1, Mercury is called "the second earth", and it is a terrestrial planet with a diameter of about 4,880 kilometers, and its density is almost the same as that of the earth. Its core is considered to be a huge iron core, accounting for three-quarters of the radius of Mercury.

As the first human probe to enter the orbit of Mercury, Messenger has made many important discoveries. For example, it confirms scientists' speculation for many years that there are billions of tons of water ice stored in the Arctic region of Mercury.

3. The temperature of Mercury in direct sunlight during the day can be as high as 430 degrees Celsius, while the temperature at night drops to minus 170 degrees Celsius, and the temperature difference between day and night reaches 600 degrees Celsius.

Extended data:

Difficulties in mercury detection:

1. Behind Mercury is the sun, which is 330,000 times heavier than the Earth. Its huge gravity will interfere with the probe's entry into the orbit of Mercury.

2. In order to successfully enter the orbit, it is necessary to conduct nine gravity-controlled orbit-changing flights near the Earth, Venus and Mercury within a flight time of seven years, which will be the most frequent orbit-changing in the history of planetary exploration.

3. In order to resist high-temperature baking, the spacecraft also adopts multi-layer heat insulation technology, the outermost layer is made of ceramic fiber, and the detector is also equipped with an efficient radiator to ensure the normal work of scientific instruments and electronic equipment.

References:

People's Network-Difficulties, Highlights and Highlights of the Third Mercury Exploration