Saturn’s moon Enceladus is quickly making a name for itself as one of the most interesting geologies in our solar system. Hidden under a top sheet of ice, the lunar body hides an ocean we suspect is being warmed by tidal forces. We learned as much in a 2005 flyby of the Cassini satellite which observed the planet spewing out water from hydrothermal vents at its south pole.
Now we’re learning that some of that icy top layer could be as thin as 2 km in some places. The findings mean we have some very interesting prospects for places to target for any future missions to drill for evidence of life in the moon’s waters. Researchers made the startling new observation using 2011 data transmitted from Cassini and the findings are published in the journal Nature.
“This discovery opens new perspectives to investigate the emergence of habitable conditions on the icy moons of the gas giant planets,” Nicolas Altobelli, ESA’s Project Scientist for Cassini–Huygens, said in a statement. “If Enceladus’ underground sea is really as close to the surface as this study indicates, then a future mission to this moon carrying an ice-penetrating radar sounding instrument might be able to detect it.”
The observations come from an arc-shaped swathe of the southern polar region next to a set of four fracture lines in the ice nicknamed the ‘tiger stripes’. Microwave observations uncovered unusually warmer temperatures in areas with geologic fractures. It’s not surprising as you’d expect to see some heat emanating from fault lines if the whole ice sheet is sitting on top of a warm ocean. But researchers found the area displayed more warmth than they expected, which suggests the ice is thinner than previous predictions.
The new findings also agree with a 2016 study led by Ondrej Cadek which estimated the thickness of Enceladus’s crust to have an average depth of 18–22 km and to reduce to below 5 km at the south pole.
Unfortunately, operational constraints limited Cassini to taking just one swath of a narrow band of the moon’s surface. But the fascinating result is cementing our interest in this region of the moon and means many more scientific missions are to come.