Cosmic Rays From Supernovae Could Be Responsible For Mass Extinction On Earth

Eddie Gonzales Jr. – MessageToEagle.com – Dangerous cosmic rays from nearby supernovae could be responsible for at least one mass extinction event, according to a new study led by Professor Brian Fields from the University of Illinois, Urbana Champaign astronomy and physics.

A simulation of a nearby supernova colliding with and compressing the solar wind. Earth’s orbit, the blue dashed circle, and the Sun, red dot, are shown for scale. Credit: Jesse Miller

Researchers explore the possibility of astronomical events being responsible for an extinction event that occurred 359 million years ago, at the boundary between the Devonian and Carboniferous periods.

The team concentrated on Devonian-Carboniferous boundary because those rocks contain hundreds of thousands of generations of plant spores that appear to be sunburnt by ultraviolet light – evidence of a long-lasting ozone-depletion event.

“Earth-based catastrophes such as large-scale volcanism and global warming can destroy the ozone layer, too, but evidence for those is inconclusive for the time interval in question,” said Fields, adding that one  or more supernova explosions, about 65 light-years away from Earth, could have been responsible for the protracted loss of ozone.”

The team explored other astrophysical causes for ozone depletion, such as meteorite impacts, solar eruptions, and gamma-ray bursts.

“But these events end quickly and are unlikely to cause the long-lasting ozone depletion that happened at the end of the Devonian period,” said graduate student and study co-author Jesse Miller.

A supernova, on the other hand, delivers a one-two punch, and the explosion immediately bathes Earth with damaging UV, X-rays, and gamma rays. Later, the blast of supernova debris slams into the solar system, subjecting the planet to long-lived irradiation from cosmic rays accelerated by the supernova. The damage to Earth and its ozone layer can last for up to 100,000 years.

However, fossil evidence indicates a 300,000-year decline in biodiversity leading up to the Devonian-Carboniferous mass extinction, suggesting the possibility of multiple catastrophes, maybe even multiple supernovae explosions. “This is entirely possible,” Miller said.

“Massive stars usually occur in clusters with other massive stars, and other supernovae are likely to occur soon after the first explosion.”

The team said the key to proving that a supernova occurred would be to find the radioactive isotopes plutonium-244 and samarium-146 in the rocks and fossils deposited at the time of extinction.

“When you see green bananas in Illinois, you know they are fresh, and you know they did not grow here. Like bananas, Pu-244 and Sm-146 decay over time,” Fields said. So if we find these radioisotopes on Earth today, we know they are fresh and not from here – the green bananas of the isotope world – and thus the smoking guns of a nearby supernova.”

Researchers will search for Pu-244 or Sm-146 in rocks from the Devonian-Carboniferous boundary. Their goal is to define the patterns of evidence in the geological record that would point to supernova explosions.

“The overarching message of our study is that life on Earth does not exist in isolation,” Fields said. “We are citizens of a larger cosmos, and the cosmos intervenes in our lives – often imperceptibly, but sometimes ferociously.”

Paper

Written by Eddie Gonzales Jr. – MessageToEagle.com Staff