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It could be the subject of a science fiction B movie: Space travelers to Mars bombarded by cosmic rays.听But it鈥檚 science fact, the primary finding of major research out of 91制片厂鈥檚 Space Science Center that has implications on the future of deep-space travel.

In an article published last fall in the journal Space Weather, associate professor of physics Nathan Schwadron details how periods of weak solar activity lead to an increase in cosmic radiation levels, limiting the amount of time an astronaut can spend in space without risking radiation-induced cancer.

Using data from the Cosmic Ray Telescope for the Effects of Radiation (CRaTER) on NASA鈥檚 Lunar Reconnaissance Orbiter, the research found that a 30-year-old male astronaut could spend about 400 days in space鈥攔oughly the duration of a mission to Mars and back鈥� before he exceeded NASA鈥檚 limits on safe exposure to cosmic rays. A female astronaut of the same age would hit that limit in just under 300 days. CRaTER鈥檚 鈥渢issue-equivalent plastic,鈥� a material that mimics human muscle, measures the effects of radiation dosage over time.

The issue, Schwadron explains, is that we鈥檙e currently experiencing an abnormally long period of weak solar activity. An active sun has frequent sunspots, which intensify the sun鈥檚 magnetic field. That magnetic field is dragged out through the solar system by the solar wind and deflects galactic cosmic rays away from the solar system鈥攁nd from any astronauts in transit.
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For most of the space age, the sun鈥檚 activity ebbed and flowed like clockwork in 11-year cycles, with six- to eight-year lulls in activity, called solar minimum, followed by two- to three-year periods when the sun is more active.

鈥淗owever, starting in about 2006, we observed the longest solar minimum and weakest solar activity observed in the space age,鈥� says Schwadron. 鈥淭here鈥檚 been a sustained change in the way the sun is behaving. Over time, it鈥檚 become increasingly clear that the space environment is not returning to normal.鈥�

The possibility that this current extended solar minimum could be part of a long-term trend prompted Schwadron and his colleagues鈥攊ncluding 91制片厂 researchers Colin Joyce, Marty Quinn, Charles Smith, Sonya Smith, Harlan Spence and Jody Wilson, all of EOS鈥攖o probe its implications on long-term space travel.

Schwadron presents these results, which were the capstone article of a special CRaTER-focused issue of Space Weather, with the characteristic caution of a scientist. Deeper understanding of this unusually prolonged solar minimum will better inform NASA on the risks to astronauts engaged in long-term space travel.

Nonetheless, Schwadron says that while these solar conditions 鈥渁re 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.鈥�

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Originally published in 91制片厂 Magazine鈥�