The image above shows one of Saturn's moons, Titan, as winter sets in at its south pole. As its southern winter approaches, a cloud system called the south polar vortex (small, bright “button”) has been forming.

(NASA/JPL-Caltech/Space Science Institute)

With the use of NASA’s Cassini spacecraft, scientists have detected a monstrous ice cloud in the low- to mid-stratosphere of one of Saturn’s moons, Titan.

“When we looked at the infrared data, this ice cloud stood out like nothing we’ve ever seen before,” said scientist Carrie Anderson of NASA’s Goddard Space Flight Center in Greenbelt, Maryland. “It practically smacked us in the face.”

The gigantic mass of frozen compounds means that , according to NASA. It was detected by Cassini’s Composite Infrared Spectrometer (CIRS), which collects profiles of the atmosphere at invisible thermal wavelengths.

For the past couple of years, Cassini has caught glimpses of Titan’s south pole transitioning from fall to winter, which is , which usually lasts about seven and a half years. Previously collected images of an impressive cloud hanging over Titan’s south pole, however, turned out to be just the beginning. An even more immense ice cloud system was spotted in the lower stratosphere, with a peak altitude of about 124 miles.

The photo above is a close-up taken in 2012 of the changes taking place at Titan’s south pole. Cassini’s camera spotted this massive cloud hovering at an altitude of about 186 miles. The spacecraft's hermal infrared instrument has now detected a massive ice cloud below it.

(NASA/JPL-Caltech/Space Science Institute)

Since Cassini’s arrival at Saturn in 2004, as it transitions into its spring. While this happens, new clouds have been forming at the south pole, and this build-up suggests that the direction of Titan’s circulation is shifting.

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“Titan’s seasonal changes continue to excite and surprise,” said Cassini deputy project scientist Scott Edgington. “Cassini, with its very capable suite of instruments, will continue to periodically study how changes occur on Titan until its Solstice mission ends in 2017.”

Titan is considered one of Saturn’s most intriguing moons, with its thick, nitrogen-dominated atmosphere and the fact that , reports Space.com. Many scientists feel Titan is one of the solar system’s best bets for hosting alien life.

The moon’s polar clouds form differently than the rain clouds common to Earth. They take shape higher in the atmosphere when . When the gas reaches the cold pole, the warm air begins to sink in a process called subsidence. The sinking gas continues to encounter colder temperatures on its way down, allowing different gases to condense at different temperatures. The result is a layering of clouds over various altitudes.

The altitude, size and composition of the polar ice clouds help scientists learn the nature and magnitude of Titan’s winter. Studying the previously spotted ice cloud, scientists determined that , at the least. This new cloud was found in even colder temperatures in the lower stratosphere, with ice particles made up of a variety of compounds including hydrogen, carbon and nitrogen.

“The opportunity to see the early stages of winter on Titan is very exciting,” said Goddard researcher Robert Samuelson. “Everything we are finding at the south pole tells us that the onset of southern winter is much more severe than the late stages of Titan’s northern winter.”

Anderson says these colder temperatures mean that Titan’s southern winter is “coming on strong.”

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