Moon Hong-kyu
The author is a principal researcher at the Korea Astronomy and Space Science Institute.
During the Chuseok holidays, I was greeted by a long stretch of monsoon-like rain. A day or two of showers can be a blessing after a dry spell, but when it lingers, we start to miss the crisp autumn sun and the deep blue sky. It made me wonder: could such watercolor-like days of rain exist beyond Earth?

If we turn our gaze toward the pitch-black expanse of the universe, we find worlds where "rain" takes on astonishing forms. Even within our solar system, Uranus and Neptune may see showers of diamonds. Under the immense pressure of their atmospheres - hundreds of thousands of times greater than Earth's - methane molecules split apart. Carbon atoms released in the process compress under heat and pressure, forming diamond crystals. These crystals then fall slowly toward the planets' cores like raindrops, layering for hundreds of thousands of years. If a probe could withstand the crushing depths, it might encounter billions of carats of "jewel rain."
On some exoplanets, however, it rains metal. WASP-76b, known as a "hot Jupiter," is a gas giant that orbits so close to its star that one hemisphere always faces it. That eternal day side is so hot that iron vaporizes into gas, which is carried by fierce winds to the cooler night side - though "cooler" still means hotter than a furnace. There, the vapor condenses and falls as molten iron droplets, a phenomenon scientists aptly call "steel rain." It is a vision of beauty and terror that defies imagination.
Another planet, HD 189733b, gleams a cobalt blue. Its vivid color does not come from oceans, but from silicate particles suspended in the atmosphere. On this world, it rains glass. Shards of silicate drizzle through the sky at five times the speed of sound, whipping sideways in violent winds. No shield could withstand such a storm. These bizarre yet real landscapes have been confirmed through telescopic observation and atmospheric modeling.
So, even if the holidays bring long rains, perhaps it's something to appreciate. After all, the water that soaks our fields and orchards nourishes the grains and fruits of autumn. Compared to diamond, steel or glass, the gentle "rain of water" is surely a gift.
This article was originally written in Korean and translated by a bilingual reporter with the help of generative AI tools. It was then edited by a native English-speaking editor. All AI-assisted translations are reviewed and refined by our newsroom.

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