ESA - Cassini-Huygens - Two more active moons around Saturn

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Two more active moons around Saturn

13 June 2007

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This is a compound image made from separate images of Saturn's two moons, Tethys (to the left) and Dione (to the right), taken by Cassini.

The two moons are flinging great streams of particles into space, according to data from the NASA/ESA/ASI Cassini mission to Saturn. The discovery suggests the possibility of some sort of geological activity, perhaps even volcanic, on these icy worlds.

The particles were traced to the two moons because of the dramatic movement of electrically charged gas in the magnetic environs of Saturn. Known as plasma, the gas is composed of negatively charged electrons and positively charged ions, which are atoms with one or more electrons missing. Because they are charged, the electrons and ions can get trapped inside a magnetic field.

Credits: NASA/ JPL

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The plasma tori of the two satellites are approximated in blue for Tethys (indicating lower energy plasma) and green for Dione (indicating higher energy plasma).

The orbit of Cassini is shown in black with red lines showing the positions of observed inward plasma injections. Butterfly electron pitch-angle distributions consistent with outward plasma flow are observed throughout the regions in between the inward injections.

Credits: SWRI (W. Lewis)

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Plumes of icy material extend above the southern polar region of Saturn's moon Enceladus, as imaged by the Cassini spacecraft in January 2005. The monochrome view is presented along with a colour-coded image on the right. The view in this image is perpendicular to the tiger stripe fractures that straddle the south pole. Another plume view, was taken one month later and looks along the tiger stripe fractures. Images like these are being analyzed by scientists as they seek to explain the processes that could be producing such incredible features. As reported in the journal Science on 10 March 2006, imaging scientists believe that the plumes are geysers erupting from pressurized subsurface reservoirs of liquid water above 0°C.

These images were taken with the Cassini spacecraft narrow-angle camera at a distance of approximately 209 400 kilometres from Enceladus at a Sun-Enceladus-spacecraft, or phase, angle of 148 degrees. The image scale is about 1.3 kilometres per pixel.

The mosaic is an orthographic projection centred at 46.8 degrees south latitude, 188 degrees west longitude, and has an image scale of 67 metres per pixel. The original images ranged in resolution from 67 metres per pixel to 350 metres per pixel and were taken at distances ranging from 11 100 to 61 300 kilometres from Enceladus.

Credits: NASA/JPL/Space Science Institute

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Magnificent blue and gold Saturn floats obliquely as one of its gravity-bound companions, Dione, hangs in the distance. The darkened rings seem to nearly touch their shadowy reverse images on the planet below.

This view looks toward the unlit side of the rings from about 9 degrees above the ring plane. The rings glow feebly in the scattered light that filters through them.

Dione is 1,126 kilometers (700 miles) across. The image was taken in visible light with the Cassini spacecraft wide-angle camera on Feb. 4, 2007, at a distance of approximately 1.2 million kilometers (800,000 miles) from Saturn. Image scale is 75 kilometers (47 miles) per pixel.

Credits: NASA/JPL/Space Science Institute

At Saturn and Titan

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