Pluto's moon Charon busted out of its skin
New analysis of Pluto's largest moon adds weight to the idea that Charon once contained an ocean. Belinda Smith reports.
If you've ever left a can of drink in the freezer, you'll know the power of expanding ice.
Now, NASA scientists suggest something similar happened to Pluto's largest moon, in the deep-freeze of the outer Solar System.
New analyses of New Horizon's photographs of the moon's equatorial region, snapped in July 2015, show a belt of deep chasms fringed by cliffs towering 11 kilometres high. These fractures, they say, are in line with the freezing and expansion of a subterranean ocean.
Eventually, the ice burst the moon's skin.
So how did Charon get a liquid sea in the first place?
When the moon formed from scraps of dust and rock 4.5 billion years ago, it also collected water. As it coagulated, pressure and radioactivity within may have kept that water from freezing.
But Charon is small. At around 1,200 kilometres in diameter, it's less than half the size of the Moon. And being way out in the Solar System's sticks, far from the warmth of the Sun, it cooled quickly.
Scientists think as the rock in Charon chilled, it dropped the temperature of the water. And as that ice froze and expanded, it stretched the moon's skin, like a forgotten can of soft drink in a freezer.