For the past ten years, the scientists at NASA have been
studying data from the Cassini space probe in orbit above Saturn. Launched October 15, 1997, the orbiter named
after Italian astronomer Giovanni Cassini, reached its destination in
mid-2004. Since then, the probe has been
collecting and sending data on Saturn’s atmosphere and rings, Titan’s
atmosphere, Iapetus and Enceladus.
Researchers noticed a slight wobble in Enceladus, the sixth
largest moon, as it orbited Saturn.
According to Carolyn Porco, the scientist leading the exploration of
Enceladus, members of her team looked for a libration, a “small, cylindrical,
back and forth deviation from uniform rotation”. They found what they were
looking for but only in the thin, outer ice shell. This means the shell and the rocky core are
separated by a liquid layer and it is global.
Had the core and the ice shell been connected, the wobble would have
been much less.
Why isn’t this liquid layer frozen?
Scientists noticed plumes rising from the surface of
Enceladus as early as 2005 and subsequently discovered icy ‘material’ emerging
from warm fractures near the south pole.
They suggest hydrothermal activity is occurring on the subsurface ocean
floor.
However, the pull of Saturn’s gravity might be generating
more heat within Enceladus, which could also explain why the liquid layer is
not frozen.
On October 28, Cassini is scheduled to fly only 30 miles
above the surface of Enceladus, its closest approach ever, through the plumes
of icy material. Perhaps it will confirm
the presence of organic material, the building blocks of life.
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