Simulated stream of dust launched between Earth and the sun. This dust cloud is shown as it crosses the disk of the sun, viewed from Earth. Streams like this one, including those launched from the moon’s surface, can act as a temporary sunshade. Credit: Ben Bromley/University of Utah
When you get too warm at the beach, you simply sit beneath your umbrella, using it as a shield from the sun. New computer simulations suggest Earth should do the same thing—except instead of a rainbow umbrella, scientists say dust particles can be used as a shield to block 1 to 2% of the sun’s radiation.
A new paper, published in PLOS Climate, explores the potential of using moon dust to block just enough of the sun’s radiation to mitigate the effects of global warming.
According to the team, led by University of Utah researchers, a sunshield’s overall effectiveness would depend on its ability to sustain an orbit that casts a shadow on Earth.
“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.
The paper tested different properties of dust particles, quantities of dust and orbits that would be best suited for shading Earth.
“Because we know the positions and masses of the major celestial bodies in our solar system, we can simply use the laws of gravity to track the position of a simulated sunshield over time for several different orbits,” said study co-author Sameer Khan, Utah undergraduate student who led the initial exploration into which orbits could hold dust in position long enough to provide adequate shading.
According to the study, two scenarios were particularly promising—at least in computer simulations.
In the first scenario, the authors positioned a space station 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.
In simulations, the researchers then shot particles from the platform to the L1 orbit, and tracked where the particles scattered. When launched precisely, the dust followed a path between Earth and the sun, effectively creating shade—at least for a while. Eventually, however, the dust was 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.
“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 Khan.
In the second scenario, the researchers shot lunar dust from a platform on the surface of the moon toward the sun. They found that the inherent properties of lunar dust were just right to effectively work as a sunshield. The simulations tested how lunar dust scattered along various courses until they found excellent trajectories aimed toward L1 that served as an effective sunshield.
The second moon-based scenario demonstrating better results was a positive for the research team, as much less energy is needed to launch dust from the moon than Earth.
"It is amazing to contemplate how moon dust—which took over four billion years to generate—might help slow the rise in the Earth’s temperature, a problem that took us less than 300 years to produce,” said study co-author Scott Kenyon, part of the team from the Harvard-Smithsonian Center fo Astrophysics. “It is astounding that the sun, earth, and moon are in just the right configuration to enable this kind of climate mitigation strategy.”
The authors stress that their new study only explores the potential impact of this strategy, rather than evaluate whether these scenarios are logistically feasible.
“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. “Our strategy could be an option in addressing climate change if what we need is more time.”