Deimos (moon)
An enhanced-color image of Deimos (MRO, 21 February 2009).
Image: NASA/JPL-Caltech/University of Arizona |
|
| Discovery | |
|---|---|
| Discovered by | Asaph Hall |
| Discovery date | 12 August 1877 |
| Designations | |
| Adjectives | Deimosian |
| Orbital characteristics | |
|
Epoch 2012-Sep-21 (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 | 15 × 12.2 × 11 km |
|
Mean radius
|
6.2 ± 0.18 km (0.97316 mEarths) |
|
495.1548 km2 (97.0755 µEarths) |
|
| Volume |
999.78 km3 (92.2979 nEarths) |
| Mass |
1.4762×1015 kg (0.247179 nEarths) |
|
Mean density
|
1.471±0.166 g/cm3 |
| 0.003 m/s2 (306 µg) |
|
| 5.556 m/s (20 km/h) |
|
| Synchronous | |
| Albedo | 0.068 ± 0.007 |
| Temperature | ≈ 233 K |
Deimos (systematic designation: Mars II) is the smaller and outer of the two natural satellites of the planet 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. The name Deimos is pronounced /ˈdaɪmɒs/ DY-mos, /'deɪmɒs/, or sometimes /ˈdiːməs/ DEE-məs or like the Greek Δεῖμος. In Greek mythology, Deimos was the twin brother of Phobos and personified terror.
Deimos is 23,460 km (14,580 mi) from Mars, much further than Mars's other moon, Phobos.
Deimos was discovered by Asaph Hall, Sr. at the United States Naval Observatory in Washington, D.C on 12 August 1877, at about 07:48 UTC (given in contemporary sources as "11 August 14:40" Washington mean time, using an astronomical convention of beginning a day at noon, so 12 hours must be added to get the actual local mean time). Hall also discovered Phobos on 18 August 1877, at about 09:14 GMT, after deliberately searching for Martian moons.
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