Why are there no moons orbiting Mercury and Venus?
The only planets that are in orbit round the Sun that don't have moons are the two innermost planets of Mercury and Venus. If you've ever wondered why, here are some reasons why that might be the case.
The planets are too close to the Sun and the Sun's gravity is too strong for the planets to keep hold of the moons.
If the planets did have a moon, they aren't there now, they'd have been sucked into the Sun. N.A.S.A.
Mercury might not have had a cataclysmic event to cause moons to form. The Moon around our planet was formed when a planetoid smashed into the Earth when the Earth was young and the debris coalesced into the Moon.
There is a theory that Venus did have a moon at one time but it lost it because it couldn't keep hold of it.
The theory that said Venus did have a moon because of a cataclysmic event. Another cataclystic event caused Venus to rotate in the opposite direction and the moon was thrown away by the change in direction. Sky and Telescope.
Mercury is the closest planet to the Sun and it also has a weak gravitation field, anything orbiting it would've been lost to the Sun. Quora