Tiny lumpy outer moon of Mars, possibly a captured asteroid.
No small telescope will show you this one; it is here to be understood, not spotted.
Deimos is roughly 1/277 as wide as the Moon.
Deimos sits about one sixteenth of the Earth-to-Moon distance from Mars.
Deimos takes about 30 hours to go once round Mars.
Deimos turns round once in about 30 hours; Earth takes about 24 hours. Its orbit takes exactly as long, so Deimos keeps the same face turned towards Mars the whole time.

| Mean diameter | 12.54 km |
|---|---|
| Distance from the centre of the planet it orbits | 23,459 km |
| Once round its orbit | 30.3 hours |
| One spin | 30.3 hours |
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