The Solar System’s top 5 most amazing moons!
In no particular order. Click images for captions if you’re unsure which is which. Incidentally, each of these is large and interesting enough that if they weren’t orbiting a gas giant, we’d unflinchingly consider them planets in their own right. (Some of us already do!)
Io
One of Jupiter’s 4 Gallilean moons, and the closest to Jupiter itself. Perpetually tormented by Jupiter’s colossal gravitational field, it’s squeezed and crushed by formidable tidal forces, making it the most volcanically active body we’ve seen. It’s also stained yellow with sulfur, and it leaves a trail of sulfur in its wake as it orbits Jupiter. Some of that sulfur ends up on the surface of…
Europa
Another Gallilean moon, Europa is expected to contain more liquid water than all of Earth’s oceans combined, locked away inside a thick icy shell. It’s also, apparently, quite active – which you can tell by how many craters its surface doesn’t have. In fact, it’s one of the smoothest objects in the Solar system!
Triton
This is Neptune’s giant moon. It’s the coldest object this side of the Kuiper belt – even colder than Pluto. It also has a retrograde (backwards) orbit, suggesting it was probably once an independent Kuiper belt object which was captured by Neptune. It also has liquid nitrogen geysers, and a thin atmosphere. It even has weather!
Ganymede
The largest moon in the entire Solar system, and the third of Jupiter’s Gallilean moons. Voyager picked up a weird radar echo from inside Ganymede. The most likely explanation is that it’s also hiding a subsurface ocean of saltwater. It’s also the only moon with a magnetic field – just like Earth!
Titan
Saturn’s giant moon. Slightly smaller than Ganymede, but the only moon with a dense atmosphere. A thick, smoggy haze (not entirely unlike downtown L.A. during rush hour). It also has weather systems, lakes and rivers which run with ethane, and both mountains and volcanoes made out of ice. The volcanoes erupt hot water.