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Prior to the ammonia discovery

Prior to the ammonia discovery - Enceladus[10 Ice at these...

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Prior to the ammonia discovery The combined analysis of imaging, mass spectrometry, and magnetospheric data suggests that the observed south polar plume emanates from pressurized sub-surface chambers, similar to geysers on Earth. [4] Because no ammonia was found in the vented material by INMS or UVIS, which could act as an anti-freeze, such a heated, pressurized chamber would consist of nearly pure liquid water with a temperature of at least 270 K (−3 °C), as illustrated in Figure 14. Pure water would require more energy to melt, either from tidal or radiogenic sources, than an ammonia-water mixture. Another possible method for generating a plume is sublimation of warm surface ice. During the July 14, 2005 flyby, the Composite Infrared Spectrometer (CIRS) found a warm region near the South Pole. Temperatures found in this region range from 85–90 K, to small areas with temperatures as high as 157 K (−116 °C), much too warm to be explained by solar heating, indicating that parts of the south polar region are heated from the interior of
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Unformatted text preview: Enceladus. [10] Ice at these temperatures is warm enough to sublimate at a much faster rate than the background surface, thus generating a plume. This hypothesis is attractive since the sub-surface layer heating the surface water ice could be an ammonia-water slurry at temperatures as low as 170 K (−103 °C), and thus not as much energy is required to produce the plume activity. However, the abundance of particles in the south polar plume favors the "cold geyser" model, as opposed to an ice sublimation model. [4] Alternatively, Kieffer et al. (2006) suggest that Enceladus's geysers originate from clathrate hydrates, where carbon dioxide, methane, and nitrogen are released when exposed to the vacuum of space by the active, tiger stripe fractures. [51] This hypothesis would not require the amount of heat needed to melt water ice as required by the "Cold Geyser" model, and would explain the lack of ammonia....
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