I whould tell them it is history and if you look at it you will see
The atmosphere is important for many reasons. Before we talk about why it is important we should define what the atmosphere is. The atmosphere is the layer of air that surrounds a planet. Earth has an atmosphere that is just right for humans, animals, and plants to live in. The gases in the atmosphere act like a blanket keeping our planet warm plus the atmosphere contains oxygen something we (humans and animals) all need to breathe.
Many planets in our solar system have a atmosphere. Venus for example has such a thick atmosphere most of the sun's energy gets trapped making the surface of Venus 864 degrees Fahrenheit! That is hotter than an oven! Mars also has an atmosphere but it is too thin making the surface of Mars -80 degrees Fahrenheit! Plus the atmospheres of Venus and Mars do not contain the oxygen we all need to breathe.
Our atmosphere allows just enough of the sun's energy back into space so that we do not get to hot like Venus or too cold like Mars. If Earth had no atmosphere, apart from having no air to breathe, the surface of the Earth would be 0 degrees Fahrenheit.
These are just two of the reasons why are atmosphere is important. The atmosphere contains the warmth we all need to survive, the oxygen we all breathe, and carries the rain we all need. Without our atmosphere life as we know it would cease to exist.
Minerals, organic matter, water and air.
