New NASA research confirms that Saturn loses its iconic rings at the maximum speed estimated from Voyager 1 and 2 observations made decades ago. The rings are drawn into Saturn through gravity as a dusty rain of ice particles affected by Saturn's magnetic field.
"We estimate that this" rain "drains a host of water products that can fill an Olympic big swimming pool from Saturn's rings in half an hour," said James O'Guard from NASA's Goddard Space Flight Center in Greenbelt, Maryland. "From this, the entire ring system will be gone for 300 million years, but add this Cassini spacecraft measured ring material discovered to fall into Saturn's equator, and the rings have less than 100 million years of living. This is relatively short compared to Saturn's age at over 4 billion years. "O & # 39; Donoghue is the leading author of a study of Saturn's rainfall that occurs in Icarus December 17th.
Researchers have long wondered if Saturn was formed with the rings or if the planet acquired them later in life. The new research favors the latter scenario, indicating that they are probably not older than 100 million years, as it would take so long for the C-ring to become what it is today assuming it was once as tight as B- ring. "We are lucky to be around to see Saturn's ring system, which seems to be in the middle of his lifetime. But if the rings are temporary, maybe we just missed seeing giant ring systems of Jupiter, Uranus and Neptune, who only have narrow ringlets today!" Allow O & # 39; Donoghue.
Various theories have been suggested for the origin of the ring. If the planet got them later in life, the rings could have formed when small, odd moons in circulation around Saturn collided, perhaps because their paths were disturbed by a gravity train from a fitting asteroid or comet.
The first remarks that rainfall existed came from Voyager observations of seemingly unrelated phenomena: Particular variations in Saturn's electrically charged upper atmosphere (ionosphere), density variations in Saturn's rings and a trio of narrow dark bands surrounding the planet at the northern latitudes. These dark bands appeared in images of Saturn's foggy upper atmosphere (stratosphere) made by NASA's Voyager 2 mission in 1981.
In 1986, Jack Connerney published from NASA Goddard a paper in geophysical research letters linking the narrow dark bands to the shape of Saturn's enormous magnetic fields, suggesting that electrically charged ice particles from Saturn's rings streamed invisible magnetic field lines, dumping water in Saturn's upper atmosphere where these lines came from planet. The influx of water from the rings, which occurs at specific latitudes, cleans the stratosphere, making it dark in reflected light, giving the narrow dark bands captured in the Voyager images.
Saturn rings are mostly pieces of isis that extend in size from microscopic dust to stone blocks several meters (meters) above. The ring particles are caught in a balanced action between the dragon of Saturn's gravity, which wants to drag them back to the planet and their orbital speed, which wants to move them outward in space. Small particles can be electrically charged by ultraviolet light from the sun or through plasma clouds resulting from micrometeoroid bombardment of the rings. When this happens, the particles can feel the drag of Saturn's magnetic fields, like curves inward toward the planet at Saturn's rings. In some parts of the rings, once loaded, the power balance of these small particles dramatically changes, and Saturn's gravity draws them into the magnetic field lines of the upper atmosphere.
Once there the evaporated ring particles evaporate and the water can react chemically with Saturn's ionosphere. A result of these reactions is an increase in the life of electrically charged particles called H3 + ions, which consists of three protons and two electrons. When solar energy is activated, the H3 + ions are illuminated in infrared light, as observed by O & # 39; Donoghue's team using special instruments connected to the Keck telescope in Mauna Kea, Hawaii.
Their observations revealed glowing bands in Saturn's northern and southern hemispheres where the magnetic field lines that cut the cutting plane into the planet. They analyzed the light to determine the amount of rain from the ring and its effects on Saturn's ionosphere. They found that the amount of rain matched surprisingly well with the surprisingly high values derived more than three decades earlier by Connerney and colleagues, with a southern region that received the most.
The team also discovered a glowing band in higher latitudes in the southern hemisphere. This is Saturn's magnetic field that intersects Orbitadus, a geologically active moon depicting geysers of water ice in space, indicating that some of these particles rain on Saturn as well. "It was not a complete surprise," said Connerney. "We identified Enceladus and the E-ring as an abundant water source, based on another narrow dark band in the old Voyager image." The geysers, first observed by the Cassini instrument in 2005, are believed to originate from a sea of liquid water under the small moon's frozen surface. Its geological activity and the waters of the sea make Enceladus one of the most promising places to seek extraterrestrial life.
The team would like to see how the ring rain changes with the seasons of Saturn. As the planet progresses in its 29.4-year orbit, the rings are exposed to different degrees in the sun. Since ultraviolet light from the sun charges the ice grains and causes them to react to Saturn's magnetic field, varying exposure to sunlight should change the amount of rainfall.