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Mars Earth Science

What Happened To the Martian Ocean and Magnetic Field? (theatlantic.com) 142

schwit1 writes with this story at The Atlantic that explores what may have destroyed the Martian atmosphere and ocean. The question of whether there is life on Mars is woven into a much larger thatch of mysteries. Among them: What happened to the ancient ocean that once covered a quarter of the planet's surface? And, relatedly, what made Mars's magnetosphere fade away? Why did a planet that may have looked something like Earth turn into a dry red husk? “We see magnetized rocks on the Mars surface,” said Bruce Banerdt, the principal investigator of the InSight mission to Mars, which is set to launch in March. “And so we know Mars had a magnetic field at one time, but it doesn't today. We would like to know the history—when that magnetic field started, when it may have shut down.”
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What Happened To the Martian Ocean and Magnetic Field?

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  • by Rei ( 128717 ) on Thursday October 08, 2015 @07:48AM (#50685047) Homepage

    ... that because of Mars' small size, it cooled faster, thus freezing its outer core and shutting down its dynamo? Isn't Venus the far greater mystery? Nearly the same size as Earth, yet no magnetic field and what appears to be occasional whole-crust overturn rather than plate tectonics? Isn't that the one we need to solve?

    • So the surface of Venus is over 460c. I would think, but do not know, that all that solar energy got absorbed into the crust combined with the exothermic reaction in it's core might be enough for rapid crust recycling? Or to ask the question: Just where does the majority of the energy come from that melts all that rock; the core or sun?

      • by Rei ( 128717 ) on Thursday October 08, 2015 @08:30AM (#50685201) Homepage

        Very little energy reaches the Venusian surface - Venus's albedo is twice that of Earth's, so most light gets reflected from the cloud deck, and what does enter gets quickly absorbed in the clouds and thick atmosphere. Also, the crust is not what drives a dynamo, the core does. Nuclear decay is what drives terrestrial planet cores, not solar input.

        Also I don't know what you mean by "rapid crust recycling", unless you mean Venus's global resurfacing events. But those only happen once every several hundred million years. And they take about 100 million years to complete, they're not rapid.

        • by p4ul13 ( 560810 )

          But those only happen once every several hundred million years. And they take about 100 million years to complete, they're not rapid.

          Not necessarily agreeing with the previous poster, but I'm under the impression that geologically speaking 100 million years is somewhat rapid for that sort of change at least compared to Earth.

          • The age of the Earth (and presumably Vanus) is about 4.5 billion years. 100 million years is about 2.2% of that. An event that takes 100 million years could happen 45 times in the Earth's lifetime. If it were a day, this would be about a half hour lunch. So more of a moderate length of time, geologically.

            Compare it to what the Earth looked like 100 million years ago [resilience.org].

    • Re: (Score:1, Informative)

      by Anonymous Coward

      A common theory to explain Venus' slow and backwards rotation is that it suffered a large impact similar to the one that formed the Earth's moon, only in a direction counter to it's original rotation, so much that it put the brakes on Venus so hard that it's now slowly spinning in reverse.

      Also it's thought that Venus is simply too close to the Sun, there was a time when the Sun wasn't as bright and water may have been on the surface but as the sun matured the "goldilocks" zone shifted outwards and Venus got

      • by lgw ( 121541 )

        A common theory to explain Venus' slow and backwards rotation is that it suffered a large impact similar to the one that formed the Earth's moon, only in a direction counter to it's original rotation, so much that it put the brakes on Venus so hard that it's now slowly spinning in reverse.

        Also it's thought that Venus is simply too close to the Sun, there was a time when the Sun wasn't as bright and water may have been on the surface but as the sun matured the "goldilocks" zone shifted outwards and Venus got cooked.

        The rotation idea doesn't really hold water. It would have needed to happen very early in planet formation, or the whole planet would still be molten today, plus the details of the impact bringing angular momentum to 0, which requires the pieces that escaped the collision to have just precisely the right parameters post-impact, are "finely tuned", which is the polite way scientists say "BS".

        Keep in mind that, at least with Earth, the surface isn't rigidly coupled to the core. While the difference in rotat

    • Re: (Score:3, Insightful)

      by Sir Foxx ( 755504 )

      ... that because of Mars' small size, it cooled faster, thus freezing its outer core and shutting down its dynamo? Isn't Venus the far greater mystery? Nearly the same size as Earth, yet no magnetic field and what appears to be occasional whole-crust overturn rather than plate tectonics? Isn't that the one we need to solve?

      ... that because of Mars' small size, it cooled faster, thus freezing its outer core and shutting down its dynamo? Isn't Venus the far greater mystery? Nearly the same size as Earth, yet no magnetic field and what appears to be occasional whole-crust overturn rather than plate tectonics? Isn't that the one we need to solve?

      Well, I think they have Venus figured out. Basically it was like us early on, complete with oceans and land and magnetic field. Back in the beginning of the solar system, the sun was cooler than it is today. As it ages it grows hotter, like in the next 1 billion years the sun will be 10% hotter. Well, as it grew hotter back then, Venus's oceans started to evaporate into the atmosphere, and the H20 became lost to space. Leaving an ever growing thick atmosphere that held in the heat and increased the

      • Um, no.

        It's speculation on a good day. The redness of Mars comes from iron. Spin iron and it magnetizes. Do this for 4+ billion years, and good grief, you get magnetized iron. There is no cogent forensic evidence of a magnetosphere on Mars.

        This earth trapped its water, and melting ice asteroid/meteorites filled it with water, I'm guessing, by plowing into it, thus causing the expansion of the Pangean continent. There's this 36000' deep trench, called the Mariana. Plates shifted, much water melted from a met

    • Re: (Score:3, Interesting)

      Venus does have a weak magnetic field [esa.int], but it's not generated in the core but in the atmosphere through collision with the solar wind:

      As on Earth, solar ultraviolet radiation removes electrons from the atoms and molecules in the upper atmosphere, creating a region of electrically charged gas known as the ionosphere. This ionised layer interacts with the solar wind and the magnetic field carried by the solar wind.

      During the continuous battle with the solar wind, this region of the upper atmosphere is able to slow and divert the flow of particles around the planet, creating a magnetosphere, shaped rather like a comet's tail, on the lee side of the planet.

      If we think of planet's iron core as a gigantic power generator, then Venus's slow rotation, when compared to Earth or Jupiter, might explain the absence of a strong internal magnetic field.

      • Whoever came up with that theory knows absolutely nothing about magnetic fields. It hurt my brain just trying to read it.
    • by G00F ( 241765 )

      Look at our moon. I believe it's the biggest reason we still have a liquid core and thus a strong magnetic field.

      Our moon is large in comparison to earth, and exerts a lot of force on the entire planet as we rotate together. If the moon wasn't tidal locked it would have a liquid core as well. basically as the moon and earth move/rotate the force direction changes, causing movement/heat.

      Also there is a theory that long before life there was no moon, and we captured it after it collided losing it's core wit

      • by Rei ( 128717 )

        It's not that simple. Mercury also has a magnetic field. Which is a real head-scratcher, as it's even smaller than Mars.

        Internal planetary dynamics are complicated. To get a dynamo you need fluid flow. But whether something is liquid or solid depends on both temperature and pressure - temperature increasing melt, pressure decreasing it. So there's a very complicated interplay.

    • Here is half, if not all of the answer,
      Radioactive decay accounts for half of Earth's heat. http://physicsworld.com/cws/ar... [physicsworld.com]
      The rest of the answer may be in the data (if known) about the distribution of heavy radioactive elements throughout the Solar System.
  • by Lumpy ( 12016 ) on Thursday October 08, 2015 @07:49AM (#50685049) Homepage

    Mars has no Magnetic field because it's core cooled and is no longer a active moving iron mass. it cooled faster as it has very little radioactive isotopes and being further away from the sun it has less energy pounding it to slow the cooling.

    http://www.scientificamerican.... [scientificamerican.com]

    Plus we had an event late after the formation of the planets in the solar system that also added a buttload of energy, when the moon was formed from a planetary sized impact.

    • While trying to figure out what scripts to allow to make moderation work I accidentally ended up modding this as flamebait. For reference, I was going for informative. I believe posting a reply will undo that. So thanks for the post, Lumpy. I owe you +1.
    • Is the loss of the magnetic field related to the disappearance of the Martian ocean? Another commenter seemed to indicate this, but I don't get the connection and it's been 30 years since I've taken chemistry or physics.

      • by Anonymous Coward on Thursday October 08, 2015 @09:36AM (#50685547)

        It is thought to be related to the disappearance of the Martian atmosphere. The magnetic poles divert the solar wind towards themselves, and prevents it from hitting most of the planet. When the magnetism disappears, the solar wind blows the atmosphere away.

        When the atmosphere disappears, the pressure is reduced, and with it the boiling point of water, until water can only have two states - ice and gas form. The water that doesn't turn into ice goes the same way as the rest of the atmosphere.

        • by Anonymous Coward

          Magnetic fields definitely help slow atmospheric loss, but I think a lot of scientists are overestimating the effect on Mars. Either Mars never had much of an atmosphere, there is some extreme tipping point between atmospheric pressure and gravity, or the atmosphere is still mostly there, just sunk into the surface of the planet. Otherwise there is no way that the atmosphere of Venus, which also has no real magnetic field, could be nearly as thick as it is today.

        • by RubberDogBone ( 851604 ) on Thursday October 08, 2015 @10:59AM (#50686165)

          It's this exactly. Without a magnetic field, the solar wind dried out the planet and blew away a large amount of the already thin atmosphere. The low gravity didn't help any. The planet had a lot going against it from the beginning and was probably never a good place for complex life to appear. Barring some sort of cosmic change like how we got our moon and added a huge amount of iron and mass, Mars was always doomed to end up freeze-dried.

          We currently have no way of fixing this problem so all the grand plans to terraform Mars won't work, unless they also restart the magnetic field, which we don't know how to do. It might take slamming a proto-planet into Mars to get things going again, which we can't currently do, and which would also make the planet essentially unusable for hundreds of millions of years, at least.

          It also risks all kinds of other issues like disturbing other planets and introducing a lot of chaos into the solar system. But luckily we don't know how to knock planets into each other. And I suppose if we DID and we had that sort of tech, we would not need to bother with Mars. We'd just find a suitable planet elsewhere, which is probably easier.

          • We currently have no way of fixing this problem so all the grand plans to terraform Mars won't work, unless they also restart the magnetic field

            The process of bleeding away the atmosphere happens over geological time spans. If we could increase the density of the atmosphere it would still be there for tens of thousands of generations. I would not call that a terraforming failure. Given that you're argument is based on that one misunderstanding, your pessimism seems to have political roots, not intellectual roots.

            • by Lumpy ( 12016 )

              The energy taken to terraform mars would be better used on Venus or towards pressurised structures. And those will be very simple as you need only about 7-8 psi capability

      • by budgenator ( 254554 ) on Thursday October 08, 2015 @11:00AM (#50686171) Journal

        The way I understand it the lost of the magnetosphere allows the solar wind to push the ozone back to the nightside and some off into space, this thins ozone lets the UV disassociate more water vapor (that's lighter than air) into hydrogen and oxygen, the hydrogen is lost to space because it's so light and the oxygen that doesn't get blown off into space oxidises any methane or carbon monoxide in the atmosphere on the way back down to the surface. This causes the atmospheric pressure to decrease, which cause the water to boil at a lower temperature, putting more water vapor into the air to be dissociated and lost, in an accelerating death spiral.

        • The way I understand it the lost of the magnetosphere allows the solar wind to push the ozone back to the nightside and some off into space, this thins ozone lets the UV disassociate more water vapor (that's lighter than air) into hydrogen and oxygen, the hydrogen is lost to space because it's so light and the oxygen that doesn't get blown off into space oxidises any methane or carbon monoxide in the atmosphere on the way back down to the surface. This causes the atmospheric pressure to decrease, which caus

    • So let's crash the moon into Mars and see if it restarts the core.
    • Also there is a theory that Mars got hit by something big on the opposite side of the planet from where Olympus Mons is and that it may have disrupted things enough to cause it's dynamo to stop earlier than it should have and for the core to lose it's heat much faster from the Olympus Mons eruptions due to the collision.
      • by Holi ( 250190 )
        Any link to that theory? I was pretty sure the accepted theory on Olympus Mons is it built up over time due to the fact that plate tectonics stopped and it was stuck over a magma hot spot.
    • Yes, and the event that formed the moon probably gave us a larger molten iron core. I have seen a hypothesis that the gravitational forces from the moon also help keep the iron dynamo moving in the core. I don't know how likely that is, not being a physicist, but it is an interesting idea.
  • Scientists already have hints that Mars’s ancient magnetic field did not operate the way Earth’s does. And in 2007, one team of researchers made a model of the Martian core that suggested it might contain flecks of solid iron—a hint that the planet's magnetism could at some point re-activate.

    Lack of a magnetic field is one of the biggest obstacles to proper terraforming. If there's really a turning point within reach, that we one day might trigger artificially, then Mars becomes a lot more

    • Don't we just have to get Quaid to Mars to fire up the alien machine?
      • If that machine did exist, it would ultimately amount to only a temporary climate change. Unless it also fixed the magnetic field, all the released air and water would simply get eroded by the solar winds and Mars would end up red and dry again.

         

    • Lack of a magnetic field is one of the biggest obstacles to proper terraforming.

      Only if "proper" means that one is fixated on creating an Earth-like habitat that is planet-wide and open to the stars. That's traditional, but it's not sensible engineering because it's not resource-efficient.

      Instead, it makes a lot more sense to create your own habitable layer no larger than is needed, to do so in segments so that not all your eggs are in one basket, and to extend it only when more space is needed. There are

      • If terraforming is your goal, Venus would be a better target. While being terraformed, there is a spot at altitude where pressure is Earth norm, and temperature is livable. The atmosphere also has everything we need to produce CO2, O2, H2O to have a life sustaining habitat built.

    • by PPH ( 736903 )

      Perhaps we should stop thinking that terraforming has to be modeled on properties of the earth alone. The question that needs to be answered: Why does Venus have a thick atmosphere and yet it also has a minimal magnetic field?

    • Triggering crystallisation of a planet's core is left as an exercise for the reader, and would be incredibly difficult, but it's a lot more plausible than trying to supply enough heat to start convection by any other means.

      interesting questions might be


      1. How much nuclear waste would have to be dumped down a borehole on Mars to remelt the planetary core; ( I know it's an insane amount, but how insane)?
      2. How long would it take to melt?
      3. How deep would the borehole have to be, at some point the waste would melt and go into "China Syndrome mode" and melt it's way down?
      4. Should we crash some icy asteroids into the planet to get some potential oxygen from water before or after we restart the core?
      5. How many rocky/metallic asteroids should w
    • Lack of a magnetic field is one of the biggest obstacles to proper terraforming. If there's really a turning point within reach, that we one day might trigger artificially, then Mars becomes a lot more attractive. If we could restart its magnetic field, it could have a stable Earthlike climate someday.

      A few superconducting rings around the planet.. about a GW of power per ring would do. You need about 50k miles of superconducting cable and supporting infrastructure. Not totally unreasonable for a project of this scale.

  • by wonkey_monkey ( 2592601 ) on Thursday October 08, 2015 @08:34AM (#50685221) Homepage

    It was Marvin the Martin, in the Valles Marineris, with an Illudium Pu-36 explosive space modulator.

  • So what would it take to re-heat the core to restart magnetic field? What kind of energy input would it take, and what could deliver it? Could we just crash a bunch of large asteroids into mars then wait for the surface to cool?
    • by Anonymous Coward

      Oh look, a space nutter. You are right, we just need to crash a bunch of asteroids into it. No big deal. We will be sipping wine on Mars in no time at all!

      • by Rakarra ( 112805 )

        Stop using the term "space nutter," thank you.
        It's second only to "SJW" and "no true scotsman" when it comes to stupid phrases used on Slashdot that people need to stop parroting.

    • A bunch of posts in the "elon musk wants to nuke mars" story said something to the effect of....

      If we can terraform mars it doesn't really matter that solar wind would blow away the atmosphere that is created. If we can crash a comet into Mars to give it water and an atmosphere, we can keep doing that periodically to recharge everything. Solar wind erosion takes a comparatively long time so you might only need a new comet every few million years or so. Once every 1000 years is still incomprehensibly long fo

      • That would be one hell of a ski run. I wonder how long it would take to get from bottom to top to bottom again.

        • by Holi ( 250190 )
          That would be one hell of a very long and boring ski run. Olympus Mons has a very gradual incline, about 5 degrees.

          "I wonder how long it would take to get from bottom to top to bottom again."

          Longer then your lift ticket was good for.
      • Don't know about you guys but I'm ready for a ski resort on Olympus Mons. 26km vertical in a single decent? Sign me up!

        A bit off topic, but that nearly 26km vertical averages a grade of only about 5 degrees at the flanks (the steeper parts of the mountain), and you'd be descending with roughly 1/3 of Earth's gravity. Sounds more like that'd be an exceptionally long and exceptionally dull bunny slope.

        Oh, another fun fact: If you were actually standing near the summit of the mountain, you'd have no idea since the slope of the mountain actually extends beyond the horizon.

        • by Holi ( 250190 )
          Not even a bunny slope. more like a very gradually inclined plane. I doubt you would overcome friction. So I think alpine skiing is out which means it would be a X-country ski park, LAME.
        • Well obviously the terraformers would smash the comets into the south side of the mountain resulting in the most epic bowl imaginable!

    • by mjr167 ( 2477430 )
      Ooo! There was a movie about this! You get a drill ship thing and drive a nuclear bomb into the core!
  • by mi ( 197448 )

    20+ posts already, and no one mentioned Global Warming yet? How could you, guys, miss this opportunity to refresh the fear in the hearts of your followers? If you keep burning fossil fuels, our planet too will become an airless desert devoid of life. Whether it will heat up or cool down is an impolite question, but something will happen, unless you install solar panels on your roof.

    The "point of now return" [scientificamerican.com] — like the second coming of a deity of some unscientific cult followed by the unwashed —

  • Then we get another movie.
  • Millions of years ago Earth, Mars and Venus formed an artificial Klemperer rosette in the habitable zone around the Sun.

    The advanced civilisations which produced this artifact went to war. Mars and Venus' orbits were wrecked. Mars was hit by 'planetbuster' bombs and cracked open, its molten core spewing out into space and collapsing on itself. Venus was subjected to bombardment by comets and turned into the hell-hole it is today. Only Earth survived mostly intact.

    Either that or the civilisation which produc

  • Even as far back as the original Cosmos series, scientists were saying that the lack of a liquid iron core to generate the magnetic field was the cause of the atmosphere leaking off into space. Okay, sounds plausible but it has me wondering why it has to be liquid when lodestone has a magnetic field and it's solid.
    And why isn't gravity enough to hold the atmosphere in? Or is the gravitational field too weak?

    • I would think - with my limited understanding of physics and cosmology- that Mars' smaller size, being about 1/3 the size/mass of Earth, would have to play some part in it's early "death". A smaller, less massive core would would probably not have the same inertia as a larger one; and less magnetic field, not to mention gravitational field, would make an atmosphere more vulnerable to the solar wind.
    • Even as far back as the original Cosmos series, scientists were saying that the lack of a liquid iron core to generate the magnetic field was the cause of the atmosphere leaking off into space. Okay, sounds plausible but it has me wondering why it has to be liquid when lodestone has a magnetic field and it's solid. And why isn't gravity enough to hold the atmosphere in? Or is the gravitational field too weak?

      Iron looses magnetic properties at 770C which is hot but still solid. A liquid iron core has a magnetic field due to convection. Once it cools and solidify, the convection stops but the core is too hot to have a magnetic field of its own.

    • by Holi ( 250190 )
      Magnetite is very hard to magnetize, and it normally does not hold a magnetic charge for very long. The prevailing theory on lodestones is that they are magnetized by lightning strikes. Magnetized magnetite is very rare and only found on the surface of the planet.
    • by Rakarra ( 112805 )

      And why isn't gravity enough to hold the atmosphere in? Or is the gravitational field too weak?

      My understanding was that the solar wind could essentially "blow away" the atmosphere over time, that the atmosphere has an external force acting on it. Earth's magnetic field is essential for deflecting the solar wind and avoiding the same fate. But that wouldn't explain why Venus, presumably dealing with a much stronger solar wind, has such a robust atmosphere with such a weak magnetic field. Venus's wikipedia article suggests that water on Venus had boiled off, and its free hydrogen and oxygen were swep

    • by Bengie ( 1121981 )

      And why isn't gravity enough to hold the atmosphere in? Or is the gravitational field too weak?

      Solar winds are very high velocity particles. While the average pressure isn't enough to strip the atmosphere, the individual particles are slamming the atmosphere to accelerate them to escape velocities.

  • Did you see the machine in Total Recall? It warmed the water, but also generated a magnetosphere. They shut it down before leaving as running without maintenance it would just break down. That does mean that once we turn it back on we need to figure out how fix it, but at least we will have blue skies and protection from the Sun while we study how the machine works.

    *This is a joke, not a troll, or a belief of intelligent life forms on mars*
  • The heavy isotopes sink down to the core of planets. If hot then the densest metals transfer heat to the lighter elements. I've given this some thought. If the horse head nebula is second generation stars then there isn't enough plutonium and uranium present to maintain heat for billions of years. The Sol system is at least a fifth generation star having components from early star collisions and nova events. The gold on earth is from neutron star collisions billions of years before this system existed. Any

  • “We see magnetized rocks on the Mars surface,” ... “And so we know Mars had a magnetic field at one time"

    I think all we can say with reasonable certainty is that rocks on the Mars surface were exposed to a magnetic field. As far as I've found, there's no observable evidence that the magnetic field must have come from Mars itself, or even that the rocks were impregnated with magnetic alignment while they were on Mars.

    Europa for example has a magnetic field that was induced by Jupiter's own

  • It's understandable science has to do it's due dillegence but seriously, i wish they'd just take Sitchin a little more seriously.

"Well, if you can't believe what you read in a comic book, what *can* you believe?!" -- Bullwinkle J. Moose

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