The physics of the sands of Mars
- URL to an article from NASA
First few paragraphs
"January 31, 2005: Imagine this scenario. The year is 2030 or thereabouts.
After voyaging six months from Earth, you and several other astronauts are the
first humans on Mars. You're standing on an alien world, dusty red dirt beneath
your feet, looking around at a bunch of mining equipment deposited by
previous robotic landers.
Echoing in your ears are the final words from mission control: "Your mission,
should you care to accept it, is to return to Earth--if possible using fuel
and oxygen you mine from the sands of Mars. Good luck!"
It sounds simple enough, mining raw materials from a rocky, sandy planet. We
do it here on Earth, why not on Mars, too? But it's not as simple as it
sounds. Nothing about granular physics ever is.
Granular physics is the science of grains, everything from kernels of corn to
grains of sand to grounds of coffee. These are common everyday substances,
but they can be vexingly difficult to predict. One moment they behave like
solids, the next like liquids. Consider a dump truck full of gravel. When the truck
begins to tilt, the gravel remains in a solid pile, until at a certain angle
it suddenly becomes a thundering river of rock.
Understanding granular physics is essential for designing industrial
machinery to handle vast quantities of small solids--like fine Martian sand.
The problem is, even here on Earth "industrial plants don't work very well
because we don't understand equations for granular materials as well as we
understand the equations for liquids and gases," says James T. Jenkins, professor
of theoretical and applied mechanics at Cornell University in Ithaca, N.Y.
"That's why coal-fired power plants operate at low efficiencies and have higher
failure rates compared to liquid-fuel or gas-fired power plants."
So "do we understand granular processing well enough to do it on Mars?" he
Let's start with excavation: "If you dig a trench on Mars, how steep can the
sides be and remain stable without caving in?" wonders Stein Sture, professor
of civil, environmental, and architectural engineering and associate dean at
the University of Colorado in Boulder. There's no definite answer, not yet. The
layering of dusty soils and rock on Mars isn't well enough known.
[Non-text portions of this message have been removed]
- --- In email@example.com, derhexer@a... wrote:
> Let's start with excavation: "If you dig a trench on Mars, howsteep can the
> sides be and remain stable without caving in?" wonders SteinSture, professor
> of civil, environmental, and architectural engineering andassociate dean at
> the University of Colorado in Boulder. There's no definite answer,not yet. The
> layering of dusty soils and rock on Mars isn't well enough known.Surely it's actually EASIER than on Earth... after all, the gravity
is lower (less risk of cave-ins), and there is considerably less
moisture about (though this might not be the case deep underground
of course), meaning less risk of landslides.