Nowadays, Mars is one of the most interesting planets in the Solar system.
The climate on Mars is very unfavorable to live there, but it is the most close to the earth climate.
Mars is the most likely candidate for the first manned expedition to another planet (we don’t count the earth's satellite - the Moon, which people have already visited).
Mars is the fourth planet from the Sun planet of the Solar system, it follows the Earth.
There are characteristics of Mars:
Average orbit radius is 227,940,000 km, diameter: 6,794 km, and its mass: 6.42*10^23 kg
Mars is about 1.5 times farther from the Sun than Earth, and its orbit has an appreciable eccentricity (the difference between the smallest and largest Sun distance is 21 million km). Complete turnover around the orbit Mars does in 687 days (a little less than two Earth years). It is interesting, that the duration of the Martian day (the period of turnover of Mars around its axis) is quite longer - at 41 minutes larger than the Earth, and the inclination of equator to orbit is very close to earth - 25°12, what has the similarity in the change of seasons, like in Earth.
The mass of Mars is in 9 times less than the mass of Earth, and its size is less in 2 times. Due to the weaker gravity, this planet has a sparse atmosphere which consists mostly from carbon dioxide. The atmospheric pressure at the surface of Mars on average is approximately in 160 times smaller than in the Earth (but because of the strong variations of elevations on Mars in the separate sites of a surface it can be in several times higher or lower).
In winter, near the poles, the carbon dioxide freezes, with the usual water ice they form the polar caps. Because of this, the mass of the atmosphere of Mars is not constant, but undergo some seasonal fluctuations. Despite the sparseness, in the atmosphere of Mars is sometimes observed a few clouds, and the wind blowing in it, sometimes raises dust storms.
Because the atmospheric pressure on Mars is low, the water on its surface cannot exist in a liquid state. However, as recently has been found, on Mars there are quite large reserves of water ice and the channels found on surface can “tell” us that in the past when the atmosphere was denser, there was a water in these channels.
The Martian climate is harsher from the earth, and the sparseness of atmosphere causes a fairly large temperature difference on the surface.
It was registered the records of temperatures change on Mars from -133°C in winter near the poles and +27°C in summer in the Equatorial region. It is unlikely that the Martian climate is much harsher than climate in Antarctica, where, as we know, life exists. This, and also dry Martian channels and ice reserves allow suggesting the presence of more favorable conditions in the past. All these conditions were the reason for proposing hypotheses about the possible existence of life on Mars. So people now send Martian automatic machines which help to investigate this planet. Unfortunately, life, and even the simplest of microorganisms on Mars has not been found yet.
The topography of the Martian surface is complicated and has many parts. Dry river channels and canyons on the surface of Mars were in the early 20th century an occasion for speculation about the existence of an advanced civilization on Mars. In addition, Mars has mountains and volcanoes. The Martian volcano Olympus, whose height is more than 27 km, is the highest mountain not only on Mars but throughout the Solar system. Scientists are observing with interest the various natural phenomena on Mars as dust storms, fog which are formed in the valleys, landslides, etc. A typical Martian landscape looks like the Earth's desert, because the surface of Mars has a reddish shade due to the high content of iron oxides in the Martian sand.
For the exploration of Mars was sent a large number of spacecrafts. The first spacecraft flew near Mars in 1965, it was the "Mariner 4", and the first devices which landed on the surface of Mars were "Mars-2" and "Mars 3" in 1971.
In 1976 spacecraft "Viking” landed on the surface of Mars, it had the equipment to search for signs of life in Martian soil.
However, the most significant expeditions of the last time were two American expeditions, during which the small wheel vehicles ("Rovers") landed on Mars could move across its surface.
In 1997 it was landed the "Pathfinder", and in 2004 - the Rovers "Spirit" and "Opportunity". These Rovers allowed to study in detail the relief of the surface of Mars in a landing zone and also they transmitted a lot of high quality pictures from the surface of this planet to Earth.
So, does Mars really have moons?
Yes, it does. Mars has two small satellites - Phobos and Deimos.
The satellites of Mars Phobos and Deimos (from Greek it means "fear" and "dread") are small, irregularly shaped bodies, they were discovered in 1877 by American astronomer Hall. Some astronomers believe that Phobos and Deimos are asteroids, which are captured by Mars.
Phobos and Deimos revolve around Mars at very small orbits, and the orbit of Phobos is strongly elongated. The periods of rotation of these satellites are very small - Phobos goes around Mars three times faster than the Mars around its axis. Three times per day Phobos manages to appear in the sky and disappear over the horizon, but the orbital period of Deimos isa little bit more than the period of rotation of Mars around its axis.
The surface of the satellites has an irregular shape, it is covered with craters and with furrows.
In 1977, the moons of Mars were photographed by the spacecraft "Viking 1".
There are some interesting facts about Phobos and Deimos
On this picture we see Phobos near Mars
The motion of the satellites differs from the movements of our own moon. Phobos rises in the West and sets in the East, committing 1 turnover in only 7 hours and 40 minutes, while Deimos, being in the vicinity of synchronous orbit, also rises in the East, but very slowly.
The orbital inclination of Phobos and Deimos to the equator of Mars is about 1 degree. The mass of these tiny moons is very small: 10×10*15 and 2×10*15 kilograms, respectively.
Phobos passes ahead of Deimos
Natural satellites of Mars are blocked by the gravity of the planet (like our Moon) and are always turned by one party to him.
A few craters on the surface of Mars, which are located near the equator, show us that perhaps the planet had a lot of other small satellites which suffered the same destiny, which can suffer Phobos. They were crashed by tidal forces. Deimos is located far enough from the planet, and its orbit is slowly increasing all the time, like in the case with our own Moon.
- READ ALSO: Does Mars have moons?