Dust Dominating Jupiter's Ring May Last For Only Hours or Days

May 30, 1996

Many of the tiny dust grains dominating Jupiter's peculiar ring may linger for less than a day before drifting down toward the planet, according to a new study co-authored by a University of Colorado at Boulder astrophysicist.

Mihaly Horanyi of the Laboratory for Atmospheric and Space Physics said the surprising finding is part of a larger effort to explain the odd structure and behavior of the dusty ring. Jupiter's solitary ring has perplexed planetary scientists since its discovery 16 years ago by NASA's two Voyager spacecraft, he said.

The dust grains in the ring are believed to be created by the bombardment of large moonlets within the ring by much tinier "micro-meteors," he said. While the outer edge of Jupiter's ring is only about 200 miles thick, its inner edge balloons into a donut-shaped "torus" some 3,000 miles thick, making it unique in the solar system, he said.

The new study, which incorporates mathematical models and existing Voyager data, indicates the swelling of the inner ring is caused by positive electrical charges on the dust grains resulting from solar radiation, he said. The process causes the grains to oscillate inside the ring before losing momentum and spiraling toward Jupiter's surface, flaring the ring's inner edge like an inner tube.

A paper on Jupiter's ring dynamics and structure by Horanyi and University of Kansas researcher Thomas Cravens will be published in the May 23 issue of Nature, one of the world's leading weekly science journals.

"When these particles lose energy, they appear to be transported from the ring into Jupiter's atmosphere very rapidly," Horanyi said. "The lifetimes of the smaller particles appear to be on the order of days or even hours, which is unheard of in ring dynamics."

Jupiter's ring is about 150,000 miles in circumference and about 3,500 miles from the outer to inner edge. Its brightness is due to roughly equal parts of the tiny dust particles and larger boulders and moonlets, said Horanyi. The largest of the moonlets are Metis and Adrastea, each more than 10 miles across and located on the inner and outer edges of the ring.

The smallest dust grains in the ring have diameters even smaller than the thickness of a human hair, said Horanyi. The smoke-like dust in Jupiter's ring is so fine that if it was gathered up and compacted into a block of material, the block would be only about the size of a small office building on Earth.

Horanyi likened the dust-manufacturing process in Jupiter's ring to that of a dump truck speeding down the road. "Just as the truck would generate a continual cloud of dust as it sped over bumps, dust is generated continually from the main ring of Jupiter by constant collisions with micro-meteors," he said.

Scientists had thought the hot, gaseous environment of the ring was dominated by negatively charged oxygen and sulfur ions drifting inwards from Jupiter's volcanically active moon, Io, he said. The process was believed to result in negatively charged dust particles within the ring.

But the new modeling study indicates most of the charged atomic particles in the ring region probably arrived from Jupiter's ionosphere -- the region where atomic particles are trapped by Jupiter's magnetic field, he said. Since the density of the electrically charged gas in the ring is so low, ultraviolet radiation from the sun is likely providing the dust grains with a positive charge, according to calculations by the two researchers.

The researchers found the "brightness distribution" of the ring produced by the mathematical modeling effort closely matches the brightness distribution observed by the Voyager spacecraft, said Horanyi. "This suggests our model captures the most important processes that shape this ring," he said.

While Saturn's prominent rings were first observed more than 300 years ago, the fainter, less spectacular rings around Jupiter, Uranus and Neptune were only discovered following the Voyager tour of the solar system beginning in 1977.

The research effort by Horanyi and Cravens was supported by grants from NASA.

University of Colorado at Boulder

Related Solar System Articles from Brightsurf:

Ultraviolet shines light on origins of the solar system
In the search to discover the origins of our solar system, an international team of researchers, including planetary scientist and cosmochemist James Lyons of Arizona State University, has compared the composition of the sun to the composition of the most ancient materials that formed in our solar system: refractory inclusions in unmetamorphosed meteorites.

Second alignment plane of solar system discovered
A study of comet motions indicates that the Solar System has a second alignment plane.

Pressure runs high at edge of solar system
Out at the boundary of our solar system, pressure runs high.

What a dying star's ashes tell us about the birth of our solar system
A UA-led team of researchers discovered a dust grain forged in a stellar explosion before our solar system was born.

What scientists found after sifting through dust in the solar system
Two recent studies report discoveries of dust rings in the inner solar system: a dust ring at Mercury's orbit, and a group of never-before-detected asteroids co-orbiting with Venus, supplying the dust in Venus' orbit.

Discovered: The most-distant solar system object ever observed
A team of astronomers has discovered the most-distant body ever observed in our solar system.

Discovery of the first body in the Solar System with an extrasolar origin
Asteroid 2015 BZ509 is the very first object in the Solar System shown to have an extrasolar origin.

First interstellar immigrant discovered in the solar system
A new study has discovered the first known permanent immigrant to our solar system.

A star disturbed the comets of the solar system in prehistory
About 70,000 years ago, when the human species was already on Earth, a small reddish star approached our solar system and gravitationally disturbed comets and asteroids.

Scientists detect comets outside our solar system
Scientists from MIT and other institutions, working closely with amateur astronomers, have spotted the dusty tails of six exocomets -- comets outside our solar system -- orbiting a faint star 800 light years from Earth.

Read More: Solar System News and Solar System Current Events
Brightsurf.com is a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for sites to earn advertising fees by advertising and linking to Amazon.com.