How many kinds of aliens are there in the world?

There are 82 kinds of aliens on the earth.

Bacteria were produced in the environment of Mars, and then they were hit by asteroids, and debris flew to the earth, giving birth to the earliest organic matter on the earth.

On Mars, the ocean and atmosphere evaporated because of the impact, which caused the planet's magnetic field to shift. The intense radiation of the solar wind aggravated the deterioration of the surface environment of Mars and made life disappear completely.

Apart from many objective factors, it is probably because aliens have visited the earth and even affected the development of earth civilization. At present, they have established a stable cooperative relationship with the government, but they have not been exposed for reasons such as social stability and avoiding panic.