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  • [ ♪ Intro ♪ ]

  • There's been a lot of talk lately about sending humans to live on Mars.

  • But it's easy to say that and a lot harder to actually do it.

  • A big part of that is because Marsisn't especially friendly to human life.

  • Or life at all.

  • It's freezing, with a super thin atmosphere that not only makes it impossible to breathe,

  • but also doesn't give you much protection from all the deadly radiation coming from space.

  • To change that, we'd have to terraform Mars, changing its geology and climate to be more

  • like Earth.

  • Which is usually a subject more appropriate for sci-fi than science.

  • But at the Planetary Science Vision 2050 Workshop in early 2017, a group of scientists led by

  • the head of NASA's Planetary Science Division suggested a way we might get started.

  • Their plan?

  • Build a giant force field — a protective magnetic fieldfor the planet.

  • And as weird and impossible as that sounds, it's not totally science fiction.

  • The idea is that this magnetic field would replace the one Mars lost long ago, which

  • would then let the planet build up a thicker atmosphere.

  • Billions of years ago, Mars might have looked a lot like modern-day Earth, with a magnetic

  • field, a warm atmosphere, and oceans on the surface with about as much water as our Arctic Ocean.

  • But for reasons scientists still don't fully understand, Mars lost its magnetic field about

  • 4.2 billion years ago.

  • And everything kinda went downhill after that.

  • Without a magnetic field to block the charged particles streaming from the Sunaka the

  • solar windmuch of the Martian atmosphere got stripped away over the course of about

  • 500 million years.

  • Without a thick atmosphere to trap heat, the planet froze and its oceans were lost forever.

  • Unless we can find a way to bring them back, that is.

  • Even today, four billion years later and with barely any left, Mars can lose up to a kilogram

  • of atmosphere to space every second.

  • We'll never get back all the stuff that's escaped into space already, but there's

  • still gas leaking out of the planet's crust, so there's at least some hope of building

  • it back up.

  • If we could, that would provide more protection against the radiation, plus help warm the

  • planet a bit.

  • Astronomers also think there might be enough water trapped in the polar ice caps to rebuild

  • about a seventh of the ancient oceans, if we can get the climate warm enough for the

  • ice to melt.

  • But first we have to get the atmosphere back, and that's where this NASA team's big

  • idea comes in.

  • If we could block the solar wind from stripping away the atmosphere, it might start to build back

  • up again.

  • At first, that might sound like it involves building something the size of a planet.

  • And that's … not super practical.

  • But the researchers proposed a way to get around the problem: by taking advantage of

  • the fact that the solar wind is only coming from one directionthe Sun.

  • So all we'd need to do isblock the Sun, kind of like what the Moon does during

  • an eclipse.

  • Which, yeah, would still require a huge shield, but we wouldn't have to build a giant solid

  • thingit would just be a magnetic field.

  • And that might actually be practical someday.

  • All we'd have to do is figure out how to generate the field.

  • Then it would reach out into space and do the rest.

  • More specifically, the team suggested putting a field-generating device about a million

  • kilometers from Mars.

  • The magnetic field would have to be a bit stronger than the Earth's, which would be

  • hard on such a large scale, but it's something we could probably figure out how to do.

  • To understand what that would do to Mars, the researchers followed a two-step process.

  • First, they used computer simulations to calculate what a magnetic shield would do to the atmosphere.

  • Then, they used climate models to predict what effects those changes would have.

  • The results suggested that Mars's climate would change a bit, but that we shouldn't

  • get our hopes up too much.

  • Although a strong enough field would stop the solar wind, that's only one of the processes

  • making Mars lose its atmosphere.

  • The planet's weak gravity and molecular interactions with sunlight also contribute.

  • In a process called photoionization, atoms and molecules in the upper atmosphere can

  • absorb energy from light and break apart.

  • Some of those pieces end up with enough energy to break free of Mars's gravity and escape

  • to spacewhich is not good if you're trying to keep the atmosphere around!

  • And although the global temperature would rise, this would mostly happen near the equator

  • which is not where the ice is.

  • In fact, because of the way atmospheric physics works, it might even get colder at the poles

  • than it is now.

  • That would keep all the dry ice, which is made up of solid carbon dioxide, trapped in

  • the polar ice caps instead of vaporizing it into gas that would thicken the atmosphere.

  • Plus, that dry ice is sitting on top of the water ice needed to refresh the global oceans.

  • And even if the shield was enough to thicken the atmosphere and bring back the oceans,

  • it would take a while.

  • Like, the researchers didn't even have an estimate of how long.

  • So I wouldn't count on taking a boat down Valles Marineris anytime soon.

  • But the idea is intriguing, because unlike many other terraforming ideas, the technology

  • seemspretty doable.

  • MRI machines use fields even stronger than what this research calls for; we just need

  • to figure out how to make a field of the right shape and size.

  • And get it into space.

  • And the idea of putting something between the Sun and Mars isn't that different from

  • some proposals for dealing with climate change here on Earth.

  • For example, some scientists have suggested that one day we might be able to launch what

  • would basically be a giant pair of sunglasses to block some of the Sun's rays and cool

  • the planet.

  • But before we give Mars its very own Hylian shield, there's another question that needs

  • to be answered: even if we can do this, should we?

  • There's a lot we still don't know about our planetary neighbor, and we still haven't

  • completely ruled out the possibility of alien life over there.

  • If there is life on Mars and we totally transformed the planet like this, we'd basically be

  • destroying its habitat.

  • But with no immediate plans to actually give Mars a magnetic shield, hopefully we have

  • plenty of time to work those questions out.

  • Thanks for watching this episode of SciShow Space!

  • If you're interested in learning more about the hardest things about living on Mars, you

  • can check out our episode about just that.

  • [ ♪ Outro ♪ ]

[ ♪ Intro ♪ ]

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