Section 1.1: The Mechanism Behind the Stripes

The narrative begins with an ocean beneath an ice shell. As Enceladus cooled in the distant past, a layer of seawater froze and expanded. This expansion, trapped by the crust, increased pressure in the ocean until, much like a glass bottle left too long in the freezer, something eventually broke.

The gravitational pull of Saturn occasionally compresses Enceladus as it orbits, thinning the crust at the poles. Hemingway and his team propose that it was the south pole that succumbed to this pressure first, resulting in the formation of the Baghdad fissure, which slices through the southernmost point of the moon.

Prior research suggested that oceanic tides caused by Saturn’s gravity prevent the crack from freezing by repeatedly pulling it apart and pushing it back together. “You’re effectively flushing water out and then pumping it back in,” Hemingway explains, which helps to keep the water warm and the crack open. Exposed to the vacuum of space, substantial amounts of water continuously escape into the atmosphere, forming plumes that Cassini encountered.

Section 1.2: The Formation of the Tiger Stripes

Ice particles from these plumes accumulated on either side of the Baghdad fissure over time, adding weight until the ice sheets fractured, leading to the creation of the Cairo and Damascus stripes, named after locations in One Thousand and One Nights. Yin likens the phenomenon to placing a child at the end of a flimsy diving board and then adding weight until it buckles.

This process continued, resulting in the Alexandria fissure and another partial crack, informally referred to as “E,” which is too shallow to reach the ocean below. The researchers estimated that forming each fissure required between one hundred thousand to one million years of seawater expulsion and ice accumulation. However, it appears that no new crevasses will develop, as the ice thickens farther from the pole.

Despite the intriguing theory, skepticism remains among some geologists regarding its accuracy. “I think the likelihood is quite low,” Yin remarked. He argues that assuming a uniform melting and freezing of the global ocean seems unrealistic, given the well-preserved craters in the northern hemisphere, which show minimal signs of historical heating or cooling.

Instead, Yin proposes a different explanation: an internal heat surge may have melted a section of a half-mile-high plateau, causing it to cascade sideways into the frozen shell. This movement would have created visible wrinkles that eventually froze in place. The increasing horizontal pressure from this ice slide might have simultaneously ruptured all five tiger stripes. Yin and his team previously detailed this theory in two publications from 2015 and 2016.

Yin welcomes the debate sparked by the ocean-bursting theory—acknowledging it as a plausible scenario—because it generates testable predictions. The evaporating water plumes should have deposited layers of ice that would weigh down the ice shelves over millennia, leaving the stripes exposed. Hemingway’s fissures should display deep cuts with seawater visible along the entire fault, while Yin’s model would show seawater only at specific points.

Current imaging technology cannot differentiate between these scenarios, but future missions to Enceladus may clarify the origins of the tiger stripes. Former Cassini team members have proposed a follow-up mission titled “Enceladus Life Finder” to revisit this icy moon, although funding has yet to be secured.

“In the future, if we can deploy spacecraft in orbit or landers,” Hemingway notes, “we will gain a much clearer understanding of the moon’s interior, allowing us to test various hypotheses.”