ElI5: how do they know what other planets are made off, how can the be so sure? Jupiter could be made of a completely unknown gas?

Question

ElI5: how do they know what other planets are made off, how can the be so sure? Jupiter could be made of a completely unknown gas?

In: 96

Answer 1

Planetologists study the atmospheres of other planets to try and understand what gases make them up. By doing this, they can rule out certain gases as being present on other planets, and therefore make an educated guess as to what those planets are made of.