back to article Mars trips could blind astronauts

A manned trip to Mars could end up blinding its astronauts suggests research by the American Academy of Ophthalmology. The report says that long amounts of time spent in space damages astronauts' eyes. It puts another obstacle in the way of manned Mars missions, which would be a three-year round trip requiring rocket power …


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  1. noroimusha

    artificial gravity

    see space odissey......

    1. xlq

      Warp drive

      see Star Trek....

    2. Chemist

      If by that...

      you mean a rotating system it has to have a considerable radius otherwise the force acting at head level is considerably different to foot level and can't be compensated for so blood pools in the legs.

      1. Ru

        "considerable radius"

        A much smaller radius sleeping section would help an awful lot; it only needs to have a large enough radius to ensure that astronauts can sleep in it without tidal forces in their inner ears reminding them that the room really is spinning.

        Doesn't make it much less of an engineering problem though.

    3. Michael H.F. Wilkinson Silver badge

      My thoughts exactly

      Does require an even bigger craft and thus even bigger rocket. It does seem to be a simple problem compared to shielding against cosmic rays and the like.

    4. TedF

      Or even space odyssey . . .

  2. Mike Bell


    Send two craft tethered to each other by a long cable. Put the show into a gentle spin and - voila - instant artificial gravity in both.

    1. Anon E Mus

      Space is never simples!

      What rate of spin (I have a feeling that even moon gravity would be a lot faster than "gentle"). How will spinning affect other systems? Will steering/manoeuvring this thing be more difficult?

      Space engineering is hard.

      1. crymble

        "What rate of spin (I have a feeling that even moon gravity would be a lot faster than "gentle"). How will spinning affect other systems? Will steering/manoeuvring this thing be more difficult?

        Space engineering is hard."

        I don't see why. I mean it's hardly rocket science is it.........

      2. Richard 12 Silver badge

        It doesn't actually require very much spin at all.

        Centripetal acceleration: a = (v*v) / r

        √(ra) = v

        For an acceleration of 10 m/s/s (Earth normal!), 100m tether: v = 22.4 m/s

        314m circumference, so that's a rotation rate of 0.07 revs per sec.

        So 4 rpm for Earth-normal centripetal gravity.

    2. Jess--

      that would be likely to disorient you even more than micro gravity due to the continuous rotation.

      if you think back to the old gravitron fairground rides which used centrifugal force to hold you to the outer wall of the ride they were doing exactly what you suggest here, you became disoriented within a minute or so because you could still feel the effects of normal gravity working at differing angles to the artificial gravity being produced by centrifugal force.

      in space that feeling may take longer to appear due to smaller amounts of gravity being present.

      another downside of having something spinning is that it would make course changes very harsh on anything inside it while also increasing the complexity of making a course change due to gyroscopic effects (from memory a force exerted on something spinning will have its direction changed by 90 degrees if it spinning fast enough and will induce a very nasty wobble if it is not spinning fast enough)

    3. Nigel 11

      Maybe not quite so simples

      I think you'd need a hub at the centre as well, for the communications dish that needs to stay pointed at Earth. That dish would have to be moved to the side when you re-join the three sections for orbital manouvering. There would be some weight penalty for the cable, and some fuel cost in generating and then shedding the angular momentum each time you re-join the modules into one.

      I doubt any of these is more than an engineering challenge, especially if the G-force needed for keeping astronauts healthy is significantly less than 1G.

      The biggest problem would be what to do in a solar storm. A rotating capsule would make it impossible to use the rest of the supplies between the atronauts and the sun as shielding. They could re-join into a single craft and orient it pointed at the sun with the crew quarters in the shadow - but there's that fuel cost every time you have to do it.

    4. Ken Hagan Gold badge

      Not so simples

      You've just doubled the cost of the mission. But then, who's counting? If we wanted "cost-effective" we'd have sent a robot.

      Prediction: The US will eventually send a manned mission to Mars, because some jackass politician will eventually decide his dick isn't big enough. However, by then some media organisation will be able to fund robot probes to deliver "exclusive live coverage" of every part of the trip, including having a camera on the ground at the landing site when the door swings open for the first time. Thus, NASA's finest hour (as it will surely be called) will be turned into a demonstration of why robots are better than people for space exploration (or indeed deep-sea diving or any other hazardous environment). Oh, and it will also have a *really* intrusive advert spashed across the screen at the crucial moment.

      1. Field Marshal Von Krakenfart

        You've just doubled the cost of the mission.

        It's a question of priorities, the 'merkins went to the moon on 1/2 of 1 percent of their GDP, while at the same time they were spending nearly 7% of their GDP making Vietnam look like the moon.

        Ohhh look, a picture from Vietnam

      2. Stevie


        For given and strictly limited values of "Cost Effective".

    5. Ragarath

      I have always wondered why they have not created a craft with a slow spin to create some gravity.

      But then again I am not a top scientific boffin so there may be other reasons this is not a plausible option!

      Any boffinry types out there able to elaborate?

  3. Voland's right hand Silver badge

    Spin That Wheel

    If we can build that multinational modular hodge-podge up there, we should also be in a position to build a proper space station and/or spaceship which has a spinning habitable section.

    In fact, in the case of the spaceship you might as well spin the whole thing. It is not like it will need docking/undocking operations before the end of the flight. Even if it does, spinning up something along its axis to sync to another spinning object is not a particularly difficult engineering problem.

    Even that may not be necessary. You can have the docking apparatus be able to separate from the main ship body via one more dock/airlock to the spinning section. You undock at that junction to accept an incoming ship, slow down the docking bay relative to the main body, stop, dock to the incoming ship, spin up together with the docked ship (shifting some ballast to stabilize as needed - just put fuel and water reserves there), equalize rotation and dock back.

    That solution was envisioned as early as Von Brown and Tciolkovski. Is it me being thick and having too much coffee in my blood system. Or am I missing something?

  4. Charlie 5

    micro gravity

    If the lack of gravity is the main culprit then any manned mission would have to have a rotating section to keep the astronauts' feet on the ground.

    Why do you say the rocketry currently beyond our capability?

    With the right political will, humanity could have put people on Mars in the 1980s.

    Read Zubrin's "The Case for Mars". It's all there

  5. Clive 3
    Thumb Up

    Artificial gravity

    What happened to spinning the spacecraft to generate artificial gravity?

  6. jubtastic1

    Centrifuge to the rescue?

    Or more simply, design the ship as a short stubby can and spin the entire thing on it's axis, it's going to have to be built in space anyway.

  7. Purlieu


    send them to specsavers

    as an aside the invisible man would also be blind, since light would pass through his transparent retinas

  8. Thomas 4


    So it looks like whatever ship is built for the task needs some way to generate even a minimal amount of gravity-like force.

  9. Wize

    Maybe the ship needs a large centrafuge like many sci-fi films.

    Or spin the whole thing round when out of Earth's gravity.

  10. Richard Scratcher

    Crew rotation

    Perhaps a rotating section of the spacecraft could solve this problem. I know that simulating gravity without causing motion sickness needs a very large diameter (100m) wheel but if the crew only used it when lying down, it should be possible to use a much smaller size.

    Various tests have been done to simulate the effects of zero G on the body by having volunteers stay in bed for hundreds of days. I don't remember reading anything about it causing eye trouble.

    So maybe sleeping in a low gravity chamber could help reduce the build up of pressure from spinal fluid.

    1. Chemist

      Staying in bed is just lazy and

      Gravity is still Earth normal not zero G

      1. Anonymous Coward

        Staying in bed all the way to Mars creates other problems...

        Before we found out about increased risk of blindness/vision problems, a well-known side effect of zero G enviornments was the atrophying of muscle (including the heart) and bone tissue. That's why you always see those shots of astronauts strapped down to a treadmill so they can run to keep up some of their muscles so they won't fall over the instant they get back to Earth.

        So even if being a couch potato all the way to Mars and back would help with the vision loss (which I don't think it would), it would only exaggerate the muscle and bone loss. So you would come back to Earth needing years of physical therapy and probably have shaved a few years off your life from the deterioration of your heart muscle.

  11. Anonymous Coward
    Anonymous Coward

    Other factors causing blindness...?

    Long lonely periods in spaceaway from your wife might also be a contributory factor? :)

    "I'm sorry Dave, I can't do that. Its not in my programming."

    1. Ian 27

      In that situation I'd really want artifical gravity - imagine having the erm... end result floating around the space ship.

      Hand covering eye icon, because... well. 'nuff said.

      1. Ru

        So you're saying,

        that for safety reasons, there must be an assistant and it is critically important they swallow?

  12. Ralthor

    Space travel.

    If little Johnny doesnt stop it, he will go blind.

  13. Steve X

    I'm not an opthalmologist, but

    Isn't it also possible that 6 months in a box where you never need to look further than about 10 feet in front of you might have an effect on eye muscles as well?

  14. Sean Baggaley 1

    Anyone who's seen "2001: A Space Odyssey" would know the answer to this.

    Artificial gravity.

    I can't imagine NASA designing an interplanetary spaceship without this feature. It's such an obvious solution to the known problems caused by long periods of free-fall.

    Design the ship such that it can spin around its major axis while on its journey, with the living compartments close to the sides. The astronauts thus get a simulation of gravity that should be good enough to prevent physical degeneration during the journey, with only a very short period of free-fall when the ship flips 180º to begin its deceleration.

    1. Bill B

      Spinning on axis needs to be tested

      Spinning the ship on its axis might be a solution, but it is one that needs to be tested. This is because unless you get the design right the occupants can get nauseous .. see "Artificial Gravity and the Architecture of Orbital Habitats" by Theodore W. Hall.

      The basic conclusion is that big radius, low RPM=good (for example, one study said that the comfort zone was achieved by 1rpm and 100m radius). The point is made that all our research habitats in space have been designed to test the effects of zero G. There haven't been any studies in space on the use of spinning habitats.

      Basically .. most of the spinning ships envisaged in books and films have had too narrow a radius. The 2001 space station probably had it right, but this wasn't going anywhere. And I bet passengers were puking up as the shuttle spun up to enter the station.

      1. Chemist

        There's also the problem ..

        of small radii generating a MUCH greater differential force head to foot so that blood pools in the lower limbs.

  15. Silverburn

    Another possible cause...

    Lemme see...

    - 3 year trip

    - long periods of boredom

    - no wives/girlfriends on board

    I can think of another self-inflicted activity which might account for the blindness...

    1. Ken Hagan Gold badge

      The crew may start out with no significant others on board, but eventually... NASA might opt instead to start with a crew who are already in stable relationships.

      1. Anonymous Coward

        That could have its problems too…

        Either that they fall out with each-other, as couples sometimes do.

        Or worse, suppose a bit of action were to occur… and 9 months later the crew numbers increment by one?

        I feel sorry for the poor squirt when he/she gets back to Earth.

        "And where were you born Suzie?"

        Girl points to the ceiling and announces "On a space ship!"

        (in the back room) "He he he… alien! Suzie's an alien!"

  16. Brian Miller 1

    Well, gee, they just have to simulate gravity then huh?

    I would have expected NASA to construct the manned section of the vessel as a toroid or cylinderand rotate the section such that the centripital force approximates 1g.

    Is it just me or wasn't this approach WIDELY publicised in 2001: A Space Odyssey?

  17. Anonymous Coward
    Anonymous Coward

    I thought Clarke had this problem solved way back in 2001.

  18. Matthew 3

    Needs some kind of hamster wheel?

    Surely NASA could come up with something that would create a facsimile of gravity. I know it's not a proper hi-tech sexy sci-fi solution but I think most people would spend an hour a day on a hamster wheel if they knew it'd stop them going blind.

  19. Anonymous Coward
    Anonymous Coward

    rising to the head?

    "especially spinal fluid – rising to the head and putting pressure on the brain and eyes"

    Just curious but how can this be the cause? If they are weightless (and even in LEO they are just that) there is no up or down so how can fluid "rise" anywhere?

    1. Poor Coco

      The rising fluid is due to the absence of gravity.

      The systems in the human body were designed for a 1g acceleration/gravity influence at all times, pulling fluids towards the feet. If there is no such influence on the body, as in microgravity, the fluids pool in the head since the compensation mechanisms are fighting nothing.

    2. Marcelo Rodrigues

      It´s all about the pressure

      We, human beings, are made to stand up. So we evolved in a way that our body pumps everything UP, to counterbalance the gravity.

      Remove gravity and the upper part of our body has to deal with a rise in pressure (no gravity to help here) of all the fluids. I can only imagine that our tiny little blood vessels that irrigate the eye get no so happy about it... :D

  20. Remy Redert

    re: Simples

    Better solution. Put a nuclear rocket engine in orbit, fly to Mars in about a month, less if it happens to be in a favourable position at a time. This also helps reduce the risks from radiation, micro-meteorites and various random failures as a result of equipment decaying over time.

    Actually, put 2 nuclear rocket engines in orbit, so that if the first suffers a failure while it's idling in Mars orbit, the second can come to the rescue. Use SpaceX's cheap rocket lift capability to put the required parts and the manpower needed to build it in orbit and you can probably have one for the same cost as the planned return to the moon.

    1. Anonymous John

      Even better.

      If you can do the trip in 1 month, you are accelerating for 2 weeks, and decelerating two weeks. So there is little or no zero-g.

      One proposal I've read of is for the astronauts on the first Mars mission to orbit without landing. I can't see the point. What can they do that an unmanned orbiter can't do?

  21. Vladimir Plouzhnikov

    Mars trip could blind astronauts?

    Well, the obvious solution is to make the crew mixed-sex, isn't it? Will also solve the problem of tools slipping out of hairy palms and creating a health hazard...

    1. Anonymous Coward
      Anonymous Coward

      Or send blind astronauts

      Why not? It's not like the rest of us need to see *through* their eyes. Systems could easily be adapted to make the journey practical.The only argument I can see against this is that it would draw attention to the utter futility of a manned martian mission in the first place.

      1. Vladimir Plouzhnikov


        "utter futility of a manned martian mission in the first place."

        Please explain.

  22. A. Lewis

    But why...

    Why bother debating about an unrelated biological issue, if we don't yet have the technology to propel the spaceship?

    How do we know the technological advances that would solve the propulsion problem won't also help solve the other problems too?

  23. Purlieu


    just include a guitarist in the crew

    everything revolves around them

  24. Anonymous Coward
    Anonymous Coward


    Just a quick note to everyone suggesting the idea of spinning / rotating sections, a la 2001.

    You are aware that it was a science _fiction_ book....?

    Can you be sure that what the author had created would actually hold true in the real world?

    1. IglooDude


      If memory serves, Arthur C. Clarke came up with the concept of communications satellites too, so I wouldn't be too quick to dismiss his stories as not-technologically-feasible.

    2. Remy Redert

      re: 2001...

      You are aware that spinning sections are in fact the only reasonably easy to do approach to generating long term artificial gravity in space? There's plenty of fiction in Space Odyssey 2001 but the spinning artificial gravity section is not.

      Other examples of the same used in fiction can be found in at least Babylon 5 and PlanetES. Others can probably provide more examples

    3. Dodgy Geezer Silver badge

      "Just a quick note to everyone suggesting the idea of spinning / rotating sections, a la 2001.

      You are aware that it was a science _fiction_ book....?

      Can you be sure that what the author had created would actually hold true in the real world?"

      Because Kubrick put a vast amount of time into researching every aspect, including checking out every technical issue with the current world experts. Had you wondered why the 'ape-men' sections were so realistic? Courtesy of the Anthropology section of New York Zoo. The fashions worn at the time? Hardy Amis. He took up a huge amount of NASA technologists time....

    4. Bounty

      "Just a quick note to everyone suggesting the idea of spinning / rotating sections, a la 2001.

      You are aware that it was a science _fiction_ book....?"

      Which is exactly why so called "tablet computers" are unpossible.

  25. andy gibson

    Specsavers Shuttle Advert

    Where the Shuttle lands at Gatwick - not so far fetched after all then!

  26. Anonymous Coward
    Anonymous Coward


    Whiling away the journey by introducing your old geezer to Mrs Palmer and her five lovely daughters would be double trouble then.

  27. Spoonsinger

    Can't scientists come up with some sort of big hat?

    just wondering like.

  28. Anonymous Coward
    Anonymous Coward

    Out of focus != Blind

    Space Adapation Syndrome affecting eyes and meaning that the astronaut needs glasses doesn't necessarily mean that they go totally blind.

  29. Owain 1

    Constant acceleration

    I thought the mission to Mars would be under constant acceleration / deceleration. Would that provide enough "gravity"? Surely they're not going to coast all the way?

  30. Mike Bell

    OK, you doubters

    Two craft tethered by a 100m cable:

    a = v*v/r

    For a reasonable amount of artificial gravity (say 0.5g), v would be about 15.7m/s, which would give you a rotation of once about every 20 seconds.

    I don't think that would make anyone space sick if you happened to be looking out of a window. And if you needed to kill the rotation to do any fancy manoeuvres, it's only like going from 35mph to 0mph. Easily achievable with modest attitude thrusters.

    1. cloudgazer

      The motion sickness is more to do with the way that apparent gravity will change as you move around, than with looking out the window. Sitting down, standing up, walking with or against the rotation - they'll all result in a change in acceleration, and the human brain interprets changes in 'g' as falling.

      I don't think it would be insurmountable though - some people are less bothered by motion sickness than others, so it might just require careful screening of candidates.

      1. Richard 12 Silver badge

        No worse than being on a ship - the ship lurches about with little apparent warning and moves around constantly.

        Some people get incredibly seasick, but most are barely affected and even those who are affected almost always get used to it after a few days.

        More surprisingly, some people actually get landsick after spending a long time on board ship because the ground *isn't* moving anymore.

  31. JDX Gold badge

    You guys should watch 2001. I can't believe nobody suggested this already.

  32. Stevie


    Well, lucky for us we're never going to really go then, innit?

    Wait: Don't the crew of submarines also go short-sighted after a tour?

  33. J.G.Harston Silver badge

    Well, spin the damn thing, or develop constant thrust drive. Bonus of CTD is a 28-day round trip.

  34. Anonymous Coward
    Anonymous Coward

    Do the Maths

    Generating 1g with a rotation needs quite a fast rotation. If you have a 10m radius arm then (assuming my maths is correct) you need a rotation period of around 6s, which puts you at about 20mph. With a 100m radius arm you are doing just under 40mph with a rotation period of around 20s.

    Generating those speeds, especially assuming a pretty heavy craft, stabilising the rotation, and stopping it at the far end won't be trivial. It will also require quite a bit of maneuvre fuel over and above the fuel to take you to Mars. Again, not impossible, but also not trivial.

    If you can get away with a tiny fraction of g then things become a lot easier. With moon gravity you have 12s per revolution at 10m, and 40s per revoluation at 100m. Half the speed means a quarter of the energy required to get there, and a quarter the fuel load.

    1. Chemist

      On Earth with 1G

      your head and feet are so far away from the centre of gravity that there is little differential effect. In a small radius centrifuge there is. That would be far from physiological.

    2. Richard 12 Silver badge

      That's why most of the serious design proposals use a tether.

      You don't actually need the whole ring, just two modules with a long rope connecting the two.

      For bonus points, add a low-mass flexible collapsible tube with a rope ladder between the two so the two halves of the crew can mix without going EVA. Basically like a child play tunnel.

      The rope does need to be pretty strong - however it's only taking the weight of *half* the craft (one module plus self weight) so it doesn't need as much strength as you might think, and is well within what we can do now.

  35. gardener21

    Problem is more widespread...

    I've spent all my life living on a planet with a surface gravity of about 1G. Yet I still have blurred vision and need to wear corrective glasses or contact lenses. I am by no means alone in this.

    1. Anonymous Coward

      @ Gardner21

      That does bring up the intriguing possibility of what happens when you send someone with blurry vision into space. Maybe their vision would improve!!

  36. This post has been deleted by its author

  37. JJSmith1950

    Dear Anna...

    Please stop writing nonsense like: "...Mars missions, which would be a three-year round trip requiring rocket power beyond what we can currently muster."

    NASA could have sent a manned mission to Mars with Apollo era tecnology. In the 1970s several landers reached the surface of the planet, we had the "rocket power" then, we certainly have a lot more now.

  38. R.P.Charlie

    long amounts of time spent in space damages astronauts' eyes

    Reduced gravity has cited as the most likely cause - known as Space Adaptation Syndrome – includes spatial disorientation, nausea and vomiting.

    So does a large amount of time spent on a bar crawl.

  39. Slabfondler

    I saw this movie once...

    It had an old ape in a big white bedroom with a bone in his hand, he was shaking it at this big red eye that called itself Dave. I *think* they had chicks bringing him (the old ape, not the big red eye) food with special slippers that kept their eyes in one place,maybe they can use this for the Mars mission?

  40. Roger Mew


    This effect was known long ago with silly sods that climbed mountains. There is too much pressure in the eye balls which in turn damages the optic nerve. I guess the answer is to give all astronauts a trabotomy to reduce this pressure.

    Apparently under 20 is OK but for a person going up ito space it needs to be a lot lower.

    As one gets older it tends to go up so giving a regular eye pressure test should keep the situation under control and drugs can be used if the situation is temporary.

  41. Anonymous Coward
    Anonymous Coward

    It is the Monitors.

    My eyes have degenerated dramatically since I started spending so much time in front of a computer. I think that this is about the same thing as staring into the sun for prolonged periods, but staring at a monitor works its damage at a much slower rate than the sun will. Monitors just seem to be paper. They aren't.

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