# Why does the earth have an atmosphere **URL:** \ **Category:** Factual Questions\ **Created:** [April 11, 2012, 12:38am UTC](https://boards.straightdope.com/t/why-does-the-earth-have-an-atmosphere/618419 "2012-04-11T00:38:58Z")\ **Posts on this page:** 10\ **Page:** 2
**Author:** ![Musicat](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/musicat/32/20189_2.png) [@Musicat](https://boards.straightdope.com/u/Musicat)\ **Post date:** [April 11, 2012, 12:03pm UTC](https://boards.straightdope.com/t/why-does-the-earth-have-an-atmosphere/618419/21 "2012-04-11T12:03:41Z")
Gravity works on atmosphere (and everything else), magnetic fields do not. Where do you get the idea that magnetic fields are a factor for creating or retaining atmosphere? ---
**Author:** ![DrFidelius](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/drfidelius/32/3447_2.png) [@DrFidelius](https://boards.straightdope.com/u/DrFidelius)\ **Post date:** [April 11, 2012, 12:12pm UTC](https://boards.straightdope.com/t/why-does-the-earth-have-an-atmosphere/618419/22 "2012-04-11T12:12:07Z")
> [@Musicat](#): > > Gravity works on atmosphere (and everything else), magnetic fields do not. Where do you get the idea that magnetic fields are a factor for creating or retaining atmosphere? Because the magnetic field diverts the solar wind and prevents our life-sustaining blanket of air from being blown off into deep space? I’ve got nothing. ---
**Author:** ![Ludovic](https://avatars.discourse-cdn.com/v4/letter/l/7ab992/32.png) [@Ludovic](https://boards.straightdope.com/u/Ludovic)\ **Post date:** [April 11, 2012, 12:19pm UTC](https://boards.straightdope.com/t/why-does-the-earth-have-an-atmosphere/618419/23 "2012-04-11T12:19:08Z")
But the magnetic field, how does it work? ---
**Author:** ![Gyrate](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/gyrate/32/3588_2.png) [@Gyrate](https://boards.straightdope.com/u/Gyrate)\ **Post date:** [April 11, 2012, 12:26pm UTC](https://boards.straightdope.com/t/why-does-the-earth-have-an-atmosphere/618419/24 "2012-04-11T12:26:11Z")
> [@Ludovic](#): > > But the magnetic field, how does it work? I’m sure there’s an Insane Cloud Posse joke to be made here, but it eludes me. ---
**Author:** ![DrFidelius](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/drfidelius/32/3447_2.png) [@DrFidelius](https://boards.straightdope.com/u/DrFidelius)\ **Post date:** [April 11, 2012, 12:57pm UTC](https://boards.straightdope.com/t/why-does-the-earth-have-an-atmosphere/618419/25 "2012-04-11T12:57:25Z")
> [@Ludovic](#): > > But the magnetic field, how does it work? It works very well, thank you. Next question! ---
**Author:** ![Gagundathar](https://avatars.discourse-cdn.com/v4/letter/g/a183cd/32.png) [@Gagundathar](https://boards.straightdope.com/u/Gagundathar)\ **Post date:** [April 11, 2012, 1:10pm UTC](https://boards.straightdope.com/t/why-does-the-earth-have-an-atmosphere/618419/26 "2012-04-11T13:10:06Z")
Assuming, as usual, that I am not being ‘whooshed’, the magnetosphere is generally posited to be generated by the movement of Earth’s molten iron inner core. This acts as a dynamo which creates magnetic lines of force that extend beyond the surface of the planet. But, this may be an old hypothesis. Any geophysicists out there with a better idea for this? ---
**Author:** ![XT](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/xt/32/456_2.png) [@XT](https://boards.straightdope.com/u/XT)\ **Post date:** [April 11, 2012, 2:10pm UTC](https://boards.straightdope.com/t/why-does-the-earth-have-an-atmosphere/618419/27 "2012-04-11T14:10:57Z")
[QUOTE=DrFidelius] Because the magnetic field diverts the solar wind and prevents our life-sustaining blanket of air from being blown off into deep space? I’ve got nothing. [/QUOTE] No, you got it in one. The answer to the OP is that the earth has enough gravity and mass to have an atmosphere, and we have a large enough magnetic field to protect the atmosphere and prevent large parts of it from being blown off into space (I’m unsure if we’d have no atmosphere at all without a magnetic field, but we’d certainly have less without it). -XT ---
**Author:** ![Grey](https://avatars.discourse-cdn.com/v4/letter/g/b782af/32.png) [@Grey](https://boards.straightdope.com/u/Grey)\ **Post date:** [April 11, 2012, 2:22pm UTC](https://boards.straightdope.com/t/why-does-the-earth-have-an-atmosphere/618419/28 "2012-04-11T14:22:25Z")
Which fails to explain the atmosphere of Venus. Venus is both closer to the sun (there by experiencing a higher flux of solar particles) and lacks a magentic field entirely. The reason planets have atmospheres is because they can gravitationally hold onto them. ---
**Author:** ![DrFidelius](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/drfidelius/32/3447_2.png) [@DrFidelius](https://boards.straightdope.com/u/DrFidelius)\ **Post date:** [April 11, 2012, 3:40pm UTC](https://boards.straightdope.com/t/why-does-the-earth-have-an-atmosphere/618419/29 "2012-04-11T15:40:29Z")
Venus has a much heavier atmosphere because the solar wind blew all the lighter components away. ---
**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:** [April 11, 2012, 8:32pm UTC](https://boards.straightdope.com/t/why-does-the-earth-have-an-atmosphere/618419/30 "2012-04-11T20:32:45Z")
The magnetic field is one relevant factor. Mars, based on its mass and temperature, should be able to support an Earthlike atmosphere, but it’s believed that it lost most of it to the solar wind, because of its fairly small magnetic field. Earth, meanwhile, should be able to support a much thicker atmosphere, and it’s not entirely clear why it doesn’t: Last I heard, the leading hypothesis is that we lost most of it in the collision which formed the Moon. [Previous page](https://boards.straightdope.com/t/why-does-the-earth-have-an-atmosphere/618419.md?page=1)