New data from MAVEN confirms how Mars lost its atmosphere

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New data from the Mars atmospheric probe MAVEN has confirmed that much of Mars’ atmosphere was stripped away over the past few billion years by the solar wind.

This result confirms data from Curiosity, but adds the detail that the solar wind was a major component in causing the loss of atmosphere.



  • Max

    The solar wind “is” atmosphere. Mars is too small to retain it. I suppose it’s a matter of perspective.

  • Laurie

    A stream of charged, high energy particles emanating from the sun doesn’t correspond with a layer of gases developed from planetary bombardment and outgassing. It appears no magnetosphere => no (meaningful) atmosphere.

  • Diane Wilson

    Venus’s magnetosphere is weaker than that of Mars, and it is much closer to the sun. It’s also weaker than Mercury’s magnetosphere. So why does Venus have any atmosphere at all?

  • Diane Wilson: Venus retained its atmosphere because it has a much heavier gravity than Mars, just as Earth does. That at least is the prime explanation usually given.

  • LocalFluff

    @Diane Wilson
    Because that’s what the theoretical models can simulate. It doesn’t fit data even in the Solar System. Small Titan far out, without a magnetic field, has an active atmosphere and hydrospheres. Small Ganymede has a magnetic field although it is a moon, but it has no atmosphere. Venus has the thickest atmosphere of all terrestrial bodies, without any magnetic field and although close to the Solar wind. So, many factors weigh in here. Great variety is to be expected.

  • LocalFluff

    Connecting to habitable zone assuming atmospheres, tidal locking is another rough assumption. The only planet in the Solar System that is tidally locked is Mercury, but it is locked in a 2:3 relationship and still rotates relative to the Sun. And a handful of moons have been observed to have chaotic spin due to gravitational influence from neighbors. I think Hyperion of Saturn is the largest one (certainly the ugliest one, well worth a look). All of Pluto’s moons have chaotic spins/days. And Pluto/Charon themselves are tidally locked, they would rotate relative to the Sun no matter how close in they were.

    Venus surface is believed to have been reformed “recently”, as in 200,000,000 to 500,000,000 years ago. Sudden global Volcanic activity is the prefered explanation. But maybe it is possible to argue for Venus being hit by a huge comet, resurfacing it and bringing lots of CO2 to form a thick atmosphere. Maybe Venus was much more Earth like before that? Or maybe Venus has a moon, like Mars has Phobos, which eventually spiraled inwards and caused a cataclysm. Phobos will do it to Mars in 10 to 30 million years or so. Maybe Venus was gifted with a similar gravitational time bomb moon that has already gone off?

  • D. Williams

    Venus simply replaces atmosphere lost to the solar wind through volcanism.

  • LocalFluff

    @D. Williams
    As does Titan (it is suggested, still poor evidence for both Venus and Titan regarding volcanism). So it seems that planetary and lunar bodies, small or large, near or far, are capable of having an atmosphere thicker than that of Earth. With or without magnetic field. Like with gravity, magnetics doesn’t seem to make any difference.

    Let’s look at terrestrial bodies and their gravitational (G+/-), magnetic (M+/-) and atmospheric (A+/-) properties:
    Mercury G- M+ A-
    Venus G+ M- A+++
    Earth G+ M+ A++
    Moon G- M- A-
    Mars G- M- A+
    Ganymede G- M+ A-
    Titan G- M- A++
    Giant planets: G++ M++ A+++
    And for all other non giant planet objects: G- M- A-

    Gravity, magnetosphere and atmosphere just doesn’t correlate in the Solar System.
    It should, on average, but there are trillions of special cases of planets each with its billion year long unique history in our galaxy. Why aren’t Mars’ huge volcanoes outgassing if they do that on Venus and Titan (both unconfirmed)?

  • Garry

    LocalFluff wrote,

    Giant planets: G++ M++ A+++

    Forgive my ignorance, but what does it mean for a gas giant to have an atmosphere? Is the atmosphere composed of gases that are different for the gases that make up the “surface” of the planet?

    I haven’t studied planets all that much, and never thought of an atmosphere in connection with a gas giant.

  • wayne

    not my bailiwick–(I only know just enough to be dangerous.)
    I’ve always thought “atmosphere” was a more generic term, in that we divide up our own atmosphere into specific sub- groupings. But I’m ignorant as to whether those are functional divisions with definitions or “traditional,” or if they are Earth specific.

    Good question.

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