The diameter of Mercury: constancy or change?

Mercury can often be seen in the morning or evening hours - at this time it seems a bright star in the twilight horizon. In ancient times, even believed that these are two different stars - the peoples who then inhabited the Earth, gave these "stars" two names - Horus and Light, Roginea and Buddha, Hermes and Apollo.

General information

Mercury is the closest to the luminary of the planets of the solar system. It is the smallest of the whole "family", but it has a very high density. Almost 80% of the total mass of the object falls on the core. The diameter of Mercury is almost 5 thousand kilometers.

Mercury rotates faster than other planets. This happens so that it does not leave its orbit. The year of Mercury is only 88 Earth days. At the same time around him during this time the planet turns only a half times. Thus, the Mercurian day is equal to 59 terrestrial. From sunrise to sunset, 179 terrestrial days pass.

Despite the fact that the planet is bright enough, and the diameter of Mercury can be seen from the Earth, we see it not so often. This is due to the fact that Mercury is too close to the Sun. To see it, thus, it is possible only at a time when it is moving away from the light at the maximum distance.

The diameter of Mercury is slightly larger than the Moon, but its density is much higher. It is possible that the density of the center is 8900 kilograms per cubic meter. This makes it possible to assume that the core consists of iron. And in this case the core, which has a radius of 1800 km, is ¾ of the radius of the planet.

Actually, it is the diameter of Mercury that allows some scientists from the XIX century to assert that earlier this planet was a satellite of Venus, which was lost as a result of the catastrophe. It is possible that this catastrophe was a collision with another planet, as a result of which Mercury not only found itself in its current orbit, but also received a lot of damage, observed today in the pictures of the planet.

Surface

To see the surface of Mercury was possible in 1974, when the passing by "Mariner 10" sent photos. It turned out that the surface of the red planet is very similar to our Moon. The "earth" of Mercury is dotted with rocks and craters, including those that have the form of divergent rays. These craters were formed from collisions with a multitude of meteorites. The rocks arose at a time when the core of the planet was contracting, drawing at the same time the bark.

Since Mercury is a planet, it can not emit light. We observe it as a star only because the surface of the planet has a good reflecting ability - the reflected light of the Sun can be seen from the Earth.

Atmosphere

Some signs indicate the presence of an atmosphere in Mercury. But it is much more - thousands of times - discharged, than terrestrial. It does not allow to save heat or protect the planet from excessive heating. That's why on the planet there is a huge difference between day and night temperatures.

Almost the conditional atmosphere of Mercury consists of helium, hydrogen, carbon dioxide, neon and argon, oxygen. The proximity to the luminary implies the influence of the solar wind on the planet. This increases the probability of the planet having an electric field twice as intense as the earth's, and at the same time much more stable.

Temperature

Given the almost complete absence of the atmosphere of the planet, the surface heats up during the day and cools significantly at night. The hemisphere, turned to the Sun, is heated to 440 degrees Celsius. At the same time, the night hemisphere, unable to withstand heat without atmosphere, cools down to -180 degrees.

Diameter

The diameter of Mercury is 4878 kilometers. It is almost 2.5 times smaller than the size of our planet, but 1.5 times the size of the moon. For a long time it was believed that the diameter of Mercury in kilometers does not change. However, recent studies and data transmitted by the spacecraft indicate that its size is changing. The new data made it possible for astrophysicists to find out that the last 4 billion years have made corrections in the volume of the planet. The diameter of the planet Mercury during this time decreased by 14 kilometers. The outer shell of the planet is just one plate, unlike the Earth, where the surface consists of several plates.

As a result of cooling and subsequent compression of the crust, the diameter of the planet Mercury was significantly reduced. And this decrease is much more significant than under the same conditions occurs on the Moon or Mars. The data transmitted by the spacecraft "Massenger" gives an opportunity to study the evolution of the planet. Perhaps, soon we are waiting for new sensations.

Forecasts

Of course, no one can give an exact scenario for the future. It is only realistic to assume that the diameter of Mercury can decrease further with the cooling of the planet.

However, there is also a version according to which in the distant future the planets of our system will collide. Mercury either falls on the Sun, or crashes into Venus. This, however, will not happen until after billions of years.

Scientists from France have created a model of the behavior of the solar system in the next 5 billion years. Based on the available data, it is concluded that in 3.5 billion years orbits of planets will intersect, provoking a collision. In this model, almost all the planets can get close to the dangerous distance from the Earth, except for Mercury, which, most likely, will fall on the Sun.

But most scientists acknowledge that the probability of such a future is only 1%. This model only shows that this, in principle, is possible. In addition, 3.5 billion years is a fairly significant time, and at that time, humanity is likely to be completely indifferent to what will happen and what it will face.