"What day is it? Do days exist without calendars? Does time pass when there are no human hands left to wind the clocks?"
-- Howard Koch, Invasion from Mars, the 1938 radio play based on H. G. Wells' The War of the Worlds

Mars Fact Sheet

SI Units

English Units

Earth Comparisons

	Earth	Mars		Moon
Mass (10²⁴ kg)	5.9736	0.64185		0.07347673
Equatorial radius (km)	6,378	3,393		1,738
Polar radius (km)	6,356	3,373		1,735
Mean density (kg/m³)	5,520	3,933		3,340
Surface gravity (m/sec²)	9.78	3.69		1.62
Escape velocity (km/sec)	11.186	5.03		2.38

Semimajor axis (10⁶ km)	149.6	227.9		0.3844
Periapsis (10⁶ km)	from Sun: 147.1	from Sun: 206.6		from Earth: 0.3633
Apoapsis (10⁶ km)	from Sun: 152.1	from Sun: 249.2		from Earth: 0.4055
Orbital eccentricity	0.0167	0.0934		0.0549
Orbital inclination (deg)	0	1.85		5.145
Equatorial inclination (deg)	23.44	25.19		6.68
Sidereal day (hrs:min:sec)	23:56:04.2	24:37:22.4		655:19
Solar day (hrs:min:sec)	24:00:00	24:39:35.2		708:44:03

	Days	Days	Sols	Lunations
Seasons				---
Spring	92.764	198.61	193.30
Summer	93.647	183.55	178.64
Autumn	89.836	146.62	142.70
Winter	88.997	158.18	153.95
Anomalistic year	365.2596	686.9957	668.6146	12.3689
Sidereal year	365.2564	686.9797	668.5991	12.3687
Vernal equinox year	365.2424	686.9710	668.5906	12.3683
Summer solstice year	365.2416	686.9683	668.5880	12.3682
Autumnal equinox year	365.2420	686.9745	668.5940	12.3683
Winter solstice year	365.2427	686.9763	668.5958	12.3683
Tropical year	365.2422	686.9725	668.5921	12.3683
Synodic period	---	779.94	759.07	29.53

Mean surface temperature (K)	288	~210		~232
Diurnal temperature range (K)	283 - 293	184 - 242		80 - 384
Mean surface pressure (mb)	1014	6.9 - 9		0
Scale height (km)	8.5	11.1		---
Atmospheric composition (%)	75.5 Nitrogen 23.1 Oxygen 1.3 Argon 0.03 Carbon Dioxide	95.3 Carbon Dioxide 2.7 Nitrogen 1.6 Argon 0.13 Oxygen 0.08 Carbon Monoxide		---
Wind speeds (m/sec)	0 - 100	2 - 7 (summer) 5 - 10 (autumn) 17 - 30 (dust storm)		---

Martian Satellites

San Francisco	Phobos	Deimos
Discovered	1877	1877
Location	Mars Orbit	Mars Orbit
Mass (10¹⁵ kg)	10.8	1.8
Major axis radius (km)	13	8
Minor axis radius (km)	9	5
Mean density (kg/m³)	1,900	1,750

Semimajor axis (km)	9,377	23,436
Periapsis (km)	9,235	23,428
Apoapsis (km)	9,519	23,444
Orbital eccentricity	0.0151	0.00033
Orbital inclination (deg)	1.08	1.79
Sidereal period (hr:min:sec)	7:39:14	30:17:55

Martian Trojans
	Provisional designation: 1999 UJ7	5261 Eureka	Provisional designation: 1998 VF31	Provisional designation: 2001 DH47	Provisional designation: 2001 FG24	Provisional designation: 2001 FR127
Discovered	1999	1990	1998	2001	2001	2001
Location (deg)	L₄	301.4	290.9	L₅	L₅	L₅
Radius (km)		1.0-2.0	0.5-1.0

Semimajor axis (x 10⁶ km)	228.0	227.8	228.0	227.4	227.1	227.8
Perihelion (x 10⁶ km)	219.2	213.2	205.1	219.6	197.3	202.6
Aphelion (x 10⁶ km)	237.0	242.7	250.9	235.2	256.9	253.1
Orbital eccentricity	0.039	0.0607	0.1005	0.034	0.131	0.111
Orbital inclination (deg)	16.8	20.2802	31.2966	24.2	19.2	28.5

Once and Future Martian Trojans
	Provisional designation: 1998 QH56	Provisional designation: 1998 SD4
Discovered	1998	1998
Location (deg)	258.5	245.5
Radius (km)	0.5-0.75	0.25-0.6

Semimajor axis (x 10⁶ km)	232.0	226.6
Perihelion (x 10⁶ km)	224.8	198.2
Aphelion (x 10⁶ km)	239.1	255.0
Orbital eccentricity	0.0307	0.1254
Orbital inclination (deg)	32.2222	13.6725

Source: Serge Tabachnik and N. Wyn Evans, "Cartography for Martian Trojans."

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Mars Fact Sheet

Earth

Mars

Moon

Martian Satellites

San Francisco

Phobos

Deimos

Martian Trojans

5261 Eureka

Once and Future Martian Trojans