Stellar explosions called gamma-ray bursts could kill pretty much everything on Earth, according to a new NASA study published Monday.
Gamma ray bursts are the brightest electromagnetic blasts in the universe, created from the collapse of massive stars or when one star slams into another. The study concluded that the amount of radiation emitted by the bursts is probably responsible for a massive extinction event during Earth’s history. Such a burst may have caused roughly 85 percent of marine species to go extinct 450 million years ago, and almost all life at the time lived in the ocean.
Researchers used computer models to figure out how devastating a burst would be today, and determined that it could potentially strip most of the ozone layer out of the atmosphere. This would raise the amounts of free ozone at ground level, which would cause respiratory failure in humans and prevent photosynthesis in plants or kill cells outright. Additionally, the weakened ozone layer would allow harmful radiation to reach the ground.
“A [gamma-ray burst] could happen over any latitude or time but we chose the South Pole mainly to look at a very high depletion case,” Dr. Brian Thomas, an astrophysicist at Washburn University, said in a press statement. “When the radiation enters the atmosphere over a pole, the depletion is concentrated there instead of spread around the globe.”
Other studies have found that a burst from a star as distant as 6,500 light years away aimed at Earth could cause acid rain and initiate a round of global cooling. Such an event would be very unlikely to occur, but be absolutely devastating.
About 450 million years ago, at the end of the Ordovician era, a gamma-ray burst likely caused the second-largest mass extinction event in Earth’s history. Researchers concluded that a burst above the South Pole would fit in well with theories of the Ordovician extinction, as measured extinction rates match with Thomas’s models.
The research was financially supported by the Exobiology and Evolutionary Biology element of NASA’s Astrobiology Program.
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