The planet with no moons is Mercury. As the closest planet to the Sun, Mercury has a very thin atmosphere and extreme temperature fluctuations, making it inhospitable for life as we know it. Being a rocky planet, it has a heavily cratered surface similar to Earth's Moon, but it does not possess any natural satellites. Mercury's lack of moons differentiates it from many other planets in the solar system, which often have multiple satellites. Its orbit around the Sun is swift, completing a revolution in just 88 Earth days, contributing to its unique position in our solar system.