One of the best places to look for life beyond Earth in our solar system is Saturn's moon Enceladus, which is said to have an ocean of liquid water beneath its icy crust. A new map of the moon, made with both visible light and infrared, now shows where regions of geological activity have deposited fresh ice on its surface.
Because Enceladus is covered in ice, it is one of the most reflective bodies in our solar system and usually looks like a brilliant white snowball. To learn more about this fascinating moon, NASA analyzed data from its Cassini mission to Saturn, which ended in 2017.
Cassini had an instrument called the Visible and Infrared Mapping Spectrometer (VIMS) that recorded the way light was reflected from Enceladus, split the light into different wavelengths, and allowed scientists to infer what materials the moon is made of.
In these detailed infrared images of Saturn's icy moon Enceladus, reddish areas indicate fresh ice that has deposited on the surface. NASA / JPL-Caltech / University of Arizona / LPG / CNRS / University of Nantes / Space Science Institute
You can also view an interactive map of Enceladus that allows you to zoom around the moon.
The bright red region is particularly interesting because it is right on the south pole of Enceladus in a region with tectonic faults known as Tiger Stripes. The red color indicates that this region is spewing ice grains and steam onto the surface, which correlates with this geological activity area. This is strong evidence that there is an ocean under the ice.
What is important is that the north pole of the moon has similar infrared characteristics. This suggests that similar geological activity took place at both poles and that the North Pole was covered in fresh ice at some point in recent history. Both poles were "resurfaced" by water from the subterranean ocean, either as icy jets or as ice moving up through fractures in the crust.
“The infrared shows us that the surface of the South Pole is young, which is no surprise, as we knew about the jets blowing up icy material there,” says Gabriel Tobie, VIMS scientist at the University of Nantes in France and co-author of the new paper said in a statement. "Thanks to those infrared eyes, you can now go back in time and say that a large region in the northern hemisphere also appears young and was probably active in geological timelines not so long ago."
The next step is for scientists to see if this technique reveals information about other icy moons in order to compare it to Enceladus.
The research is published in the journal Icarus.