Planets · Planet
Mercury
58 million km from the Sun · Light crosses it in 0.016 seconds
- Across
- 4,879 km
- Vs Earth
- 0.38× Earth
- Mass
- 5.53% of Earth
About
Mercury is the smallest planet and the closest to the Sun, with almost no atmosphere to even out its temperature. It races around the Sun in 88 days while turning on its axis so slowly that a single day–night cycle takes 176 days.
A year on Mercury is shorter than one of its days.
At a glance
| Year | 88 days |
|---|---|
| Day | 176 days, Sun to Sun |
| Temperature | −180 to 430 °C |
| Gravity | 38% of Earth's |
Did you know
- Its year is shorter than its day, so on parts of the surface the Sun rises, stops, backs up, then sets.
- Craters at its poles never see sunlight and hold water ice, a few metres from some of the hottest ground in the Solar System.
- Its huge iron core fills about 85% of its radius; the planet may have lost its outer layers in a collision.
Real photo
- Mercury as a globe, built from MESSENGER's global mapping — NASA/Johns Hopkins University Applied Physics Laboratory/Carnegie Institution of Washington · source