Lord of rings losing its halo

Scientists have been monitoring the extremely dilute cloud of oxygen ions around Saturn throughout Cassini’s journey. ‘‘We are seeing a massive amount of oxygen, about equal to the mass of the micron-sized particles in E ring,’’ Donald Shemansky, a team member from the University of Southern California, said. The E ring is Saturn’s broad, faint outer ring. That translates to about 1.2 billion lbs of oxygen suddenly being released from the rings. ‘‘Something is eating the ring system somehow,’’ he said.

His best guess at the moment to the event is that clusters of low-energy ions produced by Saturn’s magnetic field crashed into water molecules in the rings, breaking molecular bonds and scattering the oxygen.

According to Roger Clark of the US Geological Survey in Phoenix, close in to Saturn, the rings are composed of small particles of ice. Further from the planet, the particles get coarser. The primary exceptions are in the Cassini division and in the F ring, both of which contain relative large amounts of what team members call dirt. ‘‘We haven’t identified what it is,’’ Clark said, ‘‘but it looks like (the composition of) Phoebe.’’ Phoebe is Saturn’s most distant large moon, and a fly-by three weeks ago showed that it is composed of iron-containing rocks, water ice and hydrocarbons. Astronomers believe that it is an interloper from the Kuiper Belt at the distant fringes of the solar system.

The findings suggest that the rocky material in the rings could have a similar origin. Pictures of Titan taken by Cassini show an orange, fuzzy ball as the moon’s dense atmosphere is filled with organic compounds that prevent any penetration by light.

The most striking thing they have seen so far are crisscrossing linear features. Such features are generally a sign of tectonic activity, rather than impacts by asteroids.

— LAT-WP