Scientists Design Mars Bricks

W I L L I A M S B U R G,  Va.,  Aug. 14, 2001 -- Ryan McGlothlin takes a sugar-like powder, stirs in a substance that resembles flour, pours the mixinto a mold and bakes it.

The end result is not a cake but a small, shiny, black bar designed to shield against radiation. The “sugar” really is polyethylene, and the “flour” is a gray topsoil.

McGlothlin, a chemistry major at the College of William andMary, and chemistry department chairman Richard Kiefer are usingthose ingredients to develop a material to make bricks that wouldprotect astronauts against radiation on Mars. They are working withaerospace researcher Sheila Thibeault at NASA Langley ResearchCenter in nearby Hampton.

“What we’re doing is the basic research, establishing that yes,you can do this,” Kiefer said. The work also could haveapplications on Earth, such as use in shields around nuclearreactors, he said.

Thinking Ahead

NASA hopes to put people on Mars within the next severaldecades. Because of the different orbits of Earth and Mars, thewindow of opportunity for travel between the two planets occursonly once every two years. That means that anyone traveling to Marswould have to stay there for a long time.

The prospect of an extended stay on Mars prompts a number ofconcerns, among them the health effects of galactic cosmicradiation, found nearly everywhere in space. The magnetic fieldsurrounding the Earth deflects the radiation, but Mars does nothave such a field.

Radiation can cause illness or even death, depending on thedosage and length of exposure. Therefore, astronauts will need amaterial they can use to build shelters and laboratories that alsowill shield against radiation.

The lighter the material is in terms of mass, the better itsshielding properties, and research has shown that liquid hydrogenis the best possible shield, Kiefer said. “But that’s a littleimpractical to take to Mars,” he said.

So the next best thing is a solid polymer, or chemical compound,that contains a lot of hydrogen. And polyethylene, a very cheapplastic from which plastic bags are made, has more hydrogen thanother polymers, said McGlothlin, 21, of Lebanon, Va.

Using Material on Mars

Loading lots of building material onto the space shuttle wouldcreate a heavy weight at launch, which would use up a lot ofenergy. So, the researchers are trying to figure out how much — orlittle — polyethylene is needed to create bricks by mixing it witha material that astronauts can find in abundance once they get toMars: regolith, or topsoil.

“We’re trying to find the most efficient way to get the leastpayload and the maximum pay out,” Kiefer said.

Obviously, Mars topsoil isn’t easy to get on Earth. Chemicalanalysis of soil samples obtained by probes has shown that Marstopsoil is similar to that on the moon. But since that isn’tplentiful on Earth either, the researchers are using regolith froma quarry in Minnesota that is similar to lunar soil.

Regolith contains very little hydrogen, so it would not shieldvery well against radiation without the addition of polyethylene,Kiefer said.

At a laboratory at NASA, McGlothlin experiments with mixingdifferent concentrations of polyethylene and regolith to see whatworks best. He has created small “Mars bars” containing 10percent, 15 percent and 20 percent polyethylene.

Once the polyethylene and regolith are thoroughly mixed,McGlothlin puts the mixture in a drying oven to remove moisture.

The mixture then is poured into a stainless steel mold thatcreates a small sample bar, such as 3½ inches by ¾ inches. The moldis heated for a half hour at 245 degrees Fahrenheit.

Red Bricks

Back at William and Mary’s chemistry labs, McGlothlin doesthermal mechanical analyses on the samples to find out how thematerial reacts under extreme temperatures. The bricks also aretested to make sure they can withstand pressure, so bricks towardthe bottom of a building would not crumble or crack.

The topsoil the researchers are using is gray, so bricks madefrom it are black. Bricks made from Martian topsoil would be areddish color.

Kiefer said another student who since has graduated begantesting Mars bricks using a different polymer a year ago.McGlothlin picked up the project this summer and will continue theresearch until he graduates next May.