“Pluto’s core is so cold that the (rocky body that collided with the dwarf planet) remained very hard and did not melt despite the heat of the impact, and thanks to the angle of impact and the ...

“Pluto’s core is so cold that the rocks remained very hard and did not melt despite the heat of the impact,” said Ballantyne. “Thanks to the angle of impact and the low velocity, the core ...

Scientists have tried to explain why Pluto has not quite completely cooled off. Perhaps Pluto’s core has radioactive elements that impart an additional source of heat. Another theory is that the ...