One reason we decided on this planet is because we can't live on the planets that have gaseous surface.
To add on Mercury has to many X-Rays and UV radiation.
The remaining planet, Venus is not suitable because the atmospheric pressure is enough to crush a person.
Mars is a rocky planet, that has an atmosphere thinner than Earth's, it has two small moons, with an average temperature of -220 degrees F to 68 degrees F, it's called the red planet because the surface appears red because of iron and rust covered rocks, and it's almost half the size of Earth.
We would like to explore Mars because we want to study if Mars can support life.