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Thermal fatigue as the origin of regolith on small asteroids

Abstract

Space missions1,2 and thermal infrared observations3 have shown that small asteroids (kilometre-sized or smaller) are covered by a layer of centimetre-sized or smaller particles, which constitute the regolith. Regolith generation has traditionally been attributed to the fall back of impact ejecta and by the break-up of boulders by micrometeoroid impact4,5. Laboratory experiments6 and impact models4, however, show that crater ejecta velocities are typically greater than several tens of centimetres per second, which corresponds to the gravitational escape velocity of kilometre-sized asteroids. Therefore, impact debris cannot be the main source of regolith on small asteroids4. Here we report that thermal fatigue7,8,9, a mechanism of rock weathering and fragmentation with no subsequent ejection, is the dominant process governing regolith generation on small asteroids. We find that thermal fragmentation induced by the diurnal temperature variations breaks up rocks larger than a few centimetres more quickly than do micrometeoroid impacts. Because thermal fragmentation is independent of asteroid size, this process can also contribute to regolith production on larger asteroids. Production of fresh regolith originating in thermal fatigue fragmentation may be an important process for the rejuvenation of the surfaces of near-Earth asteroids, and may explain the observed lack of low-perihelion, carbonaceous, near-Earth asteroids10.

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Figure 1: Time required to break rocks on asteroids.
Figure 2: Crack growth in meteorites due to laboratory temperature cycling.
Figure 3: Regolith formation from Murchison in the laboratory.

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References

  1. Veverka, J. et al. The landing of the NEAR-Shoemaker spacecraft on asteroid 433 Eros. Nature 413, 390–393 (2001)

    Article  ADS  CAS  Google Scholar 

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

    Article  ADS  CAS  Google Scholar 

  3. Gundlach, B. & Blum, J. A new method to determine the grain size of planetary regolith. Icarus 223, 479–492 (2013)

    Article  ADS  Google Scholar 

  4. Housen, K. R., Wilkening, L. L., Chapman, C. R. & Greenberg, R. Asteroidal regoliths. Icarus 39, 317–351 (1979)

    Article  ADS  Google Scholar 

  5. Hörz, F. & Cintala, M. Impact experiments related to the evolution of planetary regoliths. Meteorit. Planet. Sci. 32, 179–209 (1997)

    Article  ADS  Google Scholar 

  6. Housen, K. R. & Holsapple, K. A. Ejecta from impact craters. Icarus 211, 856–875 (2011)

    Article  ADS  Google Scholar 

  7. McFadden, L., Eppes, M., Gillespie, A. & Hallet, B. Physical weathering in arid landscapes due to diurnal variation in the direction of solar heating. Geol. Soc. Am. Bull. 117, 161–173 (2005)

    Article  ADS  Google Scholar 

  8. Luque, A., Ruiz-Agudo, E., Cultrone, G., Sebastián, E. & Siegesmund, S. Direct observation of microcrack development in marble caused by thermal weathering. Environ. Earth Sci. 62, 1375–1386 (2011)

    Article  Google Scholar 

  9. Viles, H. et al. Simulating weathering of basalt on mars and earth by thermal cycling. Geophys. Res. Lett. 37, L18201 (2010)

    Article  ADS  MathSciNet  Google Scholar 

  10. Mainzer, A. et al. Characterizing subpopulations within the near-earth objects with NEOWISE: preliminary results. Astrophys. J. 752, 110–126 (2012)

    Article  ADS  Google Scholar 

  11. Michel, P. & Richardson, D. C. Collision and gravitational reaccumulation: possible formation mechanism of the asteroid Itokawa. Astron. Astrophys. 554, L1 (2013)

    Article  ADS  Google Scholar 

  12. Hoerz, F., Schneider, E., Gault, D. E., Hartung, J. B. & Brownlee, D. E. Catastrophic rupture of lunar rocks: a Monte Carlo simulation. Moon 13, 235–258 (1975)

    Article  ADS  Google Scholar 

  13. Nesvorný, D. et al. Cometary origin of the zodiacal cloud and carbonaceous micrometeorites. implications for hot debris disks. Astrophys. J. 713, 816–836 (2010)

    Article  ADS  Google Scholar 

  14. Briani, G., Morbidelli, A., Gounelle, M. & Nesvorný, D. Evidence for an asteroid-comet continuum from simulations of carbonaceous microxenolith dynamical evolution. Meteorit. Planet. Sci. 46, 1863–1877 (2011)

    Article  ADS  CAS  Google Scholar 

  15. Spencer, J. R., Lebofsky, L. A. & Sykes, M. V. Systematic biases in radiometric diameter determinations. Icarus 78, 337–354 (1989)

    Article  ADS  Google Scholar 

  16. Čapek, D. & Vokrouhlický, D. Thermal stresses in small meteoroids. Astron. Astrophys. 519, A75 (2010)

    Article  ADS  Google Scholar 

  17. Janssen, M., Zuidema, J. & Wanhill, R. Fracture Mechanics 2nd edn, 207–213 (Spon, 2004)

    Google Scholar 

  18. 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. Lett. 368, L39–L42 (2006)

    Article  ADS  Google Scholar 

  19. Marchi, S., Delbo, M., Morbidelli, A., Paolicchi, P. & Lazzarin, M. Heating of near-Earth objects and meteoroids due to close approaches to the sun. Mon. Not. R. Astron. Soc. 400, 147–153 (2009)

    Article  ADS  Google Scholar 

  20. Jewitt, D. The active asteroids. Astron. J. 143, 66–80 (2012)

    Article  ADS  Google Scholar 

  21. Opeil, C. P., Consolmagno, G. J. & Britt, D. T. The thermal conductivity of meteorites: new measurements and analysis. Icarus 208, 449–454 (2010)

    Article  ADS  CAS  Google Scholar 

  22. Migliazza, M., Ferrero, A. & Spagnoli, A. Experimental investigation on crack propagation in Carrara marble subjected to cyclic loads. Int. J. Rock Mech. Min. Sci. 48, 1038–1044 (2011)

    Article  Google Scholar 

  23. Christensen, R. M. Mechanics of Composite Materials 31–58 (Krieger, 1979)

    Google Scholar 

  24. Glinka, G. & Shen, G. Universal features of weight functions for cracks in mode I. Eng. Fract. Mech. 40, 1135–1146 (1991)

    Article  Google Scholar 

  25. Suresh, S. Fatigue of Materials 2nd edn, 505–507 (Cambridge Univ. Press, 1998)

    Book  Google Scholar 

  26. Medvedev, R. V., Gorbatsevich, F. I. & Zotkin, I. T. Determination of the physical properties of stony meteorites with application to the study of processes of their destruction. Meteoritika 44, 105–110 (1985)

    ADS  Google Scholar 

  27. Flynn, G. J. Physical properties of meteorites and interplanetary dust particles: clues to the properties of the meteors and their parent bodies. Earth Moon Planets 95, 361–374 (2004)

    Article  ADS  CAS  Google Scholar 

  28. Hazen, R. M. Temperature, pressure and composition: structurally analogous variables. Phys. Chem. Miner. 1, 83–94 (1977)

    Article  ADS  CAS  Google Scholar 

  29. Anderson, O., Isaak, D. & Oda, H. Thermoelastic parameters for six minerals at high temperature. J. Geophys. Res. 96, 18037–18046 (1991)

    Article  ADS  CAS  Google Scholar 

  30. Smyth, J. R. High temperature crystal chemistry of fayalite. Am. Mineral. 60, 1092–1097 (1975)

    CAS  Google Scholar 

Download references

Acknowledgements

This work was supported by the French Agence National de la Recherche (ANR) SHOCKS, the BQR of the Observatoire de la Côte d’Azur (OCA), the University of Nice-Sophia Antipolis, the Laboratory GeoAzur and the French National Program of Planetology (PNP). We benefited from discussions with K. J. Walsh and W. F. Bottke. A. Morbidelli helped with the dynamical model. M. Moumni, J.-M. Hiver and G. Thomas helped with the experiments, X-ray tomography and early data analysis. G.L. conducted part of his work as an INSU-CNRS delegate. S.M. acknowledges support from NASA SSERVI. The comments of S. Byrne improved this work fundamentally. Computations and data analysis were done on the CRIMSON cluster at OCA.

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Authors

Contributions

M.D. and S.M. inspired the laboratory experiments, which were designed by G.L., C.G., P.M., C.V. and M.D. Experiments were carried out by G.L. N.M. and M.D. developed the methods of crack volume and length measurement. N.M. and M.D. applied the methods to the experimental data. J.W., K.T.R. and M.D. worked on the thermomechanical model that was mostly developed and used by J.W. The scientific analysis was directed by M.D. with frequent discussions with G.L., P.M., J.W., K.T.R. and C.G. Computer codes were developed by M.D., J.W. and N.M. M.D., J.W., G.L., P.M., N.M., K.T.R. and C.G. jointly drafted the manuscript, with all authors reviewing it and contributing to its final form.

Corresponding authors

Correspondence to Marco Delbo or Guy Libourel.

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The authors declare no competing financial interests.

Extended data figures and tables

Extended Data Figure 1 Protocol of the thermal fatigue laboratory experiments.

We place samples of Murchison and Sahara 97210 1 cm in size in a climatic chamber where the air temperature is forced to follow cycles between 250 and 440 K with a period of 2.2 h. The air is anhydrous and at a pressure of 1 bar. Meteorites are analysed by X-ray computed tomography before the temperature cycles begin (t0), after 76 cycles (t1) and after 407 cycles (t2). From the scans, we measure (Methods) the increases in the volume and length of cracks as functions of the number of temperature cycles.

Extended Data Figure 2 Diurnal surface temperature excursions on asteroids as a function of the distance to the Sun.

Temperatures are calculated at the equator of a spherical asteroid by means of an asteroid thermophysical model15 (Methods), assuming the thermal properties (Extended Data Table 1) of a carbonaceous chondrite (the CM2 Cold-Bokkevel) and that of an ordinary chondrite (the H5 Cronstad). The asteroid rotation period is set to 6 h. The bolometric albedo is assumed to equal 0.02 for the carbonaceous chondrite and 0.1 for the ordinary chondrite.

Extended Data Figure 3 Volume growth of individual cracks as a function of the number of temperature cycles.

a, Murchison; b, Sahara 97210. Statistical errors are 1σ and are in general smaller than the plot symbols. The crack volume is measured by the procedure described in Methods. Cracks are labelled with the value of the initial slice of the corresponding volume of interest. If different volumes of interest are defined with the same initial tomographic slice, the last letter of the crack label is used to identify the crack (for example Z387a, Z378b, Z378c).

Source data

Extended Data Figure 4 Length growth of individual cracks as a function of the number of temperature cycles.

a, Murchison; b, Sahara 97210. Statistical errors are 1σ. The crack length is measured by the procedure described in Methods. See Extended Data Fig. 3 for crack labelling.

Source data

Extended Data Figure 5 No crack growth with no temperature cycles.

Volume growth of individual cracks in a specimen of Murchison that was transported from the climatic chamber to the computed tomography scanner without temperature cycling. Statistical errors are 1σ. The crack volume is measured by the procedure described in Methods. We performed three computed tomography scans: scan no. 0 (the label on the x axis) was obtained on the sample of the meteorite as it was received; scan no. 1 was carried out after the meteorite was transported from the computed tomography scanner to the climatic chamber and back; and scan no. 2 was obtained after a second transportation of the meteorite.

Source data

Extended Data Figure 6 Schematics of our micromechanical model.

a, Flow chart; b, schematic of the two-scale representation (Methods). ∂V is the surface of a body of volume V. A microscopic spherical inclusion, centred at the macroscopic point x is embedded in an infinite, effectively homogenized matrix. A general microscopic material point is located at a distance y measured from the centre of its nearest spherical inclusion located at x. The spherical inclusions of radius rc are located at the vertices of a cubic lattice with lattice parameter .

Extended Data Figure 7 Comparison of theoretical and measured crack growth.

Crack size is shown as a function of the number of temperature cycles predicted by our model and compared with experimental data for two particular cracks. Main plot: pre-existing cracks of 0.76 mm for Murchison and 0.41 mm for Sahara 97210 originating at the surface of the samples progressively propagate through the respective meteorites. The crosses indicate that the crack has reached a length equal to the meteorite diameter; therefore, full fragmentation occurs. Inset: comparison of the model with the length growth measured in our experiments for the same two cracks.

Extended Data Figure 8 Schematic of the surface layer of rocks modelled in this work.

The schematic is inspired by Fig. 3 of ref. 7. The layer is composed of rocks with different sizes. The rocks are subjected to spatial and temporal temperature gradients at the surface of the asteroid due to changes in the diurnal solar heating. The bottom of the rock layer is assumed to be in contact with bedrock that is deep enough to have a constant temperature. Temperatures are calculated assuming a uniform medium (no rock boundaries). This is probably a conservative approximation, because the presence of voids between rocks may enhance the temperature gradients owing to a reduction in the thermal conductivity. When the model starts, all rocks have a surface crack of the same length (30 μm), represented by the thin vertical line. It is very likely that cracks of this size, similar to the grain size of meteorites, are present in asteroidal material. Crack growth is from top to bottom. Crack growth is modelled until the time (survival time) the crack reaches the diameter of the rock (through-crack), and the rock is broken into two pieces. Rock survival times are shown in Fig. 1.

Extended Data Figure 9 Sensitivity of the model results to variations in Paris’s law parameters.

The stars indicate model results for the nominal values of the parameters given in Extended Data Table 1. a, Number of temperature cycles until fragmentation for a rock 1 cm in diameter as a function of the Paris’s law exponent, n. b, Discrepancy between the model and the experimental crack growth, defined by equation (4) in Methods, as a function of the Paris’s law exponent. The model–experiment discrepancy is of the order of 20% for the nominal values of the C and n. A 100% discrepancy would be clearly visible in Extended Data Fig. 7. c, Same as a, but here the number of cycles until rock fragmentation is plotted as a function of the Paris’s law factor C. d, Same as b, but here the discrepancy between the model and the experimental crack growth is plotted as a function of the Paris’s law factor C.

Extended Data Table 1 Physical properties of materials and their default values used in this work

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Delbo, M., Libourel, G., Wilkerson, J. et al. Thermal fatigue as the origin of regolith on small asteroids. Nature 508, 233–236 (2014). https://doi.org/10.1038/nature13153

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