Saturn's Spokes: Lost and Found

  title={Saturn's Spokes: Lost and Found},
  author={Colin J. Mitchell and Mih{\'a}ly Hor{\'a}nyi and Ove Havnes and Carolyn C. Porco},
  pages={1587 - 1589}
The spokes are intermittently appearing radial markings in Saturn's B ring that are believed to form when micrometer-sized dust particles are levitated above the ring by electrostatic forces. First observed by the Voyagers, the spokes disappeared from October 1998 until September 2005, when the Cassini spacecraft saw them reappear. The trajectories of the charged dust particles comprising the spokes depend critically on the background plasma density above the rings, which is a function of the… Expand

Topics from this paper

Spokes in Saturn's B Ring: Could Lightning be the Cause?
Spokes are narrow markings across Saturn's B ring, most likely caused by a cloud of micrometer-sized particles intermittently lofted from the larger boulders in the ring. They were observed by theExpand
Formation of Saturn's ring spokes by lightning-induced electron beams
Spokes are near-linear markings sometimes visible on Saturn's rings. They are widely accepted as being electrostatically-levitated sheets of similar to 0.6 micron-radius charged grains.Expand
The Behavior of Spokes in Saturn's B Ring
Abstract We present the first results from Cassini ISS observations aimed at determining both the short-term and long-term behavior of the spokes in Saturn’s B ring. We have observed multiple spokesExpand
Statistical Perspectives on the Study of the Ring Spokes of Saturn
At the beginning of the Cassini Extended mission, the VIMS spectrometer was able to collect the first images of spokes on the Saturn rings at wavelengths longer than 1.1 μm ([1]). PreviousExpand
First ground observations of Saturn's spokes around 2009 equinox
Since 1980, only spacecraft or space telescope have been able to image spokes (intermittently appearing radial or elongated dark markings in Saturn’s B-ring) around the planet equinoxes. AmateurExpand
The spectrum of a Saturn ring spoke from Cassini/VIMS
[1] On 2008, July, the Cassini/VIMS spectrometer detected spokes on the Saturn's B ring for the first time. These are the first measurements of the complete reflectance spectrum of the spokes in aExpand
The smallest particles in Saturn's A and C Rings
Radio occultations of Saturn’s main rings by spacecraft suggest a power law particle size-distribution down to sizes of the order of 1 cm (Marouf, E.A., Tyler, G.L., Zebker, H.A., Simpson, R.A.,Expand
Chapter 16 Diffuse Rings
In order to give context to Cassini’s findings about Saturn’s diffuse rings, this chapter first recalls the Voyager and telescopic observations prior to 2004. Cassini has investigated these faintExpand
The Charging of Planetary Rings
This chapter will review what is known about the charging of planetary rings, in particular the sum of the individual currents from the time-varying charge dQ/dt, of the planetary ring particle. ForExpand
Seasonal structures in Saturn's dusty Roche Division correspond to periodicities of the planet's magnetosphere
Abstract We identify multiple periodic dusty structures in Saturn's Roche Division, a faint region spanning the ∼ 3000 km between the A and F rings. The locations and extent of these features varyExpand


A model for the formation of spokes in Saturn's ring
Abstract We suggest that spokes consist of charged micron-sized dust particles elevated from the rings by radially moving dense plasma columns created by meteor impacts on the ring. Dense plasmaExpand
On the braids and spokes in Saturn's ring system
Two of the features in the Saturnian ring system recently observed by the Voyager 1 spacecraft are (a) the braiding of theF-ring and (b) the radial spokes that rotate across theB-ring. Both of theseExpand
HST observations of spokes in Saturn's B ring
As part of a long-term study of Saturn’s rings, we have used the Hubble Space Telescope’s (HST) Wide Field and Planetary Camera (WFPC2) to obtain several hundred high resolution images from 1996 toExpand
Spoke formation under moving plasma clouds
Goertz and Morfill [Goertz, C.K., Morfill, G., 1988. Icarus 53, 219–229] propose that spokes on Saturn's rings form under radially moving plasma clouds produced by meteoroid impacts. We demonstrateExpand
Radiative transfer modeling constraints on the size of the spoke particles in Saturn's rings
Abstract Color Voyager imaging data of the outer B ring of Saturn have been studied with the idea of putting constraints on the spokes' particle sizes, an important parameter for spoke formation andExpand
Plasma clouds in Saturn's rings
Abstract The expansion and ionization of vapor produced by impacts of meteorites on Saturn's rings is described. There is an “impact plasma” produced in the initial collision, and a “secondaryExpand
Oxygen Ions Observed Near Saturn's A Ring
The INMS saw signatures of molecular and atomic oxygen ions and of protons, thus demonstrating the existence of an ionosphere associated with the A ring, according to the Cassini Orbiter. Expand
A New Look at the Saturn System: The Voyager 2 Images
Within Saturn's rings, the "birth" of a spoke has been observed, and surprising azimuthal and time variability is found in the ringlet structure of the outer B ring, leading to speculations about Saturn's internal structure and about the collisional and thermal history of the rings and satellites. Expand
Encounter with saturn: voyager 1 imaging science results.
As Voyager 1 flew through the Saturn system it returned photographs revealing many new and surprising characteristics of this complicated community of bodies, including small inner satellites that interact gravitationally with one another and with the ring particles in ways not observed elsewhere in the solar system. Expand
Spoke formation under moving plasma clouds — the Goertz–Morfill model revisited
The plasma cloud mechanism of spoke formation in Saturn's rings, proposed by Goertz and Morfill in 1983, is revisited in the light of new data and the criticisms raised by Farmer and GoldreichExpand