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

Posted by samzenpus on from the what's-to-blame dept.

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.”

11 of 142 comments (clear)

  1. Isn't it widely accepted... by Rei · · Score: 4, Interesting

    ... 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?

    --
    The human body can be drained of blood in 8.6 seconds given adequate vacuuming systems.
    1. Re:Isn't it widely accepted... by Rei · · Score: 4, Informative

      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.

      --
      The human body can be drained of blood in 8.6 seconds given adequate vacuuming systems.
    2. Re:Isn't it widely accepted... by Sir+Foxx · · Score: 3, Insightful

      ... 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 pressure on the surface. Being closer to sun, as it grew hotter, it also was moving closer to the edge of the habitable zone, which was moving outward as sun grew hotter. Without water on the surface anymore, plate tectonics stopped completely. When this happened, you no longer get a nice moderate release of volcanism, you get trememdous pressure building up and then released in huge amounts all at once probably every 400 million years that covers the planet in liquid hot magma. Also, it looks like Venus got hit hard by another proto planet that unlike what happened to the earth, which was a glancing blow at angle, Venus got hit straight on, slowing down it's spin a lot, It's one of(maybe the slowest), slowest spinning bodies in our solar system. I think you couple that with the lack of water to keep plate tectonics moving, you end up disrupting it's dynamo in the core and you have a very weak magnetic field now. The Earth is going to become Venus as the sun grows hotter and the habitable zone moves out further. It's a long time from now, but it will happen.

      --
      "I don't which is worse, that everyone has a price, or that the price is always so low"--Hobbes
    3. Re:Isn't it widely accepted... by Crowd+Computing · · Score: 3, Interesting
      Venus does have a weak magnetic field, 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.

  2. This is basic planetary physics.. by Lumpy · · Score: 5, Informative

    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....

    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.

    --
    Do not look at laser with remaining good eye.
  3. Re:Yay! Another end of Life on Earth scenario by Lumpy · · Score: 4, Interesting

    We all turn into solar radiation zombies.

    You have about 1.2 Billion years to prepare for this, so start digging and stocking your bunker now.

    --
    Do not look at laser with remaining good eye.
  4. Re:This is basic planetary physics.. by Anonymous Coward · · Score: 5, Interesting

    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.

  5. Re:Global warming? by serviscope_minor · · Score: 4, Insightful

    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

    Tell me, what's the carbon footprint of burning a straw man?

    --
    SJW n. One who posts facts.
  6. Re:This is basic planetary physics.. by RubberDogBone · · Score: 4, Insightful

    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.

    --
    Sig for hire.
  7. Re:This is basic planetary physics.. by budgenator · · Score: 4, Interesting

    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.

    --
    Apocalypse Cancelled, Sorry, No Ticket Refunds
  8. Backwards spin by mschaffer · · Score: 3, Funny

    Is the backwards spin evidence that cats had used the Venerian spin to get their planet moving.