Chapter 18, Old Faithful Summary

Captain Smith navigates Universe within one hundred meters of a comet geyser that erupts at regular intervals. It is named after the famous Yellowstone Park geyser. To Captain Smith's considerable annoyance, people track dirt into the airlock from the surface of a nearby tar deposit, named Lake Tuonela. He bans any further excursions onto the deposit.

Chapter 18, Old Faithful Analysis

As the crew and passengers of Universe explore the comet, more exposition about its nature comes through. As the comet nucleus heats, geysers of water and steam erupt, causing a perpetual snow that falls upward away from the nucleus. The comet is also a dirty place, which plays an importance in the general idea of space travel. Spaceships need to be clean, and so Captain Smith's annoyance is not simply from a desire to keep things shipshape.