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Fact & Fiction: The Martian

Fact & Fiction: The Martian

Okay Earthlings - y'all have seen The Martian, yes?

The one where Matt Damon is left behind on Mars and he spends lots of time building a potato farm and driving a dune buggy.

Credit the Gorton Community Center

Credit the Gorton Community Center

Remember how Matt got stuck there in the first place? There was a dust storm coming and all the astronauts scattered to evacuate Mars ASAP. Then Matt Damon gets himself smacked in the face with space debris and he's lost in the abyss and NASA has to figure out how to save him. That’s the basic summary, anyway.

Some Caveats

It is impossible for Matt Damon to be physically thrown through the air by a dust storm on Mars. In fact, the Martian atmosphere probably couldn't pick up that door that smacked him in the first place. And the struggle those other guys went through to get back to the ship?!

IMPOSSIBLE.

Credit UCAR

Credit UCAR

A Martian dust storm would actually be more like this:

Mars dust storms would feel like a light breeze because the atmosphere is far less dense than Earth's. At an average of 6.0 mb, Mars' surface pressure is 1/1000th that of Earth's. You'd feel pretty light not bearing the weight of the world on your shoulders (hehe)but you would NOT be thrown into the air.

A frisbee wouldn't go far either. You could have the world's most lame frisbee golf tournament on Mars because the atmosphere is too thin to hold up a frisbee! Dust, on the other hand, is very light material.

By the way, when we talk about Mars dirt, we call it "dust." This used to really bother me because dust is dust and dirt is dirt, but then I remembered the term “the dust bowl” and got over it.

This is an actual photo of the 2001 (Earth year) Mars Global Dust storm from the Mars Orbiter Camera on the Mars Global Surveyor satellite.

MGS MOC

MGS MOC

These storms cause anomalies in the pressure data we receive from rovers, kind of like the low-pressure systems associated with Earth storms. A Mars dust storm will raise atmospheric pressure, though. More stuff in the atmosphere swirling around, air converging in some places over others, that convergence lifting more dust.... however, anyone with even a small history in atmospheric science will find the global nature of dust storms odd, even if you can't place why that is. There's a lot we don't understand about them, but we do know that some seasons favor dust storms more than others. Those tend to be the warm seasons.

Also, keep in mind that the Hadley Cell on Mars is different than on Earth. The Hadley Cells are the first cell above and the first cell below the equator in this photo. We tend to see rising air around the equator because of this. Earth also has a strong Coriolis effect, which is a complicated idea in atmospheric dynamics but I'll offer the simplest explanation I can:

The Coriolis Effect is the deflection of an object traveling over a long distance. In the northern hemisphere, the object is deflected to the right. In the southern hemisphere, to the left. Why? If you are on a plane traveling from Louisiana to Minnesota, you take off from a location nearer the equator and you land in a location nearer the north pole. If you could measure the distance between the surface of the Earth and the Earth's axis, you'd find the distance between Louisiana and the axis is longer than between Minnesota and the axis. The Earth turns west to east at an angular velocity (speed) of 360 degrees per day, but Louisiana is further from the axis than Minnesota, so to make that turn in a day it needs to go faster than Minnesota. When you take off from Louisiana, the airplane conserves that momentum toward the east so where you end up depends on both the speed of the plane + the speed of the Earth turning around the axis (plus friction blah blah blah I said this was a simple explanation). If the pilot doesn't correct course, you'll end up in Washington D.C. or something.

So Earth's Coriolis effect deflects winds to the right in the northern hemisphere and to the left in the southern. The Coriolis effect is largely the reason most storms don't survive crossing the equator. The storm "un-spins" itself and dies.

On Mars, there's just one Hadley Cell and it crosses the equator. There's also a weak Coriolis force because the atmosphere is so thin! Just like Matt Damon can't be pushed by the winds on Mars, neither can Mars' Coriolis force have much of an effect on large systems on the planet. This means that dust storms don't have a lot working against them. They can pretty easily take over a planet.

So I’m left to wonder why Andy Weir would choose to stick with this narrative.It is exciting, no doubt, but there are so many other physically possible ways to get stuck that would be equally exciting and factual: a lightning storm would be cool or Matt could fall in to Valles Marineris (the canyon).

So there you have it, fact & fiction about The Martian. Whatever Andy’s motives were, he wrote a thrilling novel and I enjoy the movie despite the physicality issues.

An Overview of Mars

An Overview of Mars