Why were the MAVs sent so far in advance of missions?

The movie The Martian wastes no time in getting the lead character stranded on Mars, and my question has to do with the events and details of the opening scene and how they relate to the MAV provided for the Ares IV mission, which Watney uses at the end of the film.

To recap, the scene starts off with Martinez driving out to the MAV site for the Ares III mission to make sure it's not leaning too far for proper use. When the storm hits the force of the wind and particles blowing around cause the MAV's structure to lean, which causes Martinez to note that if the MAV leans further than 12.5 degrees from upright the entire structure will fall over.

Given this, why did NASA send the Ares IV MAV, or for that matter any MAV, so far ahead of missions? Was this one storm meant to be seen as a freak incident? They note that NASA has prepared their equipment and facility to withstand certain storm forces, and that this one is beyond those design parameters, so if it's possible for storms to get this bad on Mars why risk sending the MAVs so far ahead and risk it toppling over due to a storm on the planet long before the arrival of any crew members?

I know they explained that some items were sent ahead to reduce the payload the Hermes has to carry each trip, but the risk of losing vital equipment to storm activity on Mars by sending it that far in advance just baffles me.

plot-explanation the-martian

Best Answer

Why did they send the MAV to Mars so early?

The core answer is: The MAV needs time to make fuel.

The MAV is pretty cool. Turns out, through a neat set of chemical reactions with the Martian atmosphere, for every kilogram of hydrogen you bring to Mars, you can make thirteen kilograms of fuel. It's a slow process, though. It takes twenty-four months to fill the tanks. That's why they sent it long before we got there. Ch. 1

NASA doesn't want to spend the fuel to send fuel to Mars when the fuel can just be made on Mars. There is a quote in the book/movie that supports this idea when they say something along the lines of: "NASA isn't in the habit of sending things into space when the don't have to."

Wasn't this tremendously risky because a storm could blow the MAV over?

Per the responses to another question: Yes this was a freak storm.

Both the book and the movie specify that the MAV can resist winds of up to 150 kph.

The maximum wind speeds recorded by the Viking Landers in the 1970's were about 30 meters per second (60 miles an hour) with an average of 10 m/s (20 mph). Just as on Earth, at certain latitudes, the winds tend to blow in certain directions. - NASA Mars facts

To outright steal a second quote from another answer:

60 miles per hour is about 96 kilometers per hour. So the winds would have to exceed their maximum recorded values (for where ever Viking landed) by 50% in order to reach the maximum tolerance of tilting, but NASA doesn't expect those wind speeds. It was bad luck that the Ares III mission experienced what might be called a "storm of the century" given its severity.

But wait could this really happen since the air pressure is 1/20^th Earth norm?

In a comment a user (DavidS) remarked:

The author has gone on record stating that the initial storm would not have been powerful to cause the problems it did in the book, but made a rare concession to drama in order to get Watney stranded.

^{As you can probably tell essentially all of my answer is copy/pasted from the other site since we can't duplicate across sites. I marked this as a community wiki so I can't profit from the quoted material. Furthermore the quoted material should be easy to spot.}

Please read the answers to these two questions for more information.