Oliver Shorttle

Scientists modeled the thermal evolution of sub-Neptunes and found that 98% of these worlds probably harbor a permanent magma ocean under their hydrogen atmosphere. This explains why the most common planet type in the galaxy stays hot inside, even though they were thought to have solidified long ago

When a young planet is covered in scorching liquid rock, heavy particles like iron want to sink. But the mantle melts from below, and light droplets float up, churning the ocean. On big Earth, the 'stirring' was strong—no layers formed. Mars is smaller, its rocky soup was shallower and calmer, so ir