Pluto has left astronomers puzzled ever since the world was discovered in 1930. And its mysteries only grew in the aftermath of NASA’s New Horizons probe, which cruised by the dwarf planet in 2015. One point of confusion is Sputnik Planitia, part of the now-familiar heart-shaped region on Pluto’s northern hemisphere.
New Horizons’ instruments hinted that there might be an underground ocean in the region. Otherwise, the tiny, far-off world would be so cold it would have frozen through entirely. Yet Pluto’s crust in the same region is thinner in some areas than others, and that only makes sense if it’s frozen hard — warmer slush would spread out more evenly. Astronomers have been trying to explain those apparent contradictions ever since.
But now one group of researchers thinks they have an answer. The scientists say that a thin layer of insulation — gases like methane trapped inside an ice ...
