火星最大的月亮，Phobos，正在慢慢地朝着地球落下，而不是粉碎进入表面，它可能会被切碎，而且碎片围绕着环绕的行星像环包围的戒指，木星，天王星和海王星。
Though inevitable, the demise of Phobos is not imminent. It will probably happen in 20 to 40 million years, leaving a ring that will persist for anywhere from one million to 100 million years, according to two young earth scientists at the University of California, Berkeley.
In a paper appearing online this week in自然地球科学，UC Berkeley Proddoctoral Fenjamin Black和Grandubets Tushar Mittal估计Phobos的凝聚力并得出结论，它不足以抵抗当它更接近火星时将其拉开的潮汐力。
正如地球的月亮在我们的行星上拉动在不同的方向上，例如在海洋中提升潮汐，所以在Phobos的不同部位不同。科学家们说，随着Phobos变得更接近地球，拖船足以实际地将月亮拉开。这是因为Phobos是高度骨折的，有很多毛孔和瓦砾。贬低它类似于拉开一个格兰诺拉麦片棒，黑人说，散落的碎屑和块块到处都是。
The resulting rubble from Phobos – rocks of various sizes and a lot of dust – would continue to orbit Mars and quickly distribute themselves around the planet in a ring.
While the largest chunks would eventually spiral into the planet and collide at a grazing angle to produce egg-shaped craters, the majority of the debris would circle the planet for millions of years until these pieces, too, drop onto the planet in ‘moon’ showers, like meteor showers. Only Mars’ other moon, Deimos, would remain.
不同的卫星，不同的命运
Black and Mittal, both in UC Berkeley’s Department of Earth and Planetary Science, were drawn to the question of what might happen to Phobos because its fate is expected to be so different from that of most other moons in our solar system.
“虽然我们的月亮在每年几厘米处远离地球，但Phobos每年几厘米朝火星向火星迁移，所以它几乎是不可避免的，这将崩溃到火星或分开，”黑人说。“我们研究PHOBOS的动机之一是一个考验案例，以制定月球在向内移动时可能经历的过程的想法。”
Only one other moon in the solar system, Neptune’s largest moon, Triton, is known to be moving closer to its planet.
米特拉尔说，研究这种卫星与我们早期太阳系的条件相关，当时它的行星周围有更多的卫星，这些卫星在崩溃的环中 - 外行星环的疑似起源。一些研究估计，在行星形成期间，20-30％的行星获取卫星向内移动并注定用于破坏，尽管它们从消失后将长期以来。一些火星的几千个椭圆陨石坑甚至可以通过这些月亮的残余物以放牧角度撞向表面而形成。
When tidal stresses overcome rock strength
To estimate the strength of Phobos, Black and Mittal looked data from similarly fractured rocks on Earth and from meteorites that struck Earth and have a density and composition similar to Phobos. They also constrained the strength of Phobos based on results from simulations of the 10-kilometer diameter Stickney impact crater, which formed in the past when a rock rammed into Phobos without quite smashing the moon apart. That crater spans about one-sixth the circumference of Phobos and looks as if someone took a scoop out of the moon.
一旦他们确定他们预期的潮汐力分开的潮汐力分开，米特拉特建模了环的演变，适应了解土星的戒指。
“If the moon broke apart at 1.2 Mars radii, about 680 kilometers above the surface, it would form a really narrow ring comparable in density to that of one of Saturn’s most massive rings,” Mittal said. “Over time it would spread out and get wider, reaching the top of the Martian atmosphere in a few million years, when it would start losing material because stuff would keep raining down on Mars.”
If the moon breaks up farther from Mars, the ring could persist for 100 million years before raining down on Mars, they found.
米特拉尔说，目前尚不清楚灰尘和碎片戒指是否可以从地球上看到，因为灰尘没有反射太大，而外行星环中的冰使它们易于看。但火星的戒指可能会反映足够的光线，使火星稍微明亮，如从地球上看到的，并且通过望远镜的望远镜的阴影也可以在表面上可见。
“站在火星的表面上几十多年来，看起来很壮观，”黑人说。
提起：Aerospace + defense
