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Fine-regolith production on asteroids controlled by rock porosity

Journal
Date Issued
2021
Author(s)
Cambioni, S
•
Delbo, M
•
Avdellidou, C
•
Ryan, A J
•
Deshapriya, J D P
•
Asphaug, E
•
Ballouz, R L
•
Barucci, M A
•
Bennett, C A
•
Bottke, W F
•
•
Burke, K N
•
Cloutis, E
•
DellaGiustina, D N
•
Emery, J P
•
Walsh, K J
•
Lauretta, D S
DOI
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) Bennu4 and (162173) Ryugu. However, despite observations of processes that are capable of comminuting boulders into unconsolidated materials, such as meteoroid bombardment and thermal cracking8, 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
Volume
598
Start page
49
Uri
Url
Issn Identifier
0028-0836
Ads BibCode
2021Natur.598...49C
Rights
open.access
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