I've decided that the planet I'm writing will have two moons in a horseshoe orbit, closely modeled off of Saturn's Janus and Epimetheus. For the purposes of this question, I'll be calling them Moon and Luna, and the planet Earth 2.
- Earth 2 and Moon are both a bit larger than Earth and our moon.
- Luna is half the size of Moon and composed mostly of ice.
- Moon and Luna are tidally locked, and orbit farther away from Earth 2 than Earth's moon orbits us.
- From Earth 2, Moon appears roughly the same size in the night sky as Earth's moon from Earth.
- Neither satellite is habitable.
- Assuming this configuration is stable, would both moons have the same phases, or different ones? I'm curious how this might affect the development of a calendar system by an early humanlike species.