The 100

The Ark was running out of oxygen, Clarke's father had estimated that it may last another three-four if they stretch it-years until they all die. Her father is executed for treason and when Clarke tries to finish what he started, she is put on death row. Clarke loved being alone in her room, but solitary confinement with a loudly ticking clock made her mad.

Earth was beautiful, but didn't change the fact that the animals were mutated, the plants were poisonous, and this was a death sentence.