Cassini Journals: A Shocking Encounter at Hyperion and an Ocean on Mimas

A Shocking Encounter at Hyperion:  NASA/JPL-Caltech/Space Science Institute

This week brought two new findings from the Cassini spacecraft in the Saturn system.

The first involved data from a September 26, 2005 flyby of Saturn’s bizarrely shaped moon Hyperion. According to new analysis, during the approach, Cassini was struck by a beam of electrons coming from the moon’s surface, which momentarily the connected the spacecraft to the moon, transmitting what amounted to a 200 volt electric shock.  Regrettably, (or perhaps not), the reason for the encounter encounter was not as exciting as it could have been. There was no ancient relic of an alien civilization sending out distress signals, nor was it a prelude to invasion. Instead it was the first confirmed instance of a charged surface on a world other than our own Moon. The key word is “confirmed,” as scientists believe many other celestial objects will be discovered to be similarly charged.

The complete story is here.

Also coming from the Cassini mission, a possibly very surprising finding regarding another of the Saturn’s moons, Mimas. In a study reported in the Oct 17 issue of Science, researchers have determined that a slight wobble in the moon’s orbit indicates something unusual is happening.

From the JPL news story:

“The data suggest that something is not right, so to speak, inside Mimas,” said Radwan Tajeddine, a Cassini research associate at Cornell University, Ithaca, New York, and lead author on the paper. “The amount of wobble we measured is double what was predicted.”

While the wobble could be caused by the presence of a football shaped, frozen core, another and altogether more intriguing possibility is that Mimas is hiding a subsurface ocean. If so, it adds to a growing awareness that our solar system is a much wetter place than we one thought it to be.  From discoveries of water molecules on the Moon and significant ice deposits on Mars, to the hydrocarbon seas of Titan, as well as subsurface oceans on Enceladus and Europa, we are quickly finding ours is not the only “water world.”

Mimas Mosaic
Image credit: NASA/JPL-Caltech/Space Science Institute