Climate change on Earth is an existential threat. Increased solar energy sequestration, the result of changes in the composition of the Earth’s atmosphere, is recognized as a serious problem. One strategy to reverse this trend is to intercept a fraction of the sunlight before it reaches our planet.

Space-based approaches to solar radiation management offer an alternative. Now, a new study led by scientists at the Center for Astrophysics | Harvard & Smithsonian and the University of Utah are exploring the potential of using fabric to shield sunlight.

According to scientists, lunar dust, ie lunar dust launched from the moon, could be a cheap and effective way to darken the Earth.

Moon dust takes nearly a billion years to form. Scientists think it could slow the rise in global temperatures.

For this study, a team of astronomers used a technique — generally used to study planet formation around distant stars — to the lunar dust concept. During the formation of planets, astronomical dust ejected from the process forms rings around host stars. These rings deflect the light from the central star and then re-emit it detectably.

Ben Bromley, a professor of physics and astronomy at the University of Utah and lead author of the study, said: “That was the germ of the idea; if we take a small amount of material and place it in a special orbit between the Earth and the sun and split it up, we can block a lot of sunlight with a small amount of mass.”

A sunscreen’s effectiveness would depend on, the team suggests, its ability to maintain an orbit that casts a shadow on Earth. The original research into whether webs can hold fabric in place long enough to produce adequate shade was led by Sameer Khan, an undergraduate student at the University of Utah and co-author of the paper.

There were two feasible scenarios. The L1 Lagrange point, the closest point between Earth and the sun where the gravitational forces are balanced, is where the authors placed a space station platform in the first scenario. The James Webb Space Telescope (JWST) is located at Lagrange point L2, on the far side of the Earth. This is because objects at Lagrange points tend to stay along a route between the two celestial bodies.

Scientists created computer simulations in which they shot dust particles from the platform to the L1 orbit, including the position of the Earth, sun, moon and other planets in the solar system. Then they tracked where the particle scattering occurred.

The team found that when the dust was launched precisely, it would move in a path that placed it between the Earth and the sun, casting a shadow over it for a while. The solar winds, radiation and gravity of the solar system quickly blew the dust off course. The team concluded that each platform of the L1 space station must continuously produce fresh batches of dust to launch into orbit after the initial spray has dissipated.

Khan said, “It was kind of hard to get the shield to stay on L1 long enough to cast a meaningful shadow. However, this should not be surprising since L1 is an unstable equilibrium point. Even the slightest deviation in the awning’s trajectory can cause it to quickly drift out of place, so our simulations had to be extremely accurate.”

In the second scenario, the lunar dust particles are shot toward the sun from a platform on the lunar surface. They found that the moon dust has natural properties that make it ideal for acting as a sunscreen. The models examined how lunar dust spread along different paths before identifying optimal trajectories targeting L1 and working well as a sunshade.

Scientists noted, “The results were welcome news because it takes a lot less energy to get dust off the moon than it does off the earth. This is important because the amount of fabric required for a sunscreen is large, comparable to the output of a major mining operation here on Earth.”

Study co-author Scott Kenyon of the Center for Astrophysics said: “It’s amazing that the sun, Earth and moon are in just the right configuration to allow for these kinds of climate mitigation strategies.”

bromley said, “We are not experts in climate change or the rocket science it takes to move mass from one place to another. We’re just researching different types of fabric in different lanes to see how effective this approach could be. We don’t want to miss a game changer for such a critical issue.”

Magazine reference:

  1. Benjamin C. Bromley, Sameer H. Khan, Scott J. Kenyon. Fabric as sunscreen. PLOS climate. DOI: 10.1371/journal.pclm.0000133