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Fine-grained regolith loss on sub-km asteroids

Nature Astronomy volume 6, pages 1043–1050 (2022)Cite this article

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Abstract

Fine-grained regolith, a surface layer of unconsolidated granular material, has been considered to cover the surfaces of airless bodies and determine their spectral and thermophysical properties. However, surfaces of asteroids visited by recent sample return missions are dominated by centimetre- to metre-sized boulders, indicating an active fine-grained regolith removal process at work. To understand asteroid regolith evolution, we apply recent space and laboratory experimental results to simulate regolith fragmentation processes, loss by impact ejecta, and electrostatic removal of fine-grained regolith. Here we show that coarse, boulder-rich scenery probably emerges on kilometre-sized and smaller asteroids within a few million years, as the electrostatic removal of fine-grained regolith dominates production by fragmentation. Surface thermal inertia enhancement associated with fine-grained regolith loss on small main-belt asteroids increases the Yarkovsky drift and the probability of orbital excursion to the near-Earth environment through resonances with giant planets. We suggest that the competition between electrostatic erosion and space weathering shapes the appearance of reflectance spectra of small asteroids, related to the size, spatial and spectral distributions of S-complex asteroids.

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Fig. 1: Regolith size distribution evolution for asteroids at 1 au heliocentric distance.
Fig. 2: Regolith age and processing rate evolution for asteroids at 1 au heliocentric distance.
Fig. 3: Regolith end-state statistics and fine-grained regolith removal timescale as functions of body radius and heliocentric distance.

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Data availability

Source data are provided with this paper. Modelling results presented in this work can be found in the source data files.

Code availability

Parameters and equations needed to perform the calculation are described in Methods. The codes used in this study are available from the corresponding author upon reasonable request.

References

  1. Delbo, M., Mueller, M., Emery, J. P., Rozitis, B., and Capria, M. T. Asteroid Thermophysical Modeling. In Asteroids IV (eds. Michel, P., DeMeo, F., and Bottke, W.) 107–128 (University of Arizona Press, 2015).

  2. DellaGiustina, D. N. et al. Properties of rubble-pile asteroid (101955) Bennu from OSIRIS-REx imaging and thermal analysis. Nat. Astron. 3, 341–351 (2019).

    Article  ADS  Google Scholar 

  3. Grott, M. et al. Low thermal conductivity boulder with high porosity identified on C-type asteroid (162173) Ryugu. Nat.Astron. 3, 971–976 (2019).

  4. Okada, T. et al. Highly porous nature of a primitive asteroid revealed by thermal imaging. Nature 579, 518–522 (2020).

    Article  ADS  Google Scholar 

  5. Rozitis, B. et al. Asteroid (101955) Bennu’s weak boulders and thermally anomalous equator. Sci. Adv. 6, eabc3699 (2020).

    Article  ADS  Google Scholar 

  6. Cambioni, S. et al. Fine-regolith production on asteroids controlled by rock porosity. Nature 598, 49–52 (2021).

    Article  ADS  Google Scholar 

  7. Sugita, S. et al. The geomorphology, color, and thermal properties of Ryugu: implications for parent-body processes. Science 364, 252–252 (2019).

    Article  ADS  Google Scholar 

  8. Jaumann, R. et al. Images from the surface of asteroid Ryugu show rocks similar to carbonaceous chondrite meteorites. Science 365, 817–820 (2019).

    Article  ADS  Google Scholar 

  9. Morota, T. et al. Sample collection from asteroid (162173) Ryugu by Hayabusa2: implications for surface evolution. Science 368, 654–659 (2020).

    Article  ADS  Google Scholar 

  10. Yano, H. et al. Touchdown of the Hayabusa spacecraft at the Muses Sea on Itokawa. Science 312, 1350–1353 (2006).

    Article  ADS  Google Scholar 

  11. Robinson, M. S., Thomas, P. C., Veverka, J., Murchie, S. & Carcich, B. The nature of ponded deposits on Eros. Nature 413, 396–400 (2001).

    Article  ADS  Google Scholar 

  12. Fujiwara, A. et al. The rubble-pile asteroid Itokawa as observed by Hayabusa. Science 312, 1330–1334 (2006).

    Article  ADS  Google Scholar 

  13. Watanabe, S. et al. Hayabusa2 arrives at the carbonaceous asteroid 162173 Ryugu—a spinning top-shaped rubble pile. Science 364, 268–272 (2019).

    Article  ADS  Google Scholar 

  14. Lauretta, D. S. et al. The unexpected surface of asteroid (101955) Bennu. Nature 568, 55–60 (2019).

    Article  ADS  Google Scholar 

  15. Housen, K. R. & Wilkening, L. L. Regoliths on small bodies in the solar system. Annu. Rev. Earth Planet. Sci. 10, 355–376 (1982).

    Article  ADS  Google Scholar 

  16. Delbo, M. et al. Thermal fatigue as the origin of regolith on small asteroids. Nature 508, 233–236 (2014).

    Article  ADS  Google Scholar 

  17. Molaro, J. L. et al. In situ evidence of thermally induced rock breakdown widespread on Bennu’s surface. Nat. Commun. 11, 2913 (2020).

    Article  ADS  Google Scholar 

  18. Arakawa, M. et al. An artificial impact on the asteroid 162173 Ryugu formed a crater in the gravity-dominated regime. Science 368, 67–71 (2020).

    Article  ADS  Google Scholar 

  19. Scheeres, D. J. Rotational fission of contact binary asteroids. Icarus 189(Aug), 370–385 (2007).

    Article  ADS  Google Scholar 

  20. Lauretta, D. S. et al. Episodes of particle ejection from the surface of the active asteroid (101955) Bennu. Science 366, eaay3544 (2019).

    Article  ADS  Google Scholar 

  21. Wang, X., Schwan, J., Hsu, H.-W., Grün, E. & Horányi, M. Dust charging and transport on airless planetary bodies. Geophys. Res. Lett. 43, 6103–6110 (2016).

    Article  ADS  Google Scholar 

  22. Carroll, A. et al. Laboratory measurements of initial launch velocities of electrostatically lofted dust on airless planetary bodies. Icarus 352, 113972 (2020).

    Article  Google Scholar 

  23. Horányi, M. et al. A permanent, asymmetric dust cloud around the Moon. Nature 522, 324–326 (2015).

    Article  ADS  Google Scholar 

  24. Heimsath, A. M., Dietrich, W. E., Nishiizumi, K. & Finkel, R. C. The soil production function and landscape equilibrium. Nature 388, 358–361 (1997).

    Article  ADS  Google Scholar 

  25. Szalay, J. R. & Horányi, M. The impact ejecta environment of near Earth asteroids. Astrophys. J. 830, L29 (2016).

    Article  ADS  Google Scholar 

  26. Grün, E. & Zook, H. A. Collisional balance of the meteoritic complex. Icarus 62, 244–272 (1985).

    Article  ADS  Google Scholar 

  27. Bernardoni, E., Horányi, M. & Szalay, J. Formation of the lunar dust ejecta cloud. Planet. Sci. J. 2, 67 (2021).

    Article  Google Scholar 

  28. Orger, N. C., Toyoda, K., Masui, H. & Cho, M. Experimental investigation on silica dust lofting due to charging within micro-cavities and surface electric field in the vacuum chamber. Adv. Space Res. 63, 3270–3288 (2019).

    Article  ADS  Google Scholar 

  29. Criswell, D. R. in Photon and Particle Interactions with Surfaces in Space (ed. Grard, R. J. L.) 545–556 (Astrophysics and Space Science Library Vol. 37, Springer, 1973).

  30. Hood, N. et al. Laboratory investigation of rate of electrostatic dust lofting over time on airless planetary bodies. Geophys. Res. Lett. 45, 13206–13212 (2018).

    Article  ADS  MathSciNet  Google Scholar 

  31. Jewitt, D., Weaver, H., Agarwal, J., Mutchler, M. & Drahus, M. A recent disruption of the main-belt asteroid P/2010 A2. Nature 467, 817–819 (2010).

    Article  ADS  Google Scholar 

  32. Moreno, F., Licandro, J., Cabrera-Lavers, A. & Pozuelos, F. J. Dust loss from activated asteroid P/2015 X6. Astrophys. J. 826, 137 (2016).

    Article  ADS  Google Scholar 

  33. Michikami, T. et al. Boulder size and shape distributions on asteroid Ryugu. Icarus 331, 179–191 (2019).

    Article  ADS  Google Scholar 

  34. Burke, K. N. et al. Particle size–frequency distributions of the OSIRIS-REx candidate sample sites on asteroid (101955) Bennu. Remote Sens. 13 https://doi.org/10.3390/rs13071315 (2021).

  35. Bottke, W. F., Vokrouhlický Jr., D., Rubincam, D. P. & Nesvorný, D. The Yarkovsky and YORP effects: implications for asteroid dynamics. Annu. Rev. Earth Planet. Sci. 34, 157–191 (2006).

    Article  ADS  Google Scholar 

  36. Farinella, P., Vokrouhlický, D. & Hartmann, W. K. Meteorite delivery via Yarkovsky orbital drift. Icarus 132, 378–387 (1998).

    Article  ADS  Google Scholar 

  37. Rozitis, B. & Green, S. F. The influence of rough surface thermal-infrared beaming on the Yarkovsky and YORP effects. Mon. Not. R. Astron. Soc. 423, 367–388 (2012).

    Article  ADS  Google Scholar 

  38. Bottke, W. F., Jedicke, R., Morbidelli, A., Petit, J.-M. & Gladman, B. Understanding the distribution of near-Earth asteroids. Science 288, 2190–2194 (2000).

    Article  ADS  Google Scholar 

  39. Pieters, C. M. & Noble, S. K. Space weathering on airless bodies. J. Geophys. Res.: Planets 121, 1865–1884 (2016).

    Article  ADS  Google Scholar 

  40. Nakamura, T. et al. Itokawa dust particles: a direct link between S-type asteroids and ordinary chondrites. Science 333, 1113 (2011).

    Article  ADS  Google Scholar 

  41. Nagao, K. et al. Irradiation history of Itokawa regolith material deduced from noble gases in the Hayabusa samples. Science 333, 1128 (2011).

    Article  ADS  Google Scholar 

  42. Noguchi, T. et al. Incipient space weathering observed on the surface of Itokawa dust particles. Science 333, 1121 (2011).

    Article  ADS  Google Scholar 

  43. Noguchi, T. et al. Space weathered rims found on the surfaces of the Itokawa dust particles. Meteorit. Planet. Sci. 49, 188–214 (2014).

    Article  ADS  Google Scholar 

  44. Binzel, R. P. et al. Observed spectral properties of near-Earth objects: results for population distribution, source regions, and space weathering processes. Icarus 170, 259–294 (2004).

    Article  ADS  Google Scholar 

  45. Lin, H.-W., Yoshida, F., Chen, Y. T., Ip, W. H. & Chang, C. K. A search for subkilometer-sized ordinary chondrite like asteroids in the main-belt. Icarus 254, 202–212 (2015).

    Article  ADS  Google Scholar 

  46. Noble, S. K., Pieters, C. M. & Keller, L. P. An experimental approach to understanding the optical effects of space weathering. Icarus 192, 629–642 (2007).

    Article  ADS  Google Scholar 

  47. Marsset, M. et al. Active asteroid (6478) Gault: a blue Q-type surface below the dust?. Astrophys. J. 882, L2 (2019).

    Article  ADS  Google Scholar 

  48. Hasegawa, S. et al. Q-type asteroids: possibility of non-fresh weathered surfaces. Publ. Astron. Soc. Jpn 71, 103 (2019).

    Article  ADS  Google Scholar 

  49. Marchi, S., Magrin, S., Nesvorný, D., Paolicchi, P. & Lazzarin, M. A spectral slope versus perihelion distance correlation for planet-crossing asteroids. Mon. Not. R. Astron. Soc. 368, L39–L42 (2006).

    Article  ADS  Google Scholar 

  50. Binzel, R. P. et al. Earth encounters as the origin of fresh surfaces on near-Earth asteroids. Nature 463, 331–334 (2010).

    Article  ADS  Google Scholar 

  51. Hartzell, C. M. Dynamics of 2D electrostatic dust levitation at asteroids. Icarus 333, 234–242 (2019).

    Article  ADS  Google Scholar 

  52. Walsh, K. J. et al. Craters, boulders and regolith of (101955) Bennu indicative of an old and dynamic surface. Nat. Geosci. 12, 242–246 (2019).

    Article  ADS  Google Scholar 

  53. Jawin, E. R. et al. Global patterns of recent mass movement on asteroid (101955) Bennu. J. Geophys. Res. Planets 125, e06475 (2020).

    Article  Google Scholar 

  54. Hirata, N. & Ikeya, R. Ejecta distribution from impact craters on Ryugu: possible origin of the bluer units. Icarus 364, 114474 (2021).

    Article  Google Scholar 

  55. Michikami, T. & Hagermann, A. Boulder sizes and shapes on asteroids: a comparative study of Eros, Itokawa and Ryugu. Icarus 357, 114282 (2021).

    Article  Google Scholar 

  56. Graves, K. J., Minton, D. A., Molaro, J. L. & Hirabayashi, M. Resurfacing asteroids from thermally induced surface degradation. Icarus 322, 1–12 (2019).

    Article  ADS  Google Scholar 

  57. Nesvorný, D., Bottke, W. F., Vokrouhlický, D., Chapman, C. R. & Rafkin, S. Do planetary encounters reset surfaces of near Earth asteroids?. Icarus 209, 510–519 (2010).

    Article  ADS  Google Scholar 

  58. Yu, Y., Richardson, D. C., Michel, P., Schwartz, S. R. & Ballouz, R.-L. Numerical predictions of surface effects during the 2029 close approach of asteroid 99942 Apophis. Icarus 242, 82–96 (2014).

    Article  ADS  Google Scholar 

  59. Carry, B., Solano, E., Eggl, S. & DeMeo, F. E. Spectral properties of near-Earth and Mars-crossing asteroids using Sloan photometry. Icarus 268, 340–354 (2016).

    Article  ADS  Google Scholar 

  60. Yamada, T. M., Ando, K., Morota, T. & Katsuragi, H. Timescale of asteroid resurfacing by regolith convection resulting from the impact-induced global seismic shaking. Icarus 272, 165–177 (2016).

    Article  ADS  Google Scholar 

  61. Graves, K. J., Minton, D. A., Hirabayashi, M., DeMeo, F. E. & Carry, B. Resurfacing asteroids from YORP spin-up and failure. Icarus 304, 162–171 (2018).

    Article  ADS  Google Scholar 

  62. Langevin, Y. & Arnold, J. R. The evolution of the lunar regolith. Annu. Rev. Earth Planet. Sci. 5, 449 (1977).

    Article  ADS  Google Scholar 

  63. Krivov, A. V., Sremčević, M., Spahn, F., Dikarev, V. V. & Kholshevnikov, K. V. Impact-generated dust clouds around planetary satellites: spherically symmetric case. Planet. Space Sci. 51, 251–269 (2003).

    Article  ADS  Google Scholar 

  64. Colwell, J. E., Gulbis, A. A. S., Horányi, M. & Robertson, S. Dust transport in photoelectron layers and the formation of dust ponds on Eros. Icarus 175, 159–169 (2005).

    Article  ADS  Google Scholar 

  65. Riner, M. A., Robinson, M. S., Eckart, J. M. & Desch., S. J. Global survey of color variations on 433 Eros: implications for regolith processes and asteroid environments. Icarus 198, 67–76 (2008).

    Article  ADS  Google Scholar 

  66. Lee, P. Dust levitation on asteroids. Icarus 124, 181–194 (1996).

    Article  ADS  Google Scholar 

  67. Yeo, L. H., Wang, X., Deca, J., Hsu, H.-W. & Horányi, M. Dynamics of electrostatically lofted dust on airless planetary bodies. Icarus 366, 114519 (2021).

    Article  Google Scholar 

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Acknowledgements

This work is supported by the NASA/ROSES NNH15ZDA001N-SSW Solar System Workings programme (grant number NNX16AO81G) and the NASA/SSERVI Institute for Modeling Plasma, Atmospheres and Cosmic Dust. H.-W.H. thanks M. Delbo and W.-H. Ip for fruitful discussions and T.-W. Liu, C.-Y. Wang, Li. Hsu and Lu. Hsu for their support.

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Author notes

  1. Anthony Carroll

    Present address: University of Oregon, Eugene, Oregon, USA

  2. These authors contributed equally: Hsiang-Wen Hsu, Xu Wang.

Authors and Affiliations

  1. Laboratory for Atmospheric and Space Physics, University of Colorado, Boulder, Colorado, USA

    Hsiang-Wen Hsu, Xu Wang, Anthony Carroll, Noah Hood & Mihály Horányi

  2. NASA Solar System Exploration Research Virtual Institute (SSERVI): Institute for Modeling Plasmas, Atmospheres, and Cosmic Dust (IMPACT) Boulder, Colorado, USA

    Hsiang-Wen Hsu, Xu Wang, Anthony Carroll, Noah Hood & Mihály Horányi

  3. University of California, San Diego, La Jolla, California, USA

    Noah Hood

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Contributions

H.-W.H., X.W. and M.H. coordinated this study. H.-W.H. performed the model calculation. A.C., N.H. and X.W. provided experimental results to perform the calculation. All authors contributed to discussions and editing the manuscript.

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Correspondence to Hsiang-Wen Hsu.

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Extended data

Extended Data Fig. 1 Regolith Size Distribution Evolution Modeling.

A schematic illustrates the three processes considered in shaping the regolith size evolution on airless bodies.

Extended Data Fig. 2 Size distribution of electrostatically lofted particles from laboratory experiments.

The cumulative grain size distribution of lofted particles derived from laboratory experiments based on the results shown in Figure S2B in the Supporting Information of Wang et al. (2016). Two power-law size distributions are fitted to grain radius ranges 4 to 25 μm and 25 to 70 μm. The experiment was carried out using irregular shaped Mars simulants, 38 - 48 μm in diameter, under 120 eV electron beam irradiation. The fact that there are larger grains suggests the lofted grains are in form of aggregates.

Extended Data Fig. 3 Escape probability of electrostatic-lofted dust particles.

The maximum lofting speed as a function of grain size and the relation with the escape probability of an electrostatic-lofted grain from a rotating body. The particle size range considered is from 1 to 100 μm.

Extended Data Fig. 4 Observable and modeled power-law size distribution indices considering partial coverage.

The size indices derived from Ryugu and Bennu images (Michikami et al., 2019, Burke et al., 2021) and the modeling results are also shown. The dash line marks a reference for an 1-to-1 relationship between the two.

Source data

Extended Data Table 1 The nominal values and the ranges of parameters used in the regolith size distribution evolution simulation. Note that the listed rates are the maximum values for each simulation and the actual processing rates could vary depending on the regolith size distribution
Full size table

Source data

Source Data Fig. 1

Modelling results.

Source Data Fig. 2

Modelling results.

Source Data Fig. 3

Modelling results.

Source Data Extended Data Fig. 4

Modelling results.

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Hsu, HW., Wang, X., Carroll, A. et al. Fine-grained regolith loss on sub-km asteroids. Nat Astron 6, 1043–1050 (2022). https://doi.org/10.1038/s41550-022-01717-9

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