Plunge in sunlight could have caused 'snowball Earth' – and it could happen again


Snowball Earths differ to Ice Ages as they are much harsher, and see the entire planet coated in freezing conditions. This has happened at least twice throughout the planet’s history, in quick succession around 700 million years ago, but researchers were stumped when attempting to come up with an explanation.

Scientists from the Massachusetts Institute for Technology (MIT) now believe whatever caused these extreme ice ages was due to a sudden shift in the amount of heat and radiation Earth received from the Sun.

While the process remains unclear, the MIT scientists believe a quick drop in heat triggered global ice ages.

If the drop in Sun-to-Earth activity was quick enough, it would have triggered a “runaway” effect where the polar ice expanded across the planet rapidly, not giving Earth the opportunity to recover, according to the research published in the journal Proceedings of the Royal Society A.

Lead author Constantin Arnscheidt, a graduate student in MIT’s Department of Earth, Atmospheric and Planetary Sciences (EAPS), said: “There are lots of ideas for what caused these global glaciations, but they all really boil down to some implicit modification of solar radiation coming in.

“But generally it’s been studied in the context of crossing a threshold.

“It’s reasonable to assume past glaciations were induced by geologically quick changes to solar radiation.”

One possibility for how there was such a sudden and drastic drop in temperatures could be several huge volcanic eruptions happening in quick succession, causing aerosols into the atmosphere, blocking incoming sunlight around the world.

And while the team believe there is little chance human activity could trigger a snowball Earth, researchers are wary it could happen again – and it would be out of our hands.

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The scientists also believe their findings could have implications in the search for life on other planets.

Researchers have classically focused on a star’s habitable zone – the region in space around a star where it is neither too hot nor too cold – when looking for planets which may support life.

But the team now realise just looking at the habitable zone of a planet may not be enough.

Mr Arnscheidt added: “You could have a planet that stays well within the classical habitable zone, but if incoming sunlight changes too fast, you could get a Snowball Earth.

“What this highlights is the notion that there’s so much more nuance in the concept of habitability.”





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