A distant planet's air contains water vapor https://www.scientificamerican.com/article/astronomers-find-water-and-weird-clouds-on-extrasolar-warm-neptune/

"Astronomers have spotted water vapor and evidence of exotic clouds in the atmosphere of an alien planet known as HAT-P-26b.

The researchers also determined that HAT-P-26b's atmosphere is dominated by hydrogen and helium to a much greater degree than that of Neptune or Uranus, the alien world's closest counterparts in our own solar system in terms of mass.

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HAT-P-26b lies about 430 light-years away from Earth. The alien planet circles very close to its host star, completing one orbit every 4.2 Earth days. This proximity suggests that HAT-P-26b is tidally locked, showing the same face to its star at all times, said Hannah Wakeford, co-leader of the new study and a postdoctoral researcher at NASA's Goddard Space Flight Center in Greenbelt, Maryland.

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The data also indicate that clouds scud across HAT-P-26b's skies, but relatively deep in the atmosphere; they do not block much of the water-absorption signal, Wakeford said. These clouds are probably made of disodium sulfide, not water vapor like those of Earth, she added.

"This would be a very alien sky that you would be looking at," Wakeford said. "These clouds would cause scattering in all of the colors, so you'd get a kind of scattery, washed-out, gray sky, which is interesting, if you were looking through these clouds."

Ultrabright light streaming from the nearby star would bombard an observer above the clouds, she added. "There's nothing there to really help stop that sunlight from reaching you." "

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