Time evolution of dust deposits in the Hapi region of comet 67P/Churyumov-Gerasimenko

Journal
Date Issued
2020
Author(s)
•
•
•
•
•
•
•
•
•
Bertini, Ivano
•
Bodewits, D.
•
Ceccarelli, C.
•
Ferri, F.
•
Fornasier, S.
•
Frattin, Elisa
•
Güttler, C.
•
Gutiérrez, P. J.
•
Keller, H. U.
•
Kührt, E.
•
Küppers, M.
•
•
•
Marzari, F.
•
Mottola, Stefano
•
Sierks, H.
•
Toth, I.
•
•
Vincent, J. -B.
DOI
Abstract
Aims: We provide a measurement of the seasonal evolution of the dust deposit erosion and accretion in the Hapi region of comet 67P/Churyumov-Gerasimenko with a vertical accuracy of 0.2-0.9 m. Methods: We used OSIRIS Narrow Angle Camera images with a spatial scale of lower than 1.30 m px-1 and developed a tool to monitor the time evolution of 22 boulder heights with respect to the surrounding dust deposit. The tool is based on the measurement of the shadow length projected by the boulder on the surrounding pebble deposit. Assuming the position of the boulders does not change during the observational period, boulder height variations provide an indication of how the thickness of the surrounding dust layer varies over time through erosion and accretion phenomena. Results: We measured an erosion of the dust deposit of 1.7 ± 0.2 m during the inbound orbit until 12 December, 2014. This value nearly balances the fallout from the southern hemisphere during perihelion cometary activity. During the perihelion phase, the dust deposit then increased by 1.4 ± 0.8 m. This is interpreted as a direct measurement of the fallout thickness. By comparing the erosion rate and dust volume loss rate at the Hapi region measured in the coma, the fallout represents ~96% in volume of the ejecta. The amount of the eroded pristine material from the southern hemisphere, together with its subsequent transport and fallout on the nucleus, led us to discuss the pristine water ice abundance in comet 67P. We determine that the refractory-to-ice mass ratio ranges from 6 to 110 in the perihelion-eroded pristine nucleus, providing a pristine ice mass fraction of (8 ± 7)% in mass.
Volume
636
Start page
A91
Uri
Url
Issn Identifier
0004-6361
Ads BibCode
2020A&A...636A..91C
Rights
open.access
File(s)
Loading...
Thumbnail Image
Name

aa37485-20.pdf

Description
pdf editoriale
Size

2.12 MB

Format

Adobe PDF

Checksum (MD5)

b4a405ba8fa649242b21d327ae060ae7