Space rock clay is rich in hydrogen, which blocks harmful cosmic rays Danielle Futselaar/SETI Institute

The huge rocks that hurtle through space may prove to be lifesavers for astronauts. Clays extracted from asteroids could be used on deep space missions to shield against celestial radiation.

Radiation from cosmic rays is one of the biggest health risks astronauts will face on long space missions, such as a proposed trip to Mars or settlement on the moon. A 2013 study suggested that a return trip to Mars would expose astronauts to a lifetime’s dose in one go.

But the heavy aluminium shields currently used for short missions would be too expensive to ship. For a long-term presence on the moon or Mars, we will need to use materials found in space, says Daniel Britt at the University of Central Florida.


“Eventually everything should be able to be produced off Earth if any serious size outpost, base or colony is to be considered,” says Paul van Susante at Michigan Technological University.

Asteroids could provide the answer, says Britt. Clays in asteroids are rich in hydrogen, which is the most effective shielding material for protons and cosmic rays. Britt and his colleague Leos Pohl found that the clays are up to 10 per cent more effective than aluminium – which is used in most current shields – at stopping the high-energy charged particles given off by the sun and other cosmic bodies.

Exactly how the clays could be extracted from the asteroids is still up for discussion. “No current machines exist for actual mining in zero gravity,” says van Susante.

But there are a few ways it could be done. For example, the clays are non-magnetic, so they could be separated from other materials in an asteroid using massive magnets.

“Doing anything in space is not trivial, but there are several paths forward,” Britt says.

Journal reference: Advances in Space Research, DOI: 10.1016/j.asr.2016.12.028