Enceladus Has Oceans?
Credits: NASA/JPL/Space Science Institute
Salty ice has been discovered on Saturn’s moon Enceladus. The moon replenishes the ring with material from discharging jets and it’s thought that the moon could harbor a reservoir of liquid water, perhaps an ocean, beneath its surface.
The Cassini spacecraft discovered the water ice jets in 2005 on Enceladus. These jets eject tiny ice grains and vapour, some of which escape the moon’s gravity and form Saturn’s outermost ring. Cassini’s cosmic dust analyser has examined the composition of those grains and found salt within them.
The scientists working on Cassini’s cosmic dust detector conclude that liquid water must be present because it is the only way to dissolve the significant amounts of minerals that would account for the levels of salt detected. The process of sublimation, the mechanism by which vapour is released directly from solid ice in the crust, cannot account for the presence of salt.
The outermost ring particles are almost pure water ice, but nearly every time the dust analyser has checked for the composition, it has found at least some sodium within the particles.
However, researchers doing ground-based observations did not see sodium, an important salt component. The ground-based observation team notes that the amount of sodium being expelled from Enceladus is actually less than observed around many other planetary bodies. These scientists were looking for sodium in the plume vapour and could not see it in the expelled ice grains. They argue that if the plume vapour does come from ocean water the evaporation must happen slowly deep underground rather than as a violent geyser erupting into space.
Determining the nature and origin of the plume material is a top priority for Cassini during its extended tour, called the Cassini Equinox Mission.
The Cassini-Huygens mission is a cooperative project of NASA, the European Space Agency and the Italian Space Agency.
You can find out more information at either ESA or NASA
