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Thread: Lack of a magnetosphere and effects on atmosphere

  1. #1
    Join Date
    May 2009

    Lack of a magnetosphere and effects on atmosphere

    What effects would a lack of a magnetosphere have on a planet's atmosphere, specifically in relation to the planet's ability to sustain life?

    It seems that the primary issue would involve atmospheric escape. As I understand it, induction of magnetic moments in the ionosphere by solar winds would be sufficient to prevent atmospheric stripping from being the primary form of atmospheric escape. Loss of atmosphere would therefore primarily be due to thermal escape and electric force field acceleration which, if I'm not mistaken, are unaffected by the presence or absence of a magnetic field. At any rate, atmospheric escape is a fairly slow process, and I would think it would be an extremely long time before atmospheric loss would begin to have any adverse effect on life on the planet -- sufficiently long enough to make it a non-issue.

    Another issue, and more relevant to the survival of life, would be radiation. A magnetosphere does nothing to stop electromagnetic radiation, but does deflect charged particles. But so does an ionosphere, as discussed above. And even if the ionosphere isn't as effective at blocking particulate radiation as a magnetosphere, a sufficiently thick atmosphere should, it seems, provide adequate protection.

    First, am I correct in the above, and second, what other issues might a lack of magnetosphere involve?

    (Specifically, I'm thinking of a hypothetical planet similar to Mars, but with an atmosphere thick enough to have a pressure at sea level equivalent to that of Earth's. Like Mars, this planet would be geologically inactive and therefore possess no atmosphere. It would be a similar or slightly greater distance from its star, and therefore receive somewhat less solar radiation than Earth. It's for a story I'm writing, so any help would be greatly appreciated.)

  2. #2
    Join Date
    Sep 2003
    Good question. An ionosphere may be good at protecting a planetary atmosphere from erosion by the Solar Wind, but what about more energetic events such as coronal mass ejections? Could they, over aeons of time, strip a planet of its atmosphere (especially if the atmosphere was not very dense to begin with)?

    I suspect you're right, though. Venus has no magnetic field, but its atmosphere is still very dense. And there have been regular periods in the Earth's history when a reversal of magnetic polarity involved a length period of time (how long?) when the Earth's magnetic field was very low. But these events do not seem to have led to mass extinctions.

    Off the top of my head, I can't think of any reason why life on Earth shouldn't have evolved and flourished even if there had been no magnetic field.

    Anyone else like to contribute...?

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