Could We Use Moon Dust to Block the Sun and Help Cool Earth?

It's really hard to know what to do about the climate crisis facing this planet. We are all being affected, and the problem doesn't seem to be going away, which is why scientists are scrambling to come up with solutions. Some of them seem really out there — like, really out there.

For instance, one of the recent suggestions put forth by a team of U.S. researchers, published Feb. 8, 2023, in PLOS Climate, advocates blocking the sun's rays with moon dust.

Casting a Dust Shadow Over Earth

The idea for the study came from the observation of far-flung planets in other solar systems — when planets are forming they kick up an awful lot of dust, which forms rings around the central star in the solar system. In fact, looking for stars with dusty auras is one way we can detect new solar systems.

"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 lead author Ben Bromley, professor of physics and astronomy at the University of Utah in a press release.

The idea is to cast a shadow over our planet, like a giant parasol. Some scientists specialize in coming up with options for preventing the sun's rays from over-warming our planet by reflecting sunlight back into space from here on Earth — this area of study is called solar geoengineering. Some of these options look like throwing a bunch of aerosols into the stratosphere to mimic the way volcanic eruptions cool our planet, or whitening clouds with sea salt to better reflect the sun's rays back into space. However, tinkering with our complex climate system would inevitably lead to unforeseen outcomes — sure, it might reflect the sun's rays, but it could also result in acid rain, or alter rainfall patterns worldwide.

What Are the Risks?

Because interfering with Earth's climate is risky, some scientists have set their sights on blocking the sun's rays from space. Giant light screens and fleets of mirrored spacecraft have been proposed, but if enough dust could be procured, it has a real shot at blocking the sun — at least temporarily.

Which is where the moon comes in: It's a dusty place, and because it has lower gravity than Earth, it would take less energy to send that dust out into space. Also, Earth's mining operations don't really make dust in the volume it would take to make a space shield for our planet.

The proposed plan would be to send the moon dust out into space towards a point called the "Lagrange Point 1 (L1)" between Earth and the sun, where gravitational forces are balanced enough to hold a cloud of moon dust in a path between our planet and the sun, at least for a while. The dust supply may need to be replenished every few days for the plan to work.

Although the authors haven't suggested how the dust would be catapulted off the moon to make its way to L1, they are looking at a previously worthless-seeming resource in a new light:

"It is interesting to contemplate how moon dust — which took over four billion years to generate — might help to solve climate change, a problem that took us less than 300 years to produce," said Scott Kenyon, co-author of the study from the Center for Astrophysics at Harvard + Smithsonian, in a press release.