Accretion of Phobos and Deimos in an extended debris disc stirred by transient moons
Accretion of Phobos and Deimos in an extended debris disc stirred by transient moons
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DOI：
10.1038/ngeo2742
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发表时间：
2016-08
影响因子：
18.3
通讯作者：
P. Rosenblatt;S. Charnoz;K. Dunseath;M. Terao-Dunseath;A. Trinh;R. Hyodo;H. Genda;Stéven Toupin
中科院分区：
文献类型：
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作者：
P. Rosenblatt;S. Charnoz;K. Dunseath;M. Terao-Dunseath;A. Trinh;R. Hyodo;H. Genda;Stéven Toupin
火卫一和火卫二，火星的两颗小卫星，被认为是被火星捕获的小行星，或者是在巨大的撞击后形成的围绕火星的碎片盘。然而，这两种情况都无法解释目前的火星系统。在这里，我们使用数值模拟来表明火卫一和火卫二是从火星巨大撞击后形成的碎片盘的外部吸积而来的。在我们的模拟中，较大的卫星由密度更大的内部圆盘中的物质形成，并由于与圆盘的引力相互作用而向外迁移。由此产生的轨道共振向外扩散，并聚集分散的外盘碎片，促进吸积成两颗大小类似于火卫一和火卫二的卫星。较大的内侧卫星在大约500万年后由于行星的潮汐牵引力而回落到火星，之后两颗外侧卫星演变成火卫一和火卫二类似的轨道。这个假设可以解释为什么火星有两个小卫星，而不是一个大卫星。我们的模型预测火卫一和火卫二是由火星和撞击物的混合物组成的。
Phobos and Deimos, the two small satellites of Mars, are thought either to be asteroids captured by the planet or to have formed in a disc of debris surrounding Mars following a giant impact,,,. Both scenarios, however, have been unable to account for the current Mars system,,,,,. Here we use numerical simulations to suggest that Phobos and Deimos accreted from the outer portion of a debris disc formed after a giant impact on Mars. In our simulations, larger moons form from material in the denser inner disc and migrate outwards due to gravitational interactions with the disc. The resulting orbital resonances spread outwards and gather dispersed outer disc debris, facilitating accretion into two satellites of sizes similar to Phobos and Deimos. The larger inner moons fall back to Mars after about 5 million years due to the tidal pull of the planet, after which the two outer satellites evolve into Phobos- and Deimos-like orbits. The proposed scenario can explain why Mars has two small satellites instead of one large moon. Our model predicts that Phobos and Deimos are composed of a mixture of material from Mars and the impactor.