Oxygen Debt
A hard-science survival thriller by Dax Merrin

Mars doesn't forgive mistakes-and chemical engineer Lena Roen is running out of time to fix hers.

When the oxygen-producing algae tanks begin collapsing without warning, the first Mars colony faces a slow, suffocating death. Supplies won't arrive for months. Every breath is now borrowed.

Lena traces the instability to a hidden mechanical drift-one subtle enough to evade sensors, but powerful enough to unravel the entire life-support system. As pressure drops and panic spreads, she must rebuild the oxygen backbone from the inside out, improvising solutions with failing equipment, dwindling power, and an AI that warns every choice may be the wrong one.

But the deeper she digs, the more the colony shifts around her-structures bending, corridors breathing, the habitat adapting like a living organism. And buried at the heart of it all is a truth she has tried to outrun:

The crisis began with her mistake. The only way to save them is to face it.

In a world held together by engineering and hope, Lena must choose between preserving the system she loves... or breaking it to give the colony a chance to survive.

A tense, character-driven hard sci-fi novella for fans of The Martian, Chernobyl, and Arrival.
Oxygen Debt is a story about survival, forgiveness, and the cost of one breath.