In its ceaseless wanderings around Saturn over the last two years, Cassini has delighted us Earthlings with ever-changing vistas of Saturn and its collection of rings and moons. Today, we are treated to a rare view of the Saturnian system like we've never seen it before.
A few days ago, the spacecraft carried us far from the planet and deep within its shadow, completely blocking out the direct rays of the sun. Shaded by the planet, we can peer closer to the sun -- a geometry known as `high phase' -- than our instruments can usually tolerate. From this viewpoint, the tiny particles of water ice that populate certain regions around Saturn brighten substantially, just like the dust on your car's windshield becomes very obvious as you drive into the sun. This is the process of diffraction, and scientists utilize this consequence of the interaction of electromagnetic radiation with small particles to locate and map those locales in circum-Saturnian space where small particles are being created by a variety of processes.
The new images obtained from within Saturn's shadow together span more than a million kilometers end to end -- out past the orbit of Rhea -- and clearly show the known diffuse rings, notably the G and E rings. Each is made of ice particles so small that they preferentially reflect only the smallest wavelengths and hence appear blue. Our images also show several groups of spoke features, made of small ice grains, stretching across the middle of the main Saturnian rings.
But this unique viewing perspective has shed light on a host of phenomena never seen before. We have discovered a well-defined diffuse ring coincident with the orbits of the co-orbital moons Janus and Epimetheus. This torus of fine particles, similar to those associated with other bodies throughout the solar system, is likely caused by meteoroid impacts onto Janus and Epimetheus that release small particles into Saturn orbit.
Even more startling are long tendrils of fine icy particles in the vicinity of Enceladus, extending tens of thousands of kilometers fore and aft of the moon. These are very likely the supply lanes of fine icy particles being ejected from the south polar geysers of Enceladus and into the E ring ... planetary interchange in action.
Finally, as we looked back in the direction of the sun, we captured from across the depths of space our own planet, a pale blue orb, seen amidst the pageantry and colorful splendor of Saturn's rings. Nothing has greater power to alter our perception of ourselves and our place in the cosmos than the sight of Earth from faraway places. In the end, this ever-widening view of our own little planet against the immensity of space is perhaps the greatest legacy of all our interplanetary travels.
Enjoy! Carolyn Porco Cassini Imaging Team Leader CICLOPS/Space Science Institute Boulder, CO