Another illustration from a personal project.
The USS Charleston, a Shreveport-class cruiser, witnesses a mysterious disturbance on the surface of Titan. Later investigation revealed neither Martians nor Germans, but a mysterious and deserted city made of glass.
Current hypotheses lean towards the explosion being some sort of self-destruct mechanism triggered by the emanations of the American ships gravity nullification engine. This may have been either to prevent capture of the city (and the secrets therein) or to serve as a sort of warning beacon for whoever was monitoring the site.
The mystery continues, and was the source of much speculation before more urgent matters pushed this aside.