# Phobos

*In the Solar System*

The larger of Mars's two moons, and not round: a lump about 27 by 22 by 18 kilometres, pitted by Stickney, a crater nine kilometres across on a body barely three times that. It orbits only six thousand kilometres above the surface, faster than Mars turns, so from the ground it rises in the west and sets in the east twice a day. Mars's pull is dragging it slowly inward, and within a few tens of millions of years it will break up into a ring or fall. The single radius the map draws it at is a simplification its own shape contradicts.

| | |
| --- | --- |
| Radius | 11 km |
| Around the equator | 70 km |
| From the Sun | 234,745,540 km (+186,602 km/d) |
| From the Earth | 239,665,754 km (-1,083,105 km/d) |
| A signal takes | 13 min |
| Goes round | Mars |
| Placed to within | 341 km |

Distances and speed are computed from JPL Horizons trajectories and are true of 2026-10-09, changing at the rate given beside each. The interpolation itself is good to a few kilometres; what ages these figures is the date, not the arithmetic.

## Elsewhere

- On the live map: https://www.orbitalmap.space/?world=solar-system&focus=phobos
- This object as a page: https://www.orbitalmap.space/o/phobos/
- Every object: https://www.orbitalmap.space/o/
- What this site is and what it reads: https://www.orbitalmap.space/llms.txt