- [Narrator] When it comes to colonizing new worlds,
Mars can be humanity's best option.
But the journey won't be like it was in the past
for pioneers like Magellan, Gagarin, and Neil Armstrong.
This new frontier would be the most extreme challenge yet.
It's not just learning how to survive on an alien planet
with less oxygen, a weaker gravitational pull,
and more harmful radiation.
It's enduring the changes that these extreme conditions
will have on the human body, manipulating it in ways
that we can only begin to imagine.
Even astronauts know that you don't have to spend
much time off earth to notice changes.
The lower gravity can kickstart
a whole list of physical alterations.
Just ask this guy.
Former NASA astronaut, Scott Kelly.
He lived for an entire year
on the International Space Station.
Without Earth's gravitational pull,
the zero gravity weakened his bones and muscles
and expanded the space between his vertebrae,
making him two inches taller.
Now, the zero gravity environment in space
is more extreme than on Mars.
However, these changes could still happen on smaller scales.
And if you compound them over hundreds of years
of tens of generations,
the results could be similar and even more pronounced.
Basically, humans will adapt to Mars' conditions
in one of two ways.
In the first few centuries,
our skeletons and muscles will likely shrink
and we'll become weaker versions
of our earthling counterparts.
This would almost certainly lead to shorter lifespans
and health complications.
Including neurological disorders if our skulls shrink
with the rest of us.
So to survive, we may over millennia,
actually undergo the opposite reaction.
Evolving stronger, more robust bodies
like the Tharks in Edgar Rice Burroughs' sci-fi novel,
A Princess of Mars.
Although, us having six arms and green skin is less likely.
In fact, some scientists think
we'd actually develop orange skin, not green.
It turns out, the carotenoids that make carrots,
sweet potatoes, and pumpkins look orange
offer a certain amount of protection
against harmful UV radiation.
When we eat these pigments in large amounts,
we actually get a boost of protective carotene
in our bloodstream and under our skin.
So yeah, eating too many carrots can turn you orange
but it may also be a great defense against cancer on Mars.
The planet's thin atmosphere lets in massive amounts
of UV and other high energy radiation compared to Earth.
For example, the average earthling
receives about three millisieverts of radiation
per year versus the 30 that they would get on Mars.
To compare, here's the minimum radiation dose
it takes to drastically increase your risk of cancer.
Add up the annual radiation levels on Mars over a lifetime
and the average martian would receive 5,000 times
more radiation than someone on Earth.
And our big orange bodies may not just look
different on the outside.
One of the most profound changes we could have coming
is the next species of human.
Higher levels of radiation on Mars' surface
would mutate the DNA in our cells at an accelerated pace.
Normally, a species like homo sapiens
could take a few hundred thousand years to evolve on Earth.
But some scientists say the higher mutation rate
could spawn new human species within centuries.
10 times faster than on Earth.
So, if the radiation didn't outright kill us,
the mutations that survive
will be passed down through generations.
Ultimately, diversifying the gene pool
and allowing natural selection to do its job.
As exciting as that may sound,
there is a potential downside to all of this.
If one day in the future,
a martian falls in love with an earthling,
it can only end in tragedy.
The immune systems of martians and earthlings
will be completely different.
A meeting between the two
could be just as deadly as when two foreign groups
have met in the past.
Like the European settlers who gave smallpox
to the Native Americans.
Also, depending on how genetically different they are,
even if they could meet,
they may not be able to have martian earthlings of their own
since only closely related species can reproduce.
Moving to Mars may be the best chance
for humanity's survival
but it may not be humans who live there in the end.