Watney and NASA communicate about the airlock incident. Now that the farm has been destroyed, plans for the Ares 4 resupply probe are being moved up. NASA and JPL focus on how to modify the probe as soon as possible to send food to Watney. JPL is working overtime on the probe, named Iris.

Meanwhile, Rich Purnell is introduced for the first time. He is a physicist who calculates course corrections, and he oversees calculating Iris’s course to Mars. But while he is working, he has an idea and begins working on a new plan, which the reader won’t learn about until the next chapter.

To complete the Iris probe in time for launch, Teddy Sanders decides to skip inspections for the craft. Chances of problems coming up in the inspections are slim—there is about a 1/40, or 2.5%, chance of mission failure. While normally that would be grounds for stopping a countdown, in this instance, Teddy accepts the risk as necessary. Because of this schedule shift, the Iris probe is launched on time. However, during flight, the probe develops a shimmy. While it would normally be harmless, it causes the protein cubes that they are sending to Watney to shift inside the probe.