Saturn’s Magnetic Field Pulls “Rain” Into Atmosphere from Ring System

Saturn's rings are responsible for a unique type of rain that falls into the atmosphere of the gas giant. Saturn's magnetic field is pulling charged water particles into the atmosphere which interact with the atmosphere. Scientists estimate that there's at least an Olympic pool sized amount of water being pulled into the planet every single day, that's more than 2.5 million liters (660,253 gallons)!



Voyager 2 returned this view of Saturn and its ring system Aug. 11, when the spacecraft was 13.9 million kilometers (8.6 million miles) away and approaching the large, gaseous planet at about l million km. (620,000 mi.) a day. The Voyager project is managed for NASA by the Jet Propulsion Laboratory, Pasadena, Calif.

Image Credit: NASA/JPL

Scientists first discovered evidence of "ring rain" in 1980 when Voyager 1 took images of Saturn and saw that there were unusual dark bands in the upper atmosphere. Although scientists thought they might be caused by some sort of reaction with the water particles in the rings, the bands weren't seen again until 2011 when a team of observers were viewing Saturn through the W.M. Keck Observatory in Hawaii. The scientists were tracking a pattern of emissions of a different type of hydrogen ion with three protons (a triatomic hydrogen ion) that has a specific emission spectrum and they expected to see the planet glowing in one color. Instead, they saw a series of dark and light bands around the equatorial region that corresponds with the rings and gaps in the ring system. These ions are also found in the ionosphere of Earth and Jupiter and they are evenly distributed, so finding places where the density of this ion varied (under the "ring rain") was puzzling to scientists. They surmised that the charged water particles from the "ring rain" are actually neutralizing the triatomic hydrogen ions in the atmosphere, causing the emission spectrum to change.



This view, from Cassini's imaging camera, shows the outer A ring and the F ring.

Image Credit: NASA/JPL

The rings around Saturn are made up almost entirely of water ice with traces of rocky material. The way that the water gets from the rings to the planet is via Saturn's complex magnetic field. It arches out from one hemisphere of the planet and passes through the rings and back down onto the other hemisphere. The magnetic field interacts with the rings in such a way that it pulls charged water molecules out of the rings and into the atmosphere.



This artist's concept illustrates how charged water particles flow into the Saturnian atmosphere from the planet's rings, causing a reduction in atmospheric brightness. The observations were made with the W.M. Keck Observatory on Mauna Kea, Hawaii, with NASA funding. The analysis was led by the University of Leicester, England.

Image credit: NASA/JPL-Caltech/Space Science Institute/University of Leicester

Scientists now want to utilize instruments on the Cassini probe that's currently in orbit so that they can study this phenomenon more closely and find out what other interactions it has with the composition of Saturn's atmosphere. It's also possible that this process is what has sculpted the rings into the beautiful formation we see today and further studying can answer questions on how the rings formed as well as how they may one day disappear.

Extra Content:

Today in Science History:

John James Audubon (Born April 26, 1785; died January 27, 1851 at age 65) was a French-American ornithologist, artist and naturalist known for his drawings and paintings of North American birds.

April 26, 1986, in Pripet, Russia, one of the four reactors at the Chernobyl nuclear plant exploded in the world's worst civil nuclear catastrophe, sending a radioactive cloud of dust over Europe.

Sources:

http://www.nasa.gov/mission_pages/cassini/whycassini/cassini20130410.html

http://keckobservatory.org/news/astronomers_using_keck_observatory_discover_rain_falling_from_saturns_rings

http://www.space.com/20595-saturn-rings-rain-water.html

http://www.livestrong.com/article/350103-measurements-for-an-olympic-size-swimming-pool/