6. A Planet Made of Burning Ice
On Gliese 436 b, the impossible becomes reality. This exoplanet has a surface of “hot ice”—water that remains solid even at scorching temperatures around 800°F. The planet’s immense gravity forces water molecules into a state known as ice-X, a form that shouldn’t exist under such heat. This strange world defies our expectations of planetary physics and showcases how alien exoplanets can truly be. Source: NASA Exoplanet Exploration