MarsMars is the fourth planet in order of distance from the Sun and the seventh one for dimensions.

Mars shows a solid surface characterized by the yellow-reddish color, what is due to the layer of dust with high content of limonite (Fe2O3). Such surface was modeled by numerous process: meteoritic bombardment, volcanic activity, crust's movements, aeolian erosion.

About a half of the planet, included a big part of the southern hemisphere, is a craterous plateau: there are some big basins due to impacts, the greatest of which is the Hellas Planitia, with 2.000 km of diameter.

The volcanic activity, now extinct, in past was very intense, as many volcanos testify: the greatest one is the Mons Olympus, that, with its 27 km of altitude, is the biggest volcano of the solar system.

Along the equatorial line, then, there is a system of gigantic canyons, the Valles Marineris, with a length of 5.000 km, a width up to 500 km and a depth of 6.000 meters.

Around Mars two small satellites rotate, which appear as two rocks strongly craterized: they probably are two asteroids captured by the Martian gravitational field.

Already visited by the Vikings 1 and 2 in 1976, on July 4 1997 Mars was touched by the probe Pathfinder, that released a small rover, the Sojourner.

Average distance
from the Sun
227.900.000 km
Longest distance
from the Sun
249.100.000 km
Shortest distance
from the Sun
206.700.000 km
Period of revolution687 days
Period of rotation24 hours, 37' 23''
orbital distance
24,1 km/s
Inclination of the axis23° 59'
Inclination of the orbit
compared to the ecliptic
of the orbit
Equatorial ray3.397 km
Mass6,4 x 10^23 kg
Density3,93 kg/dm³

Mars' satellites

distance (km)
period (days)
Author and year
of discovery
Phobos9.40013,50,32Hall, 1877
Deimos23.5007,51,26Hall, 1877

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