Biodiversity at mercy of cosmic rays?
LAWRENCE, Kan., Dec. 22 (UPI) -- A regular rise and fall of biodiversity in Earth's past may be linked to our solar system's rhythmic movement around the Milky Way, U.S. researchers say.
About every 60 million years, our solar system moves above the average plane of our galaxy's disk, and in the same 60-million-year cycle, the biodiversity of life on Earth drops significantly.
Researchers theorize the former occurrence drives the latter because of increased exposure to high-energy subatomic particles called cosmic rays coming from intergalactic space, SPACE.com reported Wednesday.
Usually, the Milky Way's magnetic field shields the solar system from these rays, but every 60 million years or so, our solar system pops up above the northern edge of our galaxy's disk, exposing Earth to more cosmic rays,
That radiation might be contributing to large die-offs of the creatures on Earth, scientists say.
Researchers at the University of Kansas say they've put some hard numbers to the theory for the first time.
When the solar system raises its head out of the galactic plane, radiation exposure at the Earth's surface shoots up, possible by as much as a factor of 24, they say.
"Even with the lowest assumption, this exposure provides a real stress on the biosphere periodically," said lead author Dimitra Atri.
The solar system is on the upswing now, moving toward the northern edge of the galactic disk, but researchers say it's too soon to worry.
Big increases in cosmic-ray exposure are probably still about 10 million years off, the say.
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