This article says

[Pluto] is about 20% redder than it used to be.

Have there been any further articles/Hypotheses on both the cause of the color, and more importantly, the color change? Or do we have to wait for New Horizons to gather more data?

  • $\begingroup$ Related: How long have we known Pluto is red? $\endgroup$
    – called2voyage
    Jul 10, 2015 at 13:26
  • 2
    $\begingroup$ At such distances from the Sun and given Pluto/Charon's orbit it's generally about seasonal variations in the (sometimes almost non-existant) atmosphere. $\endgroup$ Jul 10, 2015 at 13:26
  • $\begingroup$ Should questions like this be moved to SE.Astronomy? Maybe Space Exploration should have an obvious link at the top recommending SE.astronomy for purely astronomical questions? $\endgroup$
    – LocalFluff
    Jul 10, 2015 at 13:29
  • 5
    $\begingroup$ Also possible are surface volatiles transitioning from solid to liquid phase and vice versa (and forming haze and clouds) as the body moves closer of farther from the Sun in its orbit, and due to change in solar activity (solar cycles). @LocalFluff No, planetary-science is firmly on-topic here and less so on Astronomy where we don't even have this tag. This is not a purely astronomical question at all. Most recent surface and exosphere observations of Pluto were / are done with space-based telescopes and probes (though ground and air based telescopes, e.g. SOFIA, also contribute). $\endgroup$
    – TildalWave
    Jul 10, 2015 at 13:31
  • 4
    $\begingroup$ @LocalFluff Planetary science questions are on topic on both sites, but they often receive better answers over here since a lot of planetary science is planned for space missions. My rule of thumb is if the planetary science involves telescopes, I ask it on Astronomy, otherwise I ask it here because I will probably get a better answer. $\endgroup$
    – called2voyage
    Jul 10, 2015 at 13:37

1 Answer 1


The jury is still out!

That said, the community is buzzing with theories, most of which are suggesting that there may be transport processes (i.e. winds, rivers, glaciers, etc.) happening on Pluto, or that the surface and/or atmospheric chemistry is a little different because it recently hit perihelion (its point of closest approach to the Sun), so it was slightly warmer than it would have been.

For examples, check out these articles:


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