1. The problem statement, all variables and given/known data If one micrometeorite (a sphere with a diameter of 1.50×10-6 m) strikes each square meter of the surface of the Moon each second (1 micrometeorite/m2/s), how many years will it take to cover the Moon to a depth of 1.80 m? Assume that after impact, the micrometeorites spread evenly over the surface of the moon. 2. Relevant equations V = 4/3πr^3 3. The attempt at a solution I'm not sure if I'm thinking through this correctly, but here it goes. SA of Moon (SA) = 3.8x10^13 m^2 (got this out of my textbook) Thickness (T) = 1.8 m (Given in problem statement) Total Volume needed to be filled by Micrometeorites = SA * T = (3.8x10^13)(1.8) = 6.84x10^13 m^3 Volume of 1 Micrometeorite = V = 4/3πr^3 where r = (1.5x10^-6 / 2) = 4/3π(1.5x10^-6 / 2)^3 = 1.77x10^18 Micrometeorites needed = Volume needed/Volume of Micrometeorites = (6.84x10^13)/(1.767x10^-18) = 3.87x10^31 Since the rate at which they fall is 1 Micrometeorite/s that means a total of 3.87x10^31 seconds which comes out to 1.22 years. Apparently this is wrong (we have to enter our answers online, and we're told if we're right or not). Please help!