b'Carnegie Science|Spring/Summer 2020 13Global Ocean onSaturns Moon Ice crustENCELADUSGlobal oceanRocky coreSouth polar regionwith active jets * Thickness of layers is not to scaleEnceladus experiences internal heating from its eccentricweight added a new form of pressure on the ice sheet. That orbit, which is sometimes a little closer to Saturn and sometimescaused the ice sheet to flex just enough to set off a parallel crack farther. That causes the moon to be slightly deformedstretchedabout 35 kilometers away, Rudolph added. and relaxedas it responds to the giant planets gravity. ThisThe open fissures are also due to the tidal effects of Saturns keeps the moon from freezing completely solid.gravity. The moons repeated widening and narrowing of the Key to the fissures formation is that the moons polescracks and flushing water in and out of them prevents the ice experience the greatest effects of this gravitationally inducedfrom closing. deformation, so the ice sheet is thinnest over them. During periodsFor a larger moon, its own gravity would be stronger and of gradual cooling, some of the moons subsurface ocean freezes. Asprevent the additional fractures from opening all the way. So, water expands with freezing, the icy crust thickens from below, andthese stripes could only have formed on Enceladus. the pressure in the underlying ocean increases until the ice shellSince it is thanks to these fissures that we have been able to splits open, creating a fissure. Because of their comparatively thinsample and study Enceladus subsurface ocean, which is beloved ice, the poles are the most susceptible to cracks.by astrobiologists, we thought it was important to understand the The researchers believe the fissure named after the city offorces that formed and sustained them, Hemingway said. Our Baghdad was the first to form. (The stripes are named aftermodeling of the physical effects experienced by the moons icy places referred to in stories from The Arabian Nights shell points to a potentially unique sequence of events and .) However, it didnt freeze again, allowing ocean water to spew from itsprocesses that could allow for these distinctive stripes to exist.crevasse that, in turn, caused three more parallel cracks to form. Our model explains the regular spacing of the cracks, Rudolph said. The additional splits formed from the weight of ice and snowSUPPORT:building up along the edges of the Baghdad fissure as jets ofNASA and the U.S. National Science Foundation supported this work, water from the subsurface ocean froze and fell back down. Thisbased on data collected by the NASA/ESA Cassini mission to Saturn.'