Manned missions to Mars may seem like a long way away, as NASA currently has their eyes
set to get humans on Mars around the mid to late 2030s.
But in reality, this time scale is very small, because there are a number of hurdles to overcome
first, one of the most problematic being exposure to radiation in space.
So, how bad is the radiation in space and on Mars?
And what can we do about it?
Radiation can mean a lot of different things.
Light you are seeing now is a form of electromagnetic radiation.
Radiation is also heat emanating from your central heating system.
These are harmless or even beneficial to us humans.
But astronauts need to be aware of a number of different types of space radiation.
Types of radiation which can strip atoms from your body, alter your DNA, and give you acute
radiation sickness or even cause death.
The main culprit for the dangerous radiation in our Solar System is also our life giver,
the Sun.
It is constantly emitting light in many different frequencies and has a steady outflow of solar
wind, which is highly energised protons, electrons and alpha particles, or in other words sub-atomic
particles.
These particles and wavelengths can be dangerous to humans as it is, but every so often powerful
events occur on the Sun’s surface called solar flares and coronal mass ejections.
This is where, through a combination of factors, the Sun ejects billions of tons of highly
energised particles into space.
If a coronal mass ejection were to be aimed at an astronaut without much in the way of
protection, it would make them very sick.
However, while bad, this is not the biggest worry for scientists trying to overcome the
obstacle of space radiation.
There are particles hurtling through space which travel even faster than those ejected
from the Sun, known as Galactic Cosmic Rays.
These are particles which were ejected from extremely energetic events which could have
occurred millions of years ago, like a supernova.
They range from hydrogen atoms all the way to heavy elements like uranium that have had
their electrons stripped away, meaning just the nucleus of the atom remains.
These particles have been accelerated to almost the speed of light, they can pass through
an entire spaceship or body unimpeded, and any atoms they pass through will be ionised.
Luckily on Earth, we have a number of natural protections which shelter us from all this
radiation.
The Earth’s magnetic field is one, deflecting CMEs and some Galactic Cosmic Radiation around
the planet and to its poles, where it impacts the Earth’s ionosphere, producing beautiful
aurora.
This magnetic field also protects Earth’s atmosphere from being stripped away by the
Sun’s solar wind.
And it’s this atmosphere which protects us from any Galactic Cosmic Radiation that
got through the magnetic field, as these particles impact particles in the atmosphere before
they reach us on the ground.
So, how do scientists hope to protect future astronauts outside of the Earth’s magnetosphere
and atmosphere?
The first hurdle to overcome is the trip to Mars itself.
Astronauts would realistically need at least 100 days to get to Mars from Earth, meaning
they will be exposed to space radiation for that long.
Luckily, particles from solar flares and CMEs can almost all be shielded by the spacecraft’s
structure.
However, high energy waves and Galactic Cosmic Radiation can pass through the wall of a space
craft.
Recent rover missions to Mars measured how much radiation an astronaut would absorb en
route, about 0.66 sievert, or the equivalent of getting a full body CAT scan every 4-5
days.
In comparison, on Earth, we might expect to absorb 0.0025 sieverts during the same period
of time.
The thing that really prevents radiation from reaching you is putting a lot of mass in the
way.
However, simply adding more weight to the walls of the spaceship itself would make lift-off
prohibitively expensive.
So, one of the methods currently being experimented in NASA’s Orion capsule during periods of
particularly high radiation is to hide in a make-shift bunker, putting as many bags
of supplies around you as possible.
Interestingly, the best element for protecting against Galactic Cosmic Radiation is hydrogen,
so scientists are also experimenting with the idea of storing water in the walls of
the craft.
Another method currently being investigated that would also be useful on the surface of
Mars is to have spacesuits made of or at least lined with hydrogenated boron nitride nanotubes.
This substance is strong, but also contains hydrogen atoms which could protect astronauts
from radiation.
This material could even be used to make the structure of the spacecraft, as it is also
good at withstanding very high temperatures.
However, testing still needs to be done before it can be confirmed as a definite winner.
The last option currently being experimented with is building a forcefield within the spaceship,
kind of like a little replica of Earth’s magnetosphere.
However, while something like this can be built, it is not energy efficient enough to
have on a spaceship just yet.
But perhaps by the 2030s technology will have advanced enough for this to become a real
possibility.
So, let’s say that astronauts have arrived on Mars in the 2030s, will the radiation situation
get any better for them there?
A little, but not anywhere near like on Earth.
Mars has no magnetosphere, and a very thin atmosphere, meaning protection on the surface
is minimal, although it should be mentioned that the lower in altitude you go, the better
you will be protected.
Estimates put radiation exposure on the Martian surface at 0.64 millisieverts per day, which
is just over NASA’s acceptable radiation limit.
However, the plan is not just to dump astronauts on the surface.
One idea is that earlier missions could go to Mars to fabricate a base using Martian
regolith and 3D printing in preparation for any future manned missions.
Having the mass of Martian ground above any future settlement would protect the occupants
from radiation, especially from dangerous CMEs.
Should a CME come towards Mars, NASA’s fleet of Sun observing spacecraft would warn astronauts
outside the habitat to get inside with ample time to spare.
So, while perhaps we have a lot more testing to do, it does seem like there are some workarounds
in regards to space radiation.
With all of them in place, it might be that space radiation can be kept to a low enough
level to allow longer term human exploration outside of Earth’s magnetosphere.
Do you think mankind will ever be able to conquer space radiation?
And what do you think of our chances to eventually be able to colonise the solar system, or is
it all a pipe dream?
Is there an obstacle even more pressing than space radiation?
Let me know what you think in the comments!
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