Saturn has a lot of moons, but Titan is of particular interest to scientists for numerous reasons. It has a thick atmosphere, bodies of liquid on the surface, and weather patterns. Scientists from the University of Arizona studying the atmospheric processes on Titan report they happened upon a previously unidentified global feature: a ribbon of ice that wraps around the planet, covering more than 40 percent of its circumference.

Titan’s atmosphere is mostly nitrogen, but there are also traces of methane and other molecules. Solar radiation breaks down methane molecules, which rain down on the planet as organic sediments. This naturally removes methane from the atmosphere, but levels remain constant. The study led by Caitlin Griffith of the UA Lunar and Planetary Laboratory sought to find a source for the methane supply.

In the past researchers have posited that a form of cryovolcanism could be responsible for the release of methane from underground reservoirs. The only confirmed source of methane is evaporation from the planet’s hydrocarbon lakes, but that wouldn’t account for all the atmospheric methane. The team analyzed half of Titan’s surface in hopes of finding evidence of the cryovolcanoes but came up empty. They did find something else in a region called Sotra, though.

The team discovered a band of water ice while evaluating scans of Sotra from NASA’s Cassini spacecraft. What appeared at first to be a local feature proved to be just the start of a corridor of ice that stretches more than 40 percent of the way around the moon. The researchers used a technique called principal components analysis (PCA). Rather than hunt for important features pixel-by-pixel, PCA lets scientists spot trends in landscapes. Applying this to Titan, the data showed the band of water ice around the equatorial region of the moon.

This corridor of ice doesn’t appear to correlate with existing geological features, and it’s uneven across the surface. That indicates the ice could be eroding. Thus, the ice might have been deposited at some point in the past when Titan was still geologically active in a major cryovolcanic event. That doesn’t tell us if the same event or the ice band has a connection to Titan’s methane cycle, but this use of PCA could lead to many more discoveries on Saturn’s largest moon.

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