The prehistoric shark megalodon became extinct more than 2 million years ago. Findings of a new study now suggest that a supernova may have led to the extinction of the marine behemoth.

Radiation From Exploding Stars

Study researcher Adrian Melott, a physicist at the University of Kansas, and colleagues proposed in a new paper that one or more exploding stars 2.6 million years ago may have contributed to a mass extinction event that impacted the creatures thriving in the prehistoric oceans.

The researchers said that the supernovae showered onto Earth's surface high levels of muon, an elementary particle similar to an electron but is more than 200 times heavier.

The cosmic particle penetrated deep beneath the ocean surface and would have caused large marine animals such as the bus-size megalodon to absorb and accumulate lethal amounts of radiation.

The researchers said that the radiation from the exploding stars, which could have been just 160 light-years away, may have been too much for Earth's atmosphere and creatures to handle.

Melott explained that below a few meters of the ocean's surface, water normally serves as a shield against a lot of radiation, but it would not have shielded the muons.

This left marine creatures, which used to be almost isolated from radiation, to be suddenly exposed to high amounts of it.

Unlike land creatures, however, these sea animals did not likely have good defense against radiation. Thus, the spike in muon levels may have caused mutation and cancers in these creatures.

"It is reasonable to hypothesize that this increase in radiation load may have contributed to a newly documented marine megafaunal extinction at that time," the researchers wrote in their study.

Larger Marine Creatures More Vulnerable To Effect Of Muon Exposure

The researchers said that larger sea creatures, such as the megalodon, may have been more vulnerable to the effect of the muon exposure because of the Matuyama-Gauss reversal, which switched-up the Earth's magnetic poles about 2.6 million years ago.

"The magnetic reversal would increase the muon exposure," Melott said. "Normally, cosmic rays of low energy are diverted by the magnetic field and they mostly come down near the poles. But if you have a magnetic reversal, they impact all over the place."