Blowing-up asteroid to block out Sun could stop global warming - it's happened before, say scientists

Sarah Knapton
A huge asteroid collision created so much dust it started the world's first ice age  - Don Davis, Southwest Research In

Around half-a-billion years ago, a 93-mile wide asteroid broke up between Jupiter and Mars sending a vast dust cloud into the Solar System, blocking sunlight and plunging Earth into a lengthy ice age.

Now scientists have suggested that a similar man-made event could protect us from run-away global warming.

The plan would involve towing or pushing an asteroid to a Lagrange point in space, where gravitational forces even out to provide a static ‘parking spot’.

The asteroid could then be drilled into, or blown up, to create an ‘anchored dust cloud’ shielding Earth from the Sun.

It might seem extreme, but governments across the world are already looking for ways to deflect or explode asteroids in the event of an incoming space rock, so it may soon be possible to carry out astro-engineering.

New research from scientists at Lund University in Sweden and Chicago’s Field Museum shows that creating a dust cloud would definitely have the desired goal of significantly cooling the climate, because it has happened before.

Around 466 million years ago the seas started to ice over and the planet began to freeze. But the cause of this first major ice age has always proved a mystery.

The team discovered huge amounts of dust from asteroids buried in the geological record from the time period, suggesting that the falling temperatures were linked to space debris blocking out sunlight.

“Normally, Earth gains about 40,000 tons of extraterrestrial material every year,” said Dr Philipp Heck, a curator at the Field Museum, associate professor at the University of Chicago, and one of the paper's authors.

“Imagine multiplying that by a factor of a thousand or ten thousand.”

A 466-million-year-old fossil meteorite, created in the same asteroid collision that caused the dust that led to an ice age. Credit: Field Museum /John Weinstein 

The cloud cooled temperatures to such an extent that seas the climate changed from being more or less homogeneous to becoming divided into the zones we known today - from Arctic conditions at the poles, to tropical conditions at the equator.

The newly diversified climate triggered an explosion of species known as the Great Ordovician Biodiversification Event (GOBE), and the dust created by the asteroid was so great that it is still responsible for a third of meteorites which fall on Earth today.

"It is analogous to standing the middle of your living room and smashing a vacuum cleaner bag, only at a much larger scale", said Dr Birger Schmitz, professor of geology at Lund University and the leader of the study.

"Our results show for the first time that such dust, at times, has cooled Earth dramatically.”

According to the Intergovernmental Panel on Climate Change, Earth is approaching conditions prior to the asteroid collision 470 million years ago.

The mid-Ordovician limestone section studied at Kinnekulle in Sweden Credit:  Birger Schmitz, Lund University

In a new paper in the journal Science Advances, the team said the study provides ‘new empirical knowledge’ of how to combat the problem.

“In an effort to mitigate ongoing global warming, it has been suggested to capture a large near-Earth asteroid and position it at the first Lagrange point as a source of dust that could help to reduce solar insolation on Earth,” the authors wrote.

“Gravitationally “anchoring” such a dust cloud at this point would reduce dust particle dispersion and create a prolonged cooling effect.

“Such an anchored cloud can lead to insolation reductions to Earth three times larger than the reduction required to offset a CO2-induced increase of 2°C in mean global temperature.

“Studies of the extraterrestrial fraction of mid-Ordovician sediment provide new empirical knowledge that is relevant in the context of present-day climate mitigation.”

A fossil of trilobites that evolved following the mid-Ordovician ice age. Credit: Field Museum /John Weinstein 

Dr Heck said it was important to study the potential impacts of geoengineering projects to avoid adding to the problem.

“Geoengineering proposals should be evaluated very critically and very carefully, because if something goes wrong, things could become worse than before,” added Dr Heck.

“We're experiencing global warming, it's undeniable. And we need to think about how we can prevent catastrophic consequences, or minimize them. Any idea that's reasonable should be explored.”

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