Hydrology of Mars

Mars

Mars in true color imaged by the OSIRIS instrument on the Rosetta spacecraft during its February 2007 flyby
Designations
Pronunciation	UK English: /mɑːz/ US English: i/ˈmɑːrz/
Adjectives	Martian
Orbital characteristics
Epoch J2000
Aphelion	7011249230052586199♠1.6660 AU 7011249200000000000♠249.2 Gm
Perihelion	7011206654498584979♠1.3814 AU 7011206700000000000♠206.7 Gm
Semi-major axis	7011227939134030305♠1.523679 AU 7011227939200000000♠227.9392 Gm
Eccentricity	0.0934
Orbital period	7000188080000000000♠1.8808 Julian years 7007593542944000000♠686.971 d 7002668599100000000♠668.5991 sols
Synodic period	779.96 days 2.135 Julian years
Average orbital speed	7004240770000000000♠24.077 km/s
Mean anomaly	6999338122635988862♠19.373°
Inclination	1.850° to ecliptic 5.65° to Sun's equator 1.67° to invariable plane
Longitude of ascending node	49.558°
Argument of perihelion	286.502°
Satellites	2
Physical characteristics
Mean radius	7006338950000000000♠3,389.5±0.2 km
Equatorial radius	7006339620000000000♠3,396.2±0.1 km  0.533 Earths
Polar radius	7006337620000000000♠3,376.2±0.1 km  0.531 Earths
Flattening	6997589000000000000♠0.00589±0.00015
Surface area	7014144798500000000♠144,798,500 km2 0.284 Earths
Volume	7020163180000000000♠1.6318×1011 km3 0.151 Earths
Mass	7023641710000000000♠6.4171×1023 kg 0.107 Earths
Mean density	7000393350000000000♠3.9335±0.0004 g/cm³
Surface gravity	7000371100000000000♠3.711 m/s² 0.376 g
Moment of inertia factor	6999366200000000000♠0.3662±0.0017
Escape velocity	5.027 km/s
Sidereal rotation period	7004886426848000000♠1.025957 d 24h 37m 22s
Equatorial rotation velocity	868.22 km/h (241.17 m/s)
Axial tilt	25.19° to its orbital plane
North pole right ascension	21h 10m 44s 7000554458692594390♠317.68143°
North pole declination	6999923043554855983♠52.88650°
Albedo	0.170 (geometric) 0.25 (Bond)
Surface temp. min mean max Kelvin 130 K 210 K 308 K Celsius −143 °C −63 °C 35 °C Fahrenheit −226 °F −82 °F 95 °F
Apparent magnitude	+1.6 to −3.0
Angular diameter	3.5–25.1″
Atmosphere
Surface pressure	0.636 (0.4–0.87) kPa 0.00628 atm
Composition by volume	95.97% carbon dioxide 1.93% argon 1.89% nitrogen 0.146% oxygen 0.0557% carbon monoxide

7006339620000000000♠3,396.2±0.1 km 

7006337620000000000♠3,376.2±0.1 km 

7014144798500000000♠144,798,500 km²

7020163180000000000♠1.6318×10¹¹ km³

7023641710000000000♠6.4171×10²³ kg

7000371100000000000♠3.711 m/s²

7004886426848000000♠1.025957 d

21^h 10^m 44^s

Mars is the fourth planet from the Sun and the second-smallest planet in the Solar System, after Mercury. Named after the Roman god of war, it is often referred to as the "Red Planet" because the iron oxide prevalent on its surface gives it a reddish appearance. Mars is a terrestrial planet with a thin atmosphere, having surface features reminiscent both of the impact craters of the Moon and the valleys, deserts, and polar ice caps of Earth.

The rotational period and seasonal cycles of Mars are likewise similar to those of Earth, as is the tilt that produces the seasons. Mars is the site of Olympus Mons, the largest volcano and second-highest known mountain in the Solar System, and of Valles Marineris, one of the largest canyons in the Solar System. The smooth Borealis basin in the northern hemisphere covers 40% of the planet and may be a giant impact feature. Mars has two moons, Phobos and Deimos, which are small and irregularly shaped. These may be captured asteroids, similar to 5261 Eureka, a Mars trojan.