JPL: Cassini Shows Saturnian Roller Derby, Strange Weather

[bystander]

Cassini Shows Saturnian Roller Derby, Strange Weather
NASA JPL 2010-090 - 2010 March 18

From our vantage point on Earth, Saturn may look like a peaceful orb with rings worthy of a carefully raked Zen garden, but NASA's Cassini spacecraft has been shadowing the gas giant long enough to see that the rings are a rough and tumble roller derby. It has also revealed that the planet itself roils with strange weather and shifting patterns of charged particles. Two review papers to be published in the March 19 issue of the journal Science synthesize Cassini's findings since arriving at Saturn in 2004.
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In the paper describing the elegant mess of activity in the rings, lead author Jeff Cuzzi, Cassini's interdisciplinary scientist for rings and dust who is based at NASA Ames Research Center, Moffett Field, Calif., describes how Cassini has shown us that collisions are routine and chunks of ice leave trails of debris in their wakes. Spacecraft data have also revealed how small moons play tug-of-war with ring material and how bits of rubble that would otherwise join together to become moons are ultimately ripped apart by the gravitational pull that Saturn exerts.
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In the review paper on Saturn's atmosphere, ionosphere and magnetosphere, lead author Tamas Gombosi, Cassini's interdisciplinary scientist for magnetosphere and plasma science who is based at the University of Michigan in Ann Arbor, describes how Cassini helped scientists understand a south polar vortex that has a diameter 20 to 40 times that of a terrestrial hurricane, and the bizarrely stable hexagon-shaped jet stream at the planet's north pole. Cassini scientists have also calculated a variation in Saturn's wind speeds at different altitudes and latitudes that is 10 times greater than the wind speed variation on Earth.

An Evolving View of Saturn's Dynamic Rings

• Science 19 March 2010: Vol. 327. no. 5972, pp. 1470 - 1475: DOI: 10.1126/science.1179118

We review our understanding of Saturn’s rings after nearly 6 years of observations by the Cassini spacecraft. Saturn’s rings are composed mostly of water ice but also contain an undetermined reddish contaminant. The rings exhibit a range of structure across many spatial scales; some of this involves the interplay of the fluid nature and the self-gravity of innumerable orbiting centimeter- to meter-sized particles, and the effects of several peripheral and embedded moonlets, but much remains unexplained. A few aspects of ring structure change on time scales as short as days. It remains unclear whether the vigorous evolutionary processes to which the rings are subject imply a much younger age than that of the solar system. Processes on view at Saturn have parallels in circumstellar disks.

Saturn: Atmosphere, Ionosphere, and Magnetosphere

• Science 19 March 2010: Vol. 327. no. 5972, pp. 1476 - 1479: DOI: 10.1126/science.1179119

The Cassini spacecraft has been in orbit around Saturn since 30 June 2004, yielding a wealth of data about the Saturn system. This review focuses on the atmosphere and magnetosphere and briefly outlines the state of our knowledge after the Cassini prime mission. The mission has addressed a host of fundamental questions: What processes control the physics, chemistry, and dynamics of the atmosphere? Where does the magnetospheric plasma come from? What are the physical processes coupling the ionosphere and magnetosphere? And, what are the rotation rates of Saturn’s atmosphere and magnetosphere?

Mysteries of Saturn as seen by Cassini probe
New Scientist Slide Show - 2010 March 18

[bystander]

Six years in, Cassini provides insights into Saturn's rings
Cornell Chronicle - 2010 March 18

From the propeller-shaped disturbances and embedded moonlets in the A ring inward to the nearly transparent D ring and outward to the bright arc circling the faint G ring, NASA's Cassini spacecraft has given astronomers a new look at the complex system of rings circling Saturn.

Six years into the mission, rings researchers took a step back this week and reviewed some of its most important findings -- and noted a few of the many mysteries that remain -- in a paper featured on the cover of the March 18 issue of the journal Science.