Answer - The smallest planet is Mercury in our solar system.
The smallest planet in our solar system and nearest to the Sun, Mercury is only slightly larger than Earth's Moon. Mercury is a rocky planet, also known as a terrestrial planet. Mercury has a solid, cratered surface, much like the Earth's moon. Mercury's thin atmosphere, or exosphere, is composed mostly of oxygen (O2), sodium (Na), hydrogen (H2), helium (He), and potassium (K). Mercury has no moons. There are no rings around Mercury. Along with Venus, Earth, and Mars, Mercury is one of the rocky planets. It has a solid surface that is covered with craters like our Moon. It has a thin atmosphere, and it doesn’t have any moons. Mercury likes to keep things simple.
Which is the smallest planet in our solar system?
Mercury is the smallest planet in our solar system – only slightly larger than Earth's Moon. Mercury is the planet that orbits the closest to the Sun. Mercury is the fastest planet in our solar system – travelling through space at nearly 29 miles (47 kilometres) per second. The closer a planet is to the Sun, the faster it travels. Since Mercury is the fastest planet and has the shortest distance to travel around the Sun, it has the shortest year of all the planets in our solar system – 88 days.