Deimos (moon)

Deimos
	Deimos, captured by the Mars Reconnaissance Orbiter in false color
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
Semi-major axis	23463.2 km (6.92 Mars radii)
Eccentricity	0.00033
Orbital period (sidereal)	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
Surface area	522±8 km2
Volume	1033±19 km3
Mass	1.51×1015 kg
Mean density	1.465±0.051 g/cm3
Surface gravity	0.003 m/s2; (306 μg)
Escape velocity	5.556 m/s; (20 km/h)
Synodic rotation period	Synchronous
Albedo	0.068±0.007
Temperature	≈ 233 K
Apparent magnitude	12.89

Deimos /ˈdaɪməs/ (systematic designation: Mars II)^[11] 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.^[5] Deimos is 23,460 km (14,580 mi) from Mars, much farther than Mars's other moon, Phobos.^[12] It is named after Deimos, the Ancient Greek god and personification of dread and terror.

^ The Century Dictionary and Cyclopedia (1914)
^ "Moons of Mars – the Center for Planetary Science".
^ "Deimos". Lexico UK English Dictionary. Oxford University Press. Archived from the original on 22 March 2020.
^ Harry Shipman (2013) Humans in Space: 21st Century Frontiers, p. 317
^ ^a ^b ^c ^d ^e ^f "HORIZONS Web-Interface". NASA. 21 September 2013. Retrieved 4 December 2013.
^ ^a ^b ^c Cite error: The named reference NASA was invoked but never defined (see the help page).
^ ^a ^b ^c ^d ^e ^f Cite error: The named reference Ernst2023 was invoked but never defined (see the help page).
^ Jacobson (2010), as cited in Ernst et al. (2023).^[7]
^ Cite error: The named reference JPLSSD was invoked but never defined (see the help page).
^ "Mars' Moons".
^ Cite error: The named reference Blunck was invoked but never defined (see the help page).
^ Staff (2016). "Deimos". SeaSky.org. Retrieved 23 January 2016.

Discovery
Deimos, captured by the Mars Reconnaissance Orbiter in false color
Discovered by	Asaph Hall
Discovery date	12 August 1877
Designations
Designation	Mars II
Pronunciation	/ˈdaɪməs/^[1] to /ˈdiːməs/^[2] or as Greek Δεῖμος (approximated /ˈdeɪmɒs/)^[3]
Named after	Δεῖμος
Adjectives	Deimian /ˈdaɪmiən/^[4]
Orbital characteristics
Epoch 23 September 2012 (JD 2456191.5)
Periapsis	23455.5 km
Apoapsis	23470.9 km
Semi-major axis	23463.2 km^[5] (6.92 Mars radii)
Eccentricity	0.00033^[5]
Orbital period (sidereal)	1.263 d^[5] (30.312 h)
Average orbital speed	1.3513 km/s^[6]
Inclination	0.93° (to Mars's equator) 1.791° (to the local Laplace plane)^[5] 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)^[7]
Mean radius	6.27±0.07 km^[7]
Surface area	522±8 km²^[7]
Volume	1033±19 km³^[7]
Mass	1.51×10¹⁵ kg^[8]
Mean density	1.465±0.051 g/cm³^[7]
Surface gravity	0.003 m/s²^[6] (306 μ g)
Escape velocity	5.556 m/s (20 km/h)^[6]
Synodic rotation period	Synchronous^[5]
Albedo	0.068±0.007^[9]
Temperature	≈ 233 K
Apparent magnitude	12.89^[10]