But Donald had quickly discovered that each hole contained just enough to allow him to breathe for short rest. He would awake four or five hours later, choking on the stale remains, cramped and uncomfortable from sleeping almost upright, leaning against the side of a tube of weathered rock.

Slipping his helmet on over his head, he gathered together his meager belongings: the suit, the beacon, some quickly fraying rope, the water filter, a climbing hammer with half of the shaft lost in the crash, and a bag of rations that he had decided not to count until the remaining number became small enough that he wouldn’t be able not to.

He shimmied up the pit wall until he reached the surface, and  marked the edge of the hole with a notch to remind himself that he had already used this one up. Then he set out to find the next one before the air-supply in his helmet ran out.