Worth noting that those "soft and fluffy" clumps of gravel and sand still move at 18+km per second and even one the size of Dimorphos striking the earth would easily cause an explosion big enough to completely level even the largest city (think 30 to 50 megatons of explosive energy upon impact). Or for example a comet, -mostly just a sort of dirty snowball- a couple miles in diameter would cause a global climatic catastrophe and vaporize every living thing and standing structure within hundreds of miles of its impact location.
Terrifying capabilities for such soft and fluffy, brittle things.
Terrifying capabilities for such soft and fluffy, brittle things.