Moons and Icy Worlds: September 2020

For terrestrial exoplanets with thin atmospheres or no atmospheres, the surface contributes light to the reflected light signal of the planet.

Jupiter's moons are hot. Well, hotter than they should be, for being so far from the Sun. In a process called tidal heating, gravitational tugs from Jupiter's moons and the planet itself stretch and squish the moons enough to warm them.

Callisto is thought to possess a subsurface ocean, which will dissipate energy due to obliquity tides. This dissipation should have damped any primordial inclination within 1 Gyr - and yet Callisto retains a present-day inclination.