Mars’ orbit, of semimajor axis 1.5237AU, is inclined only 1.85° to the ecliptic. The orbital eccentricity of e = 0.0934, implies that at opposition, the Earth-Mars distance may range from 108km (at which time mars shows an angular diameter of 14″) to 5.5 x 107km (25″). The Martian sidereal rotation period is 24h37m22.6s and the rotation axis is inclined 25° 12′ to its orbital plane.

Mars has a radius of 3,394km (53% R). It has two moons (Phobos and Diemos), and its mass is 6.4 x 1023kg (11% M). The density is 3,900kg m-3, much lower than the Earth’s (5,500kg m-3). Mars’ core must be smaller and probably consists of iron and iron sulphide, which has a lower density than the material in the Earth’s core.

The Martian atmosphere has a surface pressure of 0.02atm and consists of 95% CO2, 0.1 to 0.4% O2, 2 to 3% N2, and 1 to 2% Ar; a similar composition to the atmosphere of Venus.

Liquid water could not exist on the surface of Mars due to the very low atmospheric pressure. However, water probably exists in a permafrost layer beneath the surface.

At the Martian equator, the difference between noon and midnight surface temperatures amounts to 100K at perihelion. The summer tropical high is 310K.

Light orange and yellow-brown regions make up almost 70% of the Martian surface. Evidence from the Viking Landers indicates a surface composition of about 20% Ferric Oxide and 44% Silica.

The rusty sand is blown by fierce winds (>100km/h) to create planet wide storms. These storms occur most commonly as Mars is closest to the Sun. The dust clouds can reach heights of up to 50km, shrouding the planet for a month.

The north polar cap contains mostly water ice, which ranges in thickness from 1mm to 1km. The outer reaches of the cap consist of CO2 ice. The southern polar cap consists exclusively of CO2 ice.

The two Martian hemispheres have different topological characteristics; the south is relatively flat, older and heavily cratered; the north is younger, has extensive lava flows, collapsed depressions, and huge volcanoes. Near the equator, separating the two hemispheres lays a huge canyon called Valles Marineris. This chasm is 5,000km long (the length of the USA) and up to 500km wide in places.

Both Viking Landers uncovered evidence of once flowing surface water: A number of channels appear to have been cut i the surface by running water. The largest of these channels having lengths up to 1,500km and widths up to 100km. Mars does not have any liquid surface water now, conditions for its presence must have occurred in the past and would have required a denser, warmer atmosphere. Craters in the water channels, give an estimated date of 3 to 3.8 x 109years, as the time of activity.

On and near a region called the Tharsis Ridge, there are clustered, several shield volcanoes. The largest of these is Olympus Mons, 550 to 600km across at its base. The cone reaches 27km above the surrounding plain (2.5 times the height of Mount Everest above sea level). The crust beneath Olympus Mons must be 120 to 130km thick, about twice the thickness of the Earth’s crust.

The southern hemisphere of Mars has a cratered terrain similar to the highlands of the Moon.

Mars has an extremely weak magnetic field of 60nT.



~ by jamesdow2013 on April 18, 2013.

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