The mystery of the smallest planet in the Solar System.

Mercury is the smallest planet in the Solar System family - Photo: Theosophy online

The planet with the most iron in the solar system.

Mercury is one of four rocky planets like Earth, and also the smallest, with a diameter of only about 4,879.4 km.

This figure is 0.383 times the diameter of the Earth and is even smaller than Jupiter's moon Ganymede and Saturn's moon Titan.

Iron makes up a large proportion of Mercury's composition. It is also the planet with the most iron in the Solar System.

Along with Venus, Mercury has no natural satellites, while the other planets all have satellites orbiting them.

The diurnal temperature range is approximately 600 degrees Celsius.

Mercury's atmosphere is extremely thin - Photo: NASA

Mercury is also the closest planet to the sun among the eight planets, at a distance of approximately 57.91 million kilometers. This, along with its small mass, makes its atmosphere very thin and unable to retain heat.

Therefore, Mercury has the largest diurnal temperature range in the Solar System, with nighttime temperatures dropping to -173°C but daytime temperatures reaching 427°C. This translates to a temperature difference of up to 600°C between day and night.

Due to its very thin atmosphere, Mercury does not have seasons like the four seasons on Earth.

Mercury's orbit is an extremely narrow ellipse with a major axis radius of 70 million km and a minor axis radius of only 46 million km. This is also one of the reasons for the large temperature differences on Mercury.

A day is equal to two-thirds of a year.

A year on Mercury is equivalent to only 88 days on Earth - Photo: NASA

Mercury orbits the sun at a very fast rate, approximately 88 Earth days. In contrast, Mercury takes about 58 Earth days to rotate on its axis.

Thus, a year on Mercury is incredibly fast, only 88 days compared to 365 days on our planet, while a single day is incredibly long, equivalent to about two Earth months.

In other words, a day on Mercury is about two-thirds the length of a year.

The surface is like the moon.

Mercury's surface is uneven, like the moon. Photo: NASA

Mercury's surface is riddled with craters of varying sizes and jagged edges, much like the surface of the moon. Much of Mercury's surface is covered in dried lava.

The surface of this planet is covered with numerous cracks, or giant cliffs extending over a vast area, resembling enormous steps. The largest of these steps is over 1,000 km long and up to 3 km high.

Mercury has more craters on its surface than any other planet in the Solar System. Interestingly, a large proportion of these craters are named after famous writers and artists.

"The Messenger God" of the Solar System

Hermes, the god in Greek mythology.

Humans have known about Mercury since very early times. As early as 3000 BC, the Sumerians knew of its existence. Because Mercury orbits the Earth, it can only be seen from Earth at dawn or dusk, not at night.

The Romans named Mercury after Mercurius (the Greeks called him Hermes) – the god of communication and messengers in mythology. Perhaps the Romans named it this way because they recognized Mercury's high speed.

It's very difficult to "get used to it".

The Messenger satellite completed its mission in 2015. Photo: NASA

Our understanding of Mercury remains limited due to the difficulty in accessing the planet. To date, only two probes have attempted to reach Mercury: Mariner 10 in 1974-1975, and Messenger, launched into space on August 3, 2004.

The Messenger spacecraft, after arriving in Mercury's orbit on March 17, 2011, carried out the mission of observing and studying the history and geology of the planet, which is closest to the sun.

Messenger traveled 7.8 billion kilometers over more than six years to reach Mercury and was the first spacecraft to successfully enter Mercury's orbit.

Messenger orbited Mercury from 2011-2015 and sent back more than 280,000 images to Earth before ending its mission by crashing into the planet.