Sol 32. Every twenty hours, Watney plans to vent 10 liters of carbon dioxide from the fuel plant into the Hab; the oxygenator will then turn it into oxygen. Then, Watney will separate the hydrazine into nitrogen and hydrogen, and gradually burn the hydrogen in as controlled a way as possible. The hydrogen and oxygen in the air will make water, which will remain in the Hab’s atmosphere as humidity. Then, the water reclaimer will pull the water out of the air and store it. Watney finishes the day with an episode of Three’s Company.
Watney has spent the day making a meticulous plan for how to turn oxygen and hydrogen into water as safely as possible. Weir takes the time to explain each step of the process to the reader—this novel takes care to show feasible science, not the kind of nonsensical solutions of many sci-fi movies. Watney’s new routine of watching Three’s Company shows that life on Mars is becoming a bit predictable.
Sol 33. Watney prepares to make water. He removes the hydrazine tanks and iridium reaction chamber from the MDV and brings them into the Hab. He has already vented one tank of carbon dioxide into the Hab’s atmosphere. He copies the log to both rovers for future astronauts to find, in case the Hab blows up and kills him.
Watney’s precaution of copying the log over twice reveals to the reader just how important it is for him to believe that someone will eventually read his story. By ending the log entry right before Watney makes water, Weir builds suspense.
Sol 33 (2). Watney dons protective clothing and an oxygen mask. He uses duct tape and clear plastic Hefty bags to cover his work table, where he has set up the hydrazine and the bowl-like iridium reaction chamber. He creates a “chimney” with a small hose. Next, he creates a “pilot light” using the only flammable thing in the Hab—splinters of wood from a religious cross that belonged to Martinez—and ignites it using an electric spark and pure oxygen. Watney turns on a slow stream of hydrazine, and his contraption works! He starts making water. Watney stays up all night converting 50 liters of hydrazine. By the time he goes to sleep, mid-way through Sol 34, the Hab is incredibly humid, and he has begun storing water in Johanssen’s space suit.
The very fact that a second log entry for Sol 33 exists tells readers that Watney has survived the process of making water. Weir gives readers a step-by-step account of how Watney converts the hydrazine into water: this attention to detail creates a heightened sense of realism. Watney’s decision to use wood from Martinez’s cross highlights how a sense of faith—in science and in himself, if not in God—is essential to Watney’s survival. Yet hope alone will not help Watney survive—he relies on creativity and science.
Sol 37. Watney tells us he is going to die. He has fled the Hab and is now writing from the Rover 2. After making water for several days, he realizes that while he should theoretically have 130 new liters of water, he has only collected 70 liters. After checking the oxygenator, he realizes he’s been gaining oxygen—which means that he hasn’t burned off all of the released hydrogen. After testing the atmosphere, he realizes the Hab’s atmosphere is now 64 percent hydrogen—the Hab is now a bomb waiting for a spark.
Watney opens this entry of the log with a sense of urgency and panic paralleled only by the first sentences of his very first log entry. It’s a very different tone from the logical, self-assured voice in the previous log entry. For both Watney and the reader it’s unsettling to realize that producing something as basic and essential to life as water could have unintended and deadly consequences.