Obize is an Eden-like moon orbiting the barren terrestrial planet Akaria. This planetary system is special in the fact that the two worlds are complete contrasts to each other. The moon has plentiful liquid water, comfortable temperatures and is perfect for life with conditions (relatively) identical to Earth with native fauna and flora adjusted to the moon's low gravity. The planet it orbits is a dead barren world no different than Mercury.
I am wondering, how could this happen?
Akaria and its moon orbit their parent star smack dab in the middle of its habitable zone. Akaria is roughly 160% the size of Earth while Obize is roughly 60%. The parent star is similar to Earth's sun.
The conditions in the rest of the system and planetary composition is unknown and up to you to decide. What could cause this odd pair to come about? Answers can range from hard scientific to those with high creative liberty. You choose. Right now I would just appreciate any ideas. I can't think of any reasons why the planet would be barren while the moon is paradise like.