I spent the time building up detailed maps of the two planets. The larger, Vulcan, had significantly more CO 2 and a thicker atmosphere, therefore a higher mean surface temperature. The smaller planet, Romulus, had actual ice caps, although judging from the change in size just since I’d been here, they might be seasonal. It was currently mid-spring in the northern hemisphere, and with a year only 285 Earth-days long, the seasons moved quickly.