PRESS PLAY, ABOVE, TO SEE NORMAL IMAGE OF MIMAS. NASA’s new temperature map of Saturn’s moon Mimas was completely unexpected, and looks like Pacman eating a dot.
Credit: NASA
Saturn's Moon Mimas, imaged in visible light.
Credit: NASA
SYDNEY: First there was the man in the Moon and the face on Mars, now astronomers have observed a temperature anomaly on Saturn's moon Mimas that looks like the 1980s computer game icon, Pacman.
Pacman is a simple game where a yellow, circular icon with a wedge-shaped mouth munches 'dots' as it progresses through simple mazes, chased by ghosts.
A similar image has been observed as the NASA spacecraft Cassini flew by Saturn's small, inner moon Mimas, which orbits the gas giant every 22 hours and 37 minutes. Cassini's composite infrared spectrometer observed temperature variations on Mimas last month.
Crater traps heat
Mimas is a 396 km diameter, water-ice moon marred by the giant Herschel crater, a 140-kilometre-wide impact that almost shattered the moon and forms a prominent 'bulls eye' on Mimas' surface.
Astronomers expected the crater to be warmer than the surrounding surface because the five-kilometre-high walls of the crater trap the Sun's heat.
The mapped temperature variations confirm this and at 84 degrees Kelvin (-153°C), the crater forms a purple dot against the colder (92°K or -159°C) surface background.
Pacman face is mysterious
But the strange pattern that forms the 'face' of Pacman in the image is a puzzle because there is no obvious reason that there should be such a sharp variation in temperature.
Also, the hotter temperatures (77°K or -144°C) occurred during Mimas' morning, and not as expected during the afternoon when the regions around the equator are heated by prolonged exposure to the Sun.
US space scientist John Spencer, from the Southwest Research Institute in Boulder, Colorado, said it could be due to textural differences on the moon's surface.
Icy surface meets warm, fluffy surface
"This probably means there's a hard, crunchy ice surface in the cold region and a soft, fluffy surface in the warm region," he told Cosmos. While crunchy ice retains the cold, the fluffy stuff remains warmer due to the differing ability of the two surfaces to conduct heat.
