"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 lbs) 13.172 1.6202 0.14153 Equatorial radius (mi) 3,963 2,108 1,080 Polar radius (mi) 3,950 2,096 1,078 Mean density (lbs/ft3) 643.4 458.4 389.2 Surface gravity (ft/sec2) 32.09 12.1 5.3 Escape velocity (mi/sec) 6.951 3.13 1.48 Semimajor axis (106 mi) 92.9 141.6 0.2389 Periapsis (106 mi) from Sun: 91.4 from Sun: 128.4 from Earth: 0.2258 Apoapsis (106 mi) from Sun: 94.5 from Sun: 154.9 from Earth: 0.2520 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 (°F) 59 ~ -81 ~ -42 Diurnal temperature range (°F) 50 - 68 -128 - -24 -315 - 232 Mean surface pressure (lbs/in2) 14.7 -.10 - 0.13 0 Scale height (mi) 5.3 6.9 --- 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 (mi/hr) 0 - 225 4- 16(summer) 11- 22 (autumn) 38 - 67(dust storm) ---

Martian Satellites
San Francisco	Phobos	Deimos
Discovered	1877	1877
Location	Mars Orbit	Mars Orbit
Mass (1015 lbs)	23.8	4.0
Major axis radius (mi)	8	5
Minor axis radius (mi)	6	3
Mean density (lbs/ft3)	221	204
Semimajor axis (mi)	5,827	14,563
Orbital eccentricity	0.0151	0.00033
Orbital inclination (deg)	1.08	1.79
Sidereal period (hr:min:sec)	7:39:14	30:17:55

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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 (mi)		0.6-1.2	0.3-0.6
Semimajor axis (x 106 mi)	141.6	141.5	141.6	141.2	141.0	141.5
Perihehion (x 106 mi)	136.1	132.4	127.4	136.4	122.5	125.8
Aphelion (x 106 mi)	147.2	150.7	155.8	146.0	159.5	157.2
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 (mi)	0.3-0.5	0.15-0.4
Semimajor axis (x 106 mi)	144.1	140.7
Perihelion (x 106 mi)	139.6	123.1
Aphelion (x 106 mi)	148.5	158.4
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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