How short is a year on Mercury?
The innermost planet circles the Sun in only 88 Earth days.
Close to the Sun, quick around the track
Mercury travels around the Sun faster than any other planet in the solar system. Its average orbital period is about 88 Earth days. A year there is therefore less than three Earth months, even though Mercury has a complicated pattern of days and nights.
A remarkable spin–orbit relationship
Mercury turns on its axis about three times for every two orbits around the Sun. This is called a 3:2 spin–orbit resonance. As a result, one full solar day—from one noon to the next—lasts about 176 Earth days, or roughly two Mercurian years.
A landscape of extremes
With almost no atmosphere to redistribute heat, Mercury experiences dramatic differences between sunlit and shaded regions. The planet’s motion and physical conditions make it a useful laboratory for studying gravity, orbital dynamics and surfaces exposed to intense solar radiation. Its short year is only one part of an unusual planetary rhythm.
External references are provided for exploration; Curio Hour’s explanation is written separately.