A NASA news alert says that Cassini has found a possible origin of the mysterious G ring.
Why is the G ring mysterious? Located between the A and E rings, next to the F ring, the G ring is not closely associated with moons that would either supply material to it, or herd it into shape. The composition and location of the G ring were unexplained, until now.
Cassini has found that a bright arc of material at the inner edge of the G ring could be what contributes the material to the G ring. It is thought that the arc is composed of icy bodies ranging in size from peas to small boulders.
Cassini images from 2004 and 2005 show that the arc within the G ring extends one-sixth of the way around Saturn and is 155 miles wide (The G ring itself is 3,700 miles wide). The arc has been observed several times since Cassini arrived in 2004, so it appears to be a long-lived structure. It is thought that the mass in the arc is absorbing charged particles trapped in Saturn’s magnetosphere, which is how the science team deduced the existence of the extra mass.
Micrometeorites collide with the particles in the arc, which releases smaller, dust-sized particles that brighten the arc. The plasma trapped in the giant planet’s magnetic field sweeps through the arc and drags the dust particles out, which creates the G ring.
More data will be coming. In 18 months Cassini will fly within 600 miles of the arc. An animation of the G ring can be found here.
[Image credit: NASA/Cassini]