Much of the US is in the grip of an unusually brutal winter, with highways shut down and entire cities being snowed in. But that’s nothing compared with Saturn’s moon Enceladus. The moon is famous for the cryovolcanism that blankets it in ice particles, but a new analysis shows the snow cover is much deeper than it should be based on current eruptions. Could it be that Enceladus has been much more active, and we’re just been observing a relative lull?
Enceladus is one of the most interesting moons in the solar system. It’s just 300 miles (500 kilometers) in diameter, but its close proximity to the gas giant Saturn causes tidal eating of the interior. Similar to Europa, scientists believe Enceladus has a subsurface liquid ocean, and while the extent of that ocean on Europa is unclear, we know there’s a lot of water inside Enceladus — Voyager 2 easily spotted water erupting from the surface in giant geysers when it swung past decades ago.
As the moon’s crust flexes due to Saturn’s gravity, pressurized water escapes through fissures in the surface. As soon as it hits the frigid vacuum, the water expands and vaporizes to rain down to the surface as snow and ice. To determine how much snow there is on the surface, a team of scientists led by Emily Martin from the National Air and Space Museum turned to geological features called pit chains.
The Cassini probe studied the Saturnian system for years before it dove into the planet’s atmosphere to end the mission in 2017. Among the images sent back were groupings of crater-like structures on Enceladus, which were later determined to be pit chains. These formations are caused by surface material sinking into an underground void. That’s not the important part — it turns out you can use the depth and width of these pits to gauge the thickness of surface regolith (or in this case, snow cover) as it crumbles around the edge.
Pit Chains on Enceladus (Credit: NASA)
After running the numbers, the researchers determined the moon’s snow cover averaged around 250 meters (820 feet), with some regions as deep as 700 meters (2,296 feet). It’s possible for the moon to have accumulated that much snow cover in the last few billion years at current rates, but only if it was all light and fluffy. The team believes it’s more likely the snow cover has a varied consistency.
That leaves one plausible explanation: the geysers on Enceladus are much less active today than they were in the past. The phenomenon goes through phases of being more or less active, or the moon’s early eons may simply have been more active. In either case, having a proper understanding of the moon’s snow cover will help inform future missions to Enceladus, which some scientists believe is more interesting than Europa.
Now read:
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