Supernovae may have caused mass extinction 359 million years ago

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The explosion of stars – or “supernovae” – just 65 light-years from Earth may have triggered the devastating mass extinction some 359 million years ago.

The Late Devonian extinction saw the disappearance of 50 percent of all genera – groups of species – and 19 percent of all families, the second largest group in the tree of life.

Among the groups most affected were jawless fish, “ rough ” corals that build reefs, and trilobites – iconic marine arthropods that resemble woodlice.

This episode of massacre has previously been blamed on the impacts of asteroids, climate change, changes in sea level and large-scale volcanic activity.

American researchers, however, have examined the boundary between the Devonian and the subsequent period, the Carboniferous.

Here are hundreds of thousands of generations of plant spores that have been scorched by ultraviolet light – suggesting a long-term weakening of the ozone layer.

This may have been caused by the impact of one or more nearby supernova explosions on the solar system – and would have been catastrophic for life.

Exploding stars, or

The explosion of stars – or “supernovae” – just 65 light-years from Earth may have triggered the devastating mass extinction some 359 million years ago. Pictured is an artist’s impression of a local supernova seen from Earth orbit

“We propose that one or more supernova explosions, about 65 light years from Earth, could have been responsible for the prolonged loss of ozone,” said author and astronomer Brian Fields of the University of the Illinois in Urbana-Champaign.

“Earth-based disasters such as large-scale volcanism and global warming can also destroy the ozone layer, but the evidence for these is inconclusive for the time interval in question.

Professor Fields and his colleagues have also ruled out other space events that could potentially have caused ozone layer depletion – such as deadly gamma-ray bursts, meteorite impacts and solar flares.

“These events end quickly and are unlikely to cause the lasting depletion of the ozone layer that occurred at the end of the Devonian period,” said author and astronomer Jesse Miller, also of the University. from Illinois.

In contrast, the researchers explained, a supernova has the potential to have a more lasting impact – especially given how it can deliver a “ one-two punch. ”

If a nearby star had become a nova, the Earth would soon have been bathed in ultraviolet rays, x-rays and gamma rays.

This would have been followed by the explosion of debris from the explosion that slammed into the solar system and subjected our planet to irradiation of cosmic rays accelerated by the supernova.

Together, the damage to the Earth’s ozone layer would likely have lasted for up to about 100,000 years, the researchers said.

While not as long as the 300,000-year decline in biodiversity that led to the end of the Devonian period, the supernova could have occurred in tandem with other disasters – or even multiple nova blasts.

“It’s entirely possible. Massive stars usually occur in clusters with other massive stars, and other supernovae are likely to occur soon after the first explosion, ”Miller explained.

If a nearby star had become a nova, the Earth would soon have been bathed in ultraviolet rays, x-rays and gamma rays. This would have been followed by the explosion of debris from the explosion slamming into the solar system. Pictured is a simulation of a nearby supernova explosion beating and compressing the solar wind - with Earth's orbit shown in blue and the Sun itself as the central red point

If a nearby star had become a nova, the Earth would soon have been bathed in ultraviolet rays, x-rays and gamma rays. This would have been followed by the explosion of debris from the explosion slamming into the solar system. Pictured is a simulation of a nearby supernova explosion beating and compressing the solar wind – with Earth’s orbit shown in blue and the Sun itself as the central red point

However, evidence for the supernova hypothesis is expected to come from the discovery of the radioactive isotopes plutonium-244 and samarium-146 in rocks and fossils deposited at the time of mass extinction.

“None of these isotopes occur naturally on Earth today and the only way to get there is through cosmic explosions,” said author and astronomer Zhenghai Liu.

Or, as Professor Fields explains, they’re like green bananas.

‘When you see green bananas [here] in Illinois, you know they’re fresh, and you know they haven’t grown here.

“Like bananas, Pu-244 and Sm-146 disintegrate over time. So if we find these radioisotopes on Earth today, we know they’re fresh and not from here – the green bananas of the isotopic world – and therefore the smoldering weapons of a nearby supernova.

Finding these metaphorical bananas, however, will be a task for the future, the researchers explained.

The Late Devonian extinction saw the disappearance of 50 percent of all genera - groups of species - and 19 percent of all families, the second largest group in the tree of life. Among the groups most affected were the `` rough '' corals that build reefs and trilobites - iconic marine arthropods that resemble woodlice (photo by this artist).

The Late Devonian extinction saw the disappearance of 50 percent of all genera – groups of species – and 19 percent of all families, the second largest group in the tree of life. Among the groups most affected were the “ rough ” corals that build reefs and the trilobites – iconic marine arthropods that resemble woodlice (photo by this artist).

“The main message of our study is that life on Earth does not exist in isolation,” concluded Professor Fields.

“We are citizens of a larger cosmos, and the cosmos intervenes in our lives – often imperceptibly, but sometimes fiercely.

The full results of the study were published in the journal Proceedings of the National Academy of Sciences.

WHEN WERE EARTH’S “BIG FIVE” EXTINGUISHING EVENTS?

Traditionally, scientists have referred to the ‘Big Five’ mass extinctions, including perhaps the most famous mass extinction triggered by a meteor impact that led to the end of the dinosaurs 66 million years ago. years.

But the other major mass extinctions were caused by phenomena originating entirely from Earth, and although they are less well known, we can learn something by exploring them that could illuminate our current environmental crises.

  1. The recent Ordovician: This ancient crisis about 445 million years ago saw two great waves of extinction, both caused by climate change associated with the advance and retreat of ice caps in the southern hemisphere. This makes it the only major extinction to be linked to global cooling.
  2. The late Devonian: This period is now considered to be a number of extinction “pulses” spread over 20 million years, starting 380 million years ago. This extinction has been linked to major climate change, possibly caused by an eruption of the Viluy Trap volcanic area in modern Siberia. A major eruption could have caused rapid fluctuations in sea level and reduced oxygen levels in the oceans.
  3. Middle Permian: Scientists recently discovered another event 262 million years ago that rivals the “Big Five”. This event coincided with the eruption of Emeishan in present-day China, and is known to have caused simultaneous extinctions in the tropics and higher latitudes.
  4. Late Permian: The Late Permian mass extinction around 252 million years ago overshadows all other events, with around 96% of species endangered. The extinction was triggered by a vast eruption of the Siberian traps, a gigantic and prolonged volcanic event that covered much of modern Siberia, leading to a cascade of environmental effects.
  5. The Late Triassic: The Late Triassic event 201 million years ago shares a number of similarities with the Late Permian event. It was caused by another large-scale eruption, this time from the magmatic central Atlantic province, which heralded the split of the supercontinent Pangea and the initial opening of what would later become the Atlantic Ocean.

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