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Why Is The Sky Blue On Pluto? — ‘The Why’

Welcome to the newest edition of The Why.Why is the sky blue on Pluto?” Good question. (OK, it’s a little “Mr. Science” but again it still beats answering inquiries about assorted, odd intimate acts. Seriously? We thought “Plating” was just something NASA used on the New Horizon, mmmkay?)


Image: NASA

If you missed the news, The National Aeronautics and Space Administration (NASA), released new photos that show that despite the fact that the dwarf planet has a reddish brown surface, Pluto’s atmosphere is blue. The pics, of course, are thanks to the New Horizons probe’s recent fly-by of Pluto (covered previously by American Live Wire, of course).

So why is the sky blue on Pluto?  Does it seem goofy?  Well, it’s basically because of something called tholins and how we see things. But fi you need more of an answer, our guest speaker, Bill Chappell, contributor to NPR, recently investigated the matter.



A group of scientists say that the color disparity is due to tholins. Tholins are, Chappell confirms, “particles formed after sunlight sparks chemical reactions between nitrogen and methane in the atmosphere.”

As scientists told Chappell: “A blue sky often results from scattering of sunlight by very small particles. On Earth, those particles are very tiny nitrogen molecules. On Pluto they appear to be larger — but still relatively small — soot-like particles we call tholins.”

Chappell concludes: “The process was first seen on Titan, Saturn’s moon; in the case of Pluto, the particles are likely gray or red — but they scatter blue light, making it the most visible to the human eye.” (As we discussed in earlier editions of this column, our perception of colors is linked to the limitations and function of the human eye.)


Image: Rotana

Why is the sky blue on Pluto? Now you know.

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About Will Phoenix

W. Scott Phoenix, B.A., B.S. was born in Hawaii, raised in Pennsylvania and resides in California. He has been a published writer since 1978. His work has appeared (under various names) in numerous places in print and online including Examiner.com. He is a single parent of three children and has also worked as an actor, singer and teacher. He has been employed by such publications as the Daily Collegian and the Los Angeles Times.