High-speed images of interaction between individual raindrops and soil particles provides new insights into the physics of water erosion

Raindrops can wreak havoc on Earth. They just do it on a microscopic scale. At that scale, raindrops hitting bare ground have nearly the force of a hammer hitting a mound of dirt. What happens when the water hits the soil is the micro-ballistic effect of displaced soil splattering around in all directions. In arid regions, such as central Arizona, this is an important process that shapes the landscape.

How do raindrops form? It's a simple question, but the answer is far from elementary. Tiny water droplets somehow merge to become full-sized raindrops, but the details remain a mystery.