Fun Fact of the Day
Mercury and Venus are the only planets in our Solar System that don't have moons.
Mercury cannot exert a strong gravitational field due to its small size, and its proximity to the Sun also complicates matters, so it is likely that moons have tried to form but did not last.
Venus is thought to have had a moon at one point, but it was thought to have been pulled towards the planet and crashed. This is because Venus began to rotate in the opposite direction after a collision with a body from that orientation, causing energy to energy to be transferred to Venus from the moon instead of the other way around.