The behavior of clouds and precipitation on planets beyond Earth is poorly understood, but understanding clouds and precipitation is important for predicting planetary climates and interpreting records of past rainfall preserved on the surfaces of Earth, Mars, and Titan. One component of the clouds and precipitation system that can be easily understood is the behavior of individual raindrops. Here, we show how to calculate three key properties that characterize raindrops: their shape, their falling speed, and the speed at which they evaporate. From these properties, we demonstrate that, across a wide range of planetary conditions, only raindrops in a relatively narrow size range can reach the surface from clouds. We are able to abstract a very simple expression to explain the behavior of falling raindrops from more complicated equations, which should facilitate improved representations of rainfall in complex climate models in the future.
Which I think is amazingly cool. The idea that we could use information about rainfall here on Earth to make some guesses about what weather is like on other planets is astonishing. I'm sure if we ever get real data from extrasolar planets, or better data from places like Titan and Enceladus here in our own Solar System, we'll still be in for plenty of surprises; I'm reminded of the cyclic violent downpours of liquid methane on the planet where the Robinsons are stranded in the remake of Lost in Space (which, unlike the original series, is actually good).
But even having a start at understanding the weather on exoplanets, based upon speculation about the conditions and knowledge of how raindrops behave on Earth, is nothing short of fascinating.
So who knows. Maybe soon I'll be able to update my wife about what the low-pressure systems are doing on Titan. With luck, that will produce a better reaction than "Yes, dear."