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MATTHEW O'DOWD: This episode is supported by Curiosity Stream.
There's been a lot of talk lately
about putting humans on Mars and even colonizing the red planet.
Is this even possible?
And what would that settlement actually look like?
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Mars is getting a lot of attention.
NASA's new budget mandates a 25-year timescale
for putting astronauts in orbit around Mars.
That's exciting.
But Elon Musk soon followed with a rather more
audacious announcement.
SpaceX plans a spacecraft capable of transporting
100 people at a time to Mars, not to visit, but to settle.
And it may be done in as little as 10 years.
The ultimate aim is for a completely self-sustaining
extraterrestrial colony of a million people
within several decades.
That's some ambition.
Here's the lowdown.
Musk announced this in an hour-long presentation
that was almost entirely about the vehicle.
First step-- a spaceship is launched into orbit by a rocket
booster.
The booster then returns to its launchpad
and is loaded with a giant fuel tank.
It relaunches and delivers to the orbiting
spaceship enough fuel for the four-month journey to Mars.
This is only feasible because of the reusability
of the components.
That means many return trips to Mars,
but it also allows the booster to carry
the spaceship and the fuel in separate launches.
As a result, the spaceship itself
can have a much bigger payload, translating to 100 passengers,
rather than, say, the four astronauts of NASA's
proposed Orion module.
Now, I could go into all of the details.
But honestly, you should just listen to
or read Musk's announcement.
Links below.
Is the vehicle actually possible?
Sure, probably.
Whether 10 years is remotely feasible is another matter.
That's the lower in the case that, as Musk puts it,
things go super well.
The plausibility of this may be governed by whether a Martian
colony could really work.
Musk says almost nothing about that,
so let's get into that today.
The vision is for a completely self-sufficient settlement.
Anything less would defeat the main point--
to be a safeguard against our extinction.
It needs to be able to thrive, even if Earth is lost.
it needs to mine, farm, process, and manufacture everything
it needs.
It also needs to be a place that people might actually
want to live.
What would that look like?
The initial habitats are going to be simple.
And in fact, the first landers probably
need to bring habitats with them.
That 450-ton cargo capacity of the spaceship will help there.
These may be inflatable, modular structures,
similar to those proposed by Mars One,
or like the Bigelow Expandable Activity Module,
BEAM, that's already in use on the International Space
Station.
An important advantage of prefabricating habitats
on Earth is that you can use advanced materials with better
radiation shielding.
Mars's thin atmosphere and lack of magnetic field
make shielding critical, especially
for a permanent settlement.
However, to protect against high-energy cosmic rays
and solar outbursts and from the micrometeorites that also pass
easily through Mars's thin atmosphere,
we really just need a very thick roof.
That means either living underground
or building dense shelters from local material.
Becoming Martian mole people may be the way to go.
For one thing, Mars does have lava tubes
that could be populated.
But with the advent of large-scale 3D printing,
it's possible to build these structures
on a planet's surface.
NASA's 3D-printed Habitat Challenge
produced some incredible concepts.
Some proposed harvesting the abundant iron and silica
from the Martian soil to print a variety of structures.
The winner, however was pretty unique--
a 3D-printed dome of ice, under which pressurized habitats
could be built. That's right.
We may end up living in Martian igloos.
The water we'd need for that is abundant as ice frozen
within the Martian surface.
That same water is really what makes
this whole endeavor possible.
We need it to drink, to grow food.
But H2O may also be the best supply
of oxygen for, well, breathing.
Mars's atmosphere is 96% CO2, and the rest equal parts
nitrogen and argon.
But scrubbed of CO2, that nitrogen-argon mix makes
a breathable buffer gas that we top up with 20% oxygen.
It's been tested on mice and crickets,
so I guess we're good to go.
Growing plants for food requires water and air, but also light.
So we need either transparent greenhouse enclosures
or artificially-illuminated hydroponic farms.
Modern hydroponic farms are proving vastly more productive
and require far less water than their dirt-based equivalents,
so that's a promising direction, especially because it's
hard to protect against radiation
with a transparent roof.
Also, those plants will help with oxygen production.
Of course, all of this requires energy,
and this may be the simplest part.
Giant solar arrays stretching across the Martian surface
are the obvious answer.
The one outstanding technical issue is the gravity.
Mars's gravity is 0.38 times that of Earth.
We know that astronauts lose around 2% of bone
mass per month in zero G. It's surely
less on the surface of Mars, but we just
don't know how serious this would be after many years.
To build a sustainable multigenerational civilization,
it may be necessary to simulate Earth gravity.
This is possible using a centrifuge, a rotating ring
that results in the feeling of an outward force,
a centrifugal force, with respect to the ring.
This has been proposed for artificial gravity
on long-term space missions, but it's also
possible on a planetary surface.
It would still involve a large rotating ring,
but with a sloped, slightly curved outer wall
so that the centrifugal and gravitational accelerations
work together to give you the right direction of down
on that surface.
To avoid annoying daily centrifuge visits, perhaps
in the long term, we'll will build entire centrifuge cities
levitating on superconducting magnetic rails
and rotating once every few minutes.
On the other hand, watching the entire sky rotate
that fast may be as bad for the stomach as 0.38 G
is for the bones.
We may want to keep that thick roof of rock or ice.
Martian cities are technically doable,
and people will certainly want to go.
200,000 signed up for the Mars One program.
Really, the feasibility of this is more
a question of economics.
Once we lose the inexorable driving
force that is Elon Musk, a Martian settlement
will have to be entirely self-sufficient or economically
productive enough to justify continued life
support from Earth.
Whether that could happen quickly enough
is the real question.
A lot of what we learn about living on Mars
will work elsewhere in the solar system, too.
In fact, the proposed spacecraft is
meant to be a general purpose solar system explorer.
Where would you go?
Mars will be fun, but we're really
holding out for those Venusian cloud cities
here at Space Time.
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Hey, guys.
Vsauce is doing an amazing series on Mars exploration
and colonization.
Jake at Vsauce 3 and I have chatted
a lot about what humanity's first experiences will
be like when we go to Mars.
Jake's take on this question will be coming out real soon.
The link will be right here when it does.
Keep your eye out for it.
Last week, we talked about the incredible, if speculative,
possibility that primordial black holes formed
in the insanely dense conditions right after the Big Bang
and that these might still be around today.
I want to address two big questions
that you had in the comments.
Several of you asked how to tell the difference
between a primordial black hole and a black hole
formed when a very massive star ends its life.
Well actually, a black hole is a black hole
is a black hole, regardless of how it formed
or what it formed from.
Even a black hole made entirely from light, a kugelblitz,
is the same thing as a black hole
formed from regular matter.
Black holes exhibit only three properties-- mass,
electric charge, and spin.
You can learn something about the formation of a black hole
from those properties.
Mass is one way to identify a primordial black hole
from a stellar black hole.
A star's core needs to be more massive than around three times
the mass of the sun in order to collapse into a black hole.
Otherwise, it becomes a neutron star.
However primordial black holes don't form from stars
and so aren't subject to this restriction.
They could in principle be any mass.
Also, if we find many PBH's spread
through the galaxy and even outside the galaxy,
their distribution may tell us that it was impossible for them
to have been produced by massive stars, which are rare,
as far as stars go.
A few of you also asked whether the supermassive black holes
that we find at the centers of galaxies
could be primordial black holes.
Well, the answer is yes.
But it's really hard to say for sure.
Those supermassive black holes started as much smaller seed
black holes.
Those seeds may have been from the very first generation
of supernovae, near the beginning of the universe.
However, they may also have been from PBH's from an even earlier
time.
Some scientists like that idea because we
see some pretty gigantic supermassive black holes
in the early universe, and it's quite tricky
to explain how they got that big if they grew from only
stellar mass black holes.
Very large primordial black holes may help explain this,
but there's no evidence for this idea.
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