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[ ♪ Intro ]

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We spend a lot of time thinking about
Mars.

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Mostly about if it could someday support human
life.

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Scientists are constantly researching and
experimenting with different ways people could potentially live on the Red Planet,

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whether
that’s underground or in specialized habitats.

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And we’ve talked about that research a lot
on SciShow Space,

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enough to make a whole compilation
of videos about it!

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One thing we know isn’t a good idea is to
just hop out of our spacecraft and walk around like we do here on Earth.

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And the reason why is a lot more interesting and complicated than I would have first assumed.

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Here’s Hank breaking down exactly how long
you could survive on Mars without a spacesuit.

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Mars is a well-mined subject here on
SciShow Space,

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whether we’re talking about the challenges of future human expeditions there

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or following
all the amazing things Curiosity is doing right now.

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But here’s one question we have yet to answer.

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How long could you just survive on the surface
of Mars without a spacesuit?

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The good news is you’d last longer than
you would on Venus,

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which is probably the most inhospitable place on the surface of any planet.

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The bad news is you’re still gonna pass
out in less than 30 seconds and be dead in a minute.

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Maybe 90 seconds if you’re lucky.

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Now, yes, Mars and Earth do have some very
basic things in common.

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Like Earth, Mercury and Venus, it’s a rocky
planet,

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so it actually has a surface that you can stand on.

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Which is nice.

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But because it’s just over half as big as
Earth, and much, much less dense,

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Mars has only 38% of Earth’s gravity.

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So as you’re fumbling for your keys to get
back into your spaceship or whatever,

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your movements might feel kind of jerky and sudden
and weird.

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But, seriously, that’s the least of your
problems.

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It’s also very cold, for one thing, thanks
to both its thin atmosphere and its greater distance from sun.

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With not much atmosphere covering the planet’s surface
to retain heat,

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the average temperature on Mars hovers around minus 60 degrees Celsius,

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though the extremes range from minus 125  at the poles to a balmy 20 degrees at the
equator.

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20 degrees! That's perfectly live-able. That's like, Earthlike.

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Well, then there’s the radiation problem.

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The atmosphere is way too thin to absorb ultraviolet
light from the Sun the way Earth’s does.

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It also doesn't have a magnetic field the way that the Earth does.

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So all that radiation is just hitting the ground pretty
much at full strength.

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And it won’t kill you right away, but should
you survive your jaunt on the Martian surface,

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problems will come up later, as that radiation
starts to cause mutations in your cells.

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But your biggest problem is the atmosphere itself.

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The surface of Mars is not technically a vacuum,

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but it’s about as close as you can get without actually being in outer space.

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What atmosphere there is on Mars is composed
almost entirely of carbon dioxide,

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with trace amounts of nitrogen, argon, and oxygen.

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That’s enough of an atmosphere to support
some clouds and wind,

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but the surface pressure on Mars is about 1/100th that of what we have on Earth.

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And the human body does not do well when suddenly
exposed to extremely low atmospheric pressure.

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Contrary to what you may have heard,

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exposure to vacuum-like conditions will not cause your blood to boil or eyes to pop out of their sockets.

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But with so little air pressure, many of
your bodily fluids will start to vaporize.

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That means your sweat, mucus, saliva and tears
are going to evaporate within a few seconds,

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which is going to be uncomfortable.

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Also, all that water in your body is about
to turn into water vapor.

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Thanks to your strong and elastic skin, you’re
not going to explode,

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but you will become bloated before you’ve had a chance to take in the view.

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The release of all the gases in your blood
and other fluids will basically give you a

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very quick and very severe form of the bends,

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the decompression sickness that affects divers who return to the surface too fast.

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So if you do become part of that generation
of explorers that makes it to Mars, and I really hope that you do,

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for the love of Pete, 
don’t forget to wear your spacesuit!

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Okay, so wear a spacesuit on the surface of
Mars.

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Got it.

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But even if you take all the health and safety
precautions,

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living on Mars would still be pretty inconvenient compared to what we’re used to now.

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In this video, Reid unpacks the hardest aspects
of living on Mars.

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Lately, there’s been a lot of talk about
building a colony on Mars.

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There’s still a lot to do before we get
to that point,

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like, we should probably figure out how to get people there.

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But even if we did set up a human habitat,
we’d still have some huge challenges to overcome.

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Because traveling to, and living on, the Red
Planet would be more dangerous than basically anything we’ve ever tried.

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Here are three of the biggest challenges the
Mars colonists would, or will, have to face.

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The danger starts long before reaching the
Martian surface.

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Depending on exactly when and how our astronauts
launch,

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it will take the crew somewhere around seven months to get to Mars.

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And as soon as they leave the protection of
Earth’s magnetic field,

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they’ll be exposed to the intense radiation environment of space.

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This radiation is mostly made of tiny subatomic
particles like protons and neutrons.

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Many stream out of the Sun as part of the
solar wind, while others, called cosmic rays,

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come from all over the galaxy.

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And sometimes, these particles can strike
a bit of DNA as they pass through the human body.

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Each hit can randomly change a little of someone’s
genetic code,

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and that can lead to mutations in new cells that ultimately cause problems like cancer or heart disease.

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Thankfully, because we’re protected by the
Earth’s magnetic field and atmosphere,

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we aren’t exposed to most of these particles.

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But things aren’t the same in space.

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Although astronauts take precautions, spending
six months on the International Space Station

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results in absorbing about three times as
much radiation as the U.S. annual legal limit,

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and a trip to Mars would be over twice as
much as on the ISS.

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And, if there happened to be an explosive
solar flare during the trip,

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the crew could receive a lethal dose of radiation
in just a few hours.

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Since Mars lacks a global magnetic field and
doesn’t have much of an atmosphere,

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things don’t get a lot better once the astronauts land, either.

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Over about 500 Earth days, they would receive
about as much radiation as on the trip there,

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and that would really add up over a lifetime.

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To protect our first interplanetary settlers,
scientists have a couple of ideas that would make MacGyver proud.

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First, it turns out that water is very effective
at absorbing radiation,

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because it’s rich in hydrogen, which is just the right size
to block these subatomic particles.

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And water is something the astronauts will
already be bringing with them.

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So one option is to line their spaceships
and habitats with tanks of it.

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Another option is tunneling underground to
escape the radiation,

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or setting up shop in giant, empty lava tubes left over from when Mars was volcanically active.

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Of course, astronauts don’t need to worry
about radiation if they starve to death first,

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and growing food on Mars won’t be a picnic.

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Well, actually, growing food might not be
too terrible.

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Laboratory experiments suggest that it is
possible to grow plants in the powdery Martian soil,

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and Mars’ atmosphere is full of yummy
carbon dioxide for photosynthesis.

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What might be more tricky is not dying from
the food you grow.

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See, Mars’ surface is full of perchlorates,
a class of salts considered industrial waste here on Earth.

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Perchlorates overwhelm the body’s thyroid
gland by blocking its ability to absorb iodine,

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which is normally used to produce a hormone
that regulates your metabolism.

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In the U.S., it’s regulated in things like
groundwater at the state level.

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Massachusetts, for example, sets the legal
limit at two parts per billion by mass.

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Meanwhile, on Mars, perchlorates are found
at a rate of around 6 million parts per billion.

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Which is just a tad higher.

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Just like we can clean up soil here at home,
it’s possible to do the same thing on Mars,

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like by introducing microbes that eat perchlorate
as an energy source.

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Which, of course, would run the risk of contaminating
Mars with even more Earth life.

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And that’s a whole different problem.

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So, either way, I’m gonna let you take the
first bite.

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To power all that soil cleanup, plus basically
everything else,

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settlers will need a reliable source of electricity.

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The obvious answer is to just throw up a bunch
of solar panels and call it a day,

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but that could be a big mistake.

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See, every year, Mars suffers from dust storms
the size of Earth’s continents,

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and, on average, those cover the globe about twice
a decade.

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The thin Martian atmosphere means these windstorms
wouldn’t blow over the solar panels,

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but all that dust flying around blocks an enormous
amount of sunlight.

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When the Mars rovers Spirit and Opportunity
got trapped in the last global dust storm in 2007,

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they were reduced to operating just
a few minutes each day.

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That’s okay if you’re a robot, but not
so good if you need to do things like,

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I don’t know, breathe or see at night.

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To get around this, the first Martian colonists
will need to bring a different kind of power source,

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like something based on plutonium,
because plutonium doesn’t care if the Sun is out.

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So, it’s not that there aren’t solutions
to these problems.

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We could clean up the soil, build radiation-proof
habitats, and figure out a reliable power supply.

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The thing is, there are a lot of problems,

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and finding the answer to each of them in a way that doesn’t break the bank will be a real challenge.

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But, hey.

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People.

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On Mars.

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If we can get that far, we’ll figure out
the rest.

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So humans living on Mars would be really cool.

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But we can’t forget that, where you have
life, you also have death.

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Hank and Reid have already talked a little
about all the things you would need to do to keep people alive on Mars,

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but what happens
to your body if you die there?

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Someday, somebody’s going to die on Mars.

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Death is not fun to think about,

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so let’s just assume it’ll be after one of the founders of the first Mars colony has lived to a ripe old age

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and watched their people grow and flourish and it’ll all be very peaceful.

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But no matter how or why it happens, the science
of what comes next is super interesting.

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First, any burial plans are going to have
to consider international law,

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because there are United Nations charters against contaminating other planets.

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And unfortunately, we humans are covered in
and filled with contaminating microbes.

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And if a person is going to die on the Red
Planet,

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all those microbes are going to have to be killed or contained.

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And there are a couple options for how to
do it.

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The first is cremation, or burning a body
into ashes.

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Fire will kill all those microbes,

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and it’s a practice that many communities already use and have rituals around.

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But there’s also an alternative that’s
being developed specifically for use in space!

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It’s called Body Back, and it’s pretty
sci-fi.

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In 2005, NASA contacted the Swedish company
Promessa,

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which specializes in environmentally-sound burials and cremations.

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NASA asked them to look into a system for
handling remains that can be used in space.

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So they came up with the Body Back, which
is basically just an adaptation of Promessa’s existing process,

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although it hasn’t been
done to anyone on Earth yet.

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First, the body of a Mars traveler would be
stuck in a weatherproof bag.

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It’d be cooled down, and then exposed to
liquid nitrogen for a bit.

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This would deep-freeze the body and make it
really brittle.

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Then, the bag would be shaken up by a machine
until the body became a powder.

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Which is really effective for saving space,
and that’s always important on a mission,

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even if it’s kinda creepy.

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Still, liquid nitrogen doesn’t always kill
bacteria.

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It can also preserve them, causing them to
stop growing without actually dying.

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So the body would have to stay in the bag
forever.

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But it’s at least an option.

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Now, if cremation or bag of powder options
aren’t available,

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like if someone’s spacesuit breaks and they’re exposed to the Martian elements,

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the process would go a little differently.

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For one, they’d technically be violating
international law,

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but there would be more immediate problems at that point.

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To know how a body would respond to being
left alone on Mars,

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scientists can actually study a similar environment on Earth: the Atacama desert in Chile.

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The Atacama is one of the driest places in
the world, and it’s super high up,

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with peaks reaching elevations of about 6000 meters.

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And the higher up you are, the thinner, cooler,
and drier the air.

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It’s a little like Mars.

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Hundreds of years ago, the Atacama was a part
of the Incan empire,

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and the Inca had a practice called capacocha.

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These were ritual child sacrifices, which,
to be clear, are horrible,

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but the bodies of these children have helped scientists with research hundreds of years later.

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Because, despite all that time, the bodies
haven’t really decayed.

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In the Atacama, it’s too cold and dry for
bacteria to grow well,

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so the bodies became natural mummies.

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And that’s close to what would happen on
Mars, too.

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It’s generally colder and drier than it
is on Earth, so not much would happen.

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The bacteria on or in someone’s body just
wouldn’t grow, or would grow much more slowly,

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so it would take centuries for a body to break
down, if it decayed at all.

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Now, if someone died closer to the Martian
equator, where the temperatures can get up to 20 degrees Celsius,

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the bacteria inside
their body might start to decompose it for a while.

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But the process wouldn’t go on forever.

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That’s because Mars also has super high
levels of bacteria-killing radiation that would finish the job.

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You’re probably familiar with UVA and UVB
radiation from sunscreen and sunglasses labels,

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but Mars also has an extra kind: UVC, which
has a shorter wavelength.

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Our atmosphere is capable of filtering out
all UVC radiation,

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so life on Earth isn’t great at dealing with it.

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UV-C is also especially deadly, because those
shorter wavelengths carry a lot more energy.

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So it would probably kill most of the surviving
microbes.

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So if someone died on Mars and there was no
way to recover the body, or turn it into a powder,

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it would probably become a mummy over
thousands of years.

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Admittedly, there is a chance some of those
bacteria could survive the UVC radiation,

212
00:12:42,840 --> 00:12:45,720
thanks to certain mechanisms that can repair
radiation damage.

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00:12:45,720 --> 00:12:48,470
If they did, they would probably decompose
the body over time.

214
00:12:48,470 --> 00:12:52,800
But then Mars would be home to a bunch of
radiation-resistant bacteria, which is a whole new problem.

215
00:12:52,800 --> 00:12:54,240
Or horror movie.

216
00:12:54,240 --> 00:12:58,860
And that’s probably why the United Nations
would require bodies to be sterilized or contained.

217
00:12:58,860 --> 00:13:05,240
Thinking about people dying on Mars isn’t
exactly something NASA or any other space agency really wants to do,

218
00:13:05,240 --> 00:13:08,120
but it’s an important
part of planning for the future.

219
00:13:08,120 --> 00:13:12,620
And even if it is a little morbid, the science
behind it is definitely worth thinking about.

220
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I love science so much.

221
00:13:15,320 --> 00:13:17,500
Okay, before we turn into Mars mummies, though,

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00:13:17,500 --> 00:13:22,300
there are other big picture ideas for how to potentially turn Mars into Earth 2.0.

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00:13:22,300 --> 00:13:25,620
Here’s Reid to talk about terraforming our
closest neighbor.

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00:13:27,400 --> 00:13:30,840
In some ways, Mars kinda sounds like a cool
place to live, doesn't it?

225
00:13:30,840 --> 00:13:33,660
The red soil, the craters, the dormant volcanoes.

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00:13:33,660 --> 00:13:34,860
Seems pretty scenic

227
00:13:34,860 --> 00:13:36,440
And, if you choose the right real estate,

228
00:13:36,440 --> 00:13:40,050
You could use one of the Viking Landers as,
like, a lawn ornament, or something.

229
00:13:40,050 --> 00:13:43,279
But, of course, you'd have to be okay with
temperatures around minus sixty,

230
00:13:43,279 --> 00:13:46,459
An unbreathable atmosphere, and deadly doses
of radiation

231
00:13:46,459 --> 00:13:48,859
Which, for most people, are kind of deal-breakers

232
00:13:48,860 --> 00:13:51,889
But, technology can do some fantastic stuff

233
00:13:51,889 --> 00:13:56,809
And scientists who study terraforming, the
science of transforming a planet to support human life,

234
00:13:56,809 --> 00:13:59,089
Have put a lot of thought into changing these
things

235
00:13:59,089 --> 00:14:01,460
Turns out, with a few centuries worth of effort,

236
00:14:01,460 --> 00:14:04,100
we might be able to make Mars habitable for humans

237
00:14:04,100 --> 00:14:07,519
But, I'm not gonna lie to you, it would be
really, really, hard.

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00:14:07,519 --> 00:14:09,850
A whole bunch of major things would have to
change

239
00:14:09,850 --> 00:14:13,100
Most importantly, Mars needs an Earth-like
atmosphere

240
00:14:13,100 --> 00:14:15,370
There are a few theories about how to create
one

241
00:14:15,370 --> 00:14:17,490
And they have a lot to do with the planet's
history

242
00:14:17,490 --> 00:14:22,269
In its younger days, about 4 billion years
ago, Mars was actually pretty similar to Earth

243
00:14:22,269 --> 00:14:25,100
It was warm, and wet, and had something of
an atmosphere.

244
00:14:25,100 --> 00:14:30,660
That's because the Martian soil absorbed a
lot of carbon dioxide and nitrogen that was floating around in the air

245
00:14:30,660 --> 00:14:35,360
But, then, active volcanoes recycled those
materials by baking them out of the soil

246
00:14:35,370 --> 00:14:37,120
So, they could be absorbed again

247
00:14:37,120 --> 00:14:40,160
The result of this was an atmosphere that
mostly stayed put

248
00:14:40,160 --> 00:14:44,060
Asteroids that kept hitting the planet helped
out too, keeping it nice and warm

249
00:14:44,060 --> 00:14:46,498
And, back then, Mars had a magnetosphere,

250
00:14:46,499 --> 00:14:51,319
A planetary magnetic field that protected
the atmosphere from being stripped away by solar winds

251
00:14:51,319 --> 00:14:53,930
But, then the planet cooled, and lost its
magnetosphere

252
00:14:53,930 --> 00:14:57,239
There were fewer asteroid collisions, and
its volcanoes stopped erupting

253
00:14:57,240 --> 00:15:01,290
Without all that help, Mars' surface absorbed
a lot of the compounds from its atmosphere

254
00:15:01,290 --> 00:15:04,300
And lost most of what was left to solar winds,

255
00:15:04,300 --> 00:15:06,740
leaving a freezing, dry, barren, world.

256
00:15:06,740 --> 00:15:08,270
Sounds pretty bleak, I know.

257
00:15:08,270 --> 00:15:10,519
But, given what we know about Mars' history,

258
00:15:10,519 --> 00:15:13,629
with a little tweaking, we might be able to
bring that atmosphere back.

259
00:15:13,629 --> 00:15:16,730
Basically, we need to start a massive global
warming effect

260
00:15:16,730 --> 00:15:19,029
Something that humans seem pretty good at

261
00:15:19,029 --> 00:15:21,589
And scientists have come up with three main
ways to do it.

262
00:15:21,589 --> 00:15:24,510
The first, and easiest, way might be to just
build factories.

263
00:15:24,510 --> 00:15:29,380
That would basically turn carbon, fluorine,
and sulfur in the Martian soil into greenhouse gasses

264
00:15:29,380 --> 00:15:31,040
and pump them into the atmosphere.

265
00:15:31,040 --> 00:15:34,980
This would unlock one of Mars' greatest assets
when it comes to warming things up:

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00:15:34,980 --> 00:15:39,649
The thick layer of dry ice, or frozen carbon
dioxide, that covers its south pole

267
00:15:39,649 --> 00:15:44,529
An initial burst of greenhouse gasses could
cause this ice to sublime directly into vapor

268
00:15:44,529 --> 00:15:48,649
Releasing carbon dioxide gas that would help
trap more heat from the sun

269
00:15:48,649 --> 00:15:51,160
In turn, releasing more greenhouse gasses

270
00:15:51,160 --> 00:15:52,719
But, all that would take a while,

271
00:15:52,720 --> 00:15:56,160
and it would be tough to supply those factories with the resources they'd need.

272
00:15:56,160 --> 00:16:01,180
So, another method might be to build giant,
200-kilometer wide mirrors in space

273
00:16:01,189 --> 00:16:03,569
They'd reflect sunlight onto the Martian icecaps,

274
00:16:03,569 --> 00:16:06,809
raising the surface temperature and releasing
that carbon dioxide.

275
00:16:06,809 --> 00:16:11,719
If neither of those ideas worked, there's
always the possibility of bombarding the planet with asteroids.

276
00:16:11,720 --> 00:16:15,340
In this scenario, we'd capture asteroids on
the edge of the solar system,

277
00:16:15,350 --> 00:16:17,980
and use rocket engines to propel them into
Mars

278
00:16:17,980 --> 00:16:21,300
The ammonia in the asteroids would act as
a greenhouse gas

279
00:16:21,300 --> 00:16:25,109
But, each asteroid would be like a 70,000
megaton hydrogen bomb

280
00:16:25,110 --> 00:16:27,850
So, aside from the obvious logistic problems,

281
00:16:27,850 --> 00:16:31,240
we'd have to do this way before humans were
ready to set up shop there.

282
00:16:31,240 --> 00:16:35,029
And, even then, once the atmosphere had some
greenhouse gasses in place,

283
00:16:35,029 --> 00:16:36,649
It would still need an ozone layer,

284
00:16:36,649 --> 00:16:41,600
A shroud of molecular oxygen that would absorb
some of the sun's dangerous ultraviolet radiation

285
00:16:41,600 --> 00:16:43,860
So, there would have to be, yet another, step

286
00:16:43,860 --> 00:16:47,939
Where we introduce organisms like cyanobacteria
or lichens,

287
00:16:47,939 --> 00:16:52,329
Which would help enrich the soil and release
oxygen, that could eventually form ozone

288
00:16:52,329 --> 00:16:57,239
Once the ozone layer was in place, the final
ingredient for an Earth-like atmosphere could be added:

289
00:16:57,240 --> 00:16:58,000
Nitrogen

290
00:16:58,000 --> 00:17:00,260
This could be introduced by asteroid bombardments,

291
00:17:00,260 --> 00:17:05,180
Or bacteria could extract it from the nitrogen-baring
compounds locked in the regolith,

292
00:17:05,180 --> 00:17:07,670
The rock layer just above the Martian bedrock

293
00:17:07,670 --> 00:17:08,670
Easy-peasy.

294
00:17:08,670 --> 00:17:09,740
Mission accomplished, right?

295
00:17:09,740 --> 00:17:10,280
No.

296
00:17:10,280 --> 00:17:11,139
Not quite

297
00:17:11,140 --> 00:17:13,760
Mars would also need a way to hold on to its
atmosphere

298
00:17:13,770 --> 00:17:16,349
And keep it from being stripped away by solar
winds

299
00:17:16,349 --> 00:17:18,799
Basically, it needs to get its magnetosphere
back

300
00:17:18,799 --> 00:17:21,199
Which is the biggest problem with terraforming

301
00:17:21,199 --> 00:17:23,350
Because we really don't know how to do that
yet

302
00:17:23,349 --> 00:17:27,539
Earth has a magnetosphere which we're pretty
sure is formed by liquid metals in the core

303
00:17:27,539 --> 00:17:32,020
That create an electromagnetic field as they
slosh around when the planet rotates

304
00:17:32,020 --> 00:17:36,240
The same effect would happen on Mars if we
could only figure out how to melt its core,

305
00:17:36,240 --> 00:17:38,419
Which appears to be solid metal, not liquid

306
00:17:38,420 --> 00:17:43,160
So, if anyone has any suggestions on how to
liquify the middle of Mars, we're all ears

307
00:17:44,660 --> 00:17:49,520
As Reid mentioned, a magnetic field is pretty
big deal for humans… and our DNA.

308
00:17:49,520 --> 00:17:51,920
So, could we give Mars a magnetic field?

309
00:17:53,820 --> 00:17:56,780
There’s been a lot of talk lately about
sending humans to live on Mars.

310
00:17:56,860 --> 00:18:00,678
But it’s easy to say that and a lot harder
to actually do it.

311
00:18:00,680 --> 00:18:04,260
A big part of that is because Mars … isn’t
especially friendly to human life.

312
00:18:04,260 --> 00:18:05,780
Or life at all.

313
00:18:05,780 --> 00:18:10,600
It’s freezing, with a super thin atmosphere
that not only makes it impossible to breathe,

314
00:18:10,600 --> 00:18:14,419
but also doesn’t give you much protection
from all the deadly radiation coming from space.

315
00:18:14,420 --> 00:18:16,660
To change that, we’d have to terraform Mars,

316
00:18:16,660 --> 00:18:19,520
changing its geology and climate to be more like Earth.

317
00:18:19,520 --> 00:18:23,340
Which is usually a subject more appropriate
for sci-fi than science.

318
00:18:23,340 --> 00:18:27,580
But at the Planetary Science Vision 2050 Workshop
in early 2017,

319
00:18:27,580 --> 00:18:33,220
a group of scientists led by the head of NASA’s Planetary Science Division suggested a way we might get started.

320
00:18:33,220 --> 00:18:34,080
Their plan?

321
00:18:34,080 --> 00:18:37,340
Build a giant force field, a protective magnetic
field, for the planet.

322
00:18:37,350 --> 00:18:41,230
And as weird and impossible as that sounds,
it’s not totally science fiction.

323
00:18:41,230 --> 00:18:45,220
The idea is that this magnetic field would
replace the one Mars lost long ago,

324
00:18:45,220 --> 00:18:47,780
which would then let the planet build up a thicker
atmosphere.

325
00:18:47,780 --> 00:18:50,920
Billions of years ago, Mars might have looked
a lot like modern-day Earth,

326
00:18:50,920 --> 00:18:56,560
with a magnetic field, a warm atmosphere, and oceans on the surface with about as much water as our Arctic Ocean.

327
00:18:56,560 --> 00:19:02,379
But for reasons scientists still don’t fully
understand, Mars lost its magnetic field about 4.2 billion years ago.

328
00:19:02,380 --> 00:19:04,160
And everything kinda went downhill after that.

329
00:19:04,160 --> 00:19:09,120
Without a magnetic field to block the charged
particles streaming from the Sun, aka the solar wind,

330
00:19:09,120 --> 00:19:13,590
much of the Martian atmosphere got stripped away over the course of about 500 million years.

331
00:19:13,590 --> 00:19:18,809
Without a thick atmosphere to trap heat, the
planet froze and its oceans were lost forever.

332
00:19:18,809 --> 00:19:21,350
Unless we can find a way to bring them back,
that is.

333
00:19:21,350 --> 00:19:24,520
Even today, four billion years later and with
barely any left,

334
00:19:24,520 --> 00:19:27,960
Mars can lose up to a kilogram of atmosphere to space every second.

335
00:19:27,960 --> 00:19:31,270
We’ll never get back all the stuff that’s
escaped into space already,

336
00:19:31,270 --> 00:19:36,800
but there’s still gas leaking out of the planet’s crust,
so there’s at least some hope of building it back up.

337
00:19:36,800 --> 00:19:40,320
If we could, that would provide more protection
against the radiation,

338
00:19:40,320 --> 00:19:41,840
plus help warm the planet a bit.

339
00:19:41,840 --> 00:19:47,939
Astronomers also think there might be enough
water trapped in the polar ice caps to rebuild about a seventh of the ancient oceans,

340
00:19:47,940 --> 00:19:50,840
if we can get the climate warm enough for the ice to melt.

341
00:19:50,840 --> 00:19:52,800
But first we have to get the atmosphere back,

342
00:19:52,800 --> 00:19:54,860
and that’s where this NASA team’s big idea comes in.

343
00:19:54,860 --> 00:19:58,100
If we could block the solar wind from stripping
away the atmosphere,

344
00:19:58,100 --> 00:19:59,719
it might start to build up again.

345
00:19:59,720 --> 00:20:03,480
At first, that might sound like it involves
building something the size of a planet.

346
00:20:03,490 --> 00:20:05,059
And that’s … not super practical.

347
00:20:05,060 --> 00:20:07,980
But the researchers proposed a way to get
around the problem:

348
00:20:07,980 --> 00:20:12,580
by taking advantage of the fact that the solar wind is only coming from one direction, the Sun.

349
00:20:12,580 --> 00:20:17,960
So all we’d need to do is block the Sun,
kind of like what the Moon does during an eclipse.

350
00:20:17,960 --> 00:20:23,180
Which, yeah, would still require a huge shield,
but we wouldn’t have to build a giant solid thing,

351
00:20:23,180 --> 00:20:24,780
it would just be a magnetic field.

352
00:20:24,800 --> 00:20:26,500
And that might actually be practical someday.

353
00:20:26,500 --> 00:20:29,260
All we’d have to do is figure out how to
generate the field.

354
00:20:29,260 --> 00:20:31,400
Then it would reach out into space and do
the rest.

355
00:20:31,400 --> 00:20:36,360
More specifically, the team suggested putting a field-generating device about a million kilometers from Mars.

356
00:20:36,360 --> 00:20:41,320
The magnetic field would have to be a bit
stronger than the Earth’s, which would be hard on such a large scale,

357
00:20:41,320 --> 00:20:43,620
but it’s something
we could probably figure out how to do.

358
00:20:43,620 --> 00:20:47,299
To understand what that would do to Mars,
the researchers followed a two-step process.

359
00:20:47,300 --> 00:20:51,960
First, they used computer simulations to calculate
what a magnetic shield would do to the atmosphere.

360
00:20:51,960 --> 00:20:55,950
Then, they used climate models to predict
what effects those changes would have.

361
00:20:55,950 --> 00:20:58,800
The results suggested that Mars’s climate
would change a bit,

362
00:20:58,800 --> 00:21:00,740
but that we shouldn’t get our hopes up too much.

363
00:21:00,740 --> 00:21:03,340
Although a strong enough field would stop
the solar wind,

364
00:21:03,340 --> 00:21:07,159
that’s only one of the processes making Mars lose its atmosphere.

365
00:21:07,160 --> 00:21:11,340
The planet’s weak gravity and molecular
interactions with sunlight also contribute.

366
00:21:11,340 --> 00:21:13,139
In a process called photoionization,

367
00:21:13,140 --> 00:21:18,020
atoms and molecules in the upper atmosphere can absorb energy from light and break apart.

368
00:21:18,020 --> 00:21:23,240
Some of those pieces end up with enough energy
to break free of Mars’s gravity and escape to space,

369
00:21:23,240 --> 00:21:25,720
which is not good if you’re
trying to keep the atmosphere around!

370
00:21:25,720 --> 00:21:29,820
And although the global temperature would
rise, this would mostly happen near the equator,

371
00:21:29,820 --> 00:21:31,159
which is not where the ice is.

372
00:21:31,160 --> 00:21:33,600
In fact, because of the way atmospheric physics
works,

373
00:21:33,600 --> 00:21:36,179
it might even get colder at the poles than it is now.

374
00:21:36,180 --> 00:21:39,880
That would keep all the dry ice, which is
made up of solid carbon dioxide,

375
00:21:39,880 --> 00:21:44,080
trapped in the polar ice caps instead of vaporizing it
into gas that would thicken the atmosphere.

376
00:21:44,090 --> 00:21:48,668
Plus, that dry ice is sitting on top of the
water ice needed to refresh the global oceans.

377
00:21:48,669 --> 00:21:52,419
And even if the shield was enough to thicken
the atmosphere and bring back the oceans,

378
00:21:52,420 --> 00:21:53,700
it would take a while.

379
00:21:53,700 --> 00:21:56,400
Like, the researchers didn’t even have an
estimate of how long.

380
00:21:56,400 --> 00:22:00,200
So I wouldn’t count on taking a boat down
Valles Marineris anytime soon.

381
00:22:00,200 --> 00:22:04,980
But the idea is intriguing, because unlike
many other terraforming ideas,

382
00:22:04,980 --> 00:22:07,420
the technology seems pretty doable.

383
00:22:07,420 --> 00:22:11,320
MRI machines use fields even stronger than
what this research calls for;

384
00:22:11,320 --> 00:22:15,780
we just need to figure out how to make a field of the right shape and size.

385
00:22:15,780 --> 00:22:16,860
And get it into space.

386
00:22:16,860 --> 00:22:19,240
And the idea of putting something between
the Sun and Mars

387
00:22:19,240 --> 00:22:22,660
isn’t that different from some proposals for dealing with climate change here on Earth.

388
00:22:22,660 --> 00:22:24,460
For example, some scientists have suggested

389
00:22:24,460 --> 00:22:28,520
that one day we might be able to launch what would basically be a giant pair of sunglasses

390
00:22:28,520 --> 00:22:30,960
to block some of the Sun’s rays and cool the planet.

391
00:22:30,960 --> 00:22:35,240
But before we give Mars its very own Hylian shield, there’s another question that needs to be answered:

392
00:22:35,240 --> 00:22:37,730
even if we can do this, should
we?

393
00:22:37,730 --> 00:22:40,000
There’s a lot we still don’t know about
our planetary neighbor,

394
00:22:40,000 --> 00:22:43,220
and we still haven’t completely ruled out the possibility of alien life over there.

395
00:22:43,220 --> 00:22:46,660
If there is life on Mars and we totally transformed
the planet like this,

396
00:22:46,660 --> 00:22:48,640
we’d basically be destroying its habitat.

397
00:22:48,640 --> 00:22:52,120
But with no immediate plans to actually give
Mars a magnetic shield,

398
00:22:52,120 --> 00:22:55,360
hopefully we have plenty of time to work those questions out.

399
00:22:56,660 --> 00:22:59,580
All this talk about Mars is making me kinda miss
Earth.

400
00:22:59,580 --> 00:23:02,949
Luckily, we can learn a lot about Mars right
here at home.

401
00:23:02,950 --> 00:23:07,400
Here’s Reid again to talk about what studying
Earth can tell us about life on Mars.

402
00:23:09,400 --> 00:23:14,320
Mars is a pretty astounding planet, and our
missions to Mars have been making fascinating

403
00:23:14,320 --> 00:23:16,620
and ground-breaking discoveries for decades
now.

404
00:23:16,620 --> 00:23:20,659
But some of the coolest Mars research isn’t
actually conducted on Mars.

405
00:23:20,660 --> 00:23:24,540
It’s done here on Earth, in environments
that are a lot like Mars,

406
00:23:24,540 --> 00:23:28,200
either as it is now, or as it was billions of years ago.

407
00:23:28,200 --> 00:23:30,540
They’re called terrestrial analogues.

408
00:23:30,540 --> 00:23:32,240
And the research done in these environments

409
00:23:32,240 --> 00:23:37,460
has changed the way we think about life on Earth, Mars, and rocky planets in general.

410
00:23:37,470 --> 00:23:40,740
There are a couple main reasons to study terrestrial
analogues for Mars.

411
00:23:40,740 --> 00:23:43,799
One is that it’s a practical approach to
space research.

412
00:23:43,799 --> 00:23:48,418
It’s difficult and expensive to get to Mars,
and we’re already here on Earth for free.

413
00:23:48,420 --> 00:23:53,640
And we have way too many questions about Mars
to be able to answer all of them with just the tools we have over there.

414
00:23:53,640 --> 00:23:58,900
So doing Mars-related research on Earth lets
us learn more about both Mars and Earth

415
00:23:58,900 --> 00:24:02,519
than we would if we only did our Mars research
on Mars.

416
00:24:02,520 --> 00:24:07,180
Another reason is that the best way to solve
some Martian mysteries is to compare Mars to Earth.

417
00:24:07,180 --> 00:24:11,420
One of the biggest questions when it comes
to Mars is whether it ever harbored life.

418
00:24:11,420 --> 00:24:14,900
And looking for life in places on Earth that
resemble Mars

419
00:24:14,900 --> 00:24:19,780
can give us a better idea of what kinds of adaptations life might have developed to survive on Mars,

420
00:24:19,780 --> 00:24:21,480
if it ever did evolve there.

421
00:24:21,480 --> 00:24:27,320
Knowing more about where life can theoretically
survive could also help us figure out where to look for signs of life on Mars.

422
00:24:27,320 --> 00:24:30,700
So, some of the best analogues for Mars here
on Earth are useful

423
00:24:30,700 --> 00:24:34,140
not just because of the insight they give us into Mars as a planet,

424
00:24:34,140 --> 00:24:38,799
but because of the insight they give us into Mars as a potentially habitable planet.

425
00:24:38,799 --> 00:24:41,149
Like the Naica mines in Mexico, for instance.

426
00:24:41,149 --> 00:24:45,719
The Naica mines and caves are probably similar
to underground environments on Mars,

427
00:24:45,720 --> 00:24:50,240
which we know exist, but haven’t been able to
explore because it’s super dangerous to

428
00:24:50,240 --> 00:24:52,399
send a rover underground on another planet.

429
00:24:52,400 --> 00:24:58,160
The caves at Naica are probably especially
similar to what it would have looked like underground on early Mars,

430
00:24:58,160 --> 00:25:00,360
when the planet
was much wetter and warmer.

431
00:25:00,360 --> 00:25:03,159
Like most mines, the Naica mines are deep
underground,

432
00:25:03,160 --> 00:25:07,040
but unlike most mines, 
they’re ridiculously hot and humid.

433
00:25:07,040 --> 00:25:09,659
Like, lethally hot and humid.

434
00:25:09,660 --> 00:25:11,940
Researchers have to take tons of precautions,

435
00:25:11,940 --> 00:25:16,280
including wearing special “ice suits” with oxygen supplies, to make sure they don’t die.

436
00:25:16,280 --> 00:25:19,379
The mines also happen to be incredibly beautiful,

437
00:25:19,380 --> 00:25:25,120
home to huge caverns containing massive gypsum crystals that dwarf elephants, let alone people.

438
00:25:25,120 --> 00:25:29,919
And from experiments started around 2009,
researchers discovered something incredible:

439
00:25:29,920 --> 00:25:33,660
there were dormant microbes in fluid inclusions
in the crystals,

440
00:25:33,660 --> 00:25:37,919
basically tiny little pockets of water that form in a crystal as it grows.

441
00:25:37,919 --> 00:25:41,030
And the researchers were able to revive them!

442
00:25:41,030 --> 00:25:44,980
That tells us two things: first, that if life
ever evolved on Mars,

443
00:25:44,980 --> 00:25:48,140
it might have been able to survive in similar cave environments;

444
00:25:48,140 --> 00:25:53,500
and second, that those are really good places to check for signs of life, past or present.

445
00:25:53,500 --> 00:25:57,740
This strategy of surviving in rock is really
weird, but super useful.

446
00:25:57,740 --> 00:26:04,300
And a similar strategy has been taken up by
the microbes living in another place on Earth that’s a great analogue for Mars:

447
00:26:04,300 --> 00:26:06,800
the McMurdo
Dry Valleys in Antarctica.

448
00:26:06,800 --> 00:26:11,620
The Dry Valleys are basically the opposite
of the Naica mines: they’re super cold deserts,

449
00:26:11,620 --> 00:26:14,959
and they’re a lot like the dry, freezing
lowlands of the Martian north pole.

450
00:26:14,960 --> 00:26:21,500
Researchers working on projects for places
like NASA use the Dry Valleys as a place to test equipment destined for Mars,

451
00:26:21,500 --> 00:26:26,320
and astrobiologists
use them to explore Mars’s potential for habitability.

452
00:26:26,320 --> 00:26:30,159
Because even though the Dry Valleys are really
cold and dry,

453
00:26:30,160 --> 00:26:34,140
scientists have discovered a few forms of life that manage to live there.

454
00:26:34,140 --> 00:26:38,280
And some of them have adopted a similar strategy
to the life in Naica,

455
00:26:38,280 --> 00:26:40,879
despite the huge difference between their habitats.

456
00:26:40,880 --> 00:26:45,300
There are endolithic phototrophs in some of
the rocks at the Dry Valleys.

457
00:26:45,300 --> 00:26:50,440
Endolithic means “inside rock,” and phototrophs
use photosynthesis.

458
00:26:50,440 --> 00:26:56,380
And that’s what these organisms do: they
live inside rock, but they still use photosynthesis.

459
00:26:56,380 --> 00:27:01,640
The rocks containing the endoliths are mostly
sandstone, which can transmit some light through it.

460
00:27:01,640 --> 00:27:08,020
So the microbes inside the rock are still
able to photosynthesize even though they’re not directly exposed to sunlight,

461
00:27:08,020 --> 00:27:12,300
and they get a nice little rocky home to protect them from the harsh Antarctic desert.

462
00:27:12,300 --> 00:27:18,830
Both Naica and the Dry Valleys host life that
has taken an approach to survival that could be outstanding on Mars.

463
00:27:18,830 --> 00:27:22,679
Since Mars doesn’t have much of an atmosphere
and has no magnetic field,

464
00:27:22,680 --> 00:27:25,500
its surface is constantly bombarded by UV light.

465
00:27:25,500 --> 00:27:29,360
If potential life on Mars lived inside rock
or underground,

466
00:27:29,360 --> 00:27:34,979
that might be enough shielding from radiation for them to have survived for a good while during Mars’s early history.

467
00:27:34,980 --> 00:27:39,160
And the neat thing about these strategies,
especially the endolithic strategy,

468
00:27:39,160 --> 00:27:42,500
is that it can work anywhere you have the right kind
of rock.

469
00:27:42,500 --> 00:27:47,560
This could work just as well at Mars’s north
pole as it could in its southern highlands,

470
00:27:47,560 --> 00:27:49,659
as long as the rock is transparent enough.

471
00:27:49,660 --> 00:27:54,560
So, these discoveries have given us a window
into Mars, and we didn’t even have to leave Earth!

472
00:27:54,560 --> 00:27:59,260
As we continue to explore beyond our solar
system and find rocky exoplanets,

473
00:27:59,260 --> 00:28:01,940
this research becomes even more important.

474
00:28:01,940 --> 00:28:06,700
It helps us define what it means to be habitable
for all planets, not just our own.

475
00:28:06,700 --> 00:28:11,250
And a bunch of little underground microbes
just gave me an existential crisis.

476
00:28:12,740 --> 00:28:13,800
Earth is so...awesome.

477
00:28:13,800 --> 00:28:15,340
And so is Mars!

478
00:28:15,340 --> 00:28:17,399
Thanks for learning about our neighbor planet
with me.

479
00:28:17,400 --> 00:28:20,020
If you want to keep up to date on all the
latest Mars news,

480
00:28:20,020 --> 00:28:23,800
be sure to go to YouTube.com/SciShowSpace
and subscribe.

481
00:28:23,800 --> 00:28:27,720
And if you listen to Hank and his brother
John’s podcast, Dear Hank & John,

482
00:28:27,720 --> 00:28:31,480
you'll get a little snippet from Hank every week
about the news from Mars.

483
00:28:31,480 --> 00:28:34,520
You can listen to that wherever you prefer
to get your podcasts.

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00:28:34,520 --> 00:28:44,560
[ ♪ Outro ]