17

It was clearly demonstrated later in the movie that the habitat could survive Martian dust storms. Why was the crew in such a rush to leave?

37

The pilot was worried that if the MAV (Mars Ascent Vehicle) tipped beyond 12 degrees, it would topple over and that they would be stranded on the planet's surface with no means to re-enter orbit. When the speed of the storm was announced (e.g. sufficient to knock over the MAV), the Captain took the decision to scrub the mission and fall back to space.

In the event, the storm hit slightly earlier and with greater force than expected and the module tipped to 13 degrees. The pilot used a reaction thruster to temporarily upright the escape module, but this was only a short-term solution that cost them fuel and bought them a few extra seconds.

To answer your specific question, had they decamped to the HAB(itat), they would have all died of starvation within around 70 days when the food supplies ran out.


The description in the book is quite similar;

“Strap in!” he yelled to the crew. “We’re tipping!”
The MAV creaked as it tilted faster and faster.
“Thirteen degrees,” Johanssen called out from her couch.
Buckling his restraints, Vogel said, “We are far past balance. We will not rock back.”
“We can’t leave her!” Beck yelled. “Let it tip, we’ll fix it!”
“Thirty-two metric tons including fuel,” Martinez said, his hands flying over the controls. “If it hits the ground, it’ll do structural damage to the tanks, frame, and probably the second-stage engine. We’d never be able to fix it.”

...

“I’ve got one trick. If that doesn’t work, I’m following her orders.” Bringing the orbital maneuvering system online, he fired a sustained burn from the nose cone array. The small thrusters fought against the lumbering mass of the slowly tilting spacecraft.
“You are firing the OMS?” Vogel asked.
“I don’t know if it’ll work. We’re not tipping very fast,” Martinez said. “I think it’s slowing down…”
“The aerodynamic caps will have automatically ejected,” Vogel said. “It will be a bumpy ascent with three holes in the side of the ship.”
“Thanks for the tip,” Martinez said, maintaining the burn and watching the tilt readout. “C’mon…“
“Still thirteen degrees,” Johanssen reported.
“What’s going on up there?” Lewis radioed. “You went quiet. Respond.”
“Stand by,” Martinez replied.
“Twelve point nine degrees,” Johanssen said.
“It is working,” Vogel said.
“For now,” Martinez said. “I don’t know if maneuvering fuel will last.”

  • 3
    This is largely the same as the reasoning given in the book. – Kevin Oct 11 '15 at 14:13
  • 1
    @ruakh you're right. It's just nowhere near the beginning of the book, thanks to the odd structure :) They are, in fact, mostly the same. – hobbs Oct 11 '15 at 18:05
  • 1
    @RobertF You can't lower the MAV gently to the side - the maneuvering thrusters have nowhere near enough force for that. The only thrusters powerful enough are the main thrusters, and those can't be used for tipping the ship over and back again. And even if you could, you'd still have a good chance of damaging the shuttle. They were ready for an emergency ascent - they probably even had training for a similar scenario. – Luaan Jun 15 '16 at 7:41
  • 1
    @Valorum Carbon fibre, or Kevlar cables strong enough to anchor the MAV from the nose cone wouldn't need to be very heavy at all. Also in an emergency ascent they presumably would just detach them from the nose cone and leave them behind. – user1751825 Oct 13 '16 at 13:10
  • 1
    @User1751825 - A system that anchors you firmly to the ground seems exactly the sort of thing you don't want to have to worry about in the case of an emergency. – Valorum Oct 13 '16 at 14:09
-5

Actually, they left for no reason whatsoever. The dust storm was never strong enough to push over the MAV, nor was it strong enough to nearly kill Watney with the antenna. It was just a plot element, not something that is scientifically accurate. So use whatever excuse you want, it just sets up the fun of the story.

The dust storm, according to the book, blew over 150kph. Very fast, for Mars. However, the surface pressure is only about 7hPa,or 0.6% of Earth's surface pressure. Even assuming wind pressure force scaled linearly with pressure [it doesn't] the force on the MAV was about what you'd feel with a 0.5 or 1/2 mph wind on earth. Even being extremely generous with the math for the weight of the dust, you're still looking at under 5mph earth equivalent. Gravity is weaker, but not nearly weak enough for that to be a issue.

  • 11
    Something doesn't need to be real-world-accurate to be true within a story. In OUR world Martian storms can't get that strong, but in THAT world they clearly can. They did leave for a reason, it's just a fictional one. Which makes sense, given that it's a fictional story. – Nerrolken Nov 2 '15 at 14:27
  • @James - This was a major oversight by the author of the book. But Nerrolken is right, the Mars in the film was definitely not the Mars of reality. – RobertF Nov 2 '15 at 15:16
  • Actually it's wasn't just the hurricane force dust storms that were unrealistic. For example, there wasn't much evidence of the lower gravity on Mars (too difficult & costly to simulate low gravity in a film). Also, the rock formations in the film were scenic but looked very Terran (since these scenes were filmed in Wadi Rum in Jordan). I imagine astronauts would not have wanted to land their rocket in mountainous terrain, but rather on a boring, flat plain. But that wouldn't have been as dramatic.The big windows on the Ares III also seemed a bit silly & made the ship look like a 5 star hotel. – RobertF Nov 2 '15 at 15:22
  • 1
    This doesn't answer the question in any meaningful sense. Within the story, the MAV is at risk. – Valorum Mar 15 '16 at 9:12
  • 2
    @RobertF It wasn't really an oversight - it was just a concession made for the sake of the story. There just isn't a danger available on Mars that would 1) not destroy the station and 2) force the crew to evacuate right now. If such storms were possible on Mars, they would be the perfect danger for such a purpose - and for most people, it doesn't break the suspension of disbelief to have a storm like that, and that's what matters in a story. – Luaan Jun 15 '16 at 7:46

protected by Community Jan 12 '16 at 22:14

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