Why doesn’t the atmosphere (air we breathe) just float off into space?
Some objects in space have atmospheres like Earth and Jupiter. Others like asteroids and the moon don’t have an atmosphere.
Why doesn’t earth atmosphere just drift away into space?
What am I missing about the concept of atmosphere?
In: Planetary Science
When it comes to gases, the temperature of a gas determines the average kinetic energy that a gas molecule has, and so also dictates its speed. To escape the gravitational field of Earth, the gas molocules have to exceed the escape velocity of Earth. Depending on the weight of the molecule, the average kinetic energy may or may not exceed that. A light molecule, like hydrogen, may exceed that escape velocity, which is why there’s not much hydrogen or helium in the atmosphere.
For heavier molecules like oxygen or nitrogen, their average speed does not allow escape. It’s also important to note that the speed occurs in a distribution, not a single value, so some gas molecules of any given molecule will still have enough speed to escape, but the fraction in that range will be much smaller for heavier molecules than lighter ones.
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