IF ASTRONAUTS ever make it to Mars, they鈥檒l need a roof over their heads.
Bricks are too heavy to lug all the way from Earth, but with just a few
bucket-loads of polyethylene powder, they could rustle them up when they get
there.
鈥淚n a couple of decades or so, humans may be going to Mars,鈥� says Richard
Kiefer of the College of William and Mary in Williamsburg, Virginia. 鈥淏ut you鈥檙e
likely to be there for a long time, so you鈥檙e going to need a habitat.鈥�
Because Mars has a very thin atmosphere and no magnetic field, astronauts
would be exposed to cosmic radiation. 鈥淥n Earth, the magnetic field and the
atmosphere protect us on the surface from cosmic radiation,鈥� says Kiefer.
Buildings on Mars would have to shield you from these.
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It鈥檚 unlikely astronauts will have enough room on their spacecraft for the
right materials to keep out high-energy particles. So Kiefer and some NASA
researchers decided to try to take advantage of the local soils. 鈥淭he idea is to
see if we can use Martian topsoil mixed with polymer powder to make bricks,鈥� he
says.
With no suitable equivalent to Martian topsoil, Kiefer tried the next best
thing: some simulated lunar topsoil sold off-the-shelf by the University of
Minnesota. 鈥淚t has very similar characteristics,鈥� he says. He mixed it with
polyethylene powder and heated the mixture to 110 掳C for half an hour at a
pressure of 100 pounds per square inch (690 kilopascals). The finished bricks
were 鈥済ood quality鈥�, as long as they weren鈥檛 more than 93 per cent topsoil, says
Kiefer.
鈥淪hielding against radiation is a tricky business because you can actually
make matters worse by interposing materials,鈥� says Roger Emory of the Space
Science and Technology Department at the Rutherford Appleton Laboratory near
Oxford. That鈥檚 because incoming radiation can break down the nuclei of the atoms
in the shield, producing more harmful particles. But Kiefer says polyethylene
bricks will minimise this risk. 鈥淧olyethylene has more hydrogen than any other
polymer, and hydrogen is good because it can鈥檛 break apart like this,鈥� he
says.
Kiefer is now checking the shielding properties of his bricks by firing high
energy particles at them at the Brookhaven National Laboratory in New York.