IF your body was laid bare to the alien environment of Mars, the vacuum of space would boil every fluid in it, then freeze-dry your remains.
Away from the shelter of the ozone layer, the intense UV radiation of the Sun would fry any exposed skin.
With Antarctic temperatures, no water, little oxygen and gravity, and deadly amounts of carbon dioxide, human life on Mars would be impossible without one of the most elaborate life support systems ever designed.
Would you want to live there?
Kiwi scientist Haritina Mogosanu wouldn't, and she's been there - or at least the closest thing on Earth to it.
Three New Zealanders are through to round two of the selection process for Mars One, which, with a privately funded plan to send colonists to the red planet by 2024, makes for the mother of all reality television concepts.
Experts and officials have cast doubt on the practicality of the crowd-funded $6 billion venture, and Nasa chief engineer Brian Muirhead last year said a private Mars mission couldn't be funded.
Ms Mogosanu, a science communicator and president of New Zealand Mars Society, also has doubts.
"I hope they will succeed, and I hope in this endeavour of theirs that humankind will unite and support them ... but I don't think it's realistic."
In 2012, Ms Mogosanu spent two weeks as one of the six-member KiwiMars team living in a simulated spacecraft at the Mars Desert Research Station in Utah.
The 10m wide, two-storey environment included a greenhouse and observatory to replicate the conditions of a Mars mission.
The crew members spent their days in space suits, carrying out research, eating dehydrated food, with limited contact with loved ones and next to no sleep.
But that was a brief jaunt compared with other simulations.
In the joint Mars 500 project, six astronauts descended into a Moscow car park for 520 days inside a space capsule completely isolated from the outside world.
"I don't think I could have gone through anything in my life that would have changed me in such a way," Ms Haritina Mogosanu said of her experience in the Utah desert.
"I went there as a scientist but had this almost spiritual experience that made me realise what I was made of."
The outcome: she'd like to visit Mars, but only if she could come back.
For the 200,000 people who put their hands up for Dutch entrepreneur Bas Lansdorp's Mars One mission - that number has now been whittled down to 1058 - the ticket was one way.
One father of four from Utah was willing to sacrifice life on Earth, but his wife, who he didn't ask before volunteering, wasn't so keen and threatened him with divorce.
Short-listed Auckland pre-school teacher Nicola Fahey, 31, said she could accept leaving her home planet behind forever to fulfil a life-long dream of being an astronaut.
Masterton woman Kristy Flower, also on the list, said that if she was selected to make the trip she would miss her family and friends the most, but also little things such as walking her dog or spending time in the sun.
"But I also think of what I'll gain," the 20-year-old told the Wairarapa Times-Age.
"Knowledge about our universe, which others and myself would not have without this opportunity."
One as yet unidentified other Kiwi is on the shortlist, which has yet to be published.
The three are undergoing a round of tests and interviews, but the odds are against a New Zealander making the final pool.
The Mars One plan is built entirely on existing technology, and organisers have formulated a detailed risk analysis protocol with highly experienced experts, some previously with Nasa and the European Space Agency.
The organisation said it was "constantly working" to reduce the risk of delay and failure of the 10-year mission.
Its Mars lander would be tested eight times before the landing of the first crew in 2025, using identical vehicles, and every component would be selected for its simplicity, durability and capacity to be repaired using facilities available on the planet.
The organisation said the risk to human life from space flight was similar to that of climbing Mount Everest. The planet's unforgiving environment meant any small mistake or accident could result in large failure, injury or death.
It said the mission's other big risk, cost overrun, was reduced by using existing technology and the fact that 66 per cent of its cost was associated with the "well understood" launch and landing.
Its budget included a "large safety margin" that would cover significant mission failures as well as costly failures of components on Mars.
If the mission did reach Mars, those on it would be unable to return as spacecraft that could take off from Mars did not exist.
Auckland Stardome astronomy educator David Britten is sceptical about the plan's chances of success.
"Going from what they have on their website, some of it sounds very well thought out, and it seems they have done their homework, but it's very hard to assess just how concrete the plans they are talking about are.
"But they are keeping so much to themselves - who are they going to get to build the rockets? - and are very careful to feed out information in a very controlled way that suits them."
Writing in Stardome's Astronomical Yearbook, Mr Britten tackles the bid's biggest hurdles point by point.
The project would not get off the ground if Mars One could not find a country that would allow the launch of vehicles, equipment and crews.
All nations with space-launch capability have signed the Outer Space Treaty, a UN document that forms the basis of space law and requires signatories to "avoid harmful contamination of space and celestial bodies".
Interplanetary contamination, he said, was a grave cause for caution when sending and returning people from Mars.
Despite the best care, the planet could be exposed to new bacteria, viruses, fungi and disease, and there was yet to be a sample-return mission from Mars.
While Mars was considered the most hospitable planet to humans next to Earth, that would matter little when people were plunged into its brutal atmosphere.
Martian gravity was about 38 per cent that of Earth, its lowest temperature was -87°C, there was no water, and the amount of CO2 in the Martian atmosphere was 950,000 parts per million.
CO2 poisoning starts at about 1,000 parts per million for human beings.
Every muscle would weaken in Martian microgravity, decreasing bone mineral density by about two per cent each month.
But first, colonists would have to get there, making a 225 million kilometre, eight-month journey in a craft far from being built or tested.
Breaking free of Earth's gravity required an escape velocity of 40,000 km/h - or 11km per second - but our planet's orbit would mean the spacecraft would be speeding around the Sun at 150,000 km/h.
The craft would have to be protected from high energy particles from the Sun during a solar mass ejection - especially as Mars One's proposed launch date was during the next most active phase of the 11-year solar cycle.
The long trip would test every aspect of life support - engineering, medicine, nutrition and psychology - and boredom, communication and extreme isolation would be serious problems, Mr Britten said.
It also required sending supplies ahead of the mission - a craft able to do so was yet to be designed - and identifying a possible landing site would require extensive evaluation.
Mars One had not yet shown how its spacecraft would perform EDL - entry, descent and landing.
Unmanned craft have arrived at Mars at a speed of 20,000 km/h and used a heat shield for initial deceleration, but a solution to landing humans safely on Martian soil was still not obvious.
And if all of these challenges could be overcome within the next decade, sustaining life on Mars still wouldn't be easy.
Mr Britten said the colonists' day-to-day survival would rely on revenue from a TV audience at home, and governments and corporations might also want a piece of the action if they hadn't already killed the Mars One dream.
Deaths, from natural causes or from accidents, would prove inevitable and bodies would be left to freeze dry outside.
"The loss of any crew before the next batch of four arrive in two years will severely strain the survival chances of the remaining crew."
And sooner or later, he said, a child would be born on Mars.
"It would be next to impossible for anyone born in the low gravity of Mars to lead a normal life if brought back to Earth."
Mr Britten believed the Mars One backers could save themselves a logistical nightmare by setting their sights lower, even creating a reality TV concept within a virtual Mars environment like that which Ms Mogosanu experienced.
Above that, they could aim for a lunar outpost, or given the Obama Administration's plans to land on one by 2021, an asteroid settlement.
But Mars One is firmly committed to its plan, quoting John F. Kennedy's famed speech: "We choose to go to the moon, not because it is easy, but because it is hard."
The organisation isn't the only venture eyeing the red planet, and among those calling for a colony is Buzz Aldrin, the second person to walk on the moon.
The first space tourist, millionaire Dennis Tito, is behind plans to send a man and a woman on a 501-day fly-by of Mars, departing in 2018, and the billionaire founder of SpaceX, Elon Musk, envisions an outpost of 10 pioneers on Mars growing to a colony of 80,000 migrants. Each would have to pay about $500,000 for the journey, which would be made aboard a large reuseable transport vehicle powered by oxygen and methane.
Like Ms Mogosanu, Mr Britten wished any expedition luck, but has strong doubts.
"Perhaps the best bet should still be on Nasa eventually sending astronauts on a return mission around 2030," he said.
"Small, sure steps may well succeed where grandiose gestures evaporate."
Anybody home? Not now
Evidence suggests Mars was once much more habitable than it is today, but whether anything ever lived there remains unknown.
Samples collected by Nasa's Curiosity rover, which landed on Mars in August 2012, showed the planet could have supported living microbes.
Scientists found sulphur, nitrogen, hydrogen, oxygen, phosphorus and carbon - some of the core chemical ingredients for life - in powder the buggy drilled out of a sedimentary rock near an ancient stream bed in one of the planet's craters.
The finds suggested the area was the end of an ancient river system or an intermittently wet lake bed that could have provided chemical energy and other favourable conditions for microbes.
Scientists were surprised to find a mixture of oxidised, less oxidised, and even non-oxidised chemicals, providing an energy gradient of the sort many microbes on Earth exploit to live.
In 2012, research led by University of Canterbury geologist Dr Christopher Oze suggested life on Mars could be detected by measuring the ratio of hydrogen to methane in the Red Planet's atmosphere.
The team's experiments involved measuring the rates of methane production during a process called olivine hydrolysis or serpentinisation, which occurred in the deep subsurface of Earth and Mars.
But what remains clear is that Mars' harsh and extreme conditions would prove deadly to life as we know it.
Its temperatures are comparable to those in Antarctica, there is no liquid water, air pressure and gravity are greatly reduced, oxygen levels are nearly zero and the atmosphere is 96 per cent carbon dioxide.
It is believed that with highly complex life support measures, human colonisation on Mars could be possible.
But whether humans could ever adapt to Martian life is another question.