Fine-regolith production on asteroids controlled by rock porosity

Cambioni, S. and Delbo, M. and Poggiali, G. and Avdellidou, C. and Ryan, A. J. and Deshapriya, J. D. P. and Asphaug, E. and Ballouz, R.-L. and Barucci, M. A. and Bennett, C. A. and Bottke, W. F. and Brucato, J. R. and Burke, K. N. and Cloutis, E. A. and DellaGiustina, D. N. and Emery, J. P. and Rozitis, B. and Walsh, K. J. and Lauretta, D. S. (2021) Fine-regolith production on asteroids controlled by rock porosity. Nature, 598 (7879). pp. 49-52. ISSN 0028-0836. doi:10.1038/s41586-021-03816-5. https://resolver.caltech.edu/CaltechAUTHORS:20210630-225411006

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Abstract

Spacecraft missions have observed regolith blankets of unconsolidated subcentimetre particles on stony asteroids. Telescopic data have suggested the presence of regolith blankets also on carbonaceous asteroids, including (101955) Bennu and (162173) Ryugu. However, despite observations of processes that are capable of comminuting boulders into unconsolidated materials, such as meteoroid bombardment and thermal cracking, Bennu and Ryugu lack extensive areas covered in subcentimetre particles. Here we report an inverse correlation between the local abundance of subcentimetre particles and the porosity of rocks on Bennu. We interpret this finding to mean that accumulation of unconsolidated subcentimetre particles is frustrated where the rocks are highly porous, which appears to be most of the surface. The highly porous rocks are compressed rather than fragmented by meteoroid impacts, consistent with laboratory experiments, and thermal cracking proceeds more slowly than in denser rocks. We infer that regolith blankets are uncommon on carbonaceous asteroids, which are the most numerous type of asteroid. By contrast, these terrains should be common on stony asteroids, which have less porous rocks and are the second-most populous group by composition. The higher porosity of carbonaceous asteroid materials may have aided in their compaction and cementation to form breccias, which dominate the carbonaceous chondrite meteorites.

Item Type:

Article

Related URLs:

URL	URL Type	Description
https://doi.org/10.1038/s41586-021-03816-5	DOI	Article
https://rdcu.be/cAJvT	Publisher	Free ReadCube access
https://sbn.psi.edu/pds/resource/orex/	Related Item	Planetary Data System
http://sbmt.jhuapl.edu/	Related Item	Small Body Mapping Tool
https://www.oca.eu/images/LAGRANGE/pages_perso/delbo/thermops.tar.gz	Related Item	Thermophysical model code
https://doi.org/10.5281/zenodo.4781752	DOI	OTES acquisitions and boresight code
https://doi.org/10.5281/zenodo.4763783	DOI	Regolith heat transfer code
https://sites.google.com/cfa.harvard.edu/saoimageds9	Related Item	SAOImageDS9 software
https://doi.org/10.5281/zenodo.4771035	DOI	Other codes

ORCID:

Author	ORCID
Cambioni, S.	0000-0001-6294-4523
Delbo, M.	0000-0002-8963-2404
Poggiali, G.	0000-0002-3239-1697
Avdellidou, C.	0000-0001-8228-8789
Asphaug, E.	0000-0003-1002-2038
Ballouz, R.-L.	0000-0002-1772-1934
Bottke, W. F.	0000-0002-1804-7814
Brucato, J. R.	0000-0002-4738-5521
Cloutis, E. A.	0000-0001-7301-0929
DellaGiustina, D. N.	0000-0002-5643-1956
Rozitis, B.	0000-0001-9893-241X

Additional Information:

© 2021 Nature Publishing Group. Received 11 March 2021; Accepted 08 July 2021; Published 06 October 2021; Issue Date 07 October 2021. This material is based on work supported by NASA under contract NNM10AA11C issued through the New Frontiers Program. We are grateful to the entire OSIRIS-REx team for making the encounter with Bennu possible, to C. Wolner and F. Murphy for editorial help, and to the OPAL infrastructure of the Observatoire de la Côte d’Azur (CRIMSON) for providing computational resources and support. S.C. thanks the University of Arizona for supporting this study. M.D., C.A., J.D.P.D. and M.A.B. acknowledge the French space agency CNES. C.A. and M.D. acknowledge support from ANR “ORIGINS” (ANR-18-CE31-0014). C.A. was supported by the French National Research Agency under the project “Investissements d’Avenir” UCAJEDI ANR-15-IDEX-01. G.P. and J.R.B. were supported by Italian Space Agency grant agreement INAF/ASI number 2017-37-H.0. B.R. acknowledges financial support from the UK Science and Technology Facilities Council (STFC). E.C. thanks CSA, NSERC, CFI, MRIF and UWinnipeg for supporting this study. Data availability: Raw through-calibrated OTES52 and OCAMS53 data are available via the Planetary Data System (https://sbn.psi.edu/pds/resource/orex/). The SPC/OLA v34 shape model is available via the Small Body Mapping Tool (http://sbmt.jhuapl.edu/). The IDs of the OTES observations used here and the best-fitting solutions for the thermophysical model are provided in Supplementary Table 1. The boulder size, location and reflectance used to test the robustness of the results are available in refs. 34,46. Source data are provided with this paper. Code availability: The thermophysical analysis reported here uses custom code based on the thermophysical model of ref. 16, available at https://www.oca.eu/images/LAGRANGE/pages_perso/delbo/thermops.tar.gz. The code to compute the geometry of the OTES acquisitions and boresight is available at https://doi.org/10.5281/zenodo.4781752 (ref. 54). The code to compute Γc for the thermophysical analysis is available at https://doi.org/10.5281/zenodo.4763783 (ref. 55). The rock mapping in Extended Data Fig. 3 was performed using the SAOImageDS9 software available at https://sites.google.com/cfa.harvard.edu/saoimageds9. Other codes that support the findings of this study are available at https://doi.org/10.5281/zenodo.4771035 (ref. 56). Author Contributions: S.C. led the project, the interpretation of the results and the manuscript development, and performed the thermophysical simulations and data analysis. M.D. provided the thermophysical software, performed the thermal cracking calculations, and contributed to the interpretation of the results and the development of the manuscript. G.P. developed the pipeline to retrieve OTES detailed survey data and performed rock mapping in PolyCam images. C.A. curated the discussion on meteoroid bombardment and contributed to writing the manuscript. A.J.R. contributed with the code to convert thermal inertia values in fine-regolith particle size and developed the iterative approach to determine the cut-off value of thermal inertia, together with S.C. J.D.P.D. extracted the observation geometry of the spacecraft and Bennu from mission kernels. R.-L.B. proposed important tests of the robustness of the results. E.A., W.F.B. and J.R.B. contributed to the interpretation of the data and writing of the manuscript. D.N.D., K.N.B., C.A.B. and K.J.W. provided support in the interpretation of spacecraft imagery. J.P.E. and B.R. contributed to the data interpretation during the OSIRIS-REx Thermal Analysis Working Group meetings, and to the design of the observations and data acquisition. M.A.B. and E.C. contributed to the interpretation of the results. D.S.L. made this study possible as the PI of the OSIRIS-REx mission and contributed to the discussion of the results. The authors declare no competing interests. Peer review information: Nature thanks Guy Consolmagno and Seiji Sugita for their contribution to the peer review of this work. Peer reviewer reports are available.

Funders:

Funding Agency	Grant Number
NASA	NNM10AA11C
University of Arizona	UNSPECIFIED
Centre National d'Études Spatiales (CNES)	UNSPECIFIED
Agence Nationale pour la Recherche (ANR)	ANR-18-CE31-0014
Agence Nationale pour la Recherche (ANR)	ANR-15-IDEX-01
Agenzia Spaziale Italiana (ASI)	2017-37-H.0
Istituto Nazionale di Astrofisica (INAF)	UNSPECIFIED
Science and Technology Facilities Council (STFC)	UNSPECIFIED
Canadian Space Agency (CSA)	UNSPECIFIED
Natural Sciences and Engineering Research Council of Canada (NSERC)	UNSPECIFIED
Canada Foundation for Innovation	UNSPECIFIED
Ministère des Relations internationales et de la Francophonie (MRIF)	UNSPECIFIED
University of Winnipeg	UNSPECIFIED

Subject Keywords:

Asteroids, comets and Kuiper belt; Geomorphology

Issue or Number:

7879

DOI:

10.1038/s41586-021-03816-5

Record Number:

CaltechAUTHORS:20210630-225411006

Persistent URL:

https://resolver.caltech.edu/CaltechAUTHORS:20210630-225411006

Official Citation:

Cambioni, S., Delbo, M., Poggiali, G. et al. Fine-regolith production on asteroids controlled by rock porosity. Nature 598, 49–52 (2021). https://doi.org/10.1038/s41586-021-03816-5

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ID Code:

109688

Collection:

CaltechAUTHORS

Deposited By:

Joy Painter

Deposited On:

24 Aug 2021 20:59

Last Modified:

03 Nov 2021 15:56

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