Researchers Want To Launch Dust From the Moon To Help Cool Earth

In a study published Wednesday in PLOS Climate, a group of astrophysicists proposes shooting lunar dust into space to help partially shield sunlight to Earth. The Washington Post reports: 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. [...] 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. In another simulation, the team shot off dust from a space platform about 1 million miles from Earth. This would be in an area known as L1 (Lagrange point 1), where objects tend to stay put because of equal gravitational pulls between the sun and Earth. This idea required more astronomical cost and effort because they would need a space platform and a dust supply that could be easily replenished. In either scenario, people on the ground wouldn't be able to see the shield or feel any difference, although some tools would probably be able to detect changes in the incoming solar radiation.

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