Atmosphere
A wisp-thin exosphere of oxygen, sodium, hydrogen, helium and potassium atoms blasted off the surface by the solar wind.
Distance from Earth today
157.5M km
In astronomical units
1.053 AU
Light travel time
8m 45s
Overview.
Mercury is the closest planet to the Sun and the smallest in the solar system — only a little larger than our Moon.
With almost no atmosphere to hold heat, its days scorch at 430 °C while its nights plunge to −180 °C.
- Diameter
- 4,879 km
- Distance from Sun
- 57.9M km
- Year
- 88 Earth days
- Day (solar)
- 176 Earth days
- Gravity
- 0.38 g
- Moons
- 0
The real Mercury
Through spacecraft eyes.
Mercury’s cratered surface in a mosaic from MESSENGER’s first flyby.
Image credit: NASA / Johns Hopkins University Applied Physics Laboratory / Carnegie Institution of Washington
Surface & interior
Grey, heavily cratered terrain much like the Moon, with long cliffs (scarps) formed as the planet’s iron core cooled and shrank.
Moons & rings
Mercury has no moons and no rings.
Missions.
- Mariner 10 (1974–75)
- MESSENGER (2011–15, orbiter)
- BepiColombo (arriving 2026)
Wow facts.
- Ice may hide in permanently shadowed craters near its poles.
- Its iron core takes up about 85% of its radius.
- From Mercury, the Sun looks three times larger than from Earth.
Yana asks
If Mercury is closest to the Sun, why isn’t it the hottest planet?
Cover: artistic illustration. Spacecraft images and radar visualizations: credited NASA mission data.