Figure 9.36: Mars has two odd-shaped small moons: Phobos (a) and Deimos (b). They are very small, only 22 km and 13 km across, respectively, which means their gravity is very weak, and as a result they do not have enough force to pull themselves into a round shape. Every hundred years Phobos moves 1.8m closer to the surface of Mars. In about 50 million years it will either crash into the planet or be torn into rubble, forming a ring like those seen around the outer planets.
asteroids. But how could Mars have captured them? Two 2016 publications actually rule out the capture of asteroids. Te first study shows that the only scenario compatible with the surface properties of Phobos and Deimos is that of a giant collision (Rosenblatt et al., 2016). Te second study used simulations to show that the satellites could form from the debris of a gigantic collision between Mars and a protoplanet a third its size (Ronnet et al., 2016).
9.2.6 It is Magic!
While the planets were forming, there was not much peace in our solar system. Jupiter made itself king, and now it seems that the destiny of our solar system has been determined by its migration. We can speculate whether, if Jupiter had migrated into the inner system, Earth would even exist today.
