General information
Mars, nicknamed the Red planet because of its dominant colour, is the fourth planet from the Sun at an average distance of 228 million kilometres. With Mercury, Venus, and Earth, it belongs to the category of telluric planets, those that have a solid surface (on the tactile image that we will produce, the surface is represented by the thick fabric on the tactile image- point 1). As on Earth, on the surface of Mars we can also find craters, signs of heavy bombardment from asteroids from space (point 3 of the tactile image).
Its equatorial diameter of 6,787 km is about half that of Venus and Earth. Because of its smaller size, its internal structure and its climatic evolution have been substantially different from that of Venus and Earth. Its atmosphere is much less dense, with an average surface pressure of 6 millibars (150 times less than on Earth), and composed of carbon dioxide (CO2: 95%), nitrogen (N2: 3%) and argon (Ar: 1.6%) with traces of oxygen and water vapour.
Canyon and volcanoes
Among the main geologic features, there is Valles Marineris, a canyon nearly 4,000 km long, with a depth that can reach 7,000 m (materialized by the deep cut in the thick fabric in the tactile image- point 2). There is also a high plateau called Tharsis, on which sit several volcanoes (materialized by the buttons on the tactile image - point 4). One of these volcanoes, Olympus Mons, is the highest in the solar system with a summit altitude of 26 km (point 5 on the tactile image).
Mars has two tiny, natural satellites, Phobos and Deimos. Their mean diameters are respectively 22 and 13 km. By their aspect and their composition, they are very similar to asteroids. Actually, they may be asteroids that were captured by the gravitational attraction of Mars.
Mars is the planet that is the easiest to reach by planetary probes: launch opportunities occur about every two years, and the travel time is about six months. Since the mid-1960s, nearly twenty probes have explored its surface, atmosphere, and natural satellites, returning many data allowing us to understand better the planet’s past. An important question that these probes are trying to answer is whether life may have existed at some point on Mars.
Polar Regions
The Polar Regions are permanently covered with a mixture of carbonic ice (frozen CO2) and water ice (these ice caps are materialized by the aluminium foil on the tactile image - point 6). The extent of the polar caps varies with seasons, so they usually appear different in size, the larger being of course in the winter hemisphere.
Clouds
Similarly, condensation clouds composed of carbon dioxide and water vapour regularly form in the atmosphere (materialized by the clumps of cotton on the tactile image - point 7). These clouds sometimes cover the summit of the highest volcanoes.