"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 1 0.1074 0.0123 Equatorial radius 1 0.5320 0.2725 Polar radius 1 0.5307 0.2730 Mean density 1 0.7125 0.6051 Surface gravity 1 0.377 0.165 Escape velocity 1 0.377 0.213 Semimajor axis (AU) 1 1.5234 0.3844 Periapsis (AU) from Sun: 0.9833 from Sun: 1.3810 from Earth: 0.3633 Apoapsis (AU) from Sun: 1.0167 from Sun: 1.6658 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 (days) 0.997271 1.025954 27.304861 Solar day (days) 1 1.027491 29.530590   Julian Years Julian Years   Seasons     ---      Spring 0.25397 0.54376        Summer 0.25639 0.50253        Autumn 0.24596 0.40142        Winter 0.24366 0.43307   Anomalistic year 1.000026 1.880892   Sidereal year 1.000018 1.880848   Vernal equinox year 0.999979 1.880824   Summer solstice year 0.999977 1.880817   Autumnal equinox year 0.999978 1.880834   Winter solstice year 0.999980 1.880839   Tropical year 0.999979 1.880828   Synodic period --- 2.135359

Martian Satellites
San Francisco	Phobos	Deimos
Discovered	1877	1877
Location	Mars Orbit	Mars Orbit
Mass (Earth = 1)	1.81 x 10-9	3.01 x 10-10
Major axis radius (Earth = 1)	2.0 x 10-3	1.3 x 10-3
Minor axis radius (Earth = 1)	1.4 x 10-3	7.9 x 10-4
Mean density (Earth = 1)	0.34	0.32
Semimajor axis (Earth = 1)	6.268 x 10-5	1.566 x 10-4
Orbital eccentricity	0.0151	0.00033
Orbital inclination (deg)	1.08	1.79
Sidereal period (days)	0.319785	1.265897

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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 (km)		1-2	0.5-1
Semimajor axis (AU)	1.524	1.5235	1.5241	1.520	1.518	1.523
Perihehion (AU)	1.465	1.425	1.371	1.468	1.319	1.354
Aphelion (AU)	1.584	1.622	1.677	1.572	1.717	1.692
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 (AU)	1.5506	1.5149
Perihelion (AU)	1.5030	1.3249
Aphelion (AU)	1.5982	1.7049
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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