The plumes of Enceladus, captured spewing from the moon's surface by the Cassini spacecraft at a distance of 14,000 kilometers (9,000 miles) in 2010. “ corrals a host of observations of Enceladus' south polar terrain and its geysering activity with a rather simple idea,” says Carolyn Porco (Space Science Institute), who was not involved in the study but led the Cassini imaging team that discovered the stripes. Scientists are commending this all-encompassing scenario. NASA / JPL / Space Science Institute / CICLOPS All In One Blue tints in this false-color view from Cassini indicate an icy surface covered with coarse grains and boulders. These are the source of its gas-and-particle plumes. A closeup of the four 80-mile-long rifts(dubbed "tiger stripes") near Enceladus's south pole (white cross). This process continued to create stripes in symmetric pairs around Baghdad Salcus: first Cairo and Damascus, then Alexandria and a feature informally named “E.” Eventually, though, the cascade ends, either because there’s not enough eruption “snow” to build up ridges or because the ice crust becomes thick enough not to bend and break. The ridge becomes heavy enough to bend, and eventually break, the icy crust, creating another crack at a specific distance - 35 kilometers - from the first one. But the geyser erupting from this fracture snows water-ice down onto its flanks, building up a ridge on either side over time. This first crack relieved the pressure from the cooling, expanding ocean - that’s why there are no like fractures at the north pole. Water fills most of the crack, boiling off at the top in geyser-like fashion where it meets the vacuum. Hemingway and colleagues suggest that Baghdad Sulcus, a stripe that cuts directly through the geographic south pole, formed in this way, a crack at the surface that eventually penetrated all the way through the ice shell. NASA / JPL-Caltech / Space Science Institute / CICLOPS / Porco et al., Astronomical Journal, 2014 The red curve is the ground track of Cassini’s October 28, 2015, flyby at the time of the spacecraft's closest approach. White circles and crosses represent locations identified by scientists as source locations for dozens of geyser-like jets along the fissures. The long, linear, bluish features are the “tiger stripe” fractures, from which a plume of water vapor and other molecules erupts. This map shows the active south polar region of Saturn's moon Enceladus. Because Enceladus’s crust is thinnest at its north and south poles, where Saturn’s gravitational pull creates the most heat, that’s where the crust breaks when it begins to pull apart. As its belowground water ocean freezes, it expands, exerting pressure from the inside. The idea is simple in concept: Once a crack forms in Enceladus’s icy crust, it creates a cascade of fractures next to it.Įnceladus is known to go through cooling periods that thicken its icy crust. Now, Douglas Hemingway (Carnegie Institution for Science and University of California, Berkeley) and his colleagues publish an explanation in Nature Astronomy that covers all the bases. No scenario has simultaneously explained all of the stripes’ characteristics. The parallel stripes, about 35 kilometers (21 miles) apart, are located only at the moon’s south pole, and they’re unlike any features found on other icy moons. But the region that hosts the geysers - an area of so-called “tiger stripes” etched into the icy crust- has long puzzled astronomers. Saturn’s moon Enceladus is famous for its water-spewing geysers, an outward sign of an underground saltwater ocean. NASA / JPL / Space Science Institute / CICLOPS The tortured surface of Saturn's moon Enceladus includes four rifts, sometimes called "tiger stripes," near its south pole. Now, a single explanation ties all the pieces together. Astronomers have struggled to understand the origin of the parallel fractures on Saturn’s icy moon Enceladus, known as “tiger stripes,” from which water-ice spews into space.
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