User blog comment:Lawliet Watari/What is the most powerful element?/@comment-67.225.19.90-20130403055202/@comment-173.59.66.236-20130412185905

All planets have "air" because air is much more than just oxygen. But all planets besides Earth have little to no oxygen in their air. The Earth doesn't have much oxygen in its air either (about 21%; a little over 78% of our air is nitrogen) but it obviously has more oxygen than all other planets which is why it's able to sustain life.