Can we get astronauts to Mars sane and healthy?

This story is Part three of Quirks & Quarks' Pathway to Mars series. Each instalment will look at one part of the huge challenges inherent in the most ambitious journey of exploration we've ever attempted — a human mission to Mars.

A mission to Mars will be aimed at putting human boots on the Martian ground, but the mission will only be a success if the human in those boots is healthy, both physically and mentally, after their long trip through interplanetary space. Mars presents new challenges to astronaut wellness that we've never faced before in on our short jaunts to the moon or our longer stays in low Earth orbit aboard the International Space Station.

The time astronauts have spent on the ISS is the closest experience we have, however. Dr. Robert Thirsk spent more time in space than any other Canadian astronaut, including a six month stretch on the ISS from May to November in 2009. His experience taught him a lot about what we still have to learn to get astronauts safely to Mars.

"It'll be much riskier — probably akin to, or maybe even greater than, the risk that the Apollo astronauts took," said Thirsk in conversation with Quirks & Quarks host Bob McDonald. "We can do it, but we can't do it today."  

Among the challenges Thirsk outlined are protecting astronauts against the intense radiation of interplanetary space, the mental health challenges of the extreme isolation of a Mars voyage, and maintaining physical fitness and wellbeing in microgravity.

The lethal radiation environment of interplanetary space

Radiation in interplanetary space is a particular concern because once astronauts leave Earth orbit, they no longer have the protection of the Earth's magnetic field. The magnetic field, which protects the ISS, redirects a lot of radiation, including harmful radiation from the sun. 

"We're exposed to more ionizing radiation in low earth orbit than here on the surface of the planet but interplanetary travel exposes to an order of magnitude more." said Dr. Thirsk.

The sun produces radiation of various kinds, including fast-travelling and dangerous charged particles. A large solar storm could cause a phenomenon called a coronal mass ejection which could be catastrophic for unshielded space travellers, said Dr. JD Polk, NASA's Chief Health and Medical Officer. "That can cause acute radiation sickness due to a lot of that energy being released toward the crew." 

The sun is not the only source of radiation in interplanetary space. High-energy cosmic rays, particles travelling through interstellar space at enormous speeds, can damage DNA and increase long term cancer risk. And, according to Dr. Polk, it's not something we can't easily do much about.

"We can shield coronal or solar radiation fairly well. Galactic cosmic radiation not as much. It will go through a lot of materials."

Dr. Polk's solution to radiation exposure is to minimize it. There will be as much radiation shielding on the Mars spacecraft as can be accommodated by the size and weight of the vehicle. Dr. Polk thinks beyond that the best solution is minimizing the amount of time the crew spends in space

"If we can increase our velocity and our speed between Earth and Mars and get there in a timely manner decreases the amount of exposure the crew has."

The unsolved challenges of microgravity

Astronauts like Dr. Thirsk are well aware of the risks of life in a microgravity environment. In the absence of full gravity muscles can weaken, bone density is lost and balance and coordination can suffer. Astronauts returning to Earth after months on the ISS find the burden of gravity almost overwhelming, and have difficulty even standing and walking on their return.

This is despite the fact that the space station has a suite of workout equipment including treadmills and resistance exercise gear that astronauts use to try to stay in shape. Dr. Thirsk warns that the relatively small size and payload of a Mars vehicle probably may not allow an onboard gym.

"We definitely do need countermeasures to protect us against the de-conditioning effects on the vestibular system, the cardiovascular system and the muscles and the bones but we're going to have to get smarter about giving the future Mars astronauts an excellent workout." 

Another unsolved challenge for astronauts on a Mars mission has to do with a subtle problem detected on the ISS by NASA physicians. After a couple of months in space astronauts begin to have difficulty with their vision. 

NASA physicians traced this to a shift in body fluids thanks to a lack of gravity. "You've got several litres of fluid in your lower extremities and that's now shifted upwards," said Dr. Polk. "You're shoving a lot of fluid that was meant for the lower extremities up into that skull"

The result, he said, is "swelling of the optic nerve and potentially a mild edema in the brain that causes a vision change."

What is clear is that NASA has work to do so astronauts don't arrive on Mars visually impaired, and too weak to move around and explore.

The mental stress of the big empty

Earth has never been very far away for astronauts on the International Space Station, said Dr. Thirsk.

"When I was aboard the shuttle and also the space station my favourite leisure time activity when I wasn't working by far, by far, was simply looking out the window at this beautiful planet down below." 

This was a common way for crew members to spend time, and along with internet access and video and voice calls, allowed them to stay in contact with loved ones on the ground.  

He says this comfort won't be there for Mars astronauts. "As soon as they leave Earth orbit and head off in that six month transit to Mars, they're looking at nothing but black space."  

The increasing distance from Earth of the Mars craft will also make real-time communication with Earth impossible.

Dr. Thirsk suggests a science fiction solution: the Star Trek "holodeck." This fictional virtual reality system could be used to give astronauts a break from the monotony of six months in a tiny, fragile spacecraft.  

"I think we really should spend a little bit of time maybe talking to the gaming industry people to see if they can come up with something similar to that maybe take it to the next level."

But according to Dr. Polk, the best way to keep astronauts mentally healthy is to work them hard. He points to evidence dating back to early Antarctic explorers like Shackleton. "They were trapped in the ice and even back then they noticed that if you kept the crew busy and the crew was working diligently toward a mission that they fared better psychologically."

"And trust me they'll be very busy on the way to Mars and on Mars."

Dr. Polk and his colleagues are keeping busy today preparing as best they can to keep future Mars astronauts healthy and happy, as the best way to ensure a safe and successful mission.  But it's not what keeps him up at night.

"My biggest concern is what I call the unknown unknowns. It's the thing that I haven't planned for or haven't considered that blindsided me. That's really the thing I worry about the most."

Written by Jim Lebans. Produced by Mark Crawley