Layerings in the nucleus of comet 67P/Churyumov-Gerasimenko. (arXiv:1912.06544v1 [astro-ph.EP])
<a href="http://arxiv.org/find/astro-ph/1/au:+Ruzicka_B/0/1/0/all/0/1">Birko-Katarina Ruzicka</a>
The Rosetta mission delivered images of comet 67P’s nucleus at unprecedented
resolution which indicate the presence of a global layering system. By merging
techniques of structural geology, statistical image processing, and solar
system science, this thesis aims to contribute to the understanding of the
formation of the layerings, and thus of cometary nuclei as a whole. I describe
the two distinctive approaches to studying the layerings’ orientation on comet
67P’s nucleus. First, I mapped layering-related linear features on a 3D shape
model of the nucleus, onto which I projected high-res OSIRIS images. I selected
only lineaments of substantial curvature, and used a plane-fitting algorithm to
find the normals to the layering planes represented by these lineaments. I used
the normals to confirm previous authors’ results, including that the layering
systems on the comet’s two lobes are geometrically independent from each other.
My results rule out the proposal that 67P’s lobes represent collisional
fragments of a much larger, layered body. Second, I developed a Fourier-based
image analysis algorithm to detect lineament structures at pixel-precision. I
analysed the layering-related features exposed on the Hathor cliff on the
comet’s Small Lobe. I found my algorithm to be a broadly applicable, powerful
tool for automating the detection of layerings in images where conventional
edge-detection algorithms are not effective. When correctly configured to the
target conditions, I found the algorithm to have a higher signal-to-noise
detection sensitivity than a human, while reducing over-interpretation due to
bias. In summary, I studied the layerings in the nucleus of comet 67P using
several unconventional approaches and constrained their lateral extent,
curvature, and to a degree also their thickness. Finally, I nominated two
mechanisms that could have formed these layerings in cometary nuclei.
The Rosetta mission delivered images of comet 67P’s nucleus at unprecedented
resolution which indicate the presence of a global layering system. By merging
techniques of structural geology, statistical image processing, and solar
system science, this thesis aims to contribute to the understanding of the
formation of the layerings, and thus of cometary nuclei as a whole. I describe
the two distinctive approaches to studying the layerings’ orientation on comet
67P’s nucleus. First, I mapped layering-related linear features on a 3D shape
model of the nucleus, onto which I projected high-res OSIRIS images. I selected
only lineaments of substantial curvature, and used a plane-fitting algorithm to
find the normals to the layering planes represented by these lineaments. I used
the normals to confirm previous authors’ results, including that the layering
systems on the comet’s two lobes are geometrically independent from each other.
My results rule out the proposal that 67P’s lobes represent collisional
fragments of a much larger, layered body. Second, I developed a Fourier-based
image analysis algorithm to detect lineament structures at pixel-precision. I
analysed the layering-related features exposed on the Hathor cliff on the
comet’s Small Lobe. I found my algorithm to be a broadly applicable, powerful
tool for automating the detection of layerings in images where conventional
edge-detection algorithms are not effective. When correctly configured to the
target conditions, I found the algorithm to have a higher signal-to-noise
detection sensitivity than a human, while reducing over-interpretation due to
bias. In summary, I studied the layerings in the nucleus of comet 67P using
several unconventional approaches and constrained their lateral extent,
curvature, and to a degree also their thickness. Finally, I nominated two
mechanisms that could have formed these layerings in cometary nuclei.
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