chemistry (atmosphere) ---URGENT

(a) The Earth is NOT the only planet that has an atmosphere. For example, Mars also has an atmosphere, or else the spaceship cannot land on its surface by parachute.

(b) It is believed that the atmosphere of the Earth is the only one that can support life among the 8 planets in the solar system. The atmosphere of Mars is mainly composed of carbon dioxide(CO2), more than 90%.

Note : There are only 8 planets in the solar system, coz Pluto(冥王星) is not considered as a planet.