Why Doesn't Earth Lose Atmosphere Over Time?

[ChemGuy]

Why doesn't the Earth lose it's atmosphere eventually? I realize that gravity generally keeps the atmosphere close to the Earth but over a long period of time I would expect that we would lose some amount to the vacuum of space and the solor winds. Over millions of years we would lose it all! Whats the deal?

 

[DaveC426913]

It will dissipate. But it is being refreshed by volcanism and other processes that liberate elements from the Earth's core.

 

[billiards]

Volcanism doesn't 'liberate elements from the Earth's core'!

Sorry but people keep talking about the core as some kind of generic name for the whole earth, and it's getting to me. Volcanism releases gases and magma which under a continental setting is recycled crust, or in an oceanic setting comes from the upper mantle.

The inner core is made of pure iron.

 

[Andre]

You're right Billiards, it seems kind of a habit. I don't think Earth is losing a lot of atmospheric molecules. The energy levels for escaping the gravity field seem to be much higher than the actual molecular speeds.

 

[DaveC426913]

Volcanism doesn't 'liberate elements from the Earth's core'!

Agreed. I thought long and hard about the right word, but came up with nothing general enough.

"Volcanism liberates elements from underground" seemed to miss the point.

 

[Peneyra]

so back to the question, there are a lot of reasons why our atomosphere does not dissapear.

First is our gravity... It requires a velocity of 11.2 km/s to escape our gravitational field, which means that it would require each particle to have very high temperature (high energy) to get out.

Second is our magnetosphere. The magnetic field created by the rotating iron core deflects charged particles from the sun (the same reason we get auras), meaning that out atmosphere doesn't get as much energy as it could= less energy= less temeperature= harder to escape.

Third is the quantity. There is about 10^21 Kg of atmosphere! (really rough estimate) Even if we were losing 2 tons of atmosphere a day, it would still take more than 14 trillion years to lose it all.

Fourth is: yes, volcanic activity. As we are losing gas into outer space, we are gaining it back from inside the earth, creating an equalibrium.

I may be missing some reasons, but the main point is, i don't think we have to worry about losing our atmosphere. A bigger focus should be cleaning it up a bit.

 

[mheslep]

Isnt the Earth also continually collecting more mass as junk falls into its gravity well? That is, the process that originally formed the big blue ball still continues to some small degree?

 

[DaveC426913]

Isnt the Earth also continually collecting more mass as junk falls into its gravity well? That is, the process that originally formed the big blue ball still continues to some small degree?

"Steel (1995) indicates that at present, about 40,000 tonnes of extraterrestrial material collides with the Earth each year but when the effects of larger impacts are taken into account the average over long periods becomes 160,000 tonnes per year."
http://users.tpg.com.au/users/horsts/transpermia.html

So only about a hefty ocean cruiser's worth.