So Peter, you ask a really good question about radiation perhaps being a limiting factor
in human exploration.
And honestly this is something that people are working on very hard right now.
It is indeed a challenge.
The astronauts on the space station are actually fairly well-protected from radiation.
The earth has a liquid metal core that generates a strong magnetic field around the earth,
and amazingly the space station, which is about 200 miles above us, is still in that
protective magnetic field.
So when you’re just orbiting the earth on a space station the astronauts may get slightly
higher doses of radiation, but they’re actually fairly well-protected.
What happens if you go beyond the earth’s magnetic field though is that all of a sudden
you’re vulnerable to the radiation of space.
And specifically it’s our wonderful friend the sun—I mean none of us would be here
without the energy and the light of the sun, but the sun actually outputs a lot of high-energy
particles and these create high radiation levels anywhere where there isn’t a protected
magnetic field.
So for example, if you went to the moon, and in fact astronauts went to the moon in the
1960s and the 1970s, had there been a very powerful solar storm when the astronauts were
there it may have made them very sick and might have even killed them.
So in some sense it was good luck that when the astronauts were up on the moon not protected
by the earth’s magnetic field the sun was relatively quiet.
However, on a trip to Mars, which might take months (up to six months), you’re not going
to be able to rely just on good luck.
There will be solar activity.
There will be bursts of high-energy particles from the sun.
So how do you protect astronauts from that?
And we’re working on technology—In some cases it’s a special kind of sleeping bag
that you can get into and zip yourself up and have some protection, other ideas one
of the best protectors against radiation is water.
So if you have liquid water tanks on one side of your spacecraft you might be able to shelter
from a solar storm by putting the water tanks between you and the sun.
But if you’re actually going to be living and working in space for a long time, this
really is a problem.
If we were to send astronauts to Mars, for example, they wouldn’t be protected from
the radiation unless they could dig under the ground and actually build their habitats—even
just as much as ten feet down would be enough.
But that’s hard.
The Martian soil is very hard and rocky and not easy to dig through, and before you could
go there you’d have to send construction equipment to actually build all of these habitats.
So we understand that this is a problem.
It’s one of the things that is limiting our exploration of the solar system.
The robots that we build that go to Mars, like the Mars Rover or the spacecraft, there’s
one orbiting Jupiter, they have to be extremely protected and shielded from the radiation
of space.
In fact our mission to Jupiter right now is called Juno and the instruments are inside
a 700-pound box of almost pure titanium to protect it from the radiation around Jupiter.
Even with that protection we only expect the instruments to last about two years; the radiation
is that intense.
So you could not go to visit Jupiter in a spacecraft and just happily sit there and
watch this beautiful planet below you, you’d be dead in probably something like a day.
So this really is a difficulty in sending astronauts out to the surface of the moon,
to Mars, and if we ever do go, beyond.
So, what are some of the very, very long-range ideas?
Obviously we’re talking about shielding, about how we maybe could get astronauts protected
under the ground, but there’s even a stranger ideas that probably won’t come to fruition
for centuries even, but they’re still neat ideas.
We are observing some microorganisms that are very, very good at protecting themselves
from radiation.
And one of them is my personal favorite animal—I have like stuffed animal version of this.
It’s a tiny, tiny little microscopic animal called a water bear or a tardigrade.
And tardigrades are just little microscopic animals with six little arms and they live
on moss, all they do is suck nutrients off of moss.
That’s all they do.
But a single tardigrade could take radiation levels that would kill a herd of a hundred
elephants, this tiny little animal is almost completely resistant to radiation and its
DNA works in a really cool way.
Radiation breaks up DNA.
It’s one of the reasons you die when there’s a lot of radiation around, and somehow tardigrade’s
DNA knows how to heal itself right back up.
So we’re studying how tardigrade DNA works in the hopes that maybe some day we could
even repair radiation damage to human DNA.
There was a Star Trek episode, I remember, where Dr. McCoy gives people a shot to protect
them from radiation.
Could that someday happen?
Well maybe.
And we’re going to get there by starting to look at these microorganisms that are resistant
to radiation, figure out how they do it and—could we do that too?
Maybe.