Mercury is about 36 million miles from the Sun, or about one-third of an Astronomical Unit—one-third the distance from the Sun to Earth. It is the smallest planet, just over a third of Earth’s diameter. Mercury is about the size of Earth’s Moon!

Mercury has almost no atmosphere, and the surface facing the Sun can reach about 800 degrees. Mercury has no moons.

MESSENGER was the first spacecraft ever to orbit Mercury. It spent four years studying the planet and even discovered evidence of water ice near the poles. Its mission ended in 2015 when it ran out of fuel and crashed into Mercury.

Today, another mission called BepiColombo, a joint European and Japanese mission, is on its way—and is scheduled to arrive at Mercury in November 2026.

To continue, move to Venus, then press Venus on your phone.