Encounter With Enceladus
After the March 12 flyby, Cassini has returned the closest pictures yet of Saturn's moon Enceladus. For the first time we are seeing the Northern hemisphere. Already we have found that the South Pole is a "hot spot." The Southern hemisphere is extremely young, being continually resurfaced. In contrast the Northern Hemisphere is much older, as evidenced by the many craters. Why are North and South so different?
Because the Southern hot spot spews materiel from the Moon's interior into Space, Cassini can sample what Enceladus is made of. The atmosphere contains nitrogen, which is produced from the decomposition of ammonia (NH3). That process requires temperatures in excess of 850 degrees Kelvin. Total energy production of Enceladus has been estimated at 10^9 Watts! The atmospheric plume also contains traces of methane (CH4), carbon dioxide (CO2), propane (C3H8) and acetylene (C2H2). Radioactive isotopes of these elements are all very short-lived.
Scientists have speculated about radioactive aluminium and iron. The only naturally-occuring isotope of aluminium is Al26, which has a half-life of only 720,000 years. The longest-lived isotope or iron, Fe60 has a half-life of 1.5 million years, an eyeblink in geologic time. Even potassium 40 has a half-life of 1.3 billion years. If these elements were found at Enceladus, (they were not) the Moon should have run out of fuel billions of years ago.
Enceladus can be modelled with a central singularity of 10^12 kg, typical for a primordial Black Hole. The singularity consumes only 2.8 kg of mass per year generating 10^9 Watts of radiation. Water and other molecules near the centre are heated to a plasma. Electrons are stripped from atoms, and the resulting ions are drawn into circular orbits around the core. The resulting electric current generates a magnetic field with the "positive" pole in the South.
Electrons and positively charged ions spiral along magnetic field lines to form bipolar jets, the classic sign of a singularity. The Northern jet is composed of electrons which are absorbed by the moon's interior. More energetic ions of the Southern jet penetrate these layers to warm the South Pole. Escaping ions spiral into Space, exactly as observed by Cassini.
Without replenishment, Saturn's Rings would decay within 100 million years. Then we would face the anthropic question of why they exist at just the right time for humans to view them. Thanks to Cassini, we have witnessed the E Ring being resupplied from Enceladus. This observation suggests that other, unseen satellites maintain the Rings.
Saturn's rings and icy moons show conditions similiar to our Solar System's formation. Discoveries about Enceladus may tell us about Earth. Our planet also produces internal heat and a magnetic field. Earth's core may also be a place to seek signs of a Black Hole. We are only beginning to undestand our Universe and its formation.