Pluto Is Still Alive and It's Leaking!

Keypoints:

• New Horizons data reveals the first evidence of liquid nitrogen recently flowing on Pluto's surface
• The liquid appears to rise through cracks in Sputnik Planitia, Pluto's massive heart-shaped glacier
• Researchers compared the dark surface patterns to liquid-water features on Greenland's ice sheet
• Pluto's atmosphere makes liquid nitrogen rain physically impossible, so the source must come from below
• Findings were led by Dr. Alan Stern, principal investigator of the New Horizons mission, and published this week

For a decade, Pluto has been treated as a frozen, largely inert world, most of what's known about it still comes from a single flyby New Horizons made back in 2015. A new analysis of that same flyby data just overturned that picture, revealing the first evidence that liquid nitrogen has recently flowed across Pluto's surface.

The clues sit in Sputnik Planitia, a nitrogen glacier larger than Texas and Oklahoma combined that forms the western lobe of Pluto's famous heart. Dark, narrow streaks and diffuse patches along its northern edge appear to have been wetted by liquid rising up through cracks from deep beneath the ice, then darkening the surface as it spread, a pattern with no obvious source above ground, since Pluto's thin atmosphere and extreme cold make liquid nitrogen rain physically impossible.

Researchers led by Dr. Alan Stern compared the New Horizons images directly against NASA Landsat 9 photos of Greenland's ice sheet, where liquid water is known to darken snow and ice in strikingly similar patterns. The resemblance held up closely enough that the team concluded basal melting, nitrogen ice melting far below the surface and rising through narrow conduits, is the most likely explanation. 

"Pluto never stops surprising us," Stern said. "In addition to suggesting that liquids have recently expressed themselves on Pluto's surface, it also suggests a new kind of time-variable feature on Pluto."

The bigger shift here is conceptual. A dwarf planet sitting billions of miles from the sun, cold enough that nitrogen itself freezes solid, apparently still generates enough internal heat to melt that same nitrogen and push it to the surface. 

That's a level of ongoing geological activity nobody expected to find on a world this small and this far from any obvious heat source, and it raises real questions about what else might be happening beneath Pluto's ice that a single decade-old flyby was never positioned to catch in the act.