Occasional paper: Inconstant moon

I said a while back that nobody’s going to Mars any time soon. Which is true. But that doesn’t mean Mars isn’t interesting! Mars is very interesting.So today’s paper is about Mars. Okay, it’s about a moon of Mars. TLDR: one of Mars’ moons may periodically tear itself apart, turn into a system of rings around the planet, and then put itself back together.You may recall that Mars has two small moons, Deimos and Phobos. Emphasis on small; they’re about 12 km and 20 km across, respectively. They’re so small that their weak gravity doesn’t pull them into spheres. They’re both irregular lumps, vaguely potato-shaped.Now we have to take a step back and talk a little bit about the physics of moons.You’ve probably heard of geosynchronous orbits. There’s a particular distance from the Earth — it’s about 40,000 kilometers — where a satellite will take exactly 24 hours to complete one orbit. Mars rotates much like Earth, so there are geosynchronous (1) orbits around Mars too.So an interesting fact…