Rings, volcanoes, shepherd moons

Like shepherds, small moons use their gravity to herd dust and boulders in Jupiter’s faint rings, NASA scientists reported Tuesday.

The finding is one of several discoveries made from images captured in late February by NASA’s New Horizons probe as it flew by Jupiter, 16 months into its mission to Pluto.

The images also provided the closest look yet at the Little Red Spot -- an Earth-sized swirling storm -- and dramatic views of volcanic eruptions on Jupiter’s moon Io.

The postcards from Jupiter were taken by the piano-sized robotic probe’s seven cameras as it came within 1.4 million miles of Jupiter.

The close encounter allowed New Horizons to make use of Jupiter’s gravity to shave three years from its travel time to Pluto. It is expected to arrive in 2015.

Pictures of Jupiter’s faint rings revealed the moons Metis and Adrastea herding rocks with their gravitational pull.

“The boulder-sized particles are definitely being controlled by these shepherding satellites,” said Jeff Moore of the NASA Ames Research Center near Mountain View.

Also spied were what appeared to be remnants of an object that had recently collided with the rings. “Individual clusters of particles in the rings is a really new discovery,” Moore said.

On Io, New Horizons revealed an umbrella-shaped plume rising 200 miles into space from the volcano Tvashtar.

The probe also revealed a mystery volcano so young its lava has just reached Io’s surface, not yet emitting enough gas to produce a plume.

“We’re seeing the birth of a new volcano here,” said John Spencer of the Southwest Research Institute in Boulder, Colo.