On a winter day when it’s cold, the sun feels good. But, people are letting out more and more of a type of gas known as greenhouse gases which is trapping heat in the atmosphere and making our planet hotter. To stop this warming trend, some scientists believe putting up objects in the sky that can block 1-2% of sunlight before it reaches the Earth could help.
A recent study at the University of Utah has shown that using dust to block the sun could potentially be a useful way to protect our planet. They worked out what type and how much dust would be needed, as well as which paths it should take. But they also found that sending the dust off this planet (such as way station between Earth and the Sun) is expensive and difficult. An easier, cheaper option would be to launch moon dust from our own moon, which could also help in shading Earth.
A group of astronomers used a technique they usually use to study planets forming around distant stars. This messy process produces dust that makes rings around the star, which reflect light we can detect from Earth. That way, we can recognize stars that are creating new planets by looking for these dusty rings.
Ben Bromley, a professor of Physics and Astronomy, had an idea. He suggested that if we take a tiny bit of material and place it into a special kind of orbit around the Earth and Sun, it could block out lots of sunlight with just a little amount of mass.
Scott Kenyon from the Center for Astrophysics | Harvard & Smithsonian said “It’s incredible to think moon dust which formed over four billion years ago, might help reduce the temperature increase on Earth, which happened way faster – in less than 300 years.” His research was published recently in a journal called PLOS Climate.
Using Gravity to Calculate a Sunshield
How well a shield can protect us from sunlight depends on the path it takes around Earth so that it makes a big enough shadow. Sameer Khan, an undergrad student and co-author of this study, researched which orbits would be able to keep dust in place long enough to shade us. His work showed how hard it is to make sure that the dust stays in the right spot.
Khan explained that since we know the locations and sizes of planets in our Solar System, we can use gravity to figure out where a sunshield will end up depending on its orbit.
There were two ideas on the table. The first one was to put a space station right next to Earth and the Sun, a place called the L1 Lagrange Point. It is so special because things placed there will stay between both bodies because of the balance of gravity forces. This is why the James Webb Space Telescope (JWST) is located at L2, which is near the opposite side of our planet.
In experiments on computers, scientists studied the trajectory of tiny particles flying around the Earth, the Sun and the Moon. They saw that if these particles were launched correctly by a special platform in space, there would be a “shade” created between them – Earth and Sun. Yet, this shade doesn’t last long as solar winds, radiation and gravity blast away these particles quickly. So to keep up this “shade” of protection from the heat of the Sun, new batches of dust must be sent into orbit every few days after that first spray fades away.
Khan said that it was tough to keep the shield in an area called L1 for long enough so that a shadow could be made. This wasn’t surprising since L1 is an unsteady sort of balance point. Meaning, any imperfection in its orbit could cause it to move away quickly, so our calculations had to be very exact.
In the second experiment, researchers shot moon dust towards the sun and discovered that it had just the right properties to form a ‘sun shield’. They tested how this dust scattered along various paths before finding one path that could be used as an effective shield. This is great news because launching the dust from the moon needs less energy than doing so from Earth. This matters because a lot of dust is needed to make a shield, like what you would get from a big mining operation. Also, with these new trajectories, sending lunar dust to a platform near the sun may not be necessary.
Exploring the Possibility of Using Dust Clouds to Combat Climate Change
The authors are trying to find out how much difference this strategy could make, rather than seeing if it is something that can be done.
“We don’t know a lot about climate change or how to move stuff from one point to another. We’re just looking into different types of dust and the orbits they can travel on, to see if it might help with the climate problem,” said Bromley.
One of the main issues faced is that dust clouds needs to be replaced every few days. However, this is actually a good thing since eventually the sun’s rays will make all the dust particles spread throughout space and none will reach Earth. The authors also made sure that their process won’t turn Earth into an icy planet like the one from “Snowpiercer” which was a sci-fi movie.
Bromley said that his team’s technique could be useful for helping against climate change if we need more time to fix it. The research mentioned in the passage is called “Dust as a Solar Shield” and was published in PLOS Climate on February 8, 2023. It covers two topics: the coronavirus outbreak in Beijing’s Xinfadi Market and emphasizing diagnosis and treatment of Demodex Blepharitis.
Journal Reference: Benjamin C. Bromley, Sameer H. Khan, Scott J. Kenyon. Dust as a solar shield. PLOS Climate, 2023; 2 (2): e0000133 DOI: 10.1371/journal.pclm.0000133
