Deimos (moon)
Deimos /ˈdaɪməs/ (systematic designation: Mars II) is the smaller and outer of the two natural satellites of Mars, the other being Phobos. Deimos has a mean radius of 6.2 km (3.9 mi) and takes 30.3 hours to orbit Mars. Deimos is 23,460 km (14,580 mi) from Mars, much farther than Mars's other moon, Phobos. It is named after Deimos, the Ancient Greek god and personification of dread and terror.
An enhanced-color image of Deimos by Mars Reconnaissance Orbiter (2009) | |
| Discovery | |
|---|---|
| Discovered by | Asaph Hall |
| Discovery date | 12 August 1877 |
| Designations | |
Designation | Mars II |
| Pronunciation | /ˈdaɪməs/ to /ˈdiːməs/ or as Greek Δεῖμος (approximated /ˈdeɪmɒs/) |
Named after | Δεῖμος |
| Adjectives | Deimian /ˈdaɪmiən/ |
| Orbital characteristics | |
| Epoch 23 September 2012 (JD 2456191.5) | |
| Periapsis | 23455.5 km |
| Apoapsis | 23470.9 km |
| 23463.2 km (6.92 Mars radii) | |
| Eccentricity | 0.00033 |
| 1.263 d (30.312 h) | |
Average orbital speed | 1.3513 km/s |
| Inclination | 0.93° (to Mars's equator) 1.791° (to the local Laplace plane) 27.58° (to the ecliptic) |
| Satellite of | Mars |
| Physical characteristics | |
| Dimensions | 16.08 × 11.78 × 10.22 km (0.16 × 0.12 × 0.10 km) |
Mean radius | 6.27±0.07 km |
| 522±8 km2 | |
| Volume | 1033±19 km3 |
| Mass | 1.4762×1015 kg |
Mean density | 1.465±0.051 g/cm3 |
| 0.003 m/s2 (306 µg) | |
| 5.556 m/s (20 km/h) | |
| Synchronous | |
| Albedo | 0.068±0.007 |
| Temperature | ≈ 233 K |
| 12.89 | |
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