I have not read the book of The Martian, but there was one glaring omission in the movie that struck me.

How were the crew in the Hermes protected from radiation?

In space, especially interplanetary space, radiation is a big problem. Look at this from Wired:

A new study highlights one of the big problems with extended space travel: galactic cosmic ray radiation. According to the report, astronauts on the International Space Station would receive doses that exceed their lifetime limits after just 18 months for women and two years for men. A Mars mission crew would be spending at least this long in the harsh radiation of deep space.

The Hermes looks very pretty, but it is all windows and gyms. Not much that would protect from a radiation storm. Even when the crew are discussing doing another round trip, the fact that they are massively increasing their own cancer risk is not mentioned.

Is this covered in the book at all?

  • 2
    Valeri Polyakov spent 14 months in space in one go, and 22 months total. Gennady Padalka spent 27 months total. So I guess the 18 months limit is a safe bet.
    – Agent_L
    Mar 15, 2016 at 16:06
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    @Agent_L: apollo's answer adds some detail, the NASA lifetime limit "would raise the lifetime risk of cancer by 3 percent". So not precisely "safe", but it's by no means surprising if those two people exceeded it and are fine so far. Mar 16, 2016 at 13:16
  • @SteveJessop My point exactly - it's an acceptable trade-off for someone willing to risk life by travel to Mars.
    – Agent_L
    Mar 16, 2016 at 16:02
  • He also addresses the question in this video. youtube.com/watch?v=Wq3xtZ8AjPE
    – Brady Gilg
    Mar 21, 2016 at 22:33
  • 1
    @Agent_L, both Valeri Polyakov and Gennady Padalka were on a space station. That is completely different from a trip to Mars or even to the moon because the space stations are always inside the outer boundaries of the Van Allen belt (generally on a low earth orbit). Any travel outside of the Van Allen belt requires better radiation shielding than what is used on the space station.
    – user40760
    Apr 8, 2017 at 18:32

2 Answers 2


It was handwaved.

“In the book they have this really thin, light, flexible material that blocks all radiation,” says Andy Weir, author of the book The Martian on which the film was based. “There’s nothing even remotely like that in the real world. That was the magic I gave him so the story would progress. Otherwise Mark would have different kinds of cancer.”

  • 5
    "Hand Waved" not something I was familiar with tvtropes.org/pmwiki/pmwiki.php/Main/HandWave (warning TV tropes link) Mar 14, 2016 at 11:53
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    @JeremyFrench There was actually a lot of handwaving in the book/film. For example even the big Martian storm is unrealistic as Martian winds are very mild (estimated to top out ~6mph). That being said Andy Weir acknowledged a lot of it and its all for the purpose of moving the story forward. Mar 14, 2016 at 13:44
  • 39
    @DavidGrinberg Martian winds are a lot faster than 6mph (mars.nasa.gov/news/whatsnew/… says 60mph). They may top out at the force of an Earthly 6mph wind though because of the thin air.
    – ceejayoz
    Mar 14, 2016 at 14:10
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    @ceejayoz Thats probably what I meant :) Mar 14, 2016 at 14:42
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    Material that blocks all radiation... an interesting choise for a window... just saying.
    – einpoklum
    Mar 14, 2016 at 21:28

He would die with that kind of protection.

There were some inaccuracies in the book and the plot. But it was a great book anyway.

That list of doom:

1. Atmosphere

On a reddit Q&A, one fan asked Weir if such withering storms were possible on Mars.

Weir's answer: "No. Mars’s atmosphere is too thin. This was a deliberate concession to drama that I made because it’s a man-versus-nature story and I wanted nature to get the first punch in."

2. Cosmic Rays (Radiaiton Poisoning) (ANSWERING YOU HERE)

After being left alone on Mars, Watney makes his way toward the Schiaparelli crater. Spending that much time on the planet would expose him to a dangerous, and probably fatal, amount of cosmic rays, if not for his handy (and fictional) radiation blocker.

"The book has a completely fictional material that blocks radiation. No such thin, flexible, light radiation shielding exists in the real world" — Andy Weir, author, 'The Martian'

NASA limits its astronauts to between .8 and 1.2 sieverts of lifetime radiation exposure, which would raise the lifetime risk of cancer by 3 percent. Because the sample size of astronauts who have spent a considerable time in space is so small, the exact health effects of cosmic ray exposure is clouded with uncertainty.

The most effective shields against cosmic rays, like water or liquid hydrogen, tend to be heavy and not portable—meaning they’re suitable inside the walls of a space capsule, but impractical in a spacesuit. Researchers are working on plastic cosmic ray shields, but haven’t gotten there yet.

3. Producing Water

Watney mixes hydrazine, a toxic substance usually handled by people in hazmat suits, and oxygen to make drinking water. The admixture also produces ammonia which is poisonous.

“Yes, very toxic. I didn’t know that at the time. Had I known, I would have had him wear his EVA suit during the process,” Weir replied during the Q&A.

  • 49
    At least this author did all the research and made conscious decisions about when to break the realm of scientific reason for the sake of plot instead of simply being oblivious to it, or in the few cases he actually messed up, admitted to it.
    – corsiKa
    Mar 14, 2016 at 16:36
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    @corsiKa I agree, in fact The Martian is one of my all time favourites. He is also a developer, which makes him even cooler.
    – burcu
    Mar 14, 2016 at 16:49
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    @Paul No, I actually meant what it says. Read the second explanation. The provided protection is not enough to survive the cosmic rays. He would die because of radiation poisoning.
    – burcu
    Mar 14, 2016 at 20:42
  • 3
    Oh, "that kind of protection" means "normal thin shielding". I was reading it as "radiation shielding" in general.
    – Paul
    Mar 14, 2016 at 23:50
  • 1
    I was confused by that header as well, and eventually decided you meant he would die with windows and gyms as protection, which is also confusing since you seem to be talking about Mark on the planet, not on the ship.
    – DCShannon
    Mar 15, 2016 at 2:23

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