NASA's Cassini spacecraft collected the clearest images of Saturn's icy moon Mimas, whose resemblance to the Death Star is often remarked upon. And when Cassini mapped Mimas' temperatures, they found... Pac Man? It's the pop-culture crossover you never expected.
Scientists working with the composite infrared spectrometer, which mapped Mimas' temperatures, expected smoothly varying temperatures peaking in the early afternoon near the equator. Instead, the warmest region was in the morning, along one edge of the moon's disk, making a sharply defined Pac-Man shape, with temperatures around 92 Kelvin (minus 294 degrees Fahrenheit). The rest of the moon was much colder, around 77 Kelvin (minus 320 degrees Fahrenheit). A smaller warm spot — the dot in Pac-Man's mouth — showed up around Herschel, with a temperature around 84 Kelvin (minus 310 degrees Fahrenheit).
"Even though we can't explain the observed pattern of surface temperatures on Mimas, the giant Herschel crater is a leading suspect," said Dr. Mike Flasar, composite infrared spectrometer principal investigator from NASA Goddard Space Flight Center in Greenbelt, Md. "The energy of impact that created it several billion years ago has been estimated to be one-seventh of Mimas's own gravitational energy. Anything much larger would likely have torn the moon apart. We really would like to see if there is also an anomalous temperature pattern on the other side of Herschel, which has not been observed so closely."
The warm spot around Herschel makes sense because tall crater walls (about 5 kilometers, or 3 miles, high) can trap heat inside the crater. But scientists were completely baffled by the Pac-Man shape.
"We suspect the temperatures are revealing differences in texture on the surface," said John Spencer, a composite infrared spectrometer team member based at Southwest Research Institute in Boulder, Colo. "It's maybe something like the difference between old, dense snow and freshly fallen powder."