Oxygen Debt

Mara was in the second year of her orbital assignment. She gazed through the window at the endless darkness glittering with stars. “Beautiful,” she thought. “Doesn’t make it any less scary.” She remembered it was payday. “Even in space, payday is payday.” She opened her account. “Looks a little low... Let me check the details.” She frowned at one charge. “An oxygen deduction? What is this?” She turned to Tomas. “For God’s sake, what’s an oxygen deduction? Do they expect us to photosynthesize?” Tomas just grinned. “You didn’t know? Better calm down, or you’ll breathe even more.”