Quote 1
"You really think I'll leave you behind?" Martinez said.
"I just ordered you to," Lewis replied. (12.111-112)
This takes a lot of guts. If you had any doubts about Commander Lewis' leadership skills, then this exchange surely must've changed your mind. Lewis would willingly trade places with Mark if given the opportunity.
"With a reduced diet I could stretch it to nine. But it'll be seventeen months before I get back."
"So how would you survive?"
"The supplies wouldn't be the only source of food," she said. (19.169-171)
In case you don't grasp the creepy undertones, allow us to make everything crystal clear: Johanssen is talking about eating her (former) crewmates if everything goes wrong. Might as well call herself Johanssen Lector. If we were in this situation, we'd almost rather be the ones getting eaten.
Quote 3
"If I can't reach Mark, I want you to release my tether."
"Dr. Beck," Vogel said, "the commander has said no to this." (26.44-45)
Beck is one tough cookie. In one moment, he decides to go against his orders and perform a risky maneuver, even though it could lead to a very nasty death. This is something we see time and time again over the course of The Martian.