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dwkeith t1_j280owa wrote

Reply to comment by team-tree-syndicate in How much does the liquid magma of the Earth affect it's surface temperature? by tripperfunster

Deflects solar winds which would otherwise strip the atmosphere.

Wikipedia has a good overview of how it works https://en.wikipedia.org/wiki/Magnetosphere

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CrustalTrudger t1_j28zd88 wrote

This is not correct though. Good counterpoints are Venus, which has no intrinsic magnetic field, only a relatively weak induced one, and yet still has a thick atmosphere or Mercury, which has an intrinsic magnetic field and effectively no atmosphere. This comes up a lot on AskScience and there are numerous threads considering the relative role of gravity, active volcanism, and magnetospheres for keeping planetary atmospheres, e.g., this thread where various posters lay out the details and highlight that gravity / escape velocity is the dominant factor in whether a planetary atmosphere is maintained, this specific comment by one of our panelists addresses this misconception directly.

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pmalleable t1_j2b4g17 wrote

So is the relatively small atmosphere on Mars entirely or mostly due to the lower mass of the planet?

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Gohanthebarbarian t1_j2bbu3v wrote

Yeah it makes intuitive sense that the higher mass rock balls would be more likely to hold onto their atmospheres.

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