Aiming to help keep crews safe when NASA sends humans to Mars, scientists at the US space agency have developed a new device to monitor radiation exposure to neutrons and are testing it on the International Space Station.

The Fast Neutron Spectrometer is designed to detect and measure the energy of neutrons, which are known to be specifically harmful to humans. 

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"There are multiple types of radiation in space," said Mark Christl, team lead for the study at NASA's Marshall Space Flight Center in Huntsville, Alabama. 

"While there are already advanced instruments to detect gamma rays produced by supernovas or black holes, X-rays and other charged particles, we needed a way to detect and measure neutron radiation to quantify the impact on human biology. Neutron detection techniques have not seen the same leap in technology advancement," Christl added in a statement on Tuesday.

Neutron radiation is created when the high-energy particles from our sun and outside our solar system interact with other particles or matter, such as a spacecraft or a planetary surface. 

But these neutrons are only viable for approximately 13 minutes before they decay into charged particles.

"If they're more than 13 minutes away from you, it's not really a problem," Christl said. 

"If you're in a capsule or on a planet's surface with little or no magnetic field or atmosphere, you can potentially be covered in a neutron field," Christl added.

The Fast Neutron Spectrometer is mainly a passive tool, waiting for neutrons to strike it. 

It is comprised of an aluminum housing with a plastic scintillator that slows down the neutron when it hits the device, and glass scintillator fibers that absorb the neutrons and re-emit the energy in the form of light. 

This advanced version provides two distinct signals for measurement — the first to measure its energy and the second to confirm a neutron was detected rather than another kind of particle. 

The standard, all-plastic devices can't clearly determine the differences between these signals.

Even though the space station's radiation environment is not considered "deep space," the spectrometer is a new capability ready for validation in a space environment, the scientists said.

"These radiation detectors may force missions to change in mid-stream, but it will help keep our astronauts safe," Christl said.