Okay kiddo, let me explain extraterrestrial atmospheres to you in a way you can understand!
So, you know how we live on Earth and we breathe air? Well, other planets and moons can have air too, but it might be really different from what we're used to. We call this air an 'atmosphere'.
For example, Mars has a very thin atmosphere made up mostly of carbon dioxide. That means there's not enough air for humans to breathe, and it's also really cold there!
Jupiter, on the other hand, is a gas giant that doesn't have a solid surface. It's atmosphere is made up of hydrogen, helium, and a bunch of other gases that would be dangerous for us to breathe.
Some planets, like Venus, have really thick and acidic atmospheres that would be deadly to us. And some moons, like Titan, have atmospheres made up of gases like methane and nitrogen.
Scientists study extraterrestrial atmospheres to learn more about the planets and moons they belong to. They use telescopes, spacecraft, and other tools to measure the air and figure out what it's made of.
In summary, extraterrestrial atmospheres are the air around planets and moons that can be really different from what we're used to on Earth, and scientists study them to learn more about space!