Science & Technology Researchers want to launch dust from the moon to help cool Earth

Imagine a world where global warming on Earth has meaningfully diminished. Fossil fuels are on the back burner. Affordable renewable energy sources run most of our activities. Oh, and there’s a cannon on the moon shooting lunar dust into space to help partially shield sunlight to Earth.

That’s one eyebrow-raising approach for cooling our planet proposed by a group of astrophysicists in a study published Wednesday in PLOS Climate. The team used computer simulations to model various scenarios where massive quantities of dust (and we mean a lot of dust) in space can reduce the amount of Earthbound sunlight by 1 to 2 percent, or up to about six days of an obscured sun in a year. Their cheapest and most efficient idea is to launch dust from the moon, which would land into orbit between the sun and Earth and create a sunshade.

Yes, the idea sounds like science fiction. Yes, it would require (a lot of) new engineering. Yes, there are more feasible climate mitigation tactics that can be employed now and in the near future. But the researchers view this rigorous physics experiment as a backup option that could aid — not replace — existing strategies to help humankind live on a more comfortable Earth.

“We cannot as humanity let go of our primary goal of reducing greenhouse gas emissions here on our planet. That’s got to be the first job,” said Ben Bromley, the study’s lead author and an astrophysicist at University of Utah. “Our idea is one — and it’s a very, very intensive one — to contribute to climate change mitigation, if we need more time here at home.”

Some climate scientists, however, see such projects as distractions from more permanent climate solutions, such as reducing fossil fuel consumption.

THIS ISN’T THE FIRST IDEA FOR A SPACE-BASED SOLUTION

The astrophysicists came up with a space dust shield by borrowing concepts from their usual research focused on how planets form around distant stars. Bromley explained that planets form through a messy process involving a lot of collisions, which kick up dust that can intercept a large amount of starlight. So why not explore strategically using such lightblocking dust for Earth’s benefit?

The team is not the first to propose using a physical object in space to block sunlight to Earth, which some categorize as solar-based geoengineering. Ideas showed up as early as 1989 when James Early at Lawrence Livermore National Laboratory proposed placing a thin, 2,000 km-wide glass shield between the

A view of the Earth from the moon sun and Earth (that’s nearly 1,250 miles). In 2006, astronomer Roger Angel explored the idea of sending trillions of small spacecraft with umbrella-like shields to block the sun. In 2012, Scottish researchers investigated blasting off a dust cloud from an asteroid placed between the sun and Earth. Last year, a group of MIT researchers proposed deploying a raft of bubbles that could pop without leaving space debris.

Yet those ideas have run into myriad issues: Too much material is needed. It would require construction in space. It’s dangerous. Irreversible.

“The literature around spacebased geoengineering now spans more than three decades and is filled with creative, often outlandish ideas,” Chad M. Baum, a behavioural scientist at Aarhus University who was not involved in the new study, said in an email. “Some have claimed that seeing these kinds of climate solutions being discussed might bring home the urgency of the situation we are in.”

Still, he said such space-based projects to reduce incoming sunlight are “currently among the very least feasible,” given the cost and numerous technical, political, social and legal obstacles.

Shooting From The Moon

In the new study, the authors concede their idea isn’t perfect but say it addresses some problems with previous concepts.

For instance, the amount of material needed to actually shade the sun exceeds 10 billion kilograms (22 billion pounds), which is about 100 times more mass than humans have ever sent into space. Bromley says dust is very efficient at scattering sunlight relative to its size. The team considered different types of dust, scattering properties and size. The team found that aggregates of fluffy and highly porous particles scattered light the best, but they opted for a particle perhaps more easily accessible in space: moon dust.

“We really do focus on lunar dust, just plain old, as-it-is lunar dust, without any indication of changing its shape,” said Bromley, who said future moon mining could excavate the dust needed. Perhaps the greatest challenge is getting the right material exactly where you need it, Bromley said.

In one computer simulation, the team shot lunar dust from the moon’s surface toward the sun. Bromley said the device to launch the lunar dust into space could be something similar to an electromagnetic gun, cannon or rocket — picture a T-shirt cannon sending dust into orbit. In the simulation, the dust scattered along various routes until the team found suitable trajectories, which allowed the dust to concentrate temporarily and act as a sun shield. Bromley said the dust would periodically disperse away from Earth and throughout the solar system.