NASA's DimSun concept aims to reduce solar insolation by 1.16% using a controlled dust cloud at L1

NASA’s Jet Propulsion Laboratory has proposed a new geoengineering concept called Dimming the Sun (DimSun) that would use a controlled dust cloud at the Sun–Earth Lagrangian L1 point to reduce solar radiation reaching Earth. The mission aims to decrease solar insolation by 1.16% using hollow spherical particles with a radius of 0.3 micrometers, maintained by multiple spacecraft that apply repulsive forces to prevent orbital decay.

The concept builds on earlier research that envisioned an uncontrolled dust cloud of small regolith particles at L1, which required replenishment every 100 days. DimSun’s key innovation eliminates the need for replenishment by actively controlling the cloud, and the system can be reversed within 100 days by deactivating the control spacecraft, causing the dust to disperse.

According to the proposal, DimSun carries a one-time fixed cost of roughly $134 billion, including a 43% margin, plus recurring maintenance expenses. This makes it significantly more affordable than other geoengineering approaches: it is 150 times cheaper than space-based solar occulter methods and six times cheaper than Stratospheric Aerosol Injection over the 21st century.

The concept was selected for study under NASA’s Innovative Advanced Concepts (NIAC) program in 2026. The next steps would involve further research and development to assess feasibility, with implications for global climate intervention strategies if pursued.