Saturns largest and most densely packed ring is composed of dense clumps of particles separated by nearly empty gaps, according to new findings from NASAs Cassini spacecraft. These clumps in Saturns B ring are neatly organised and constantly colliding, which surprised scientists. Previous interpretations assumed the ring particles were distributed uniformly and so scientists underestimated the total mass of Saturns rings. The mass may actually be two or more times previous estimates.
The Cassini spacecraft imaged Saturn's ring system in the infrared from a vantage point high above the planet's northern latitudes on April 5, 2007 at a distance of approximately 1.4 million kilometres. Nearly the full expanse of the main rings is visible here -- from the C ring to the outer edge of the A ring (in the upper left corner). Ring shadows are visible on the planet at lower left, and two large storms swirl near the centre. This view looks toward the unilluminated side of the rings from about 52 degrees above the ringplane.
Expand (233kb, 1012 x1012) Credit: NASA/JPL/Space Science Institute
The image was taken with the Cassini spacecraft wide-angle camera using a combination of spectral filters sensitive to wavelengths of infrared light centred at 752 (red channel), 890 (blue channel) and 728 (green channel) nanometers. Image scale is 81 kilometres per pixel.
Dark, radial spokes in the rings of Saturn have puzzled planetary astronomers ever since they were discovered by the Voyager spacecraft in the early 1980's. Today, at the Royal Astronomical Society National Astronomy Meeting here, scientists described how the enigmatic features could be caused by thunderstorms and lightning.
"It's one of the best theories I've heard so far" - Carl Murray of Queen Mary University of London.
The moon Pan can been seen near the centre of the image approximately 1,479,247 kilometres away. Pan is about 20 30 kilometres across and orbits within the Encke division in Saturn's A Ring The image was taken using the CL1 and CL2 filters.
The Cassini spacecraft gazes toward a distant star as Saturn's rings slip past in the foreground. At upper left is the outer A ring, with its dark Keeler Gap. At lower right, a train of bright clumps shuttles past in the wispy F ring. A temporal sequence of images like this allows Cassini scientists to correlate features in the rings with stellar occultation data acquired by other instruments. As the star passes behind the rings, the changes in its brightness indicate how much empty space is between particles at different locations on the rings.
Expand (21kb, 1008 x 1008) Credit: NASA/JPL/Space Science Institute
This view looks toward the lit side of the rings from about 56 degrees below the ringplane. The image was taken in visible light with the Cassini spacecraft narrow-angle camera on Dec. 30, 2006 at a distance of approximately 633,440 kilometres from Saturn. Image scale is 4 kilometres per pixel.
The Cassini spacecraft continues to observe brightness variations along the orbital direction within Saturn's B ring.
Expand (124.5kb, 1008 x 1008) Credit: NASA/JPL/Space Science Institute
This view looks toward the unlit side of the rings from about 53 degrees above the ringplane. The image was taken in visible red light with the Cassini spacecraft narrow-angle camera on Dec. 17, 2006 at a distance of approximately 1.3 million kilometres from Saturn. Image scale is 8 kilometres per pixel.