Blasting lunar dust into orbit could help tackle global warming, scientists say

The Earth is slowly warming up as humanity emits greenhouse gases which cause the atmosphere to trap an increasing amount of the sun’s energy.

But astronomers at the University of Utah believe that one strategy to reverse this trend is to intercept a fraction of sunlight before it reaches our planet.

For decades, scientists have considered using screens, objects or dust particles to block just enough of the sun’s radiation – between 1 and 2 per cent – to mitigate the effects of global warming.

The authors of the new study argue that launching lunar dust from the moon could be a cheap and effective way to shade the Earth.

They applied a technique used to study planet formation around distant stars, which is typically a messy process that kicks up lots of astronomical dust that can form rings around the host star.

These rings intercept light from the central star and re-radiate it in a way that we can detect on Earth. One way to discover stars that are forming new planets is to look for these dusty rings.

“That was the seed of the idea; if we took a small amount of material and put it on a special orbit between the Earth and the sun and broke it up, we could block out a lot of sunlight with a little amount of mass,” said Professor Ben Bromley, lead author of the study.

A sunshield’s overall effectiveness depends on its ability to sustain an orbit that casts a shadow on Earth.

Two scenarios were considered, in the first scenario, the authors positioned a space platform at the L1 Lagrange point, the closest point between Earth and the sun where the gravitational forces are balanced.

Objects at Lagrange points tend to stay along a path between the two celestial bodies, which is why the James Webb Space Telescope (JWST) is located at L2, a Lagrange point on the opposite side of the Earth.

In computer simulations, the researchers shot test particles along the L1 orbit, including the position of Earth, the sun, the moon and other solar system planets, and tracked where the particles scattered. The authors found that when launched precisely, the dust would follow a path between Earth and the sun, effectively creating shade, at least for a while.

Unlike the 6,500kg JWST, the dust was easily blown off course by the solar winds, radiation, and gravity within the solar system. Any L1 platform would need to create an endless supply of new dust batches to blast into orbit every few days after the initial spray dissipates.

“It was rather difficult to get the shield to stay at L1 long enough to cast a meaningful shadow. This shouldn’t come as a surprise, though, since L1 is an unstable equilibrium point. Even the slightest deviation in the sunshield’s orbit can cause it to rapidly drift out of place, so our simulations had to be extremely precise,” said the study’s co-author Sameer Khan.

In the second scenario, the authors shot lunar dust from the surface of the moon towards the sun. They found that the inherent properties of lunar dust were just right to effectively work as a sun shield. The simulations tested how lunar dust scattered along various courses until they found excellent trajectories aimed toward L1 that served as an effective sunshield.

Much less energy is needed to launch dust from the moon than from Earth, which is important because the amount of dust in a solar shield is large, comparable to the output of a big mining operation on Earth. 

Furthermore, the discovery of the new sun-shielding trajectories means delivering the lunar dust to a separate platform at L1 may not be necessary.

“We aren’t experts in climate change, or the rocket science needed to move mass from one place to the other. We’re just exploring different kinds of dust on a variety of orbits to see how effective this approach might be. We do not want to miss a game-changer for such a critical problem,” said Bromley.