Answer
Mars has the closest structure to Earth.
Explanation:
Out of all the planets in our solar system (Pluto is no longer in the picture), there are 2 planets (Venus and Mercury) that resemble Earth in the slightest, but 1 (Mars) that is the closest match.
I will be explaining the structure of the planets based on this list:
Matter state of the planet surface:
Atmosphere:
Weather:
Day/Night:
Human Life:
Other:
Earth
First, I want to clarify the structure of Earth. Earth has a solid and liquid surface, so it has a ground and bodies of water. Earth has an atmosphere, therefore we have a sky.
The weather on earth contains rain, wind, snow, fog, dust storms and clouds. Uncommon weathers include tornadoes, ice storms, typhoons, and hurricanes. Earth does rotate in its orbit, so it has a day and night cycle. It can also be seen that Earth can, in fact, support human life, and all known carbon-based life for that matter.
Mars
Mars has a solid, rocky surface, so there is a ground. The atmosphere there is thin, meaning there is a sky. It does not raid on mars, but it does, in fact, have weather like very large sandstorms and it has different seasons.
Mars has a day and night cycle roughly the same lengths as days on Earth. A human can survive on Mar for a long time with a spacesuit.
Venus
Venus has a solid, rocky surface meaning it has a ground. It has a very thick atmosphere. This means it has a sky. Because of its thick atmosphere, it has constant cloud cover. So thick you may not see the sun during the days and definitely not the stars during the night. Previously mentioned, it has a day and night cycle. Its days are roughly 117 earth-days long.
Whether it be day or night, Venus is fiery hot with extremely high atmospheric pressure. It also rains sulfuric acid frequently. Without being said, a human in a space suit would die very quickly upon entering the atmosphere.
Mercury
Mercury is a solid and rocky planet so it's given that there is a ground. It does not have an atmosphere meaning that it does not have a sky. It rotates very slowly in orbit and its days are about 176 earth days long with a day and night cycle.
The heat on Mercury is extremely hot under the sun but during the nights, the ground is extremely cold, too cold for insulation on a normal spacesuit. Humans would die very quickly on this planet.