Atmosphere of Mercury: composition. What is Mercury's atmosphere?

Mercury is the planet closest to the Sun. It refers to the cosmic bodies of the terrestrial group and is located relatively close to us. However, relatively little is known about Mercury today. Some time ago it was considered the least explored planet. Various parameters (the nature of the surface, the climate, the atmosphere, its composition) of Mercury remained a mystery because of the extremely uncomfortable position of the planet for observation and research with the help of spacecraft. The reason for this - the proximity to the Sun, which spoils any directed to him or approaching him equipment. And yet, for centuries of constant attempts at observation, an impressive material was collected, which, after the beginning of the space era, was supplemented by data from interplanetary stations. The atmosphere of Mercury is included in the list of characteristics studied by Mariner 10 and Messenger. The thin air envelope of the planet, like everything on it, is subject to the constant influence of the luminary. The sun is the main factor determining and shaping the atmosphere of Mercury.

Observation from the Earth

To admire Mercury from the surface of our planet is inconvenient because of its proximity to the Sun and features of the orbit. It appears in the sky quite close to the horizon. And always during sunset or sunrise. The time of observation is negligible. Under the most favorable coincidence, it is about two hours before dawn and as much after sunset. In most cases, the observation period does not exceed 20-30 minutes.

Phases

Mercury has the same phases as the Moon. Overlying the Sun, it turns into a narrow sickle, it becomes a full circle. In all its glory, the planet is visible when it is opposite the Earth, beyond the Sun. At this time for the observer, the "full moon" of Mercury comes. However, the planet is at the maximum distance from the Earth, and bright sunlight interferes with observation.

Moving around the star, Mercury begins to visually increase in size, as it approaches us. At the same time, the area of the illuminated surface is reduced. In the end, the planet turns to us with its dark side and disappears from sight. Once every few years, at such a time, Mercury passes exactly between the Sun and the Earth. Then you can observe its movement along the disk of the star.

Observation methods

Mercury can be seen with the naked eye or watched through binoculars shortly before dawn and after sunset, that is, at dusk. With the help of a small amateur telescope, the planet will be noticed in the daytime, but it will not be possible to see any details. It is important during such observations - do not forget about safety precautions. Mercury never leaves much distance from the Sun, which means that both eyes and equipment must be protected from its rays.

The ideal place to observe the planet closest to the light is mountain observatories and low latitudes. Here, to help the astronomer comes clean air, cloudless sky, a short duration of twilight.

It was earthly observations that helped to establish the fact that Mercury does not have an atmosphere. Powerful telescopes allowed to consider many features of the surface relief of the planet and to calculate the approximate temperature difference on the illuminated and dark side. However, only flights of AMC (automatic interplanetary stations) were able to shed light on other characteristics of the planet and clarify the data already received.

Mariner 10

In the history of space travel, only two vehicles were sent to Mercury. The reason is a complex and expensive maneuver, which is necessary for the station to enter the orbit of the planet. The first Mariner 10 went to Mercury. In 1974-1975, he flew three times around the planet nearest to the Sun. The minimum distance that the apparatus and Mercury shared was 320 km. "Mariner 10" transferred to Earth several thousand images of the surface of the planet. It was covered about 45% of Mercury. "Mariner 10" measured the surface temperature on the illuminated and dark side, as well as the magnetic field of the planet. In addition, the apparatus found that the atmosphere of Mercury is practically absent, replaces its thin air shell, which contains helium.

"Messenger"

The second AMC, sent to Mercury, became the "Messenger". He started in August 2004. He transmitted to the Earth an image of that part of the surface that the Mariner 10 did not capture, measured the terrain of the planet, looked into its craters and found spots of an incomprehensible dark matter (possibly, marks from the impacts of meteorites), often found here. The apparatus studied solar flares, the magnetosphere of Mercury, its gas envelope.

His mission "Messenger" completed in 2015. He fell on Mercury, leaving a crater on the surface 15 meters deep.

Is there an atmosphere on Mercury?

If you carefully read the previous text, you can see a slight contradiction. On the one hand, ground observations indicated the absence of any kind of gas envelope. On the other hand, the device "Mariner-10" transmitted information to the Earth according to which the atmosphere of the planet Mercury still exists and contains helium. In the scientific community this message also caused surprise. And it's not that it contradicted previous observations. Simply Mercury does not have characteristics that contribute to the formation of a gas shell.

What is the atmosphere? It is a mixture of gases, volatile substances, which can only be retained by a gravity force of a certain magnitude. A small by the cosmic standards Mercury such a characteristic can not boast. Gravity on its surface is three times less than on Earth. Thus, the planet is unable to retain not only helium and hydrogen, but also heavier gases. And nevertheless, it was Helium that was discovered by Mariner 10.

Temperature

There is another factor that casts doubt on the presence of Mercury's atmosphere. This is the surface temperature of the planet. Mercury in this respect is a record holder. In light time, the temperature on the surface sometimes reaches 420-450 ° C. At such high values, the molecules and atoms of the gas begin to move faster and gradually reach the second cosmic velocity, that is, at the surface they can not be retained by anything. In the temperature conditions of Mercury, the first helium must escape first. In theory, it should not be on the planet nearest to the Sun at all, and almost from the moment of its formation.

Special position

And yet the answer to the question of whether there is an atmosphere on Mercury is positive, although it is somewhat different from what is usually hidden behind this astronomical concept. The reason for such a fantastic and at the same time quite real state of things lies in the unique location of the planet. The closeness of the star determines many characteristics of this cosmic body, and the atmosphere of Mercury is no exception.

The planet's gas shell is constantly exposed to the so-called solar wind. It originates in the corona of the star and represents a stream of nuclei, protons and helium electrons. With the solar wind, fresh portions of the volatile matter are delivered to Mercury. Without such replenishment, all helium would disappear from the surface of the planet in about two hundred days.

Atmosphere of Mercury: composition

Careful research helped to discover other elements that make up the gas shell of the planet. The atmosphere of Mercury also contains hydrogen, oxygen, potassium, calcium and sodium. The percentage of these elements is very small. In addition, the atmosphere of the planet Mercury is characterized by the presence of traces of carbon dioxide.

The air envelope is strongly rarefied. The molecules of gas in it do not actually interact with each other, but only move across the surface without collisions and collisions. Scientists managed to establish the factors that determine the presence of the atmosphere of Mercury. Hydrogen, like helium, is supplied to its surface by the solar wind. The source of other elements is the planet itself or meteorites falling on it. The atmosphere of Mercury, the composition of which is planned to be thoroughly studied in the near future, is presumably formed as a result of the evaporation of rocks under the influence of solar wind or diffusion from the interior of the planet. Most likely, each of these factors contributes to its contribution.

So, what kind of atmosphere does Mercury have? Strongly rarefied, consisting of helium, hydrogen, traces of alkali metals and carbon dioxide. Often in the scientific literature it is called an exosphere, which only emphasizes the strong difference of this shell from a similar formation, for example, on Earth.

Despite all the difficulties in the lists of goals of space research is still listed and the planet Mercury. The atmosphere and surface of this cosmic body are likely to be studied more than once by means of various apparatuses. Mercury is still a lot of interesting and unknown. In addition, the study of such planets as Venus, Mars or Mercury, devoid of an atmosphere or not, sheds light on the history of the formation and development of the Earth.