1. The problem statement, all variables and given/known data To protect the lunar base against space and sun radiation, astronauts covered it with 4m thick layer of regolith (moon soil). However, they found that they level of radiation was still 50% higher than on the Earth's surface, which they want to match. How many more meters of regolith do they need to add for proper protection? 2. Relevant equations I = I˳e-µx 3. The attempt at a solution I know that they want to reduce the radiation by 1/3, to 2/3 of the current value. However, no half layer value or absorption coefficient is given for regolith.