2008 Woodie Awards
Saturn's largest moon has a (smaller) ring of its own
Issue date: 3/27/08
Saturn is one of the most intriguing objects in the solar system. It was the most distant planet known to the ancients, it is actually less dense than water and it spins faster than all but one planet, with a day lasting just over 10 and a half hours.
Several spacecraft have been sent to study the Saturnian system since the earliest days of the space program: Pioneer, Voyager 1 and 2, and Cassini.
Cassini, the most recent, was launched in 1997 with the intent to study not only the planet, but also its astounding ring system and its satellites.
Saturn has 52 named moons, each of which is just as interesting and complex as Saturn itself. They range from tiny, airless rocks to icy worlds almost equal in size to the inner planets like Earth and Mars.
An international team of scientists, including several from Hopkins, is using the Cassini spacecraft to learn more about these mysterious moons.
A recent publication from the group looks at the moon Rhea, the largest icy moon orbiting Saturn. Even though the moon was discovered in 1672, little is truly known about it.
Recent observations have made a surprising discovery: Rhea has a ring, just like the more famous rings around Saturn.
Previous observations had suggested that Rhea had an atmosphere that was strong enough to interfere with Saturn's magnetic field.
The new findings actually show that the magnetic interference is not due to Rhea's atmosphere but rather to a thin ring of debris in orbit around Rhea's equator.
This debris is thought to be the result of meteoroid impacts with the moon's surface millions of years ago, which threw microscopic particles of rock and ice into orbit.
Using Cassini's instruments scientists have been able to observe Rhea's interactions with Saturn's magnetic field in much more detail than ever before, allowing for unprecedented calculations of the system's behavior.
The team found, unexpectedly, that the moon is actually "stealing" some of Saturn's magnetism - charged particles in orbit around Saturn are attracted to Rhea.
What exactly is causing this attraction is unclear, but scientists think the small dust particles in Rhea's ring and atmosphere are likely culprits.
Since a model of Rhea's atmosphere did not include enough dust particles to effect this change, they concluded that there must be another electron absorber on Rhea: a disk of larger debris.
The disk is quite sparse and consists only of small particles. Unlike the much more visually impressive disks of Saturn, Rhea's disk is not much to look at.
Nevertheless, this is the first time a disk or ring has been found around a moon in our solar system.
Several spacecraft have been sent to study the Saturnian system since the earliest days of the space program: Pioneer, Voyager 1 and 2, and Cassini.
Cassini, the most recent, was launched in 1997 with the intent to study not only the planet, but also its astounding ring system and its satellites.
Saturn has 52 named moons, each of which is just as interesting and complex as Saturn itself. They range from tiny, airless rocks to icy worlds almost equal in size to the inner planets like Earth and Mars.
An international team of scientists, including several from Hopkins, is using the Cassini spacecraft to learn more about these mysterious moons.
A recent publication from the group looks at the moon Rhea, the largest icy moon orbiting Saturn. Even though the moon was discovered in 1672, little is truly known about it.
Recent observations have made a surprising discovery: Rhea has a ring, just like the more famous rings around Saturn.
Previous observations had suggested that Rhea had an atmosphere that was strong enough to interfere with Saturn's magnetic field.
The new findings actually show that the magnetic interference is not due to Rhea's atmosphere but rather to a thin ring of debris in orbit around Rhea's equator.
This debris is thought to be the result of meteoroid impacts with the moon's surface millions of years ago, which threw microscopic particles of rock and ice into orbit.
Using Cassini's instruments scientists have been able to observe Rhea's interactions with Saturn's magnetic field in much more detail than ever before, allowing for unprecedented calculations of the system's behavior.
The team found, unexpectedly, that the moon is actually "stealing" some of Saturn's magnetism - charged particles in orbit around Saturn are attracted to Rhea.
What exactly is causing this attraction is unclear, but scientists think the small dust particles in Rhea's ring and atmosphere are likely culprits.
Since a model of Rhea's atmosphere did not include enough dust particles to effect this change, they concluded that there must be another electron absorber on Rhea: a disk of larger debris.
The disk is quite sparse and consists only of small particles. Unlike the much more visually impressive disks of Saturn, Rhea's disk is not much to look at.
Nevertheless, this is the first time a disk or ring has been found around a moon in our solar system.
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