Surrounding the Earth with regolith, the moon dust, would reduce exposure to sunlight to our planet by 1.8% and lower the global temperature and impact climate change. However, it is not clear whether it would be worth spending so many resources on such a strategy.
First of all, the project would require more than a decade of research before it can become a reality. In addition, the risks associated with such an approach, in terms of its influence on agriculture, ecosystems, and water quality, are not at all clear. Despite the uncertainties, carrying 100 million tons of dust between the Earth and the Sun is not a recent idea.
A layer of regolith in orbit
The regolith would shade the Earth, absorbing part of the light energy and scattering the photons away from our planet. To achieve this goal, the dust should be placed 1.5 million kilometers away, where the gravitational attraction of the Sun and our planet cancels out. In this area, objects remain in a fixed position known as the first Lagrange point, or L1.
A research group explored the possibility of positioning the dust on L1 by publishing the results in a scientific paper (ref.). The main problem is represented by the energy of photons expelled from the Sun, known as the solar wind. This phenomenon can push the regolith further away from the desired position. Now, after performing thousands of computer simulations, Benjamin Bromley of the University of Utah has found a possible solution.
The simulations predict that each particle of dust would spend about five days before dispersing throughout the Solar System. Launching instead a continuous flow of moon dust from the north pole of the Moon towards L1 could be a better approach.
How realistic is this solution?
Simulations have found that maintaining a dust shield for one year could obscure the sun’s light by 1.8%. This would be equivalent to blocking out six full days of sunlight. If the approach were sustained over time, it would offset the increase in carbon dioxide levels that has occurred since the start of the industrial revolution. “If this method works, it would certainly be effective in reducing global temperatures, but it is difficult to say whether it would be worth it in terms of the effort and resources used” says Ben Kravitz of Indiana University, Bloomington.
Analyses have not predicted the use of any machinery to launch the lunar dust towards the L1 point. In this sense, the researchers suggest using a railgun. “This system would be perfect because it could be powered by a few square kilometers of solar panels positioned near the launch site” says Bromley. Despite these possible solutions, shading the Earth will have unequal effects in different regions. “Temperature, precipitation, winds, and many other things will change and they will change differently in different places” says Kravitz.
“These changes will, of course, have effects on agriculture, ecosystems, and water quality.” Before a strategy like this can be implemented, large-scale engineering studies must be conducted by multiple agencies such as the United Nations, says Curtis Struck of Iowa State University.
“Considering this approach should not replace our efforts to reduce carbon emissions. We must continue to reduce greenhouse gases in our atmosphere, whatever happens” says Bromley. “Regolith would simply give us more time on the ongoing climate change.”