One of the most surprising and intriguing finds during the decade-long Cassini mission has been the discovery of geysers on the Moon Enceladus. Originally spotted in 2005, scientists have spent the last decade trying to understand how they work. And now they finally have a working model.
How does an eruption on a frigid Moon last so long? Eruptions on Earth are not long-lived, and if they are, they are very spread out. For Enceladus to have a ton of localized geysers in the South polar region, you need some pretty specific scenarios. Aside from the fact that a constant stream of material could clog up it’s own geyser, how does the vent not freeze over when exposed to the frigid vacuum of space?
One of the clues to solving the mystery was the fact that the peak of the geyser activity comes 5 hours later than it should, based on the tidal forces of Saturn. In the new model, scientists suggest that a series of parallel vertical slots connect the surface to the deep liquid ocean below. The variable is how wide or narrow the slots are, and the wider they are, the more quickly they can respond to the tidal forces from Saturn. Wide slots can respond almost instantly, while narrow slots take 8 hours to respond. This pointed to a sweet spot right in the middle, where the tidal forces turn the movement of water into heat, forcing it to blast through the surface 5 hours after the peak tidal forces are felt.
The model is yet to be confirmed, but it gives astronomers a tool for understanding the mechanisms within Enceladus that respond to the tidal heating from Saturn. This level of understanding can tell us whether Enceladus really is conducive to life, and if so, it can give us clues to what might lurk below the frozen world.