Looking back, 2014 was one heck of a year for discoveries in space. We had an unprecedented rendezvous between man and comet, as the Rosetta probe hooked up with it’s target after a 10-year journey. A small, mobile lab called Philae was even sent down to the comet, giving us our first direct view of its surface, and some surprisingly nice audio. But that’s far from the only accomplishment we’ve had this year. NASA’s Kepler space telescope discovered an earth-size planet within the “habitable” range of its star – the first such object found. We also saw a huge victory from a rising space program as India’s Mangalyaan spacecraft reached Martian orbit without incident.
And if high flight’s not quite your style, pop culture had your back. Looking at you, Interstellar.
So it was a good year. One good enough to hopefully have us lifting our gazes further afield, and start thinking about the future of manned space flight. Or, well, keep thinking. It’s possible NASA and similar agencies already have someone on it. But as we lift those gazes, we should probably find some way to protect them. Vision problems are common enough here on earth, but space brings a whole new set of risks that have to be identified and accounted for.
One of the most worrying risks to astronauts that we currently know of is also, frustratingly, one of the most difficult to combat. Long periods of weightlessness result in a problem known as papilledema in male astronauts (women get a pass on this one). Papilledema is swelling in the area of the eye known as the optic disc, a chokepoint for nerve fibers leaving the eye. The swelling’s caused by an increase in intracranial pressure, or pressure within an astronaut’s head. It’s a worrying phenomenon, and one occasionally experienced after six-month stretches on the International Space Station. If severe enough, papilledema can actually flatten out the optic nerve, leaving some astronauts farsighted.
So what exactly is behind what researchers have come to call Space Obstructive Syndrome? The answer appears to lie in the changes that occur to fluids in the human body and the way they behave in response to microgravity. One researcher points to compression of a vein, which in turn leads to larger problems down the line. That said, SOS is still a bit of a mystery, and until that changes, solving it may prove to be difficult. As microgravity appears to be the root cause, artificial gravity might provide one fix.
The further you get away from earth’s friendly, protective atmosphere, the more radiation you’re going to soak up. Even frequent airplane fliers have some cause to worry about the extra rays, and they’re a good ways down from where astronauts live. Even the men and women aboard the ISS aren’t quite receiving a full dose, as they remain within the earth’s magnetosphere, an area within which the earth’s magnetic field can still affect charged, radioactive particles. Once we start thinking about interstellar flight, then even that bit of protection vanishes. Truly massive radioactive events, such as so-called “superflares” (large solar flares, which are sudden surges in the sun’s energy output), could conceivably result in radiation poisoning and death in unprotected astronauts.
Radiation isn’t what you’d call an exclusively ocular threat. The high energy protons present in cosmic rays or solar events can damage just about every part of a human body. Acute exposure can smash DNA, which quickly leads to cellular degeneration, with further diseases, including cancer, possibly appearing later. Radiation poisoning (surprise surprise) is no joke. Victims of the disasters seen at Fukushima and Chernobyl illustrate how dangerous heavy doses of radiation can be. While superflares might subject astronauts to similar conditions, the main danger they’re likely to face is a lower, but consistent exposure to radiation far beyond what they would on earth. As we haven’t had too many galactic travelers, the actual effects are largely up for debate. Cancer, tissue degeneration, and nervous system impairment are all potential worries. However, there is at least one concretely understood threat: radiation cataracts.
Cataracts manifest as a clouding of an eye’s lens, and result in a decrease in vision. Untreated cataracts are a leading cause of blindness, and even less severe cases can severely limit an individual’s autonomy and quality of life. They have a wide range of potential causes, one of them being consistent exposure to multiple forms of radiation. As a result, astronauts are known to have a higher incidence of cataracts than other professions. One famous example of the damage cataracts can do is the case of Soviet Cosmonaut Valentin Lebedev. Lebedev spent 221 days in orbit, the most of any person to date, and eventually went blind due to cataracts exacerbated by his time in space.
As a result, it’s important to think of ways to shield astronauts from radiation. Aluminum is currently used, but likely won’t suffice for interstellar travel. Researchers are currently searching for a lighter, more shielding material to replace it. Polyethylene may provide one solution, as its hydrogen-heavy composition has been proven to effectively disperse and absorb radiation.
There’s another more organic solution available. Researchers have found that plants grown under specific conditions produce larger amounts of a compound called zeaxanthin. In plants, zeaxanthin helps safely absorb excess sunlight which might otherwise damage an organism, and can actually play a similar role in the human eye. By carefully cultivating plants, the spaceship crews of tomorrow may be able to get the nutrients they need to fight off excess radiation. Good to know for anyone involved in the Mars One Mission.