Big Idea of 2015: Pluto’s Unmatched Magnificence

This summer, NASA astounded the world with a long-awaited accomplishment: the New Horizons Pluto fly-by.

We now know that the loneliest body in the solar system wears its heart on its sleeve—and is home to a vanishing atmosphere, far-reaching nitrogen glaciers, and volatile geologic activity driven by heat leaking from internal radioactive elements.

After NASA released its first close-up image of Pluto, New Horizons scientists congregated both in private and before audiences of journalists to describe their initial impressions. Here’s what I wrote back in July, reported live from mission control at the Johns Hopkins Applied Physics Laboratory:

Undulating terrain, multi-hued tendrils, and other linear features populate the snapshot, and to the left of the prominent heart feature (which scientists presume is some form of ice) lies a large crater and a veneer of dark material—probably made from complex hydrocarbons called tholin. Tholin forms when ultraviolet rays and galactic cosmic rays disturb methane, breaking down the molecules and generating a reddish gunk that gives Pluto its color.

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Pluto, as seen from New Horizons on the anti-Charon side of the dwarf planet

Pluto might be one of the youngest surfaces we’ve ever encountered. What’s more, its terrain is like a mosaic of planetary features that resemble others in the solar system, as Alexandra Witze reported in October for Scientific American. And as I wrote for NOVA Next, the Pluto-Charon binary system is giving geophysicists a lot to think about:

Tidal heating—thermal energy generated by gravitational interactions between planetary bodies—is typically a prerequisite for mountain formation. Or at least, that’s what scientists have always assumed. But Pluto begs to differ; it can’t have tidal energy because Charon and Pluto are in tidal equilibrium. The presence of towering mountain ranges, then, suggests that tidal heating is not needed to power recent geological activity. “This is going to send a lot geophysicists back to the drawing board,” said Stern. “We have to get a bit more clever.” Pluto is now the only icy world that doesn’t orbit a giant planet—and a fledgling example of a brand-new geophysical law.

We can expect more in-depth analysis from the New Horizons team in the year ahead.