The US space agency, which recently awarded $12,000 to five winners of a challenge to mitigate radiation exposure on deep space missions, is developing the capabilities needed to send humans to an asteroid by 2025 and Mars in the 2030s.

"We are very impressed with the enthusiasm and sheer number of people from the public, who showed interest in solving this very difficult problem for human space exploration," said Steve Rader, deputy manager of the NASA-supported Center of Excellence for Collaborative Innovation.

"We look forward to seeing what people will come up with in this next challenge to find the optimal configuration for these different protection approaches," Mr Rader noted.

Galactic cosmic rays (GCRs), high-energy radiation that originates outside the solar system are a major issue facing future space travellers venturing beyond low-Earth orbit.

These charged particles permeate the universe and exposure to them is inevitable during space exploration.

Because missions to Mars will require crews to remain beyond the protection of Earth's magnetic field and atmosphere for approximately 500 days, learning how to protect human explorers from the effect of exposure to GCRs is a high priority.

The new challenge will measure which ideas come closer to NASA's goal of identifying key solutions that will reduce crew members' total radiation dose from exposure to GCRs on long duration deep space missions by at least a factor of four.

Anyone can participate in the challenge, which will be open from April 29 to June 29, 2015.