20 Mar 2011 'Pac-Man' in space: 1980s video game icon glows on Saturn's moon Mimas

Other moons usually grab the spotlight, but it turns out Mimas is more bizarre than we thought it was, said Linda Spilker, Cassini project scientist at NASA's Jet Propulsion Laboratory in Pasadena, Calif. It has certainly given us some new puzzles.Cassini collected the data on Feb. 13, Rosetta Stone Greekduring its closest flyby of the moon, which is marked by an enormous scar called Herschel Crater and resembles the Death Star from Star Wars.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).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 sharp, V-shaped pattern.We suspect the temperatures are revealing differences in texture on the surface, said John Spencer, a Cassini 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.Denser ice quickly conducts the heat of the sun away from the surface, keeping it cold during the day. Powdery ice is more insulating and traps the sun's heat at the surface, so the surface warms up.Even if surface texture variations are to blame, scientists are still trying to figure out why there are such sharp boundaries between the regions, Spencer said. It is possible that the impact that created Herschel learn french Saturn, the visibility of these contrasts on a moon continually re-paved with small particles from the E ring helps scientists estimate rates of change on other satellites.These processes are not unique to Mimas, but the new high-definition images are like Rosetta stones for interpreting them, Helfenstein said.