Observations of Saturn's
moon Enceladus by the Cassini space probe have revealed a number of
sulci (linear structures) in the southern polar region. These have
been named the Alexandria, Baghdad, Cairo and Damascus Sulci, or
informally the 'Tiger Stripes'. A number of jets of water vapour and
ice particles have been seen emerging from these sulci, and infrared
images suggest that they are warmer than the surrounding terrain.
In a paper published in
the journal Nature on 7 May 2015, Joseph Spitale of the PlanetaryScience Institute, Terry Hurford of NASA's Goddard Space Flight Center, Alyson Rhoden of the Applied Physics Laboratory at Johns Hopkins University, Emily Berkson of the Rochester Institute ofTechnology and Symeon Platts of the Film and Television Department at
the University of Arizona discuss the results of a re-examination of
a series of images of Enceladus taken by the Cassini Space Probe in
2010.
Spitale et al.
found that rather than discrete and isolated jets issuing from
particular points on the sulci, there were in fact curtains of
material being expelled all along the length of these feature,
strongly supporting the idea that these are fissures from which
material from the interior of the moon is escaping.
Curtain eruptions issuing from fissures in the southern polar region of Saturn's moon Enceladus. Cassini/JPL/NASA.
The
'jets' could be observed as discrete brighter features within these
curtains, however attemps to calculate the precise position of these
features by triangulation from different images failed, and proved
more inaccurate when more widely spaced observations were used. Such
widely spaced observations would be expected to give a more precise
estimate of the position of an object, which suggests that these
features are in fact illusionary; their position appears to vary
depending on the position of the observer (like a rainbow). It is
therefore concluded that the jets do not represent areas where
material is being expelled at a higher rate than elsewhere on these
fissures.
See
also...
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