Why are there no liquid planets in our solar system?

The answer is simply because the Solar System didn't form that way. More truthfully, it is not possible to have an entirely liquid planet (the liquid at the core would compact into a solid anyway). read more

In our Solar System, there is simply not enough matter capable of becoming liquid at the temperatures that we have. Earth could have been entirely water-surfaced, but we didn't have enough H2O. Saturn's moon, Titan, could have been entirely methane-surfaced, but it didn't have enough CH4. read more

"Many details as to why Earth is the only planet with liquid water in our solar system need to be worked out," said Diana Valencia, a graduate student in Earth and Planetary Sciences at Harvard University. "Certainly the distance to the sun has made it possible. read more