Tantalizing Pluto views suggest active surface but won't be seen again for 161 years

ref cited in the space.com article - Pluto in Glory: Discovery of Its Huge Opposition Surge, https://agupubs.onlinelibrary.wiley.com/doi/abs/10.1029/2021GL092562

The abstract reports "Pluto's unusual phase curve may be due to an unusual surface texture caused by seasonal volatile transport and active geologic processes." Plain language summary states "Observations at Palomar Observatory show that both hemispheres of Pluto, as well as its main moon Charon, exhibit a surge of over 30% in brightness at opposition, suggesting an unusual surface texture due to activity and volatile transport."

Some of the language here suggests Pluto presented some surprises for the current thinking on Pluto and its origin :) Pluto's present orbital period extrapolated back 4.5 billion years ago, more than 18 million revolutions completed around the Sun in the heliocentric solar system. The Pluto system would form in a much more massive KBO disk, perhaps at least 30 earth masses originally according to various sources too.
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"There never was a good war, or a bad peace."
OK, that works for a planar situation, but, due to the high inclination of Pluto's orbit, are not the degrees of illumination going to vary greatly from one opposition to another?

It may be an opposition in the horizontal plane, but very variable in the vertical plane.

Cat :)

"By looking at how much an object brightens when it gets full, you can tell something about the surface texture and what the surface is like — is it fluffy? Is it snowy? Is it compact?"

Is this not going to be invalidated by the 'vertical' variation, except in those (very) rare cases where Pluto deigns to join us in the Ecliptic? Far more than 160 years apart?
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