Sputtering: How Mars May Have Lost Its Atmosphere

Article written: 12 Sep , 2012
Updated: 23 Dec , 2015

Why is Mars cold and dry? While some recent studies hint that early Mars may have never been wet or warm, many scientists think that long ago, Mars once had a denser atmosphere that supported liquid water on the surface. If so, Mars might have had environmental conditions to support microbial life. However, for some reason, most of the Martian atmosphere was lost to space long ago and the thin wispy atmosphere no longer allows water to be stable at the surface. Scientists aren’t sure how or why this happened, but one way a planet can lose its atmosphere is through a process called ‘sputtering.’ In this process, atoms are knocked away from the atmosphere due to impacts from energetic particles.

Since Mars doesn’t have a strong intrinsic magnetic field, the atmosphere could have been eroded by interactions with the solar wind, and this video shows how that occurs. Also, the conditions in the early solar-system conditions enhanced the sputtering loss, and so the loss of Martian atmosphere could be caused by a complex set of mechanisms working simultaneously.

An upcoming mission could tell us what happened to Mars’ atmosphere. The Mars Atmosphere and Volatile Evolution spacecraft or MAVEN is equipped with eight different sensors designed to sort out what happened to the planet’s atmosphere.

MAVEN will be the first spacecraft ever to make direct measurements of the Martian atmosphere, and is the first mission to Mars specifically designed to help scientists understand the past – also the ongoing — escape of CO2 and other gases into space. MAVEN will orbit Mars for at least one Earth-year, about a half of a Martian year. MAVEN will provide information on how and how fast atmospheric gases are being lost to space today, and infer from those detailed studies what happened in the past.

Studying how the Martian atmosphere was lost to space can reveal clues about the impact that change had on the Martian climate, geologic, and geochemical conditions over time, all of which are important in understanding whether Mars had an environment able to support life.

The MAVEN will carry eight science instruments that will take measurements of the upper Martian atmosphere during one Earth year, equivalent to about half of a Martian year.

MAVEN is scheduled to launch in 2013, with a launch window from Nov. 18 to Dec 7, 2013. Mars Orbit Insertion will be in mid-September2014.


17 Responses

  1. how long is since that solar explosion blasted Mars and threaten the Curiosity in it`s way to Mars? 2 or 3 months? I guess something like that could blast a planet`s like Mars athmosphere in one blow, since Mars`s gravity is less than half the Earth`s gravity. It`s just a supposition.

    • Torbjörn Larsson says

      A CME is sizable enough to “blast” all of a planets atmosphere, but not massive enough to remove it which is why they look at sputtering et cetera.

      Gravity isn’t all what matters for an atmosphere, compare Titan that has a denser and higher atmosphere than Earth despite having ~ 0.02 Earth mass. Location, temperature, atmosphere composition is part of it.

      The dominant atmospheric escape process differ between Venus, Earth and Mars.

    • lcrowell says

      A CME reaches Earth in a few days. A CME directed at Mars might only take an extra day to reach it.

      CMEs are not enough to blast away an atmosphere in one blow. A CME contains on the order of 10^8 to 10^9 tons of ionized gas. Earth’s atmosphere is on the order to 10^{19}kg (10^{16} tons) and an estimate might put the martian atmosphere at about 10^{13} tons. Given that a very small percentage of a CME actually passes a planet it is clear that it would take a lot of CMEs to blast away an atmosphere.


      • i know it`s much lighter (mostly hidrogen atoms), but a CME is also having a huge speed, that might add some to the impulse.

      • lcrowell says

        By the time a CME reaches Mars maybe only a million tons interacts with the planet. This is probably far too small.

        There are probably a lot of things left to learn about Mars. it could also be that the Martian atmosphere is continually replenished by volcanic out gassing. So even if CME might take out the existing atmosphere in a certain period to time, say a million years, the atmosphere might be continually replenished to prevent that.


    • Olaf2 says

      A CME might look big but it is still near vacuum in density and the global mass is tiny.
      It is a bit like the mass of a mosquito against a big huge completely filled oil tanker.

      An atmosphere can only lose it’s particle when it gets accelerated to the escape velocity of that planet. Otherwise it just falls back. And in addition, every CME molecule that accelerates an atmospheric molecule to escape velocity by collision ,slows down in speed and becomes part of the very atmosphere it hits because it gets below escape velocity.

  2. Member
    Aqua4U says

    I think that whatever it was that smacked into Mars and created the Hellas Basin was somehow responsible for the loss of the rotating magnetic field within Mars? Then as that field diminished, the atmosphere went away, mostly due to ‘sputtering’…. Yas….

    • Torbjörn Larsson says

      An impact would not stop the motions of the liquid conducting core that participates in a geodynamo field in most planets. We can see this tested in Earth, a proportionally as large impact as that which may have created the Borealis basin (~ 1/10th of Mars mass) created the Moon (~ 1/10 of Earth mass). And we still retain a large field.

      Moon’s and Mars’ fields are practically gone because their liquid cores, if any remains, are too small to generate an appreciable field. Earth, Mercury, the gas giants and the ice giants retain large hot liquid cores and have strong fields.*

      Venus is an interesting case. It has no geodynamo field and, coincidentally, seems to have no current plate tectonics. One hypothesis is that the heat flow is such that a liquid core and much of the mantle is at equitemperature so little convective motion is present. If so, the runaway greenhouse killed more than any early biosphere, it killed much of Venus dynamics.

      * I believe there are theories for the giants that supplements or replace liquid core models. But I wanted to keep this as a simple comparison of principle.

      • gopher652003 says

        You made a little typo. You meant to say “created the Moon (~ 1/100 of Earth mass).”

      • Torbjörn Larsson says

        I was unclear rather, the mass figure was for the impactors.

        On Earth a Mars massed impactor (~ 1/10 of Earth mass) caused the Moon from ejecta.

        On Mars, a Moon sized impactor (~ 1/10 of Mars mass, as you imply) is believed to have caused the Borealis Basin, and presumably a set of moons from ejecta of which Phobos and Deimos still remain in orbit.

      • Member
        Aqua4U says

        “An impact would not stop the motions of the liquid conducting core…”
        I disagree… totally. A sufficiently dense (Nickel Iron or predominantly metal object) and large enough object, coming in at the ‘correct’ angle, might penetrate deeply enough to do the deed? Indeed, whatever created the Hellas Planitia appears to have been large enough to send shock waves completely thru the planet. Antipodal to that impact basin are the Valle Marinaris, the four gigantic shield volcanoes Arsia Mons, Pavonis Mons, Ascraeus Mons and Olympus Mons itself! Three of these, Arsia Mons, Pavonis Mons and Ascraeus Mons are aligned nearly perpendicular to the Hellas Basin, the fourth, Mons Olympus lies on a bearing further along a line drawn from the Hellas Planitia. Also worth noting is the actual obround shape of Hellas Planitia and it’s location 180 degrees opposite. The very shape of the Solis, Sinai and Syria Planum(s) ‘mimics’ the shape of Hellas Planitia and appears more than simply coincidental. IF that impact created those features opposite.. then surely it would have been big enough to disrupt the magnetic field!


      • Torbjörn Larsson says

        You may disagree, but you don’t present data how an impact would stop convection caused by the thermal differential between a heated core and a radiation cooled surface. Moreover, I gave an example that shows this doesn’t have to happen.

        Are you possibly thinking of how some types of permanent magnets (such as magnetized steel) can lose magnetization by mechanical shocks tumbling their domains and randomizing the resulting fields? That is a different physical situation.

      • Member
        Aqua4U says

        Yes, intense mechanical shock wave(s) rebound off the denser inner core. The ‘reflected’ energy fractures the crust above. The fractures become conduits for HOT magma which begins to flow freely onto the surface eventually becoming Mons Olympus and the three nearby big volcano’s.

        BIG heat sinks – Cool yer core and rust your crust Mister?

  3. Andres says

    Jupiter must have sucked it up leaving some traces of the Martian atmosphere around the Jovian moons and the Kuiper belt.

  4. here’s a random theory: maybe mars was once earth-like with water and life but every like 26,000 years (1 Platonic Year) the sun aligns with? the center of the milky way galaxy. now it is going to happen again this year and earth is said to be in that alignment. what if mars was in the last alignment 26,000 years ago and the reason it is dead like it is now is the radiation of the galaxy’s center and our sun stopped it’s core. our planet would look a lot like mars if our core stopped spinning. (unresearched so don’t make a big deal if you think I’m wrong)

    • Torbjörn Larsson says

      It isn’t even a theory because it is all wrong, based on a series of misunderstanding the physics and throwing unbased myths in.

      – Earth is always aligned with the galactic center. You may mean that it will pass the galactic plane, the center plane of the Milky Way disk.

      This was a understanding.

      – Earth will not pass the galactic plane anytime soon. It is a myth. There is no such thing as a “Platonic Year” in astronomy.

      The Sun orbits the Milky Way every ~ 250 million years. During that time it oscillates up and down through the disk with a period of roughly ~ 2.5 times/orbit or every ~ 100 million years.

      The Sun is ~ 20 – 100 light years (ly) from the disk plane, a ~ 1000 ly thick disk IIRC. If the Sun was traveling directly towards the plane it would take it ~ 70 000 years at an orbital speed ~ 220 km/s relative to the Milky Way. [I’m lazy and using the figures in the article.]

      This was a myth.

      – Since the solar system has passed through the disk, and is traveling with a tilt relative to it, Earth would have passed through many times. Yet we can observe no effects.

      This was a misunderstanding.

      – The central plane of the disk signifies no change in the environment of the solar system in particular. There is no radiation.

      This was a myth.

      – The Sun has no spinning core. It has a convective core but it rotates as a body. This rotation has a tremendous angular momentum and kinetic energy, and can’t be stopped. Especially not by radiation, which doesn’t couple with angular momentum (except for certain forms of EM, i.e. light and radio).

      This was a misunderstanding.

      – The angular momentum of the Sun’s core has nothing to do with its fusion dynamics. Convection movements has, but they are driven by the same dynamics.

      So a non-rotating Sun would still radiate.

      This was a misunderstanding.

      Look, I know we will hear the idiotic myth of a solar catastrophe caused by the Milky Way disk, based on taking the ever repeating calendar of the Maya and mix it with the doom myths of the Inca, repeated incessantly the rest of the year as it was doing the rounds last year and the year before that.

      Hath not a science supporters eyes?

      Hath not a science supporters hands, organs, dimensions, senses, affections, passions;

      fed with the same food, hurt with the same weapons, subject to the same diseases, heal’d by the same means, warm’d and cool’d by the same winter and summer

      as a science ignorant is?

      If you bugger us endlessly, do we not tire?

      If you try to fool us, do we not laugh?
      If you poison our minds, do we not die a little?
      And if you bore us, shall we not respond?

      If we are like you in the rest, we will resemble you in that.

      I also know that the purveyors of such inanity will ask us to not make “a big deal” out of it. But it stands against all what science is for, making us know and love the world based on facts instead of fearing it based on myth.

      And this is a science blog. So I will make “a big deal” out of every instance of 2012 catastrophe myths.

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