2024-11-20 NASA
＜関連情報＞
- https://www.nasa.gov/solar-system/planets/mars/making-mars-moons-supercomputers-offer-disruptive-new-explanation-2/
- https://www.sciencedirect.com/science/article/abs/pii/S001910352400397X
火星の衛星の起源は小惑星の破壊的な部分捕獲によるもの Origin of Mars’s moons by disruptive partial capture of an asteroid
Jacob A. Kegerreis, Jack J. Lissauer, Vincent R. Eke, Thomas D. Sandnes, Richard C. Elphic
Icarus Available online: 1 October 2024
DOI:https://doi.org/10.1016/j.icarus.2024.116337
Highlights
- New option to make Mars proto-satellite disk: partial capture of a disrupted asteroid
- Combine SPH tidal-disruption simulations with orbital evolution of captured fragments
- Tens of percent of an unbound asteroid can be captured beyond collisional timescales
- A smaller asteroid could make the moons via this scenario than a giant impact
- Each scenario predicts different properties of the moons upcoming missions will test
Abstract
The origin of Mars’s small moons, Phobos and Deimos, remains unknown. They are typically thought either to be captured asteroids or to have accreted from a debris disk produced by a giant impact. Here, we present an alternative scenario wherein fragments of a tidally disrupted asteroid are captured and evolve into a collisional proto-satellite disk. We simulate the initial disruption and the fragments’ subsequent orbital evolution. We find that tens of percent of an unbound asteroid’s mass can be captured and survive beyond collisional timescales, across a broad range of periapsis distances, speeds, masses, spins, and orientations in the Sun–Mars frame. Furthermore, more than one percent of the asteroid’s mass could evolve to circularise in the moons’ accretion region. This implies a lower mass requirement for the parent body than that for a giant impact, which could increase the likelihood of this route to forming a proto-satellite disk that, unlike direct capture, could also naturally explain the moons’ orbits. These three formation scenarios each imply different properties of Mars’s moons to be tested by upcoming spacecraft missions.
