Neptune
Position on the route: 26/45 · level needed 230 · journey (Mk0 engine) 50.1 h
By the numbers
| Distance from Sun | 4.5 billion km (30 AU) |
|---|---|
| Diameter | 49,244 km |
| Gravity | 11.2 m/s² (cloud tops) |
| Day | 16 h |
| Year | 165 years |
| Temperature | −214 °C |
| Wind | 2,100 km/h (fastest in the system) |
| Big moon | Triton |
The story
The planet found with pen and paper rather than a telescope: computed from the wobbles in Uranus’s orbit and seen in 1846 exactly where predicted. It receives so little sunlight that its storms run on internal heat; its winds approach the speed of sound. The Great Dark Spot Voyager 2 saw in 1989 had vanished a few years later.
Triton is the only large moon in the system orbiting backwards, probably a captured Kuiper belt object. It has nitrogen geysers and, at −235 °C, one of the coldest surfaces known. Neptune itself is an ice giant with no surface to land on.
Voyager 2 (1989) is the only visit; the craft is now in interstellar space. Orbiter proposals exist (Trident, Neptune Odyssey), but the journey takes 12–15 years.
Missions
- Voyager 2 (1989): the only flyby; Triton’s geysers
- Neptune Odyssey / Trident: proposed missions
Colony note
No surface; an orbital habitat is needed. Triton would make more sense as a base: nitrogen ice, solid ground.
☠ A gas giant: there is no surface to land on. With the orbital-habitat research a station is built in orbit.
What probes bring back
- Winds of 2,100 km/h: near the speed of sound.
- Triton orbits backwards; nitrogen geysers on its surface.
- Internal heat 2.6 times what it gets from the Sun.