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.