Mercury
The smallest planet and the closest to the Sun.
Mercury is the planet closest to the Sun and the smallest in the Solar System. It is a rocky world with a trace atmosphere and a cratered surface like the Moon's; its largest crater, Caloris Planitia, is about 1,550 km across.
It orbits the Sun every 88 Earth days and rotates once every 58.65 days, so a full solar day lasts about 176 Earth days. It always appears close to the Sun in our sky, as a morning or evening star.
Quick Facts
- Synodic period
- 115.88 d
- Average speed
- 47.36 km/s
- Inclination
- 7.005° to ecliptic
- 3.38° to Sun's equator
- 6.35° to invariable plane
- Flattening
- 0.0009
- Surface gravity
- 3.7 m/s2
- Moment of inertia factor
- 0.346, 0.014
- Escape velocity
- 4.25 km/s
- Axial tilt
- 2.04 ± 0.08 (to orbit) (0.034°)
More in Celestial Bodies & Worlds
Elsewhere in Cosmos Codex
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