Geoengineering: Sending “moon dust” to cool planets

Sending dust from the moon could help combat global climate change. Photo by Paola Iamunno

Warm sunshine is popular on cold winter days. However, as humans emit more and more greenhouse gases, more and more solar energy is captured in the Earth’s atmosphere, steadily raising the Earth’s temperature. One strategy to reverse this trend is to intercept a small fraction of sunlight before it reaches Earth.

For decades, scientists have considered using barriers, objects or dust particles to block 1 to 2 percent of solar radiation to mitigate the effects of global warming.

A study by the University of Utah in the United States explored the possibility of using dust to block sunlight. The paper was published February 8 in PLoS Climate.

The researchers analyzed the nature of the dust grain, its number and the orbit most suitable for shading the Earth, and found that launching it from Earth to the “Lagrange point” (L1), located between the Earth and the Sun, is the most efficient, but it comes at astronomical cost and effort.

Another option is to use moondust. The authors suggest that sending dust from the moon could be a cheap and effective way to shade Earth.

The team of astronomers employed a technique that studies how planets around distant stars form. The formation of planets produces a lot of dust, and the latter can form rings around stars. These rings intercept light from the star and re-radiate it in a way we can detect it on Earth. One way to look for stars that are forming new planets is to search for these dust rings.

“That’s where the idea came from.” Lead author Ben Bromley, professor of physics and astronomy, said: “If we put a small amount of material in a special orbit between the Earth and the sun and crush it, we can block a lot of sunlight. ”

Scott Kenyon, co-author of the Harvard-Smithsonian Center for Astrophysics, said: “Surprisingly, lunar dust took 4 billion years to produce and may help slow the rise in Earth’s temperature, while this problem took less than 300 years. ”

The overall effectiveness of the parasol depends on its ability to maintain an orbit that casts shadows on Earth. It can be challenging to keep dust where it needs to be and thus provide enough shade.

“Because we know the position and mass of the major celestial bodies in the solar system, we can simply use the laws of gravity to track the position of the ‘parasol’ in several different orbits.” Paper co-author Sameer Khan said.

In the first scenario, the researchers positioned a spatial platform on L1. In computer simulations, the researchers fired test particles along an L1 orbit and tracked where they scattered. It was found that when precisely emitted, dust follows the path between Earth and the Sun, creating an effective shadow for at least a while.

However, dust can easily be blown out of orbit by the solar wind, radiation, and gravity within the solar system. This requires a steady stream of new dust to be sent into orbit every few days after the dust has dissipated. “It’s hard to get the ‘parasol’ to stay in L1 long enough to cast an effective shadow.” Khan said.

In the second scene, the researchers shot dust from the lunar surface towards the sun and found that the inherent nature of lunar dust was just right for effective sun protection. They simulated how lunar dust dispersed along different paths until they found an excellent trajectory pointing to L1. This is an effective barrier.

In addition, it takes much less energy to launch dust from the moon than from Earth. This is important because the amount of dust in the “umbrella” is large, equivalent to the output of a large mining operation on Earth.

The authors emphasize that the study only explores the potential impact of this strategy, rather than assessing whether these scenarios are logically feasible. (Source: Wang Fang, China Science News)

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