#markwatneysquad

Accuracies  ✔️

(📖/🎥) The orbital dynamics is correct. Andy even had to pick an exact mission date for it to work on! It had to coincide with both Thanksgiving (for the potatoes) and the departure window for Mars (when earth and mars are closest in orbit). The dates used for the movie are those dates! Andy modeled the flight paths of the Hermes, which you can see here.

(📖/🎥) Everything with Pathfinder is correct as well. The earth-mars communication time delay is right; the delay is on average 13 minutes and 48 seconds, about mid-way between the minimum delay of around 4 minutes and the maximum of around 24 minutes. Mark re-using the pathfinder is accurate too.

(📖/🎥) Mars Pathfinder was also a real mission that sent a lander and the Sojourner rover to Ares Vallis on Mars. While both lander and rover outlived their expected design lives, the last transmission was September 27, 1997. It was suspected they stopped responding because the batteries stopped working (they lasted 12X what they were expected to). So, as seen in the book/movie, re-powering it should make it work again.

(📖/🎥) Chris Hadfield, an astronaut and mission commander, said that Andy captured exactly the personality of an astronaut. He says that things like having to ‘work the problem’ are what their every day is.

Inaccuracies  ❌

(📖/🎥) The one everyone mentions is the dust storm that leads to the sol 6/19 abort. It is the biggest inaccuracy, and one Andy knew about and deliberately ignored. Mars’ atmosphere is very thin, at about 0.6% of earth’s atmospheric pressure. So while there are sand storms that are 150 km/h, the inertia of the wind would make it feel more like a 1 km/h breeze - which wouldn’t damage anything.

As mentioned Andy Weir was 100% aware of the inaccuracy. He says that he did have an original beginning in mind at first – instead making it a MAV engine test malfunction that lead to Mark being stranded. He decided against it because in a story of man vs nature he wanted “nature to have the first punch”. (He also says he wanted it to be awesome)

(🎥) Ridley Scott changed the day that the storm occurs on to sol 18, rather than the book’s sol 6, to make it so that Mark’s manure moment had more impact. What this did however, was create a plot hole. As I’ve mentioned in the 'accuracies’ section, Weir calculated all the orbital trajectories so that the crew’s time on Mars would coincide with Thanksgiving so that Mark would have potatoes; all the dates are accurate. This would make it so that the crew arrived at Mars on the 7th of November, 2035. If the crew aborted on sol 6, like in the book, they would abort on November 13th. The sol 18 abort, in contrast, would take place on the 25th. Now comes the question: what day is Thanksgiving in 2035? The answer is November 22nd. Three days before the movie’s abort date. There shouldn’t have been any potatoes left for Mark to grow.

(📖/🎥) (✔️)The hydrazine reduction, removal of oxygen from the CO2, and subsequent combustion to form water is 100% accurate. The chemistry behind it is right; the reaction and the amounts of everything made etc. (❌) But Andy got a little bit wrong. Reducing hydrazine is obviously very exothermic (it is rocket fuel). Andy also told how much hydrazine Mark reduced, how long it took him to reduce it, the volume of the Hab, and the make-up of the air inside the Hab. From that the increase in temperature inside the Hab can be calculated. Which would be 400°C (752°F). Which is fatal.

If Mark had put large rocks in the Hab they would have acted like heat sinks to absorb all the excess heat and Mark would have been able to preform the reaction safely.

(📖/🎥) Another inaccuracy, though more partial, that Andy knew about was the hand-waving around the topic of radiation protection. Currently there is no lightweight, flexible material that protects against radiation. Mars’ atmosphere, as I mentioned before, is very thin and offers very little protection from ionizing radiation from the sun. After how long Mark was on Mars he should have been exposed to enough radiation that he would be riddled with cancer. In the book there is like a throwaway sentence about it.

“With no magnetic field, Mars has no defense against harsh solar radiation. If I were exposed to it, I’d get so much cancer, the cancer would have cancer. So the Hab canvas shields from electromagnetic waves.”

It isn’t even mentioned in the movie from what I remember. Seeing as how the story takes place in the future (2035) however, this may not be an inaccuracy per se?

(📖/🎥) Another inaccuracy that might be solved by a future technology is rapid EVAS. The time in which it takes to go from deciding to go on an EVA to being outside is very very reduced. In actuality it takes about 4 hours to go out to do an EVA. 

(🎥) Another thing about EVA suits (especially the one used in the rescue at the end) - I’m like 90% sure that the visor is opaque in real life. I think it is to reflect sun and reduce glare like sunglasses (as well as used to protect against radiation, extreme temperature and small projectiles). In the movie however, you can clearly see their faces. 

(📖) There are some inaccuracies that have only become inaccurate since after the book was published. For example the EVA suit PLSS (primary life support system) is now able to separate CO2 from the air without the use of filters. In the book the limited filter supply meant that Mark had to ration EVAs. This was not mentioned in the movie.

(📖/🎥) Furthermore, thanks to Curiosity it has also been found that for every cubic meter of soil on Mars there is about 35 L of water. You remember that a big part of the plot was Mark needing enough water to grow food. It’s what made him resort to the hydrazine reduction. It would not have been as big of an issue if Andy knew that.

Andy Weir maintains that where curiosity is (Gale Crater) and Acadalia Planitia are in different Martian climates, as they are about 5,000 km (3,107 mi) apart! Much like Earth has varying climates. And obviously no one can prove him wrong until they send a probe to the location. 

(📖/🎥) The Ares 3 landing site described in the book is not how the actual site looks on mars. when andy was writing the book all that was known about acidalia planitia was that it was a featureless plain, a desert with a lot of flat land - that’s how he described it. Andy also gave the exact coordinates of the site (31.2°N, 28.5°W) on Mars. So the University of Arizona, which runs the HiRISE camera on NASA’s Mars Reconnaissance Orbiter, took a photo of the actual coordinates! It looks nothing like described, naturally.

This is what it actually looks like: