The novel once again takes up the log-entry structure. It is Sol 63. Watney has finished making water and the potatoes are growing. He describes things as “stable.” His new goal is to find a way to get to the Ares 4 MAV at the Schiaparelli crater, 3200 km away. He’ll have to across the relatively flat Acidalia Planitia, and then over the remaining, more rugged territory. To do so, he’ll need to modify the rover for a long trip—he’ll need a way to carry solar cells to recharge the battery, and bring oxygen, food, and water. He decides to use Rover 2.
Watney often uses the log to work through the problems that he’s solving. His decision to record his problem-solving process and not just the solutions suggests that he finds it helpful to write out the ideas as he brainstorms and that he is invested in giving future readers of the log a detailed record of the scientific and engineering aspects of his time on Mars.
Watney can double Rover 2’s battery life by wiring Rover 1’s battery into it. Watney decides that, since the Rover is well insulated, he’ll just rely on his own body heat, which will avoid spending battery life on heating. He’ll drive for about three and a half hours each day during twilight, then recharge during the sunny part of the day. To recharge the batteries, he’ll need to bring fourteen solar panels.
After assessing his situation and identifying his goals, Watney begins to problem-solve. His first problem to solve is his lack of power: the batteries only have a limited charge, and this lack of electric energy highlights Watney’s metaphorical powerlessness as well.
Sol 64. Watney begins modifying Rover 2. Using extra canvas and resin meant for Hab repairs, Watney makes “saddlebags,” which he uses to carry the Rover 1 battery. When one battery runs out, he’ll plug the other battery back in.
Watney’s problem solving once again requires him to use his limited supplies in unconventional ways—his survival depends on creative, innovative thinking.
Sol 65. Watney begins disassembling the solar cell array. Since there’s only Watney in the Hab now (not a crew of 6), it needs less energy—removing 14 solar cells won’t cause problems. Watney straps the 14 cells onto the roof. When charging, he’ll spread them out on the ground beside the rover. Returning to the Hab, Watney digs up the potatoes, cuts them up into pieces with one eye each, and reseeds them. At the end of the day, he relaxes by reading an Agatha Christie e-book from Johanssen’s laptop.
Watney is able to survive because he is stranded on Mars alone. It would be impossible to stretch food supplies or repurpose solar cells and space suits in the way that he does if he had been somehow stranded on Mars with the rest of the Ares crew. In this way, his solitude is a stroke of good luck.
Sol 66. Watney decides that he’ll call his trips with the rover Sirius missions (it’s a dog pun). For his first mission, he’ll do a three-hour test drive, staying within a short walk of the Hab at all times. Sol 67. Watney explains that Sirius 1 didn’t go as well as planned—without the heater, the rover got very cold, very quickly. Watney ended the trip after an hour.
“Rover” is a common name for a dog, and Sirius (known as the dog star) is part of the constellation Canis Major (Greater Dog). Watney’s pun shows that he is writing his log with future readers in mind—he wants to be likeable.
Sol 68. Watney decides that he’ll heat the rover using the RTG (radioisotope thermoelectric generator), a box of highly unstable radioactive plutonium. NASA uses RTGs to power unmanned probes, as well as using them on the Ares missions to power the MAV before the crew arrives. Upon the Ares 3 crew’s arrival, Commander Lewis removed the RTG from the MAV, buried it 4 km south of the Hab, and marked it with a flag. The RTG will put out more than enough heat to keep the rover warm; on Sirius 2, Watney is going to go dig it up.
Watney has already used NASA equipment in creative and unconventional ways, but in deciding to use the RTG as a heat source, he is making a choice that is both unconventional and risky. NASA keeps its astronauts as far from RTGs as possible and surely would not approve of this choice. Yet Watney needs to take this risk in order to survive in Mars’ cold climate.
Sol 69. Driving towards the RTG, Watney is out of sight of the Hab for the first time. He is struck by how utterly alone he is. These feelings make him uncomfortable, so he tries not to think about them. Watney digs up the RTG, puts it in the rover, turns off the heater, and drives back to the Hab. The RTG makes the Hab uncomfortably warm; Watney will have to remove some insulation.
Watney rarely uses the log to reflect on his feelings, so this entry gives readers rare insight into how he is responding to total solitude. Yet Watney’s insistence on hiding his feelings from the log’s readers could suggest his fears and uncertainties are too painful to admit even to himself.
Sol 70. Watney tests the Rover using the RTG for heat and uses its 100 watts to boost the battery power; it works beautifully. Watney knows that if NASA knew he was using the RTG, they’d have a fit.
Watney’s inability to contact NASA may be an advantage in that he doesn't need official approval to take risks like using the RTG.
Sol 71. Watney starts planning for Sirius 4, which will be a twenty-day trip. He can easily bring food and water for a few days. He decides he’ll use oxygen and carbon dioxide filters to breathe, and moves one of the Hab’s liquid oxygen tanks into the rover. Watney reveals that he has a specific goal for the trip: it’s not just to test the Rover in preparation for the drive to the Ares 4 MAV, but he doesn’t yet say what it is. To keep the potatoes alive, he’ll make the Hab very humid and vent in carbon dioxide from the MAV fuel plant before he leaves.
When outlining a plan, Watney usually records all the details in the log, but here he doesn’t explain what his goal is for the trip. Perhaps Watney does not want an official record of the trip’s goal in case he fails to accomplish it—but whatever Watney’s reasoning might be, Weir uses this omission to build a sense of suspense for the reader. As chapter seven closes, we’re left wondering where Watney is going.