terrestrial planet
Mercury
The smallest planet and the closest to the Sun: a cratered, airless world of scorching days and freezing nights.
- Distance from Earth today
- 101.1 million km0.676 AU · light: 5 min 37 s
- Distance from the Sun today
- 49.07 million km0.328 AU
- As of
- 2 November 2026Live distance and chart →
Where it is today
Top view of the plane of Earth’s orbit, compressed distance scale. Open on the big map with the time slider →
Facts
- Diameter
- 4,879 km
- Mass
- 0.330 × 10²⁴ kg
- Density
- 5,429 kg/m³
- Surface gravity
- 3.7 m/s²
- Escape velocity
- 4.3 km/s
- Rotation period
- 58.7 days
- Length of day
- 175.9 days
- Mean distance from the Sun
- 57.90 million km (0.387 AU)
- Perihelion
- 46.00 million km
- Aphelion
- 69.80 million km
- Orbital period
- 88.0 days
- Mean orbital velocity
- 47.4 km/s
- Orbital eccentricity
- 0.206
- Orbital inclination
- 7.0°
- Axial tilt
- 0.0°
- Mean temperature
- 167 °C
- Surface pressure
- 0 bar
- Known moons
- 0
- Rings
- no
- Global magnetic field
- yes
Source of the figures: NASA Planetary Fact Sheet (public domain).
Description
Mercury is the innermost planet, a rocky body only a little larger than our Moon. With almost no atmosphere to hold heat, its surface swings between extreme heat on the day side and deep cold at night. The planet spins exactly three times for every two trips around the Sun, so a single solar day there lasts longer than its year. An unusually large iron core takes up most of its interior, and the giant Caloris impact basin scars one hemisphere. Mariner 10 made the first flybys in the 1970s, MESSENGER orbited it and found water ice hidden in permanently shadowed polar craters, and the European–Japanese BepiColombo is now arriving to continue the work.
Surface map
Texture: Solar System Scope (CC BY 4.0) · names: IAU/USGS Gazetteer of Planetary Nomenclature