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I read Andy Weir's "The Martian" and saw the movie, which is supposed to be realistic science fiction. And I immediately saw a couple of huge flaws, one of which I'd like to tackle with this question:

Warning: Spoilers ahead

In one scene a storm occurs on the surface of Mars. The winds are strong enough to cause humans to struggle to stand and to tear a satellite dish from its anchor. However, the atmosphere of Mars is much less dense than Earth's and I don't think even the winds of the strongest of Martian storms could have such an effect.

Could the winds of a Martian storm cause the average human to stumble or fall?

Or lift and throw a satellite dish?

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The winds on Mars are much faster than typically on Earth, however, the atmosphere is much thinner. This can cause some unusual effects, somewhat analogous to high speed/ low torque vs low speed/ high torque.

Let's assume the satellite dish had a surface area of $1 m^2$, a reasonable assumption. Also, let's use the math from this question, and let's use the Martian listed wind, of 175 kph. That's 48.61 m/s, which is a high wind speed. That creates a pressure of

${q_M}$ ${=}$ ${0.5(0.02)(48.61)^2}$ ${=}$ ${23.62}$ ${Pa}$

For our $1 m^2$ antenna, that exerts a force of 23.6N, or about the force of gravity with a 2.5 kg weight on it. That would probably be enough to bend the dish, if build on Earth. However, there are other things to keep in mind.

  1. This dish would be built to survive on Mars, and thus would likely be lighter than an analogous Earth antenna. This would make it break more easily.
  2. Anything on Mars will have to survive thermal cycles, making it more brittle.
  3. Once something is torn, it will tend to move up to the actual wind speed. This could cause damage for anything that actually gets loose.
  4. The pressure on Mars effectively goes up in a dust storm, as there is more mass in the air, likely causing the pressure to be higher.
  5. The abrasive nature of dust likely reduced the strength of the antenna over time, in particular during the very storm mentioned in the book/movie.
  6. The Hermes 3 landing site is one of the lower portions of Mars. In fact, most of the landing sites for landers are in the lower regions (Parachutes work better there). Thus, there is likely higher atmospheric pressure than there would be at other locations, increasing the effect of the wind even more. According to Wikipedia, the highest pressure on Mars is about twice that of the mean.

Taking all of the above into account, it could be possible to have at least a 4 times higher effective pressure, which makes the story a bit more believable. Still, I think this is one of the less scientifically accurate parts of the book, but it's not completely impossible.

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  • $\begingroup$ Point 3 is particularly interesting - things wouldn't blow away easily, but when they do they will end up travelling pretty fast... eventually $\endgroup$ – Jon Story Oct 6 '15 at 14:45
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    $\begingroup$ In fact Andy Weir has acknowledged that that part is not scientifically accurate and that he was aware of that but included it for dramatic purposes: reddit.com/r/books/comments/2tyz6p/… $\endgroup$ – Pepijn Schmitz Oct 7 '15 at 15:37
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Andy Weir himself considers this the biggest scientific inaccuracy in the movie in an interview with NPR he stated:

The biggest inaccuracy in the movie is straight from the book, so it's also a big inaccuracy in the book. It's right at the beginning, the sandstorm that strands him there. (So this is not a spoiler; everyone knows he gets stranded there due to a sandstorm.)

In reality, Mars' atmosphere is 1/200th the density of Earth's. So while they do get 150 km/hr sandstorms, the inertia behind them — because their air is so thin — it would feel like a gentle breeze on Earth. A Martian sandstorm can't do any damage. And I knew that at the time I wrote it.

I had an alternate beginning in mind where they're doing an engine test on their ascent vehicle, and there's an explosion and that causes all the problems. But it just wasn't as interesting and it wasn't as cool. And it's a man-versus-nature story. I wanted nature to get the first punch.

So I went ahead and made that deliberate concession to reality, figuring, "Ah, not that many people will know it." And then now that the movie's come out, all the experts are saying, "Hey, everyone should be aware that this sandstorm thing doesn't really work and Mars isn't like that."

So I have inadvertently educated the public about Martian sandstorms. And I feel pretty good about that.

So in summary, the level of wind as shown in the movie or in the book is not possible on Mars but was done for storytelling reasons.

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  • $\begingroup$ IMO the plastic wrap over a large opening holding together under 1 atm of pressure (or an appreciable fraction there of) is a much more egregious error.. $\endgroup$ – pericynthion Dec 9 '18 at 1:36
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    $\begingroup$ @pericynthion I agree but that's only in the movie, in the book Mark uses "hab canvas" which is the same material his habitat is made out of. This would withstand the pressure. I think the movie producers just liked duct tape. $\endgroup$ – Dragongeek Dec 9 '18 at 1:42
  • $\begingroup$ In an interview, he also said that if he had to rewrite the book, the sandstorm may have been replaced by a lightning strike. $\endgroup$ – Eth Dec 10 '18 at 14:30
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The martian winds are not as strong as portrayed in the Martian. The air pressure on Mars is 1% of Earth sea level, and 200kph, while enough to notice, would not be enough to blow you over. Calculating the earth equivalent speed using the formulas in the related question posted by @1337joe 200kph on mars is 25kph on the earth, or 15mph. That's a breeze, not a gale strong enough to make you stumble even in lower gravity, and I can't imagine it ripping a satellite dish off its mountings. Even if it did come off the dish would be going only 25kph, that's more of a tumbleweed than a projectile.

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