nASA has a mission protocol which says
if a low Earth orbit mission increases
the lifetime risk of the crew getting
cancer by more than three percent then
they won't go ahead with it but the
upcoming Mars missions may expose the
crews to levels which will be beyond
that limits and to other hazards so how
dangerous is deep space travel to Mars
and beyond Ravel and musk pushing to get
men on to Mars by the mid-2020s and NASA
looking to do the same for the 2030s
just how much have we learned since
Apollo and from the space stations fifty
years on from the beginning of the
Apollo missions and we have yet to send
any man back to the moon let alone on
the much more arduous journey to our
nearest viable planet Mars now whilst
much of this has been down to the lack
of political will in the face of our own
man-made problems here on earth it's
also down to the increasing
sophistication of robotic probes and
Landers that are much cheaper to make
launch can go where no man could go and
can continue working for years at a time
the Voyager probes for example are still
going 40 years after their launch if we
relied upon man discovery only we would
know a fraction of what we know now
we've data from probes that we have sent
around the solar system since then we
have built up a picture which is far
from a vision of just whizzing through
interplanetary space that and along with
the joint NASA Russian experiment of
having men in space for a year from
board the International Space Station we
now have a much better understanding of
what they may experience on the
two-and-a-half year round trip to Mars
we humans evolved on earth and our
bodies are adapted from moving around
under the effects of 1g of gravity take
that away and problems start to arise
with our physiology we often forget what
a sheltered life we all lead here on our
little blue dot in the harshness of
space we're protected from 99.9% of
harmful radiation not only from a Sun
but also from other galactic sources by
our atmosphere the Earth's magnetic
field and the Van Allen belt
yes they may be a paying for space
travel but they do protect us from
further radiation on earth get beyond
the shelter of these an open space is
far from empty it's teeming with not
only radiation from our Sun but also
much more powerful radiation from
outside our solar system in the form of
galactic cosmic rays and gamma rays most
of the hard data we have about the
levels of radiation in deep space comes
from the radiation assessment detector
instrument which was onboard Mars rover
Curiosity part of the Mars Science
Laboratory which was launched in
November 2011 the radiation assessment
detector was turned on for about 228 for
250 three-day journey to Mars and showed
that the radiation levels were between
100 and 1000 times higher than that on
the earth for an unshielded occupant but
it was highly variable and depended a
lot on the solar activity at the time
experiments done on earth with beam
accelerators computer modeling and
confirmation from a cosmic ray teiescope
on the Lunar Reconnaissance Orbiter as
it goes around the moon have shown that
plastics with high hydrogen contents are
more effective than the same weight of
aluminium at stopping particle radiation
from both the Sun and galactic cosmic
rays and this is being incorporated into
the latest spacecraft designs like the
NASA Orion and the SpaceX Dragon two
galactic cosmic rays are protons and
nuclei of atoms which have been expelled
from supernovas and other violent cosmic
events and have been accelerated to near
the speed of light because of this they
have a much greater energy level and can
pass right through the spacecraft and
the crew shielding helps but it's a
compromise between the thickness of the
shield and the extra weight involved
which makes it more difficult then to
get it into space from Earth to contend
with solar flares a radiation shelter in
the craft where there is extra shielding
has been proposed from SpaceX Mars
mission liquid hydrogen or water storage
tanks around the crew areas provide a
good shield against particle radiation
and creating a strong magnetic shield
around the crew areas are all possible
but don't protect well against
electromagnetic wave radiation like
gamma rays using the Curiosity data it's
been calculated that the radiation risk
of a return journey to Mars will be
about 600 millisieverts equivalent to
about 50 full-body CT scans over that
period or being on the International
Space Station for four years straight
this is also about 30 times the yearly
allowance for a radiation worker and
that doesn't include the stay on Mars
itself a dose of one sievert or 1000
millisieverts is associated with a
lifetime increase in fatal cancers by
about 5% which is near the level of the
whole mission including stay on Mars
this would be a career limit for any of
the crew and young women are at a higher
risk of cancer from radiation compared
to older men so that could affect the
crew makeup along with the cancer risk
varies also the increased chance of
developing cataracts as the radiation
passes through the eye recent research
has also suggested that the effects of
galactic cosmic rays damaging brain
cells at the molecular level could cause
brain damage similar to the onset of
dementia which could show within the
duration of the journey away from the
radiation risks there also the
physiological effects of microgravity on
the human body
nasa astronaut scott kelly spent 340
days in space on International Space
Station and even with a tough two and a
half hour exercise regime each day he
still experienced problems with
circulation
eyesight as well as loss of bone and
muscle mass once in space the fluids in
the body no longer have gravity to pull
them into the lower extremities and are
equally distributed around the body one
of the effects of this is to make the
backs of the ice swell up not
shake which affects the vision stays on
the International Space Station of a
week were quickly reversed when back on
earth but lasted for much longer after
several months in microgravity on earth
the heart pumps blood around the body
and the veins in your legs squeeze the
blood back to the heart in space the
same amount of blood is being pumped by
the heart but there is much less effort
required to return it to the body this
allows for cardio muscular system in the
legs to weaken over time again when
returning to a gravity environment this
can cause extreme dizziness and fainting
due to the lack of blood been returned
to the upper body and brain which could
occur when they reach Mars within five
months of being in a microgravity
environment astronauts can lose up to
40% of their muscle mass and 12% of bone
mass this increases the risk of bone
fractures when returning to a gravity
environment and it's like turning a 20
year old into a 60 year old in just a
few months psychological issues are also
a problem for people in isolated areas
for long periods some scientists that
work all year around in Antarctica
suffer from a mental health disorder
called winter / syndrome which is
characterized by symptoms such as
depression irritability aggressive
behavior insomnia and memory problems
all the sort of things you don't want to
happen when trying to perform
mission-critical tasks in space or on
Mars
humans traveling in open space is always
going to be a risky business and in the
end some say the risk is worth the
reward of getting men to Mars they can
do much more than a robot in a short
space of time and are much better at
handling unexpected situations but dead
or dying crew is something no one wants
to see being back to earth so it's in
all our interests that their risks are
minimized as much as possible it will be
over 50 years since the last Apollo
flight by the time the earliest Mars
missions come around so even if it does
take a little bit longer than expect
it won't make that much difference to
make sure that we get it right what do
you think of a Mars missions and the
risk of traveling in deep space let me
know in the comments below and don't
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