# How much mass could Earth safely lose and retain its atmosphere?

**URL:** <https://boards.straightdope.com/t/how-much-mass-could-earth-safely-lose-and-retain-its-atmosphere/546074>\
**Category:** Factual Questions\
**Created:** [July 9, 2010, 7:06am UTC](https://boards.straightdope.com/t/how-much-mass-could-earth-safely-lose-and-retain-its-atmosphere/546074 "2010-07-09T07:06:32Z")\
**Posts on this page:** 3\
**Page:** 2

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**Author:** ![Chronos](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/chronos/32/134_2.png) [@Chronos](https://boards.straightdope.com/u/Chronos)\
**Post date:** [July 12, 2010, 4:51pm UTC](https://boards.straightdope.com/t/how-much-mass-could-earth-safely-lose-and-retain-its-atmosphere/546074/21 "2010-07-12T16:51:59Z")

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Not unless the mass loss were all in the same direction. Given that the Sun is much more massive than the Earth, what the Earth’s mass is is essentially irrelevant. If you replaced the Earth with a grain of sand, it’d orbit just the same as it does now.

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**Author:** ![TimeWinder](https://avatars.discourse-cdn.com/v4/letter/t/bcef8e/32.png) [@TimeWinder](https://boards.straightdope.com/u/TimeWinder)\
**Post date:** [July 12, 2010, 6:18pm UTC](https://boards.straightdope.com/t/how-much-mass-could-earth-safely-lose-and-retain-its-atmosphere/546074/22 "2010-07-12T18:18:03Z")

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> [@Quartz](#):
>
> Currently, yes, but what about the future? And besides, as Global Warming proponents tell us, there are inflection points.

Another way to get at this is: if we sent the entire crust layer of the Earth into space, would that lose enough mass? If not, we’re pretty much safe forever, I’d say. We don’t make use of anything beneath the crust, and if we sent all of it into space life here would be unpleasant anyway, atmosphere or no. (The large sub-mantle living spaces seen in the documentary _The Core_ notwithstanding).

Given how little of the Earth’s mass is crust, I don’t expect this is an issue.

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**Author:** ![MikeS](https://avatars.discourse-cdn.com/v4/letter/m/919ad9/32.png) [@MikeS](https://boards.straightdope.com/u/MikeS)\
**Post date:** [July 12, 2010, 7:07pm UTC](https://boards.straightdope.com/t/how-much-mass-could-earth-safely-lose-and-retain-its-atmosphere/546074/23 "2010-07-12T19:07:37Z")

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> [@Simplicio](#):
>
> I get something crazy small, like .0004 the current mass till the average velocity of N2 at 300K is at the escape velocity. Is late though, I’ll try again in the morning when I’m more awake.

[This flowchart](http://www.astronomynotes.com/solarsys/atmosesc.htm) implies that the criterion for a long-lived atmosphere is that the average thermal velocity (more accurately, its vertical component) has to be less than about one-fifth the escape velocity.

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