Macro and micro structures of pebble-made cometary nuclei reconciled by seasonal evolution
Journal
Date Issued
2022
Author(s)
•
•
•
•
•
•
•
•
•
•
•
•
•
Beck, Pierre
•
•
Kappel, David
•
•
Mottola, Stefano
•
•
Arnold, Gabriele
Abstract
Comets evolve due to sublimation of ices embedded inside porous dust, triggering dust emission (that is, erosion) followed by mass loss, mass redistribution and surface modifications. Surface changes were revealed by the Deep Impact and Stardust NExT missions for comet 9P/Tempel 1 (ref. 1), and a full inventory of the processes modifying cometary nuclei was provided by Rosetta while it escorted comet 67P/Churyumov–Gerasimenko for approximately two years2–4. Such observations also showed puzzling water-ice-rich spots that stood out as patches optically brighter and spectrally bluer than the average cometary surface5–9. These are up to tens of metres large and indicate macroscopic compositional dishomogeneities apparently in contrast with the structural homogeneity above centimetre scales of pebble-made nuclei10. Here we show that the occurrence of blue patches determines the seasonal variability of the nucleus colour4,11,12 and gives insight into the internal structure of comets. We define a new model that links the centimetre-sized pebbles composing the nucleus10 and driving cometary activity13,14 to metre-sized water-ice-enriched blocks embedded in a drier matrix. The emergence of blue patches is due to the matrix erosion driven by CO2-ice sublimation that exposes the water-ice-enriched blocks, which in turn are eroded by water-ice sublimation when exposed to sunlight. Our model explains the observed seasonal evolution of the nucleus and reconciles the available data at micro (sub-centimetre) and macro (metre) scales.
Volume
6
Issue
5
Start page
546
Issn Identifier
2397-3366
Ads BibCode
2022NatAs...6..546C
Rights
open.access
File(s)![Thumbnail Image]()
![Thumbnail Image]()
Loading...
Name
Ciarniello_et_al_2022_SI.pdf
Description
Materiale Supplementare
Size
3.57 MB
Format
Adobe PDF
Checksum (MD5)
0f7911cc433a9294389c45bb9943988b
Loading...
Name
Ciarniello_et_al_2022.pdf
Description
[Administrators only]
Size
2.01 MB
Format
Adobe PDF
Checksum (MD5)
09dcd12316c28ee4c0f9131fb57e1e8b