Mercury has an unusual property: it is quite dark compared to other planets and solids of the solar system. The albedo of Mercury - a measure of light reflection by the body - is lower than that of Earth, Venus and Mars. Depending on which definition of albedo you use, the reflected light is even lower than the moonlight. A simple explanation would be that the outer layers of Mercury are simply richer in a dark element like iron, but the outer crust of the Moon actually contains even more iron than the crust of Mercury (most of the iron of Mercury is believed to be in the planet’s liquid core). Why is Mercury so hard to see?
The answer to this question, as shown by the data alreadyMessenger's broken spacecraft, is carbon in the form of graphite. In a paper published in Nature Geoscience, scientists believe that Mercury once had a “flotation crust” from a giant ocean of magma the size of a planet.
Generally, Mercury is strange. Its core is believed to be 42% of its mass (the core of the Earth, by comparison, is only 17% of the mass of the planet). Its bark is much thinner than ours and covered with this mysterious layer of graphite. So far, this is the only body in the solar system that has a carbon layer of this kind.
There are tons of theories that could explain thesefeatures, but they all start with Mercury, which is twice as heavy as the current one. Perhaps this excess material evaporated under the influence of the Sun or a giant blow broke the planet, throwing a significant amount of its material into the sun. In any case, Mercury must be part of another planet.
Messenger data suggests that carbon onMercury’s surface appeared from inside the planet - it may have precipitated out of the raging ocean of magma. Such an ocean could form in the period after a massive collision - possibly similar to the one after which the Moon was created, and the Earth's surface melted.
Mercury is unique for another reason: many of the exoplanets we discovered were the so-called “hot Jupiters,” gas giants with very close orbits to their native star. However, we do not see any planets the size of Mercury, whose orbits would be close to the stars. Gas giants simply do not leave space for the existence of planets such as Mercury.
We have discovered many planets since we began to search - but not one of the solar systems discovered to date is like ours. However, this can be a very simple explanation.