London - The first people to make the perilous journey to Mars will have to cope with long periods of boredom, the constant worry that they might not return home safely and the joy and pain of each other's company.
According to the latest research into long-duration space travel, they will also be exposed to the sort of radiation exposure that few people of Earth have experienced.
A study has found that astronauts will receive more than half a lifetime's radiation dose during the return journey of a manned mission to Mars - a calculation that does not taking into account the time spent on the surface of the Red Planet.
Measurements of cosmic rays within the Mars Science Laboratory, the unmanned spacecraft that delivered the Curiosity rover to the planet last year, showed that radiation exposure during such a mission would be higher than some experts had predicted.
The researchers found that during the 360-day round trip to Mars a person on board would receive more than 60 percent of the maximum lifetime dose allowed for an astronaut.
A person exploring the surface would be exposed to further radiation during the 500 days or so they would be spending on the surface of the planet. Nasa stipulates that its astronauts should not receive more than 1 000 milli-Sieverts of radiation over their lifetime - which equates to a five percent increase in the risk of cancer. The radiation device on the Mars Science Laboratory measured about 660mSv - equivalent to getting a whole body CT scan once every five or six days.
Cary Zeitlin of Southwest Research Institute in Boulder, Colorado, who led the study published in the journal Science, said the relatively high radiation exposure would pose serious problems for a future manned mission to Mars, which Nasa is tentatively planning for some time beyond 2020.
“Radiation exposure at the level we measured is right at the edge, or possibly over the edge, of what is considered acceptable in terms of career exposure limits defined by Nasa and other space agencies,” Dr Zeitlin said.
“Those limits depend on our understanding of the health risks associated with exposure to cosmic radiation, and at present that understanding is quite limited,” he said.
But all is not lost. Other experts believe that the risk is manageable. They argue that new materials could improve the shielding against cosmic and solar radiation and that astronauts could be selected on the basis of their genetic resistance to radiation damage, which increases the risk of cancer by damaging DNA.
“These results show that cosmic rays are not a showstopper. This confirms what you might expect: the radiation risk is quite acceptable. Frankly, it's a modest portion of the risks on a Mars mission,” Robert Zubrin, president of the Mars Society in Colorado, told Science.
Those other risks would also have to managed if a Mars mission were to be successful. So what would they entail, and how can they be mitigated?
Sleep deprivation
The Mars500 project, where six men spent 520 days and nights confined to a terrestrial “spacecraft” in a research institute near Moscow, found that one of the biggest problems was getting enough of the right sort of sleep.
Wide variations occurred in the circadian rhythms - the 24-hour sleep-wake cycle - of the six-crew. One man shifted to a 25-hour period, meaning that every 12th day his body was telling him it was midnight when it was in fact midday.
Lack of natural light, fresh air and contact with the outside world disturbed the sleeping patterns of the six volunteers. Only one of the crew retained a near-normal sleep pattern in which he was active during the day and rested at night.
Selecting astronauts on the basis of their being regular sleepers could help to overcome this difficulty.
Microgravity
It is well established that long periods in low or zero gravity causes big changes to the physiology of the body. The lack of gravity causes muscles to waste away and bones to become frail, while the heart becomes weaker at pumping blood around the body.
Regular exercise using a cycle-like device, a zero-gravity treadmill and a set of resistance “weights” not only boosts muscle power and bone strength, it also maintains levels of red blood cells, which are crucial to overall fitness.
Cabin fever
Being cooped up for a year or more in the claustrophobic confines of a spacecraft can severely test “interpersonal relationships”. One suggestion is to send a pair of astronauts who are already in an established personal relationship, such as a married couple. This could lead to the introduction of interplanetary marriage guidance if strains develop.
Food
Space food tends to be an acquired taste. Spicing up the menu with something fresh and tasty would be good for morale as well as for health and psychological well-being. Growing your own food in some kind of cosmic greenhouse attached to a space ship would be one solution - a cosmic allotment would also give astronauts something to do.
Astronauts on board the International Space Station reported that the cuisine of the European Space Agency was favoured over the American or Russian equivalent. So, hiring a French or Italian chef to prepare the space menu may help to maintain the mood of anyone exploring the Martian surface.
Getting back home
One of the biggest technical challenges is working out how to get home again. If a manned mission to Mars manages to explore the surface of the planet it may be necessary to find a source of water and fuel that could be used both for drinking and for the journey back to Earth.
Mars is thought to have deposits of water, which with the help of solar panels could be converted into oxygen and hydrogen, the raw material of rocket fuel. Any return mission to Mars will need a lot of planning to ensure that astronauts are able to come back - although some exceptionally dedicated or foolhardy people may be prepared to volunteer for a one-way ticket.In that case, the radiation may be less of an issue than anticipated. - The Independent