Mars craters 200-400 miles wide : google earth

Mars

From Wikipedia, the free encyclopedia

http://en.wikipedia.org/wiki/Mars

Mars is the fourth planet from the Sun and the second smallest planet in the Solar System. Named after the Roman god of war, it is often described as the "Red Planet", as the iron oxide prevalent on its surface gives it a reddish appearance.[14] Mars is a terrestrial planet with a thin atmosphere, having surface features reminiscent both of the impact craters of the Moon and the volcanoes, 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 second highest known mountain within the Solar System (the tallest on a planet), and of Valles Marineris, one of the largest canyons. The smooth Borealis basin in the northern hemisphere covers 40% of the planet and may be a giant impact feature.[15][16] Mars has two known moons, Phobos and Deimos, which are small and irregularly shaped. These may be captured asteroids,[17][18] similar to 5261 Eureka, a Martian trojan asteroid.

Until the first successful Mars flyby in 1965 by Mariner 4, many speculated about the presence of liquid water on the planet's surface. This was based on observed periodic variations in light and dark patches, particularly in the polar latitudes, which appeared to be seas and continents; long, dark striations were interpreted by some as irrigation channels for liquid water. These straight line features were later explained as optical illusions, though geological evidence gathered by unmanned missions suggest that Mars once had large-scale water coverage on its surface.[19] In 2005, radar data revealed the presence of large quantities of water ice at the poles[20] and at mid-latitudes.[21][22] The Mars rover Spirit sampled chemical compounds containing water molecules in March 2007. The Phoenix lander directly sampled water ice in shallow Martian soil on July 31, 2008.[23]

Mars is currently host to five functioning spacecraft: three in orbit -- the Mars Odyssey, Mars Express, and Mars Reconnaissance Orbiter; and two on the surface -- Mars Exploration Rover Opportunity and the Mars Science Laboratory Curiosity. Defunct spacecraft on the surface include MER-A Spirit, and several other inert landers and rovers such as the Phoenix lander, which completed its mission in 2008. Observations by the Mars Reconnaissance Orbiter have revealed possible flowing water during the warmest months on Mars.[24]

Mars can easily be seen from Earth with the naked eye. Its apparent magnitude reaches −3.0,[7] which is surpassed only by Jupiter, Venus, the Moon, and the Sun. Optical ground-based telescopes are typically limited to resolving features about 300 km (186 miles) across when Earth and Mars are closest, because of Earth's atmosphere.[25]

Orbital period

686.971 days
1.8808 Julian years

668.5991 sols

Average orbital speed
24.077 km/s

Inclination
1.850° to ecliptic
5.65° to Sun's equator
1.67° to invariable plane[1]

Satellites
2

Physical characteristics

Equatorial radius
3,396.2 ± 0.1 km[a] [3]
0.533 Earths

Polar radius
3,376.2 ± 0.1 km[a] [3]
0.531 Earths

Surface area

144,798,500 km2
0.284 Earths

Volume
1.6318×1011 km3[4]
0.151 Earths

Mass
6.4185×1023 kg[4]
0.107 Earths

Mean density
3.9335 ± 0.0004[4] g/cm³

Equatorial surface gravity
3.711 m/s²[4]
0.376 g

Equatorial rotation velocity
868.22 km/h (241.17 m/s)

Axial tilt
25.19°

Surface temp.

Kelvin

130 K

308 K


Celsius

−143 °C[8]

35 °C[9]

Atmosphere

95.32% carbon dioxide
2.7% nitrogen
1.6% argon
0.13% oxygen

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Closed Caption:

large craters have Mars
ski out for Ellie
about 273 miles across
I'm
hyphens
about 278 miles across
Olympus month
about 362 miles across
boo
this one is ending
about 4 186 miles across
some traders don't have names
probably because they haven't been
identified as
graders that have a crater shape so
could be ratings