Mars (Planet)

Article

August 19, 2022

Mars is the fourth planet in the solar system counted from the sun and the outer neighbor of the earth. It is one of the earth-like (terrestrial) planets. At almost 6800 kilometers, its diameter is about half that of the earth, and its volume is a good seventh of the earth's volume. This makes Mars the second smallest planet in the solar system after Mercury, but it has a diverse geology and the highest volcanoes in the solar system. At an average distance of 228 million kilometers, it is around 1.5 times as far from the sun as Earth. The mass of Mars is about one tenth the mass of Earth. The gravitational acceleration on its surface is 3.69 m/s², which corresponds to about 38% of that on Earth. With a density of 3.9 g/cm³, Mars has the lowest value of the terrestrial planets. Because of this, gravity on it is even slightly lower than on the smaller but denser Mercury. Mars is also known as the Red Planet. This coloring is due to iron oxide dust (rust) that has spread on the surface and in the thin CO2 atmosphere. Its orange to blood-red color and its fluctuations in brightness in the terrestrial night sky are also the reason for its naming after the Roman god of war Mars. The two polar caps and several dark levels are clearly visible in larger telescopes, which change color somewhat in spring. Photos from spacecraft show a partially cratered surface and strong evidence of past tectonics (deep canyons and a volcano over 20 km high). Mars robots have already geologically examined several areas. Mars has two small, irregularly shaped moons discovered in 1877: Phobos and Deimos (Greek for fear and terror). The astronomical symbol of Mars is ♂.

Orbit and rotation

Orbit

Mars moves in an elliptical orbit around the Sun at a distance of 206.62 to 249.23 million kilometers (1.38 AU to 1.67 AU) in just under 687 days (about 1.9 years). The orbital plane is inclined at 1.85° to the earth's orbital plane. Its orbital speed varies with the distance from the sun between 26.50 km/s and 21.97 km/s and averages 24.13 km/s. The orbital eccentricity is 0.0935. After the orbit of Mercury, this is the second largest deviation from circularity among all the planetary orbits in the solar system. In the past, Mars had a less eccentric orbit. 1.35 million years ago, the eccentricity was only about 0.002, less than Earth's today. The period of eccentricity of Mars is about 96,000 years, that of Earth is about 100,000 years. However, Mars still has a longer cycle of eccentricity with a period of 2.2 million years superimposed on that with the period of 96,000 years. Over the past 35,000 years, the orbit has become slightly more eccentric due to the gravitational forces of the other planets. The minimum distance between Earth and Mars will decrease slightly over the next 25,000 years. There are five numbered asteroids that share the same orbit with Mars (Mars Trojans). They are located at the L4 and L5 Lagrangian points, which means they lead the planet by 60° or lag it by 60°.

Rotation

Mars rotates around its own axis in 24 hours and 37.4 minutes (Siderian day). In relation to the sun, this results in a Martian day (also called sol) of 24 hours, 39 minutes and 35 seconds. The planet's equatorial plane is tilted 25.19° to its orbital plane (Earth's 23.44°), so there are seasons similar to Earth's. However, these last almost twice as long, since the sidereal Martian year has 687 Earth days. However, since the orbit of Mars has a significantly greater eccentricity than that of Earth and Mars North tends towards de