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| Titel |
Granular convection and its application to asteroidal resurfacing timescale |
| VerfasserIn |
Tomoya Yamada, Kosuke Ando, Tomokatsu Morota, Hiroaki Katsuragi |
| Konferenz |
EGU General Assembly 2016
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| Medientyp |
Artikel
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| Sprache |
en
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 18 (2016) |
| Datensatznummer |
250123216
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| Publikation (Nr.) |
 EGU/EGU2016-2430.pdf |
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| Zusammenfassung |
| A model for the asteroid resurfacing resulting from regolith convection is built to estimate its
timescale. The regolith convection by impact-induced global seismic shaking could be a
possible reason for regolith migration and resultant segregated terrain which were found on
the asteroids Itokawa [1]. Some recent studies [2, 3] experimentally investigated the
convective velocity of the vibrated granular bed to discuss the feasibility of regolith
convection under the microgravity condition such as small asteroids. These studies found that
the granular convective velocity is almost proportional to the gravitational acceleration [2, 3].
Namely, the granular (regolith) convective velocity would be very low under the
microgravity condition. Therefore, the timescale of resurfacing by regolith convection
would become very long. In order to examine the feasibility of the resurfacing
by regolith convection on asteroids, its timescale have to be compared with the
surface age or the lifetime of asteroids. In this study, we aim at developing a model of
asteroid resurfacing process induced by regolith convection. The model allows
us to estimate the resurfacing timescale for various-sized asteroids covered with
regolith.
In the model, regolith convection is driven by the impact-induced global seismic shaking.
The model consists of three phases,
(i) Impact phase: An impactor intermittently collides with a target asteroid [4],
(ii) Vibration phase: The collision results in a global seismic shaking [5],
(iii) Convection phase: The global seismic shaking induces the regolith convection on the
asteroid [3].
For the feasibility assessment of the resurfacing process driven by regolith convection, we
estimate the regolith-convection-based resurfacing timescale T as a function of the size of a
target asteroid Da.
According to the estimated result, the resurfacing time scale is 40 Myr for the
Itokawa-sized asteroid, and this value is shorter than the mean collisional lifetime of Itokawa
(about 170 Myr [4]). We find that T(Da) is shorter than the mean collisional lifetime as long
as the target asteroid is small (Da < 10 km). This means that the regolith convection is a
possible mechanism for the asteroid resurfacing process. However, the timescale depends on
various uncertain parameters such as seismic efficiency and convective roll size. To clarify the
parameter dependences, we develop an approximated scaling form for the resurfacing
timescale.
[1] H. Miyamoto et al., Science 316, 1011 (2007).
[2] C. Gütteler et al., Physical Review E 86, 050301 (2013)
[3] T. M. Yamada and H. Katsuragi, Planetary and Space Science 100, 79-86
(2014).
[4] D. P. O’Brien and R. Greenberg, Icarus 178, 179-212 (2005).
[5] J. E. Richardson Jr. et al., Icarus 179, 325-349 (2005) |
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