Launching Dust From the Moon Could Help Cool Earth, Scientists Say

To prevent further damage to the planet, humans need to limit global warming to no more than 1.5 degrees Celsius above pre-industrial levels, experts agree. In a new study, researchers explore an outlandish way to help do that: launching dust into space from the surface of the moon to shade the Earth.

To say the least, this would be an advanced feat of engineering. In a paper published last week in the journal PLOS Climate, researchers used computer modeling to explore how such a strategy might work. The most promising technique they found involves launching a massive amount of dust from the moon’s surface toward the first Lagrange point—one of five areas in space where the Earth and sun’s gravity cancel each other out. There, objects (like a gargantuan cloud of moon dust) essentially stay in place. The specks could block about 1.8 percent of the sun’s light—equal to about six days of sunlight per year—but it would take a whopping 10 billion kilograms of dust annually to do so, write the authors.

Attempts to block the sun from space are “currently among the very least feasible” engineering projects to combat climate change due to financial, technical and political challenges, Chad M. Baum, a behavioral scientist at Aarhus University in Denmark who did not contribute to the paper, tells the Washington Post’s Kasha Patel in an email. Still, “some have claimed that seeing these kinds of climate solutions being discussed might bring home the urgency of the situation we are in.”

Over the years, scientists have proposed a variety of strategies for cooling the Earth by shielding it from the sun’s rays. These range from deploying a cloud of small spacecraft to constructing a planetary sunshade that might stretch for thousands of miles, writes Popular Science’s Rahul Rao. Researchers have also considered releasing aerosols into the atmosphere to aid cloud formation, but doing so could have unintended consequences, including impacting rainfall patterns and damaging the ozone layer.

Using moon dust to block the sun has been proposed before. Theoretically, launching dust from the moon is easier than sending it from Earth because of the moon’s weaker gravity, Benjamin Bromley, a co-author of the new paper and a theoretical astrophysicist at the University of Utah, tells CNET’s Jackson Ryan.

Moon dust could also be an effective shield. “First, it can be pretty efficient at deflecting sunlight, and second, it turns out that the most efficient grain size is the most plentiful on the moon’s surface,” Bromley says to CNET.

But it could take decades for the necessary mining infrastructure and launching system to get set up on the moon, Aaron Tang, who studies efforts to address climate change at Australian National University and did not participate in the research, writes in the Conversation. And ejecting the dust would require incredible amounts of energy—more than the energy used in 20,000 Saturn V rocket launches, according to the paper. Beyond the technological challenges, there’s the question of how mining moon dust would be governed—and whether it’s even legal.

Others worry that such solar engineering projects distract from more straightforward solutions, like burning fewer fossil fuels and using more renewable energy. “The solutions to climate change are right in front of us, not in the stars,” Tang writes in the Conversation.

“There is a much simpler, safer and cheaper solution: Leave the fossil fuels in the ground and run the world on solar and wind power, of which there is enough to supply power for everyone,” Alan Robock, a climate scientist at Rutgers University, tells the Post in an email.

Even if a lunar dust shield ever existed, it would come long after the need to drastically curb carbon emissions. Such an endeavor would be something for the 22nd century, Peter Irvine, a solar geoengineer at University College London who did not contribute to the research, tells Popular Science. “Climate change,” Irvine says, “is a 21st century problem.”

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Will Sullivan is a science writer based in Washington, D.C. His work has appeared in Inside Science and NOVA Next.