J/A+A/678/A179 Cometary dust collected by MIDAS on-board Rosetta (Kim+, 2023)
Cometary dust collected by MIDAS on board Rosetta.
II. Particle shape descriptors and pristineness evaluation.
Kim M., Mannel T., Lasue J., Longobardo A., Bentley M.S., Moissl R.,
The MIDAS team
<Astron. Astrophys. 678, A179 (2023)>
=2023A&A...678A.179K 2023A&A...678A.179K (SIMBAD/NED BibCode)
ADC_Keywords: Solar system ; Comets
Keywords: comets: indivudal: 67P/Churyumov-Gerasimenko -
space vehicles: instruments - planets and satellites: formation -
protoplanetary disks
Abstract:
The MIDAS (Micro-Imaging Dust Analysis System) atomic force microscope
on board the Rosetta comet orbiter investigated and measured the 3D
topography of a few hundred nm to tens of mu sized dust particles of
67P/Churyumov-Gerasimenko with resolutions down to a few nanometers,
giving insights into the physical processes of our early Solar System.
We analyze the shapes of the cometary dust particles collected by
MIDAS on the basis of a recently updated particle catalog with the aim
to determine which structural properties remained pristine.
We develop a set of shape descriptors and metrics such as aspect
ratio, elongation, circularity, convexity, and particle surface/volume
distribution, which can be used to describe the distribution of
particle shapes. Furthermore, we compare the structure of the MIDAS
dust particles and the clusters in which the particles were deposited
to those found in previous laboratory experiments and by
Rosetta/COSIMA. Finally, we combine our findings to calculate a
pristineness score for MIDAS particles and determine the most pristine
particles and their properties.
We find that the morphological properties of all cometary dust
particles at the micrometer scale are surprisingly homogeneous despite
originating from diverse cometary environments (e.g., different
collection targets that are associated with cometary activities/source
regions and collection velocities/periods). There is only a weak trend
between shape descriptors and particle characteristics like size,
collection targets, and cluster morphology. We next find that the
types of clusters found by MIDAS show good agreement with those
defined by previous laboratory experiments, however, there are some
differences to those found by Rosetta/COSIMA. Furthermore, our
pristineness score shows that almost half of MIDAS particles suffered
severe alteration by impact, which indicates structural modification
by impact (e.g., flattening and/or fragmentation) is inevitable
despite the very low collection speeds (i.e., ∼3-7m/s). Based on our
result, we rate 19 out of 1082 MIDAS particles at least moderately
pristine, i.e., they are not substantially flattened by impact, not
fragmented, and/or not part of a fragmentation cluster.
Description:
The particle shape descriptor catalog of cometary dust collected by
MIDAS on-board Rosetta is developed to describe the distribution of
particle shapes and determine which structural properties remained
pristine. A set of shape descriptors and metrics such as aspect ratio,
elongation, circularity, convexity, and particle surface/volume
distribution are derived.
The particle shape descriptor catalog presented in this paper contains
in total of 1080 scans of particles. From ultimately chosen 1857
particles from J/A+A/673/A129 Cometary dust collected by MIDAS
on-board Rosetta (Kim et al., 2023A&A...673A.129K 2023A&A...673A.129K, Cat.
J/A+A/673/A129), particles with a very small number of pixels in
images (e.g., <10) due to the physical difficulties of further
analysis with a small number of pixel particles is excluded.
More detailed information about MIDAS particle selection for further
investigation can be found in previous MIDAS studies in Section 2.2.
File Summary:
--------------------------------------------------------------------------------
FileName Lrecl Records Explanations
--------------------------------------------------------------------------------
ReadMe 80 . This file
appena.dat 120 1080 A set of shape descriptors and metrics such as
aspect ratio, elongation, circularity,
convexity, and particle surface/volume
distribution, cluster information,
pristineness evaluation (table A1)
--------------------------------------------------------------------------------
See also:
J/A+A/520/A92 : Global plasma parameter simulation of Comet 67P
(Gortsas+, 2010)
J/A+A/527/A113 : 67P/Churyumov-Gerasimenko R-band light curve
(Tubiana+, 2011)
J/A+A/548/A12 : 67P/Churyumov-Gerasimenko R-band light curve (Lowry+, 2012)
J/MNRAS/462/S138 : Robotic view of 67P perihelion (Snodgrass+, 2016)
J/A+A/647/A119 : Comet 67P/Churyumov-Gerasimenko FUV aurora
(Stephenson+, 2021)
J/A+A/673/A129 : Cometary dust collected by MIDAS on-board Rosetta
(Kim+, 2023)
Byte-by-byte Description of file: appena.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 26 A26 --- Particle Particle ID
28- 29 I02 --- Target Target number
31- 37 F7.3 um+2 Area Area of MIDAS particle
39- 43 F5.3 um Radius 2D radius
45- 48 F4.2 um Height Height of of MIDAS particle
50- 54 F5.3 -- Asprat Aspect ratio of MIDAS particle
56- 61 F6.3 --- Elongat Elongation of MIDAS particle
63- 67 F5.3 --- Circular Circularity of MIDAS particle
69- 73 F5.3 --- Convexity Convexity of MIDAS particle
75- 86 A12 --- PSVD Particle surface/volume distribution
88- 90 I3 --- CluNum Cluster Number
92-100 A9 --- Ellerbr Particle classification by Ellerbroek
102-118 A17 --- COSIMA Particle classification by COSIMA
120 I1 --- PriSco Pristineness Score
--------------------------------------------------------------------------------
Acknowledgements:
Minjae Kim, minjae.k.kim(at)warwick.ac.uk
References:
Kim et al., Paper I, 2023A&A...673A.129K 2023A&A...673A.129K, Cat. J/A+A/673/A129
(End) Patricia Vannier [CDS] 17-Aug-2023