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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.

  • Here's Reid to talk about terraforming our closest neighbor.

  • In some ways, Mars kinda sounds like a cool place to live, doesn't it?

  • The red soil, the craters, the dormant volcanoes.

  • Seems pretty scenic

  • And, if you choose the right real estate,

  • You could use one of the Viking Landers as, like, a lawn ornament, or something.

  • But, of course, you'd have to be okay with temperatures around minus sixty,

  • An unbreathable atmosphere, and deadly doses of radiation

  • Which, for most people, are kind of deal-breakers

  • But, technology can do some fantastic stuff

  • And scientists who study terraforming, the science of transforming a planet to support human life,

  • Have put a lot of thought into changing these things

  • Turns out, with a few centuries worth of effort,

  • we might be able to make Mars habitable for humans

  • But, I'm not gonna lie to you, it would be really, really, hard.

  • A whole bunch of major things would have to change

  • Most importantly, Mars needs an Earth-like atmosphere

  • There are a few theories about how to create one

  • And they have a lot to do with the planet's history

  • In its younger days, about 4 billion years ago, Mars was actually pretty similar to Earth

  • It was warm, and wet, and had something of an atmosphere.

  • That's because the Martian soil absorbed a lot of carbon dioxide and nitrogen that was floating around in the air

  • But, then, active volcanoes recycled those materials by baking them out of the soil

  • So, they could be absorbed again

  • The result of this was an atmosphere that mostly stayed put

  • Asteroids that kept hitting the planet helped out too, keeping it nice and warm

  • And, back then, Mars had a magnetosphere,

  • A planetary magnetic field that protected the atmosphere from being stripped away by solar winds

  • But, then the planet cooled, and lost its magnetosphere

  • There were fewer asteroid collisions, and its volcanoes stopped erupting

  • Without all that help, Mars' surface absorbed a lot of the compounds from its atmosphere

  • And lost most of what was left to solar winds,

  • leaving a freezing, dry, barren, world.

  • Sounds pretty bleak, I know.

  • But, given what we know about Mars' history,

  • with a little tweaking, we might be able to bring that atmosphere back.

  • Basically, we need to start a massive global warming effect

  • Something that humans seem pretty good at

  • And scientists have come up with three main ways to do it.

  • The first, and easiest, way might be to just build factories.

  • That would basically turn carbon, fluorine, and sulfur in the Martian soil into greenhouse gasses

  • and pump them into the atmosphere.

  • This would unlock one of Mars' greatest assets when it comes to warming things up:

  • The thick layer of dry ice, or frozen carbon dioxide, that covers its south pole

  • An initial burst of greenhouse gasses could cause this ice to sublime directly into vapor

  • Releasing carbon dioxide gas that would help trap more heat from the sun

  • In turn, releasing more greenhouse gasses

  • But, all that would take a while,

  • and it would be tough to supply those factories with the resources they'd need.

  • So, another method might be to build giant, 200-kilometer wide mirrors in space

  • They'd reflect sunlight onto the Martian icecaps,

  • raising the surface temperature and releasing that carbon dioxide.

  • If neither of those ideas worked, there's always the possibility of bombarding the planet with asteroids.

  • In this scenario, we'd capture asteroids on the edge of the solar system,

  • and use rocket engines to propel them into Mars

  • The ammonia in the asteroids would act as a greenhouse gas

  • But, each asteroid would be like a 70,000 megaton hydrogen bomb

  • So, aside from the obvious logistic problems,

  • we'd have to do this way before humans were ready to set up shop there.

  • And, even then, once the atmosphere had some greenhouse gasses in place,

  • It would still need an ozone layer,

  • A shroud of molecular oxygen that would absorb some of the sun's dangerous ultraviolet radiation

  • So, there would have to be, yet another, step

  • Where we introduce organisms like cyanobacteria or lichens,

  • Which would help enrich the soil and release oxygen, that could eventually form ozone

  • Once the ozone layer was in place, the final ingredient for an Earth-like atmosphere could be added:

  • Nitrogen

  • This could be introduced by asteroid bombardments,

  • Or bacteria could extract it from the nitrogen-baring compounds locked in the regolith,

  • The rock layer just above the Martian bedrock

  • Easy-peasy.

  • Mission accomplished, right?

  • No.

  • Not quite

  • Mars would also need a way to hold on to its atmosphere

  • And keep it from being stripped away by solar winds

  • Basically, it needs to get its magnetosphere back

  • Which is the biggest problem with terraforming

  • Because we really don't know how to do that yet

  • Earth has a magnetosphere which we're pretty sure is formed by liquid metals in the core

  • That create an electromagnetic field as they slosh around when the planet rotates

  • The same effect would happen on Mars if we could only figure out how to melt its core,

  • Which appears to be solid metal, not liquid

  • So, if anyone has any suggestions on how to liquify the middle of Mars, we're all ears

  • As Reid mentioned, a magnetic field is pretty big deal for humansand our DNA.

  • So, could we give Mars a magnetic field?

  • 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 field, for 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 Sun, aka the solar wind,

  • much 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 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 direction, the Sun.

  • So all we'd need to do is block 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 thing,

  • it 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 space,

  • which 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 seems pretty 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.

  • All this talk about Mars is making me kinda miss Earth.

  • Luckily, we can learn a lot about Mars right here at home.

  • Here's Reid again to talk about what studying Earth can tell us about life on Mars.

  • Mars is a pretty astounding planet, and our missions to Mars have been making fascinating

  • and ground-breaking discoveries for decades now.

  • But some of the coolest Mars research isn't actually conducted on Mars.

  • It's done here on Earth, in environments that are a lot like Mars,

  • either as it is now, or as it was billions of years ago.

  • They're called terrestrial analogues.

  • And the research done in these environments

  • has changed the way we think about life on Earth, Mars, and rocky planets in general.

  • There are a couple main reasons to study terrestrial analogues for Mars.

  • One is that it's a practical approach to space research.

  • It's difficult and expensive to get to Mars, and we're already here on Earth for free.

  • 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.

  • So doing Mars-related research on Earth lets us learn more about both Mars and Earth

  • than we would if we only did our Mars research on Mars.

  • Another reason is that the best way to solve some Martian mysteries is to compare Mars to Earth.

  • One of the biggest questions when it comes to Mars is whether it ever harbored life.

  • And looking for life in places on Earth that resemble Mars

  • can give us a better idea of what kinds of adaptations life might have developed to survive on Mars,

  • if it ever did evolve there.

  • Knowing more about where life can theoretically survive could also help us figure out where to look for signs of life on Mars.

  • So, some of the best analogues for Mars here on Earth are useful

  • not just because of the insight they give us into Mars as a planet,

  • but because of the insight they give us into Mars as a potentially habitable planet.

  • Like the Naica mines in Mexico, for instance.

  • The Naica mines and caves are probably similar to underground environments on Mars,

  • which we know exist, but haven't been able to explore because it's super dangerous to

  • send a rover underground on another planet.

  • The caves at Naica are probably especially similar to what it would have looked like underground on early Mars,

  • when the planet was much wetter and warmer.

  • Like most mines, the Naica mines are deep underground,

  • but unlike most mines, they're ridiculously hot and humid.

  • Like, lethally hot and humid.

  • Researchers have to take tons of precautions,

  • including wearing specialice suitswith oxygen supplies, to make sure they don't die.

  • The mines also happen to be incredibly beautiful,

  • home to huge caverns containing massive gypsum crystals that dwarf elephants, let alone people.

  • And from experiments started around 2009, researchers discovered something incredible:

  • there were dormant microbes in fluid inclusions in the crystals,

  • basically tiny little pockets of water that form in a crystal as it grows.

  • And the researchers were able to revive them!

  • That tells us two things: first, that if life ever evolved on Mars,

  • it might have been able to survive in similar cave environments;

  • and second, that those are really good places to check for signs of life, past or present.

  • This strategy of surviving in rock is really weird, but super useful.

  • And a similar strategy has been taken up by the microbes living in another place on Earth that's a great analogue for Mars:

  • the McMurdo Dry Valleys in Antarctica.

  • The Dry Valleys are basically the opposite of the Naica mines: they're super cold deserts,

  • and they're a lot like the dry, freezing lowlands of the Martian north pole.

  • Researchers working on projects for places like NASA use the Dry Valleys as a place to test equipment destined for Mars,

  • and astrobiologists use them to explore Mars's potential for habitability.

  • Because even though the Dry Valleys are really cold and dry,

  • scientists have discovered a few forms of life that manage to live there.

  • And some of them have adopted a similar strategy to the life in Naica,

  • despite the huge difference between their habitats.

  • There are endolithic phototrophs in some of the rocks at the Dry Valleys.

  • Endolithic meansinside rock,” and phototrophs use photosynthesis.

  • And that's what these organisms do: they live inside rock, but they still use photosynthesis.

  • The rocks containing the endoliths are mostly sandstone, which can transmit some light through it.

  • So the microbes inside the rock are still able to photosynthesize even though they're not directly exposed to sunlight,

  • and they get a nice little rocky home to protect them from the harsh Antarctic desert.

  • Both Naica and the Dry Valleys host life that has taken an approach to survival that could be outstanding on Mars.

  • Since Mars doesn't have much of an atmosphere and has no magnetic field,

  • its surface is constantly bombarded by UV light.

  • If potential life on Mars lived inside rock or underground,

  • that might be enough shielding from radiation for them to have survived for a good while during Mars's early history.

  • And the neat thing about these strategies, especially the endolithic strategy,

  • is that it can work anywhere you have the right kind of rock.

  • This could work just as well at Mars's north pole as it could in its southern highlands,

  • as long as the rock is transparent enough.

  • So, these discoveries have given us a window into Mars, and we didn't even have to leave Earth!

  • As we continue to explore beyond our solar system and find rocky exoplanets,

  • this research becomes even more important.

  • It helps us define what it means to be habitable for all planets, not just our own.

  • And a bunch of little underground microbes just gave me an existential crisis.

  • Earth is so...awesome.

  • And so is Mars!

  • Thanks for learning about our neighbor planet with me.

  • If you want to keep up to date on all the latest Mars news,

  • be sure to go to YouTube.com/SciShowSpace and subscribe.

  • And if you listen to Hank and his brother John's podcast, Dear Hank & John,

  • you'll get a little snippet from Hank every week about the news from Mars.

  • You can listen to that wherever you prefer to get your podcasts.

  • [ ♪ Outro ]

[ ♪ Intro ]

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