When President John F. Kennedy declared in 1962 that the United States would go to the moon, not because it is easy, but “because [it is] hard,” he had no idea how hard. Nevertheless, the success of the Apollo 11 moon landing and subsequent manned missions inspired space explorers of all stripes to justify their journeys to other cosmic outposts in the same vein: because it’s the ultimate challenge. But with each new study, the passage to Mars and other planets seems fraught with more danger than ever thought possible.
Just lifting off the surface of Earth and landing on another planet is bad enough. But how intense are the dangers of actually traveling in space? Here are five of the most dangerous threats astronauts will face when traveling to Mars and beyond.
En route to another world, astronauts will be bombarded with cosmic radiation: tiny, high-energy atom fragments that whiz through space and can damage cells and DNA. People on Earth are protected from cosmic rays thanks to Earth’s magnetic field, but an unprotected, Mars-bound astronaut would receive 0.3 sieverts of radiation on a one-way trip—that’s hardly close to the lethal dose of 8 sieverts or even the radiation sickness–causing dose of 1 sievert, but researchers think that amount (equivalent to 24 computerized tomography scans) is enough to cause irreversible damage to brain cells and other cells that aren’t readily replenished.
“The central nervous system is the 800-pound gorilla in all of this,” says Charles Limoli, a radiation oncologist at the University of California, Irvine. In a recent rodent study in Scientific Reports, Limoli suggests that cosmic rays would cause long-term brain damage in astronauts on the way to another planet, resulting in dementia, memory deficits, anxiety, depression, and impaired decision-making. “This is not positive news for astronauts deployed on a 2- to 3-year round trip to Mars,” he says. But it might be a problem we can fix. Several research groups, including Limoli’s, are working on a drug that could protect cells and DNA from being broken apart. Still, others are trying to invent shields that would deflect the rays altogether.
Going stir crazy
If you’ve ever been on a long family road trip, you’ve had a taste of what a trip to Mars might be like—except that when your dad plays too much ABBA, you can eventually exit the vehicle. In a years-long deep space voyage without pit stops, a spat could mean life and death for crewmembers. In a NASA-funded report published this year on long space flights, Jack Stuster, a cultural anthropologist at private research corporation Anacapa Sciences in Santa Barbara, California, writes that U.S. astronauts’ No. 1 concern on missions to the International Space Station (ISS) was getting along with crewmates. Their journals, positive overall, reflected that concern: “I think I do need to get out of here,” one astronaut wrote. “Living in close quarters with people over a long period of time, definitely even things that normally wouldn't bother you much at all can bother you after a while … that can drive anybody crazy.”
And that was when Earth was right out the window. If astronauts start to feel this way when both Earth and their destination are but tiny pinpoints in space, things will feel even grimmer, Stuster says. Though these feelings can be limited by keeping busy, and by the intense psychological screenings that crewmembers undergo, the spectre of violence—and even mutiny—will always be a possibility.
We’ve known since the 1960s that some microorganisms can survive the perils of space, including microgravity, extreme temperatures, and radiation. And given that our best efforts to wipe space vessels clean of microorganisms often fails, exposure to these potentially pathogenic organisms is unavoidable. Now, a new study supports that claim. In October, researchers found that the airborne fungus Aspergillus fumigatus, the most common cause of invasive fungal infection in humans, grows just as well on the ISS as it does on Earth. And if fumigatus lives just fine in space, the researchers write, so could many other, more lethal pathogens. The researchers say this calls for a better detection and cleaning policy to avoid sending a ship full of astronauts into the dangers of deep space, only to have them killed by an earthly pathogen.
From YouTube videos of astronauts playing with floating blobs of water or doing effortless backflips, it seems like microgravity would be a blast. But up in space, the reality is much more serious. The absence of gravity causes bones and muscles to deteriorate, leading to a number of physiological problems. Astronauts on the ISS exercise for 2 hours a day to protect their muscles from wasting away, but losing bone density is unavoidable.
Microgravity could also affect the body in other, unpredictable ways. Many astronauts, including Scott Kelly, have returned to Earth with blurred vision. The cause, according to research presented this week at the Radiology Society of North America’s annual meeting, is an increased volume of spinal fluid that pushes against the optic nerve and eyeballs, causing farsightedness. In another study, scientists discovered that the spinal muscles of ISS astronauts—essential for support and movement—shrank significantly during their time in space, decreasing by 19%. That could be the reason more than half of all ISS crew members report spinal pain and are four times more likely than Earth-bound citizens to have herniated disks, the researchers write in Spine. One solution? Space yoga—researchers say it might help increase spine mobility and strength. Exactly which poses they’ll do is yet to be determined.
Making mistakes is something humans are extraordinarily good at, and in space, mistakes tend to hold heavier consequences. Andy Weir, the author of the science-fiction novel The Martian, took full advantage of that, crafting his entire plot around how a stranded astronaut must expertly solve dozens of problems or face certain death. Real-life space explorers are not always as lucky. Take the space shuttle Challenger and Columbia disasters, for example. Both shuttles broke apart because of mechanical problems, killing all seven astronauts on board each time. With Challenger, rubber O-rings were the culprit, causing the shuttle to break apart in the sky when they couldn’t seal properly in the cold. Columbia broke apart during re-entry when insulating foam separated from the shuttle and punctured its left wing. NASA management knew about mechanical issues in both cases, but considered them unimportant because they had never derailed a mission in the past.
On long spaceflights where tensions might be running high or radiation could cause unusual anxiety, depression, or confusion, it’d be no surprise to see human-caused errors like a crash landing, leaky space suits, or even the loss of the water supply. Finding a way to limit the dangers of space and learning from past mistakes will ensure the safest flight to Mars and beyond. And with a little luck, our astronauts could end up as successful as Weir’s.