Mercury was observed, it was showing the same face towards Earth, so it was thought that the planet had a hot day side always facing the Sun and a cold night side always turned away. Any science fiction written before that date assumes this.Then, in 1965, radar observations disclosed that Mercury in fact rotates three times for every two revolutions.
Thus, the opening story of Larry Niven's Known Space future history became scientifically out of date between writing and publication. The hot and cold sides of Mercury are a myth of the Solar System like the canals of Mars and the oceans of Venus.
I have started to read Poul Anderson's "Vulcan's Forge" (Space Folk, New York, 1989), set on and around Mercury but published in 1983. Thus, this is a modern Mercury with a sunrise. Both title and text refer to another myth, Vulcan. Anomalies in Mercury's orbit were once explained by postulating another planet even closer to the Sun and appropriately named "Vulcan." Then the anomalies were instead explained by relativity. Inappropriately, the name "Vulcan" was later transferred to a fictitious extra-solar planet in Star Trek. In the first volume of his prose adaptations of Star Trek scripts, James Blish rightly describes this nomenclature as confusing.
Italicized passages in "Vulcan's Forge" are narrated by what seems to be a human consciousness directly controlling a spaceship approaching "Vulcan." It was known in 1983 that the postulated Solar planet Vulcan did not exist so I have yet to learn how Anderson is using the term here. Meanwhile, here is another of Anderson's unusual words: "...cabochons..." (p. 30).