While some of the planets in our solar system have just one Moon – like Earth, some of them have to many like Saturn with its 82 moons, but there two planets in our solar system that have no moon. I am talking about Mercury and Venus.
Mercury is the smallest and innermost planet in the Solar System. Its orbit around the Sun takes 87.97 days, the shortest of all the planets in the Solar System. It is named after the Roman deity Mercury, the messenger of the goods.
Because of the glare of the Sun, it can only be seen in twilight. Timocharis made the first recorded observation of Mercury in 265 BC. Other early astronomers that studied Mercury include Zupus (1639), who studied the planet’s orbit.
Mercury has no Moon because is so close to the Sun and its gravity, it wouldn’t be able to hold on to its own moon. Any moon would most likely crash into Mercury or maybe go into orbit around the Sun and eventually get pulled in.
“Hypothetical”, in 1970s Mercury was believed to have a natural satellite orbiting the planet, but it turned out to be a misinterpreted data from a star. Observation of a moon on Mercury from Earth would be difficult because Mercury is relatively close to the Sun. For example, Mercury was not observed in the infrared spectrum until 1995. NASA’s Messenger spacecraft, which orbited Mercury from 2011 to 2015, did not detect any moon.
Venus is the second planet from the Sun. It is named after the Roman goddess of love and beauty. As the second-brightest natural object in the night sky after the Moon, Venus can cast shadows and can be, on rare occasion, visible to the naked eye in broad daylight.
Galileo pointed his telescope at Venus in 1610, and confirmed Copernicus’ theory by showing that Venus went through distinct phases, just like the Moon. The phases matched the predictions made by Copernicus, and demonstrated that Venus was really a planet, orbiting the Sun and not the Earth.
Same like it’s buddy Mercury, Venus is relatively close to the Sun and any moon with too great distance from these planets would be an unstable orbit and be captured by the Sun. If they were to close to these planets they would be destroyed by the tidal gravitational forces.
Reports of a moon around Venus have circulated since the 17th century, but it turned out that it is not at all true.