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This is what rain is like on other planets

Published Apr 7th, 2021 5:01PM EDT
alien rain
Image: NASA/JPL/University of Arizona

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Rain on Earth is something that we’ve come to know well. It’s relatively predictable in size and shape, and while we’re noticing more extreme weather and lack of rain in some parts of the world (thanks to climate change, which is our fault, by the way), rain itself doesn’t change much. As it turns out, the same may be true on other planets, and a new study suggests that while the makeup of precipitation could vary dramatically on alien worlds, the raindrops would look very familiar to human travelers.

The research, which was published in the Journal of Geophysical Research: Planets, suggests that the physics that govern how water droplets form and fall on Earth will likely result in similar precipitation on other planets, even if the makeup of the “rain” is much different. In modeling raindrops falling through the atmospheres of planets like Jupiter and Saturn, which are vastly different from rocky planets like Earth, they found that the type of planet doesn’t matter all that much when it comes to rain.

The researchers simulated precipitation through different types of atmospheres and found that what determines the size of raindrops on Earth seems to be universally true across the board. When drops are too small they evaporate before reaching the surface, but when they’re too big they end up splitting apart into smaller drops before impact. The middle ground is where the overwhelming majority of drops end up after falling a significant distance, regardless of what type of atmosphere is present or the makeup of the rain itself.

Some worlds have slightly larger rain than Earth, such as Saturn’s moon Titan. Raindrops on Titan, which are made of methane rather than liquid water, are thought to be around twice the size of raindrops on Earth, but that’s still a very small change for such a wildly different planet. It sounds wild but it makes a lot of sense. Physics doesn’t care what planet you’re on and will govern everything in the same way.

What’s even more exciting is that we may soon have the telescope technology to make even more accurate estimates of rainfall on other worlds, that is if the James Webb Space Telescope ever launches.

“Now with instruments like [the James Webb Space Telescope], which hopefully will soon be launched, we will have the capability to detect really fine spectra of exoplanetary atmospheres, including ones that are quite cooler than ones we’re usually able to characterize, in which clouds and rain will occur,” planetary scientist Tristan Guillot, who was not part of the research team, said of the work. “So these kinds of tools as they are developed will be very useful and important to interpret those spectra.”