A manned mission to Mars, Earth’s nearest neighbor, would undoubtedly be NASA’s greatest achievement since putting a man on the moon. However, a problem is emerging besides the usual logistical questions: Researchers at the University of New Hampshire have found that such travels would likely expose astronauts to dangerous levels of cosmic radiation due to depressed solar activity.

“The behavior of the sun has recently changed and is now in a state not observed for almost 100 years,” says Schwadron, lead author of the paper and principal investigator for the Cosmic Ray Telescope for
the Effects of Radiation (CRaTER) on NASA’s Lunar Reconnaissance Orbiter (LRO).

Due to the lack of solar activity, solar winds are experiencing abnormally low densities and magnetic field strengths, allowing the hazardous radiation to proliferate nearby outer space. The researchers say this began in 2006 and is the lowest observed level of solar activity in the Space Age.

Though the radiation levels don’t appear to be high enough to limit space exploration altogether, they could have a major impact on the duration of missions with regards to astronaut safety.

“While these conditions are not necessarily a showstopper for long-duration missions to the moon, an asteroid, or even Mars, galactic cosmic ray radiation in particular remains a significant and worsening factor that limits mission durations,” says Schwadron.

The CRaTER testing involves a novel approach – a material called “tissue equivalent plastic,” which mimics human muscle and can accurately measure radiation exposure. The difficulty with radiation is that the effects are not always immediate. While high doses might result in radiation sickness, lower levels of exposure can lead to cancer and organ damage well after an astronaut has returned to the safety of Earth.

The bottom line? The maximum allowable mission duration for astronauts shielded by spacecraft is dropping, and is expected to shorten by as much as 20% in the upcoming solar minimum cycle compared to the previous one. MArs may have to wait.