Scottish scientists have proposed to use a giant space-based dust cloud, blasted off an asteroid, to shade the Earth from the sun. Deliberately manipulating the Earth’s climate with large-scale engineering projects is called geoengineering and these proposals are always controversial because of the risk that they entail.
The scientists will publish their findings in the journal Advances for Space Research on November 12. Instead of altering the climate by targeting the oceans or the atmosphere, these types of geoengineering projects would affect the entire Earth from space.
A cloud of dust could be obtained by gravitationally anchoring an asteroid to block sunlight and cool the Earth. The dust cloud wouldn’t be a permanent solution, but it could offset the effects of climate change for some time and allow slower-acting measures like carbon capture to take effect.
The asteroid would be placed at Lagrange point L1, where the gravitational pull of the Sun and Earth are canceled out. L1 is 1.5 million kilometers away from Earth. The asteroid could be fitted with a “mass driver,” which could hurl asteroid-derived matter away from the rock. It could also serve as a rocket to push the asteroid to the L1 point.
The nearest large near-Earth asteroid is 1036 Ganymed, and this asteroid could maintain a dust cloud large enough to block out 6.58% of solar radiation that would normally reach Earth. This would be more than enough to combat any current global warming trends. The cloud would be about 5 quadrillion kilograms in mass and about 2,600 km in width. Ganymed has a mass of 130 quadrillion kilograms.
The challenging part of this proposal would be how to push an asteroid of this size into L1. However, smaller asteroids could be moved and clustered together at L1 instead.
Like many geoengineering schemes, there’s no way of fully testing this dust cloud’s effectiveness before implementing it.
Reference: “Gravitationally bound geoengineering dust shade at the inner Lagrange point” by R. Bewick, J. P. Sanchez and C. R. McInnes, 14 July 2012, Advances for Space Research.