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
Fun fact.
It is.
Gravity acts to hold it down. There is no force trying to pull it away. So left alone, it’ll settle down and stay stuck to the planet.
However, the air also moves as it is warmed by the sun. And if itoves fast enough it won’t come back (this speed is escape velocity)
Most of the air is cool and goes slowly. It doesn’t go fast enough to fling itself into space. But the speeds are randomly distributed. Even at low temperatures some small percentage is moving with enough energy to get away. So eventually the gas will leave.
And lighter gases go faster. So really light gases like hydrogen are more likely to go “to fast” and escape into space faster, on the order of tens of millions of years for Earth.
Helium is hundreds of millions of years before most is gone.
Oxygen (O2), nitrogen (N2) and co2 are much heavier and take even longer. Like a couple billion years. That should be plenty long enough…
..
.
But Earth is 4.5 billion. Even the normal gas in our air should be gone!!!
But don’t panic more gas is being added through “outgassing” processes than we lose, for now. Gas is liberated from the earth through chemical, physical or thermodynamic processes. Like volcanoes.
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