The Hole Man
In this story, a team of explorers and scientists on Mars encounter an alien base, in which there is a still-functional communication device. One scientist believes that at the center of the device is a tiny black hole, but his superior does not believe him. During a heated argument with his superior, the scientist turns off the containment field, releasing the black hole. The hole drops right through his superior, killing him as it falls towards the center of the planet. At the end of the story, the release of the black hole is revealed to possibly endanger the explorers as it consumes Mars.