Why is only Mars suitable for human habitation?

Mars is not suitable for human habitation now. One is the problem of oxygen. People on the mainland can't live without oxygen, so people must have oxygen if they want to live on Mars. The atmosphere on Mars is thin, only 1% of that on Earth. It is mainly composed of carbon dioxide (95.3%), nitrogen (2.7%), argon (1.6%), trace oxygen (0. 15%) and water vapor (0.03%).

Due to the thin atmosphere and low carbon dioxide content, the temperature of Mars has been kept below zero, with an average temperature of minus 50 degrees in summer and minus 120 degrees in winter. Without oxygen, people will suffocate immediately.

The similarity between Mars and the Earth is 1. The rotation speed of Mars is only over 40 minutes, which is 24 degrees from axial inclination, while that of the Earth is 23.5 degrees. The distance from the Sun is also relatively close, and the four seasons are obvious. These are obviously similar to the earth.

2. 95% of the thin atmosphere of Mars is carbon dioxide, which is the same as the origin of the earth as we know it. At that time, there was no oxygen on the earth and it was desolate. The atmosphere is mainly carbon dioxide and nitrogen.

3. The most similar thing between Mars and the Earth is the rotation period of 24.62 hours, which is only more than 30 minutes slower than the rotation period of 24 hours of the Earth, which makes Mars appear a phenomenon similar to the alternation of day and night of the Earth.