Rain is not unique to our planet: Titan has methane rain and exoplanet WASP 78b is home to iron rain (ouch). A new study examines rainfall across planets from the perspective of individual rain drops. The authors examine raindrop shape, terminal velocity, and evaporation rate as a function of droplet size for a wide range of known and speculated atmospheres.
They found that raindrops are surprisingly universal. Although planets with higher gravity tend to produce smaller raindrops, they found a remarkably narrow range for maximum drop size. That’s a pretty wild result, all things considered! The idea that iron, ammonia, methane, and countless other fluids falling through vastly different atmospheres all share very common characteristics is fascinating. (Image credit: NASA/JPL-Caltech/SwRI/MSSS/Brian Swift; research credit: K. Loftus and R. Wordsworth; via Science News; submitted by Kam-Yung Soh)