Die Rolle der Aktivität auf die Evolution der primordialen Kernstrukturen und der Morphologie der Jupiter Family Comets
Zusammenfassung der Projektergebnisse
The subject of this investigation was based on the simple proposition that comets should be considered as evolving objects. We aimed to study both large- and small-scale morphological features of small icy bodies in our solar system that are subject to weak but prolonged mass loss by sublimation of various volatile ices. The overall aim was to consider, for the first time in 3D geometry, the entire life cycle of short-period comets, as many candidates pass through several stages dictated by orbital dynamics. From their region of origin at ~30-100 AU, through their so-called "Centaur" stage at ~10-20 AU, until some of them become trapped in the inner Solar System as short-period comets, awaiting their final demise by becoming dormant as they lose accessible ice, collide with other bodies, or undergo spin induced disintegration. The recent European Space Agency's Rosetta mission to comet 67P/Churyumov-Gerasimenko has reignited intense debate in the cometary community as to whether the ice abundance ratios, dust fragments, large scale nucleus shape and morphology, and small scale features such as pits are truly primordial. The timing for such an open scientific investigation seems right, given that there are several observational datasets from similar space missions (e.g. comets 1P/Haley, 19P/Borrelly, 9P Tempel 1, 81P/Wild2, 103P/Hartley 2), and the New Horizons flyby of Arrokoth (486958) in 2019 as well as ground-based telescopic observations to constrain our models. The 3D code (MONET) developed within this project can handle spin-orbit coupling and mass loss induced torques in a self-consistent manner, which allowed for the first time to study the long term evolution of active bodies. Our numerical studies indicate that even in the far and cold reaches of our solar system, depending on the volatile ice composition, these bodies undergo slow but definite evolution. In connection with a closer inspection of the scientific data collected from ground-based as well as spacecraft explorations reveal a more complex picture of comets and other such bodies. Rather than being a pure, pristine time-capsules storing their initial conditions to be revealed four billion years later they are closer to being a disequilibrated collection of materials that may sometimes undergo significant evolutionary transformations. Our 3D numerical studies of comet shape evolution by mass loss include revealed the key parameters that have been shown to be coupled, namely large-scale shape, orbital parameters and spin state. Under solar driven outgassing conditions the coupling may acts over relatively long timescales, however it is non-negligible even at distances of 100-150 AU (for instance due to CO ice sublimation). Within this project, we have proposed one of the leading hypotheses to explain the observed flattened shape of Arrokoth, which is consistent with a weak but long term mass loss due to CO activity, given its spin/orbit characteristics. Among other results, our model also revealed a rarely acknowledged ambiguity in the interpretation of total gas production rates from unresolved nucleus measurements by ground-based telescopes. To make sense of such data in terms of the physics of nuclear activity, it is essential to know the true shape and spin axis orientation. The 3D morphology model also revealed several conditions under which the global shape characteristic can be uniquely related to orbital eccentricity in one case and to the homogeneity of the ice distribution in another. Finally, we have also used another 3D model to understand the instantaneous measured H2O data from Rosetta/MIRO, challenging some of the simple interpretations of the surface source of outgassing from such remote sensing measurements.
Projektbezogene Publikationen (Auswahl)
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Dynamical properties and acceleration of hierarchical dust in the vicinity of comet 67P/Churyumov–Gerasimenko. Monthly Notices of the Royal Astronomical Society, 477(4), 4896-4907.
Skorov, Yu; Reshetnyk, V.; Rezac, L.; Zhao, Y.; Marschall, R.; Blum, J. & Hartogh, P.
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Constraining spatial pattern of early activity of comet 67P/C–G with 3D modelling of the MIRO observations. Monthly Notices of the Royal Astronomical Society, 494(2), 2374-2384.
Zhao, Y.; Rezac, L.; Hartogh, P.; Ji, J.; Marschall, R. & Keller, H. U.
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Interpretation of heliocentric water production rates of comets. Astronomy & Astrophysics, 623, A120.
Marshall, D.; Rezac, L.; Hartogh, P.; Zhao, Y. & Attree, N.
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Three-dimensional analysis of spatial resolution of MIRO/Rosetta measurements at 67P/Churyumov-Gersimenko. Astronomy & Astrophysics, 630, A34.
Rezac, L.; Zhao, Y.; Hartogh, P.; Ji, J.; Marshall, D. & Shi, X.
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Accuracy of view factor calculations for digital terrain models of comets and asteroids. Astronomy & Astrophysics, 642, A167.
Rezac, L. & Zhao, Y.
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Sublimation as an effective mechanism for flattened lobes of (486958) Arrokoth. Nature Astronomy, 5(2), 139-144.
Zhao, Y.; Rezac, L.; Skorov, Y.; Hu, S. C.; Samarasinha, N. H. & Li, J.-Y.
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The phenomenon of shape evolution from solardriven outgassing for analogues of small Kuiper belt objects. Monthly Notices of the Royal Astronomical Society, 492(4), 5152-5166.
Zhao, Y., Rezac, L., Skorov, Y. & Li, J. Y.
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Gas terminal velocity from MIRO/Rosetta data using neural network approach. Astronomy & Astrophysics, 648, A21.
Rezac, L.; Zorzi, A.; Hartogh, P.; Pinzón-Rodríguez, O.; Marshall, D.; Biver, N.; Bockelée-Morvan, D.; Crovisier, J.; Ip, W. H. & Gulkis, S.
