Our solar system contains eight major planets, and more than 400 known moons orbiting six of these planets. Where did they all come from? There are multiple formation mechanisms. The case for large moons, like the four Galilean satellites around Jupiter, is that they condensed out of a dust and gas disk encircling the planet when it formed. But that would have happened over 4 billion years ago, and there is scant forensic evidence today.

NASA's James Webb Space Telescope has provided the first direct view of material in a disk around a large exoplanet, which is located over 625 light-years away. This disk is a possible construction yard for moons. Moons likely outnumber planets in our galaxy, and some might be habitats for life as we know it. So, understanding formation scenarios for moons is critical.