a low-earth orbit mission increases the

life time risk of the crew getting

cancer by more than 3% then

they won't go ahead with it but the

upcoming Mars missions may expose the

crews to levels which will be beyond

that limit and two other hazards,

so how dangerous is deep space travel to

Mars and Beyond. With Ellen musk pushing

to get men onto Mars by the mid-2020s

and NASA looking to do the same for

the 2013 just how much we learned since

Apollo and from space stations. 50 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 as being down to the lack of

political will in the face of our own

man-made problems here on earth

it's also down to be increasing

sophistication of robotic probes and

Landers that are much cheaper to make

launch, can go where no man could go and

continue working for years of the 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. With

data from probes that we have sent

around solar system since then we have

built up a picture which is far from

the vision of just whizzing through

interplanetary space that along with the

joint NASA-Russian experiment of having

been in space for a year on board the

International Space Station, we now have

a much better understanding of what they

may experience from the two-and-a-half

year round trip tomorrow. We humans

evolved on earth and our bodies are

adapted from moving around under the

effects of 1g of gravity, take that away

and problem start to arise our

physiology. We often forget what a

sheltered life we all leave here on our

little blue dot in the harshness of space.

We are protected from 99.9% of

harmful radiation not only from the Sun

but also from other galactic sources by

our atmosphere the Earth's magnetic

field and the Van Allen belt,

yes they make a pain for space travel

but they do protect us from further

radiation on earth. Get beyond the

shelter of these and 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 a 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 aboard Mars rover Curiosity,

part of the bar science laboratory which

was launched in November 2011. The

radiation assessment detector was turned

on for about 220 out of 253 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 the

cosmic-ray scope on the lunar

reconnaissance orbiter as it goes around

the moon has shown that plastics with a high hydrogen

content are more effective than the same

weight of aluminium at stopping particle

radiation from both the Sun and galactic

cosmic rays and this has been

incorporated into the latest spacecraft

design like the NASA Orion and the SpaceX Dragon 2. 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 right through space craft

and the crew.

Shielding helps but it's a compromise

between thickness of the shield the

extra weight involved which makes it more

difficult then to get into space from

Earth. To contend with solar flares, a

radiation shelter in the craft where

there is extra shielding has been

proposed with 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 gamma-rays. Using the curiosity

data has 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 4 years

straight.

This is also about 30 times the yearly

allowance for a radiation worker and

that doesn't include 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 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 make

up. Along with the cancer risk there's

also be 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

they're also physiological effects of

microgravity on the human body.

NASA astronaut Scott Kelly spent 340

days in space on the International Space

Station and even with a tough

two-and-a-half-hour exercise regime each

day, he still experience problems

with circulation, eye sight as well as a

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 back of the eye

swell up and alter their shape which effects

vision. Stays on the International

Space Station of about 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

the 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 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 the when they reach Mars. Within five

months of being in a microgravity

environment, astronauts can lose up

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

to people in isolated areas for long

periods. Some scientists that worked all

year round in Antarctica suffer mental

health disorder called "Winter Over 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 and they can

do much more than a robot in a short

space of time and they are much better

at handling unexpected situations. But dead

or dying crew is something no one wants

to see beamed back to earth so it's in

all our interests

to make sure the 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 just take a little bit longer than

expected, it won't make that much

difference to make sure that we get it

right.

What do you think of the Mars mission

and the risk of traveling in deep space?

let me know in the comments below and

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