Introductory text to the planet Mercury
Of the Mercury is the smallest planet in the solar system and at the same time the celestial body, with the shortest distance to the sun. As a rock planet, Mercury circles the sun in just 88 days. The temperatures are between -170 ° C and + 425 ° C. On no other planet in the solar system do temperatures fluctuate in such a wide range. And the planet also holds the record in terms of Bahnexzentrität. The orbit around the sun is highly elliptical. At its sunniest point, Mercury reaches the sun up to 45 million kilometers, at its most remote point there are 70 million kilometers between star and planet. This is a major reason for the strong temperature fluctuations.
Named after the messenger of the god Mercurius, the planet owes its name to the Romans, as do the other celestial bodies. No other planet revolves so fast around the sun, which is why the Roman name suggests. Incidentally, Mercurius in Greek mythology corresponds to Hermes. But observing Mercury in the sky turns out to be extremely difficult. Only at dusk, or at a solar eclipse, can one recognize the planet. During the day, the sun prevents a view of the small planet.
Structure, atmosphere and surface
The surface of Mercury is quite similar to that of the Moon. Deep craters, with diameters of more than 700km, testify to heavy impacts in the past.
Unlike Earth, Mercury has no normal atmosphere that could possibly protect it from meteorites. There are two reasons for this: The gravity on Mercury is only 1/3 of the Earth's gravity. Molecules return to the exosphere more easily. Furthermore, strong solar winds prevent an atmosphere on Mercury from remaining long term.
In terms of structure, Mercury belongs to the earth-like planets. Inside the planet is a core of liquid iron and nickel. The surface mostly consists of silicates (see: silicon) and so Mercury, after the earth, is the planet with the highest density.
Mercury as a threat to the solar system?
The orbit of Mercury is not stable and tends to become increasingly eccentric. This means that the orbit around the sun is getting bigger and bigger. Not only the sun exerts an influence on Mercury through its gravitational field. Each planet has a different strong gravitational field depending on its mass. The gas planet Jupiter, the most massive planet in the solar system, slowly pulls Mercury out of its orbit. In the long term, that could be a problem, namely, when Mercury crosses the orbit of the other planets. In the worst case, it comes to a collision. For the earth with dramatic consequences, especially when Mercury collides with our planet. It would also be conceivable that Mercury - instead of colliding with a neighboring planet - falls into the sun. At best, Mercury will slowly spin out of the solar system without hitting the sun or a planet. These scenarios are considered by astronomers to be very unlikely, if possible. For the moment, this can not matter to humans, because before Mercury becomes a danger, 1 to 1.5 billion years pass.
Life on Mercury?
Although Mercury comes as close to the sun as no other celestial body, it is not the hottest planet. Venus reaches even higher temperatures. As already mentioned, Mercury has no atmosphere. Heat radiates comparatively quickly back into space. On Venus, a carbon dioxide atmosphere not only provides better heat absorption but also a greenhouse effect.
Despite the temperatures of over 400 ° C, frozen water exists on the much cooler poles of Mercury. This suggests that microbial life may or may not have been possible there. Due to its proximity to the sun, this seems to be nothing more than an almost impossible hypothesis. The conditions on the planet are too extreme (temperature + high radiant energy) for microbes to survive for a long time. For humans, a manned mission would be deadly. In general, only two space probes have dared to make their way to Mercury.