Enceladus

context: en: Images taken by Cassini during the flyby on July 14, 2005, revealed a distinctive, tectonically deformed region surrounding Enceladus's south pole. This area, reaching as far north as 60° south latitude, is covered in tectonic fractures and ridges. The area has few sizable impact craters, suggesting that it is the youngest surface on Enceladus and on any of the mid-sized icy satellites; modeling of the cratering rate suggests that some regions of the south polar terrain are possibly as young as 500,000 years or less. Near the center of this terrain are four fractures bounded by ridges, unofficially called "tiger stripes". They appear to be the youngest features in this region and are surrounded by mint-green-colored (in false color, UV–green–near IR images), coarse-grained water ice, seen elsewhere on the surface within outcrops and fracture walls. Here the "blue" ice is on a flat surface, indicating that the region is young enough not to have been coated by fine-grained water ice from the E ring. Results from the visual and infrared spectrometer (VIMS) instrument suggest that the green-colored material surrounding the tiger stripes is chemically distinct from the rest of the surface of Enceladus. VIMS detected crystalline water ice in the stripes, suggesting that they are quite young (likely less than 1,000 years old) or the surface ice has been thermally altered in the recent past. VIMS also detected simple organic (carbon-containing) compounds in the tiger stripes, chemistry not found anywhere else on Enceladus thus far. And in 27 June 2018, scientists reported the detection of complex macromolecular organics on Enceladus' jet plumes, as sampled by the Cassini orbiter.One of these areas of "blue" ice in the south polar region was observed at high resolution during the July 14, 2005 flyby, revealing an area of extreme tectonic deformation and blocky terrain, with some areas covered in boulders 10–100 m across.
qas: question: zh_tw: 哪一年拍攝了土衛二的南極？
answers: en: text: 2005

context: en: The discoveries Cassini made at Enceladus have prompted studies into follow-up mission concepts, including a probe flyby (Journey to Enceladus and Titan or JET) to analyze plume contents in-situ, a lander by the German Aerospace Center to study the habitability potential of its subsurface ocean (Enceladus Explorer), and two astrobiology-oriented mission concepts (the Enceladus Life Finder and Life Investigation For Enceladus (LIFE)).The European Space Agency (ESA) was assessing concepts in 2008 to send a probe to Enceladus in a mission to be combined with studies of Titan: Titan Saturn System Mission (TSSM). TSSM was a joint NASA/ESA flagship-class proposal for exploration of Saturn's moons, with a focus on Enceladus, and it was competing against the Europa Jupiter System Mission (EJSM) proposal for funding. In February 2009, it was announced that NASA/ESA had given the EJSM mission priority ahead of TSSM, although TSSM will continue to be studied and evaluated.
qas: question: zh_tw: 哪一個計劃被 NASA 認為更加重要
answers: en: text: the EJSM mission

context: en: Voyager 2 was the first spacecraft to observe Enceladus's surface in detail, in August 1981. Examination of the resulting highest-resolution imagery revealed at least five different types of terrain, including several regions of cratered terrain, regions of smooth (young) terrain, and lanes of ridged terrain often bordering the smooth areas. In addition, extensive linear cracks and scarps were observed. Given the relative lack of craters on the smooth plains, these regions are probably less than a few hundred million years old. Accordingly, Enceladus must have been recently active with "water volcanism" or other processes that renew the surface. The fresh, clean ice that dominates its surface gives Enceladus the most reflective surface of any body in the Solar System, with a visual geometric albedo of 1.38 and bolometric Bond albedo of 0.81±0.04. Because it reflects so much sunlight, its surface only reaches a mean noon temperature of −198 °C (−324 °F), somewhat colder than other Saturnian satellites.Observations during three flybys by Cassini on February 17, March 9, and July 14, 2005, revealed Enceladus' surface features in much greater detail than the Voyager 2 observations. The smooth plains, which Voyager 2 had observed, resolved into relatively crater-free regions filled with numerous small ridges and scarps. Numerous fractures were found within the older, cratered terrain, suggesting that the surface has been subjected to extensive deformation since the craters were formed. Some areas contain no craters, indicating major resurfacing events in the geologically recent past. There are fissures, plains, corrugated terrain and other crustal deformations. Several additional regions of young terrain were discovered in areas not well-imaged by either Voyager spacecraft, such as the bizarre terrain near the south pole. All of this indicates that Enceladus's interior may be liquid today, even though it should have been frozen long ago.
qas: question: zh_tw: 在哪裡發現了年輕的地形？
answers: en: text: near the south pole