Blast from the past inspires idea to cool planet

Scientists believe the dust created by blowing up an asteroid could cool the Earth. Image / Nasa

Around half-a-billion years ago, a 150km wide asteroid broke up between Jupiter and Mars, sending out a vast dust cloud that blocked sunlight and plunged Earth into an ice age.

Now scientists have suggested that a similar man-made event could protect our planet from runaway global warming. The plan would involve towing or pushing an asteroid to a point in space, where gravitational forces even out to provide a static "parking spot", known as a Lagrange spot. The asteroid could then be drilled into, or blown up, to create an "anchored dust cloud" that would shield Earth from the Sun.

It might seem extreme, but governments are already looking for ways to deflect or explode asteroids in the event of an incoming space rock.

Research by scientists at Lund University in Sweden and Chicago's Field Museum shows that creating a dust cloud would 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 ice age has always proved a mystery. The team discovered huge amounts of asteroid dust buried in the geological record from the time, suggesting temperature falls were linked to space debris blocking out sunlight.

Dr Philipp Heck, a curator at the Field Museum, associate professor at the University of Chicago, and one of the paper's authors, said: "Our results show for the first time that such dust, at times, has cooled Earth dramatically."

In a paper in the journal Science Advances, the team said the study provided "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. "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 2C in mean global temperature."

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