Mercury
Site with an overview of Mercury:
http://www.susutan.com/genre1/mercury/
～Problems when traveling to Mercury～
①It is dificult for living things to live because the temperature of the ground surface is too high.
Mercury is the closest planet to the Sun. In other words, it is most affected by solar radiation on the planet.
Also, since there is almost no atmosphere, there is little reflection on the universe, which may be the cause of the high temparature.
If the solar constant of the earthis So(1370J), it is about 6So for Mercury.If the diameter of Mercury is R（5000km）
π×R^2×6So/2πR^2 = 3So = 4100J 4J can raise 1g of water once.
Thinking that way, it turns out that this is h huge amount of heat. In reality, the reflection of the atmosphere lowers the heat a little more, but it is still difficult for living things to live in.
②The atmosphere is extremly thin
Mercury's atmosphere contains hydrogen, helium, oxygen, sodium, calcium, pottassium, water vapor, and more.
At first glance, it may be possible to live because it contains oxygen, but there is a big problem with this.
"The atmosphere is extremly thin." The air on Mercury is one trillionth of the Earth and very thin.
This also involves issues such as gravity, and unless this is addressed, Mercuru travel may be tough.
Countermeasures
The countermeasure is easy to describe in one word.
①Make heat-resistant space suits
②Make a devise that can return even if it is about to be blown into outer space
About ① Heat-resistant substances are used in rockets and the like. Speaking of more familiar things, it is used for tea bowls. It is ceramics.
We wonder how the journey to Mercury will be related to how we make use of these substances.
About ② When you go out from the rocket, you go out by connecting your body to the string, but that is not the case because you have to move on Mercury. We need to find something that can move freely in outer space. We thought that we could move freely in outer space by using the "jet" that is also used for the propulsion of rockets. I think there are many problems with this operation, but I think one of the keys to travelling to Mercury is how to solve them.