Mercury It is the closest planet to the Sun and the smallest in the Solar System. It is smaller than Earth, but larger than the Moon.
Mercury is part of the so-called inner planets or terrestrial, and it has no satellites. It is a very dense planet, the second with the highest density in the Solar System, after Earth. In its chemical composition there are 70% metallic elements; The rest are silicates.
The Romans named him their god of commerce, Mercury, who was also a messenger of the gods, because he moved faster than the other planets. On behalf it also applies to the chemical element mercury, a mineral that stays liquid at room temperature.
Mercury, the planet, goes around the Sun in less than three months. his orbit It is the most eccentric among the minor planets. Instead, it rotates slowly on its axis, once every 58 and a half days. It used to do it faster, but it slows down because of the gravitational influence of the Sun.
If we were placed on the Mercurian surface, the Sun would seem to us two and a half times larger. The sky, however, we would always see it black, because it has no atmosphere that can scatter the light.
The following table shows some basic data of the planet Mercury compared to those on Earth:
|Basic data||Mercury||The earth|
|Size: equatorial radius||2,440 km.||6,378 km.|
|Average distance to the Sun||57,909,175 km.||149,600,000 km.|
|Day: period of rotation on the axis||1,404 hours||23.93 hours|
|Year: orbit around the Sun||87.97 days||365,256 days|
|Average surface temperature||167 º C||15 º C|
|Surface gravity in the equator||2.78 m / s2||9.78 m / s2|
When one side of the planet faces the Sun, the surface temperature rises above 400 ° C. In the shadow areas it drops to 170 below zero. The mercury poles They are always very cold. This leads to think that there may be some water (frozen, of course).
He mercury relief It is very similar to that of our satellite, the Moon. The landscape is full of craters and cracks, in the midst of many marks caused by the impacts of meteorites. The older craters are very eroded, probably because of the sudden temperature changes. The planet has also had volcanic activity; lava formed basins, depressions and plains similar to seas of our moon.
It is believed that Mercury may have formed beyond Mars, as it releases more volatile matter than would correspond to a planet so close to the Sun. It could have been expelled from its previous position for some unknown cause and trapped in its orbit current.
Mercury is now very close to the Sun. That is why, having an inner orbit to that of the Earth, it periodically passes in front of our star, as does Venus. This phenomenon is called astronomical transit.
The interaction with the solar wind reveals that Mercury is enveloped by a magnetic layer, the magnetosphere. The presence of this magnetic field indicates that it has a partially liquid metallic core, which occupies almost half of the planet's volume.
A surprising Mercurian rarity is the phenomenon of double dawn. In some places and moments, the sun rises, stops, hides again and rises again. At other points on the surface it does not hide after leaving, but it does stop. This "stop and reverse" of the Sun occurs from the four days prior to the perihelion until the subsequent four, when the orbital and rotational angular velocities of Mercury equalize.
• Orbit of Mercury: double dawn and advance of the perihelion
• The relief of Mercury
• Ice at the poles of Mercury
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|Rocky planets||The planet Venus|