Composition of the Martian Atmosphere
On Earth, the atmosphere is composed of mostly of nitrogen (78%) and oxygen (21%). On Mars, the atmosphere is made mostly of carbon dioxide (95.3%), with a little nitrogen (2.7%), and a lot of dust particles mixed in. This means that there is no oxygen, which is important for some forms of life. (Can you think of some forms of life which do not need oxygen?)
There is very little water vapor in the atmosphere of Mars. This means that clouds are rarely seen and the chances of a morning rain shower are extremely doubtful!