Nakamae, K., Matsushita, M. & Ueda, Y. The lowest surface free energy based on –CF3 alignment. Langmuir 15, 4321–4323 (1999).

    Article  Google Scholar 

  39. Morley, C. V. et al. Quantitatively assessing the role of clouds in the transmission spectrum of GJ 1214b. Astrophys. J. 775, 33 (2013).

    Article  ADS  Google Scholar 

  40. Gao, P. & Benneke, B. Microphysics of KCl and ZnS Clouds on GJ 1214 b. Astrophys. J. 863, 165 (2018).

    Article  ADS  Google Scholar 

  41. Zhang, X. Atmospheric regimes and trends on exoplanets and brown dwarfs. Res. Astron. Astrophys. 20, 99 (2020).

    Article  ADS  Google Scholar 

  42. Rannou, P. et al. Titan haze distribution and optical properties retrieved from recent observations. Icarus 208, 850–867 (2010).

    Article  ADS  Google Scholar 

  43. France, K. et al. The MUSCLES Treasury Survey. I. Motivation and overview. Astrophys. J. 820, 89 (2016).

    Article  ADS  Google Scholar 

  44. Fraine, J. et al. Water vapour absorption in the clear atmosphere of a Neptune-sized exoplanet. Nature 513, 526–529 (2014).

    Article  ADS  Google Scholar 

  45. Benneke, B. et al. A sub-Neptune exoplanet with a low-metallicity methane-depleted atmosphere and Mie-scattering clouds. Nat. Astron. 3, 813–821 (2019).

    Article  ADS  Google Scholar 

  46. Benneke, B. et al. Water vapor and clouds on the habitable-zone sub-Neptune exoplanet K2-18b. Astrophys. J. 887, L14 (2019).

    Article  ADS  Google Scholar 

  47. Guo, X. et al. Updated parameters and a new transmission spectrum of HD 97658b. Astron. J. 159, 239 (2020).

    Article  ADS  Google Scholar 

  48. Edwards, B. et al. Hubble WFC3 spectroscopy of the habitable-zone super-Earth LHS 1140 b. Astron. J. 161, 44 (2021).

    Article  ADS  Google Scholar 

  49. Cable, M. L. et al. Titan tholins: simulating Titan organic chemistry in the Cassini–Huygens era. Chem. Rev. 112, 1882–1909 (2012).

    Article  Google Scholar 

  50. Sebree, J. A., Trainer, M. G., Loeffler, M. J. & Anderson, C. M. Titan aerosol analog absorption features produced from aromatics in the far infrared. Icarus 236, 146–152 (2014).

    Article  ADS  Google Scholar 

  51. Schneider, C. A., Rasband, W. S. & Eliceiri, K. W. NIH Image to ImageJ: 25 years of image analysis. Nat. Methods 9, 671–675 (2012).

    Article  Google Scholar 

  52. Extrand, C. W. & Moon, S. I. Contact angles of liquid drops on super hydrophobic surfaces: understanding the role of flattening of drops by gravity. Langmuir 26, 17090–17099 (2010).

    Article  Google Scholar 

  53. Law, K. Y. & Zhao, H. Surface Wetting: Characterization, Contact Angle, and Fundamentals (Springer, 2016).

  54. Owens, D. K. & Wendt, R. C. Estimation of the surface free energy of polymers. J. Appl. Polym. Sci. 13, 1741–1747 (1969).

    Article  Google Scholar 

  55. Rabel, W. Einige Aspekte der Benetzungstheorie und ihre Anwendung auf die Untersuchung und Veränderung der Oberflächeneigenschaften von Polymeren. Farbe Lack 77, 997–1005 (1971).

    Google Scholar 

  56. Kaelble, D. H. Dispersion-polar surface tension properties of organic solids. J. Adhes. 2, 66–81 (1970).

    Article  Google Scholar 

  57. Lifshitz, E. M. & Hamermesh, M. in Perspectives in Theoretical Physics (ed. Pitaevski, L.P.) Ch. 26 (Pergamon, 1992).

  58. Ninham, B. W. & Parsegian, V. A. Van der Waals forces: special characteristics in lipid–water systems and a general method of calculation based on the Lifshitz theory. Biophys. J. 10, 646–663 (1970).

    Article  Google Scholar 

  59. Maxwell, J. C. A dynamical theory of the electromagnetic field. Phil. Trans. R. Soc. Lond. I 155, 459–512 (1865).

    ADS  Google Scholar 

  60. van Oss, C. J. Interfacial Forces in Aqueous Media 2nd edn (CRC Press, 2006).

  61. Stevenson, K. B. Quantifying and predicting the presence of clouds in exoplanet atmospheres. Astrophys. J. 817, L16 (2016).

    Article  ADS  Google Scholar 

  62. Fu, G. et al. Statistical analysis of Hubble/WFC3 transit spectroscopy of extrasolar planets. Astrophys. J. 847, L22 (2017).

    Article  ADS  Google Scholar 

  63. Crossfield, I. J. M. & Kreidberg, L. Trends in atmospheric properties of Neptune-size exoplanets. Astron. J. 154, 261 (2017).

    Article  ADS  Google Scholar 

  64. Tsiaras, A., Waldmann, I. P., Tinetti, G., Tennyson, J. & Yurchenko, S. N. Water vapour in the atmosphere of the habitable-zone eight-Earth-mass planet K2-18b. Nat. Astron. 3, 1086–1091 (2019).

    Article  ADS  Google Scholar 

  65. Kloubek, J. Calculation of surface free energy components of ice according to its wettability by water, chlorobenzene, and carbon disulfide. J. Colloid Interface Sci. 46, 185–190 (1974).

    Article  ADS  Google Scholar 

  66. Yaw, C. L. Thermophysical Properties of Chemicals and Hydrocarbons 1st edn (William Andrew, 2009).

  67. Kaltenegger, L. & Sasselov, D. Exploring the habitable zone for Kepler planetary candidates. Astrophys. J. 736, L25 (2011).

    Article  ADS  Google Scholar 

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Acknowledgements

X.Y. is supported by a 51 Pegasi b Fellowship from the Heising-Simons Foundation. X.Z. is supported by the NASA Solar System Workings Program (grant no. 80NSSC19K0791). C.H. and S.M.H. are supported by the NASA Exoplanets Research Program (grant no. NNX16AB45G). P.M. is supported by a 3M Non-Tenured Faculty Grant. S.E.M. is supported by a NASA Earth and Space Science Fellowship (grant no. 80NSSC18K1109).

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Contributions

X.Y., C.H., X.Z. and S.M.H. conceived the study. C.H. prepared the samples. X.Y. and C.H. performed the surface energy measurements. P.M. helped with interpretation of the surface energy measurements. X.Y. and A.H.D. performed the water amplitude calculations. X.Y., C.H., S.M.H. and J.I.M. discussed the chemistry for haze formation. X.Y. and X.Z. discussed the implication of the results for haze removal. X.Y. conducted the data analysis and prepared the manuscript. X.Y., C.H., X.Z., S.M.H., A.H.D., P.M., J.I.M., N.K.L., J.J.F., P.G., E.M.-R.K., S.E.M., C.V.M., D.P., J.A.V. and V.V. contributed to discussing the results and editing the manuscript.

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Correspondence to Xinting Yu.

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Yu, X., He, C., Zhang, X. et al. Haze evolution in temperate exoplanet atmospheres through surface energy measurements. Nat Astron 5, 822–831 (2021). https://doi.org/10.1038/s41550-021-01375-3

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