NEWS FROM Mimas
Mimas ploughs through Saturn’s rings
major moons, Mimas may be the smallest of Saturn’s has cleared but it sure is mighty. The tiny, icy body
(2,980mile) enough material to create a 4,800-kilometre largest rings. wide gap between Saturn’s two after its
This void is known as the Cassini Division in 1675, Giovanni Cassini, who observed it discoverer and B rings. and is located between Saturn’s A had been
The formation of the Cassini Division suggested that poorly understood until scientists the ice
Mimas acted as a snowplough, clearing its path and particles that make up the rings from gap. paving the way for the substantial inwards towards Mimas is thought to have migrated approximately 9,000 kilometres (5,600 Saturn by recently in miles) over a few million years – relatively of the original cosmic terms – leading to the widening
Division. gap and the establishment of the Cassini has begun to This rift will not last forever, as Mimas million years the migrate outwards, and in about 40 again.
Cassini Division will have closed up
Peculiar surface temperatures give rise to a ‘Pac-Man’ moon
on 13 February 2010, During the Cassini flyby of Mimas temperatures was an unexpected pattern of daytime
When the Composite observed on the little moon’s surface. was analysed and then Infrared Spectrometer (CIRS) data of Mimas, a strange PacMan mapped onto a visible-light image the moon’s surface. like scene was presented across to see a uniform This baffled scientists, who expected that were highest distribution of surface temperatures we see on Earth. in the early afternoon, similar to what into a warm part (left) Instead Mimas appears to be divided boundary between and a cold part (right), with a V-shaped warmer region were them. Typical temperatures in the degrees Fahrenheit), around -181 degrees Celsius (-294 drop to -196 while the colder region saw temperatures
The stark degrees Celsius (-320 degrees Fahrenheit). be due to thermal difference between the regions could
If the colder region conductivity of the surface material. a higher thermal is made up of surface materials with heat will be soaked conductivity, then more of the Sun’s the material itself. into the subsurface instead of warming
What’s behind Mimas’ wobble?
from Cassini In 2014, scientists analysing data collected around its polar noticed the moon librates (wobbles) libration being axis. While this isn’t unusual, with came when observed in many moons, the surprise wobble is double the libration was measured. Mimas’ in one spot, than expected and is more pronounced uniform. Scientists suggesting that Mimas’ interior is not is masking one suggested the heavily cratered surface is that the moon of two interesting possibilities. One core, and the contains a rather odd, rugby ball-shaped or densities of other is that there are different materials a subsurface ocean. material below the icy shell, such as been unable to Since the discovery, scientists have and many confirm or deny any of these possibilities, has an ovalshaped questions remain unanswered. If Mimas to take on a slightly core, we’d expect the moon
And if there’s a different shape to the one we see. source the heat subsurface ocean, how does Mimas energy to maintain such an ocean?