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  • We spend a lot of time thinking about Mars.

  • Mostly about if it could someday support human life.

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

  • whether that's underground or in specialized habitats.

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

  • enough to make a whole compilation of videos about it!

  • 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.

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

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

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

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

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

  • But here's one question we have yet to answer.

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

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

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

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

  • Maybe 90 seconds if you're lucky.

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

  • Like Earth, Mercury and Venus, it's a rocky planet,

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

  • Which is nice.

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

  • Mars has only 38% of Earth's gravity.

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

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

  • But, seriously, that's the least of your problems.

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

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

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

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

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

  • Well, then there's the radiation problem.

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

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

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

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

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

  • But your biggest problem is the atmosphere itself.

  • The surface of Mars is not technically a vacuum,

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

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

  • with trace amounts of nitrogen, argon, and oxygen.

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

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

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

  • Contrary to what you may have heard,

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

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

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

  • which is going to be uncomfortable.

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

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

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

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

  • very quick and very severe form of the bends,

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

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

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

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

  • Got it.

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

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

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

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

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

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

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

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

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

  • The danger starts long before reaching the Martian surface.

  • Depending on exactly when and how our astronauts launch,

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

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

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

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

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

  • come from all over the galaxy.

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

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

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

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

  • we aren't exposed to most of these particles.

  • But things aren't the same in space.

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

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

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

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

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

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

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

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

  • and that would really add up over a lifetime.

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

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

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

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

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

  • Another option is tunneling underground to escape the radiation,

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

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

  • and growing food on Mars won't be a picnic.

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

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

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

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

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

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

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

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

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

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

  • Which is just a tad higher.

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

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

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

  • And that's a whole different problem.

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

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

  • settlers will need a reliable source of electricity.

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

  • but that could be a big mistake.

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

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

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

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

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

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

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

  • I don't know, breathe or see at night.

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

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

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

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

  • The thing is, there are a lot of problems,

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

  • But, hey.

  • People.

  • On Mars.

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

  • So humans living on Mars would be really cool.

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

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

  • but what happens to your body if you die there?

  • Someday, somebody's going to die on Mars.

  • Death is not fun to think about,

  • 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

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

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

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

  • because there are United Nations charters against contaminating other planets.

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

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

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

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

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

  • Fire will kill all those microbes,

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

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

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

  • In 2005, NASA contacted the Swedish company Promessa,

  • which specializes in environmentally-sound burials and cremations.

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

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

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

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

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

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

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

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

  • even if it's kinda creepy.

  • Still, liquid nitrogen doesn't always kill bacteria.

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

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

  • But it's at least an option.

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

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

  • the process would go a little differently.

  • For one, they'd technically be violating international law,

  • but there would be more immediate problems at that point.

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

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

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

  • with peaks reaching elevations of about 6000 meters.

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

  • It's a little like Mars.

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

  • and the Inca had a practice called capacocha.

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

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

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

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

  • so the bodies became natural mummies.

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

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

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

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

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

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

  • But the process wouldn't go on forever.

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

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

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

  • Our atmosphere is capable of filtering out all UVC radiation,

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

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

  • So it would probably kill most of the surviving microbes.

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

  • it would probably become a mummy over thousands of years.

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

  • thanks to certain mechanisms that can repair radiation damage.

  • If they did, they would probably decompose the body over time.

  • But then Mars would be home to a bunch of radiation-resistant bacteria, which is a whole new problem.

  • Or horror movie.

  • And that's probably why the United Nations would require bodies to be sterilized or contained.

  • Thinking about people dying on Mars isn't exactly something NASA or any other space agency really wants to do,

  • but it's an important part of planning for the future.

  • And even if it is a little morbid, the science behind it is definitely worth thinking about.

  • I love science so much.

  • Okay, before we turn into Mars mummies, though,

  • there are other big picture ideas for how to potentially turn Mars into Earth 2.0.