The Martian

Question: If the MAV could be blown over by a storm of sufficient force, wasn't it very risky dropping the Ares IV Mav five years in advance of the mission?

Answer: The crew (and mission control) are in constant contact with the previously dropped MAV and would have aborted the mission and continued back to Earth had the MAV become inoperable before their arrival. Weir states this explicitly early in the book.

Answer: Yes, it is very risky unless the new Ares MAV is in an area with much calmer weather patterns.

Question: Exactly how long has Mark Watney been alone on Mars during the course of the movie?

Answer: In the book, he's stranded on sol 6, and leaves on sol 549, making it 543 sols (554 days). In the movie, he's stranded on Sol 18 and leaves on sol 561, making it 542 sols.

Question: Why would NASA decide to send a botanist on a mission to Mars? A planet where no plants can grow.

Answer: Part of his job, aside from also being a mechanical engineer, was to use soil taken from Earth to Mars, mix it with Martian soil then grow seeds in it to see how Martian soil is for growing crops. This would be preparing for a longer term mission where growing full crops to feed the crew would be part of the mission.

Answer: Botanists going to mars can study the ground and the dirt so they could make life on mars. Botanists are also helpful due to oxygen in space, he grows plants on the spacecraft for the oxygen that they give off.

Question: Is it realistic that Mars vehicles like Mark's rover or in some scenes his handcart would use rubber tyres? No Mars rover before used them and I would think they could not stand the low Martian atmosphere and temperature differences.


Chosen answer: Whatever was used before on Mars is irrelevant as to date, only robotic vehicles have been used. As this is depicting how humans would live and function on Mars, the vehicles would be designed quite differently. Presumably, the "rubber" tires have been specially manufactured to withstand Martian conditions. Mostly likely they would be solid and not have an inner tube filled with air or some other gas that is affected by the atmosphere.

raywest Premium member

Question: In the movie, the stripped down capsule that Mark is in tumbles uncontrollably through space. Admittedly it was a non-standard launch, but since this was the standard return vehicle, how was it intended to rendezvous/dock with the mothership? Wouldn't there be maneuvering thrusters?

Answer: He removed the thrusters to save weight for the launch.

Grumpy Scot

Question: Mark says he will have to get to the crater, which is 3200 kilometers away. Mark says he has one working rover, designed to go a max distance of 35 kilometers, before the battery has to be recharged at the hab. During the nighttime scene, he says he has doubled his battery by scavenging Rover 1, but if he uses the heater he will burn through half his battery everyday. I did some math, and worked out that the max distance his rover would be able to go without using the heater would only be about 140 kilometers. How would he travel 3200 kilometers to get to the crater?

Answer: Mark says he has 1 Rover that can travel 35km before recharging. He estimated he would need to travel for 50 days to reach the Ares IV site (down to approximately 22 days when not using the heater, as per your maths). Mark is shown using the solar panels (stolen from the Hab) to recharge the Rover during his journey. He drives for 4 hours before noon, waits 13 hours for the Rover to recharge to full and then starts driving again.

What does 22 days per my maths mean? I'm autistic.

"Per your maths" means according to how you calculated the math, the answer is 22 days.

raywest Premium member

Answer: He wouldn't need to use the heater because he salvaged the Radioisotope thermoelectric generator (RTG) and this also saves his power.

Question: #1 Wouldn't the space suits used on Mars have a heating device built into them, being it's so cold on Mars? Why did he have to rely on the RTG for heat in the rover? #2 Just before lifting off from Mars we see Watney cutting his hair and beard. He appears to be in another Hab, but when he's approaching the MAV in the rover, there's no Hab in site.

Answer: 1) The suits are heated, however this uses power (something he is rationing) and requires him to wear the suit at all times. He often removes it whilst in the rover. This is elaborated upon in the book. 2) He is shaving in the base of the MAV, in the area containing the ascent spacesuit.

Question: How can you tell the speed of a spacecraft from the inside when there is no way to measure it in relationship to anything else?

Answer: Using readings from an inertial guidance system (accelerometers and gyroscopes) a computer calculates the current velocity by detecting every instance of acceleration, deceleration and trajectory change. Another way is to measure the Doppler shift in radio waves from the spacecraft to mission control.

Sierra1 Premium member

Chosen answer: No reason is given in the film. But the books make mention that he has to have room for the oxygenator, water reclaimer and atmospheric regulator. All of which only work in pressurized areas.


Question: Watney leaves the Hab for the long trip to the Aries 4 site in the rover. Is there a restroom on board?


Chosen answer: No. The book answers this by stating that he uses a bucket for his waste.


Question: Mark finds pathfinder, and takes it back to the hab, and recharges it. Wouldn't he have to repair it first? The rover is very old, and hasn't been used in decades.

Answer: Maybe some slight repairs sure, but it wouldn't have been nearly as damaged as you would think. Unlike on Earth, the Martian atmosphere lacks enough oxygen to cause corrosion or rust. And since the Pathfinder has been buried, it wouldn't have really taken much damage from weathering or light past that point. In other words, the conditions of Mars would have actually preserved it pretty well.

Quantom X Premium member

I am not asking whether or not he would have to repair the rover due to the effects of corrosion, or rust. I am asking whether or not he would to repair the rover due to the effects of aging.

What I said still stands for that. A lot of the issues with equipment aging is due to being exposed to the elements. Oxygen in the air oxidizing metals, sun light cracking plastics and rubber, the presence of bacteria and other microscopic life forms causing bio degradation, etc. Those are the main reasons why machinery and equipment here on Earth are subject to deteriorating with time and age. The environment the Pathfinder was in is a stark contrast and it was basically kept preserved like in a museum... so to speak. Yes, it's been up there for 2-3 decades. But the amount of aging it would have taken from that might only be equivalent to a couple years or so if it were here on Earth. The environment, and especially the air and exposure to sunlight, are the main contributors to the aging process of non living items. Being buried under the Martian soil for 30 years most protected it from any exposure to the elements that would cause aging.

Quantom X Premium member

But being buried in sand could damage it too though right, Given that it could allow sand to get inside the rover, and damage the electronics?

No. Dust storms are a part of life on Mars - any rover would be designed to withstand sand intrusion, or not be affected by it to any serious extent, otherwise they'd stop working. Spirit and Opportunity massively outlasted their original mission parameters despite frequent dust storms which would apply much more pressure than being buried.

Yeah basically what he said. They are designed to withstand the strong winds on Mars picking up dust and small rocks that hit it at a much harder force and pressure than just the weight of dirt on it buried.

Quantom X Premium member

Question: How did Mark manage to make the hab last longer? He said he was in a hab designed to last 31 days.

Answer: It was designed to last a month with six occupants, but with only one the supplies would last a lot longer. As far as the structure itself, the "design" lifetimes are always conservative, as evidenced by the Mars rovers still running around Mars, such as Opportunity was designed to last at least 90 days, but is still ticking after 5000 days.


I thought that after 31 days the hab would run out of air.

Air for 31 days would assume they were using only canned air, and NASA included no extra for safety (like if they couldn't leave on time). Assuming they were using canned air, then with only one occupant the remaining air would last 6 times as long, so would still go well past the 31 day mark, though they were almost certainly using systems to recycle the air by scrubbing the CO2 so the air would last a lot longer. This is the same way air is handled in current NASA spacecraft. An offset though is we have a flame which is using oxygen at a greater rate than a person would, and plants that are also helping remove CO2 to produce oxygen, though the net of this would almost certainly be to have a higher oxygen use rate.

It's explained in greater detail in the book. There was a plentiful supply of oxygen for him to survive a long time, even using up some of it to produce water for the soil. The real risk was a potential build up of carbon dioxide, which would prevent the diffusion of carbon dioxide out of his blood and into his lungs.

He had an oxygenator in the Hab. That meant there was not a finite amount of oxygen.


Question: Look how Mark Watney is able to walk, and stand on earth just fine. In reality, wouldn't he have had a hard time readjusting to earth's gravity if he was stranded on Mars as long as he was, especially since Mars gravity is much lower than earth's?

Answer: The scene where Mark is back on Earth does not take place as soon as he got back. This takes places months after returning. He likely would have faced some difficulties readjusting to the Earth's atmosphere upon returning, but would have adapted to the atmosphere, and be able to walk and move around properly after some time had passed.

Casual Person

How do we know it takes months after returning? I didn't see any words saying months later.

A number of factors indicate it is much later. He has regained much of the weight he lost (which he could have gained during the journey back, along with using the gravitational wheel of the ship to help his recuperation), he now wears glasses, he has become more grey. Most importantly, the Ares V mission is about to launch, which was scheduled to be 5 years after the main events of the film.

Answer: He's gained a lot of weight and has been hired for a teaching position. It's safe to say a bit of time has gone by.

Brian Katcher

Answer: During the journey back from Mars, Mark would have been able to use the exercise equipment present on the Hermes. This would have helped his body re-adapt to heavier gravity. He would also be able to regain much of his lost body mass during the long journey back. NASA knew that the crew would spend a long time in low-gravity so the equipment was designed to keep them fit. Despite this, he would have had a fairly long recuperation time on Earth. The epilogue of the film is set after he has fully recovered and is able to return to work as a lecturer.

Question: When Watney causes an explosion while trying to hydrate his plants with hydrogen, he states that it was because he didn't account for the oxygen he'd been exhaling. We exhale carbon dioxide, with only trace amounts of oxygen. Could such tiny amounts of oxygen actually be calculated in his circumstances?


Chosen answer: It's not about calculating the precise amount of oxygen. What Watney means is he failed to take into account the fact that he would be exhaling some oxygen, so he wasn't careful to make sure his exhaled air didn't get anywhere near the still (by wearing a sealed, airtight helmet/spacesuit). (Also, there's more than just a tiny trace of oxygen in our exhaled air - for example, it's enough to support someone receiving mouth-to-mouth resuscitation - as Watney recalls in the aftermath of the book version of this scene).


I did check the book, then did further research. You were right-we exhale about 16-17 % oxygen. I understand what you were saying about the percentage not being the issue now. Thx for the informed reply.


I looked it up before asking the question. That's how I found out only trace amounts were being exhaled. I'll recheck the book as you stated.


Question: When Mark went to get Pathfinder he took about a 30+ days round trip. We didn't see him have to recharge the batteries like his 50 day trip to Aries IV. Why didn't he need the same equipment eg. Oxygenator for the Pathfinder trip?

Answer: No we didn't see him recharge, doesn't mean he didn't stop. He would have to recharge. He didn't need the big 3 because the trip was not as long, and he was able to make do with air filters, and his water supply.

Question: How is Mark communicating with the crew members through his headset when he is in the MAV? Why didn't they do that to begin with, instead of doing the alphabet thing with earth?

Answer: The same storm that marooned Watney destroyed the Hab's communications dish. The Hab couldn't directly communicate with Earth. The MAV had a communications system built in that was fully functional. How could he do that to begin with when the MAV at Ares 4 was 3200km from the Hab at Ares 3?

Grumpy Scot

Question: When the HAB blows and he loses his crop of potatoes, how do the other potatoes already harvested survive? They are just sitting in trays in the HAB and surely should have been destroyed by the vacuum.

Answer: Given the thin atmosphere and cold, the potatoes would have been nearly instantly frozen and partially dehydrated. They would still be edible and nutritious.

Grumpy Scot

Indeed-in the book, he mentions storing the extra potatoes in bags outside, so they would freeze and not rot. This especially came into play when he was making the journey to the other landing site.


Question: Watney digs up the plutonium and places it in the rover. Why is the rover so cold later after the HAB blows up?

Answer: He used the RTG to warm the rover on his trip to get Pathfinder. Once he returned he buried it again, since it posed a radiation hazard.

Grumpy Scot

I rechecked the book. He did NOT rebury it. In fact, he tore out extra insulation inside the rover so the interior would not get too warm during his upcoming trip to the other landing site. The RTG was, in fact, an integral part of his equipment for the journey. However, by tearing out an appropriate amount of insulation, he pointed out that the heat from the RTG would leak out some during regular operation. But sitting unoccupied for a while, enough heat might have leaked out to make it chilly.


Answer: Is that mentioned in the book? Don't remember it being mentioned, but I can recheck.


Question: Would it really be possible to make water using the method Mark Watney uses in the movie?

Answer: According to Internet sources, yes, it's possible to do this. Here's one link with more information:

raywest Premium member

Question: The gravity acceleration on Mars is 3.71/ms2 a little more than double our Moon and approximately 1/3 of Earth gravity. For this reason every falling object or walking/running people or bouncing object should be attracted to Mars in a "slow motion" fashion. Watching the movie I didn't notice such slow-motion effect. Was that a deliberate error in order to avoid huge additional costs and probably making the movie less tedious?

Answer: Most likely, yes. Though it is worth noting that is probably also part of the reason why the number of falling objects on screen is kept to a minimum, and there is one more thing: there is much less air resistance on Mars than there is on earth because of the thin atmosphere. For a real world comparison, look at the footage of Apollo 15 where David Scott drops a hammer and a feather, and the hammer doesn't fall much slower than it would on earth.


Factual error: When the crew is walking around the area of the Hermes with artificial gravity created by spinning the ship, the angle of the crew members' bodies should be perpendicular to the curved floor of the ship. However, in multiple shots, the crew standing at different locations of the room are seen standing at the same angle, directly upright.

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Trivia: The secret project created to use the Hermes to return to Mars to rescue Watney was called Project Elrond, a reference from the Lord of the Rings (also used in the original book of The Martian). Mitch Henderson, played by Sean Bean, was an attendee at the Project Elrond meeting. Sean Bean also played Boromir, who was an attendee at the Council of Elrond in the LOTR movie.


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