Saturn's rings

What are Saturn’s Rings Made Of?

Saturn’s rings are made of billions of pieces of ice, dust and rocks. Some of these particles are as small as a grain of salt, while others are as big as houses. These chucks of rock and ice are thought to be pieces of comets, asteroids or even moons which were torn apart by the strong gravity of Saturn before they could reach the planet.

The rings are about 400,000 kilometers (240,000 miles) wide. That’s the distance from the Earth to the Moon! But the rings are as little as 100 meters (330 feet) thick. They range from particles too tiny to see to “particles” the size of a bus. Scientists think they are icy snowballs or ice covered rocks.

There are actually many rings—maybe 500 to 1000. There are also gaps in the rings.

Saturns Rings Formed After Dinosaurs Died

Scientists have discovered Saturn’s rings are much younger than once thought, having formed as little as 10 million years ago. After Dinosaurs walked the Earth. This is far later than the when Saturn first formed—around 4.2 billion years ago—and means the planet’s iconic rings probably only appeared after the dinosaurs went extinct around 65 million years ago.

A recent study published in the journal Icarus suggested that Saturn’s rings will be completely gone in around 300 million years. Researchers found the rings are losing mass at the maximum rate predicted, with the ice particles being tugged into Saturn by its gravitational pull.

In a new study published in Science, a team of researchers led by Luciano Iess, used data from NASA’s Cassini mission to show new measurements of the gravitational field around Saturn and its rings. They used data from Cassini’s “Grand Finale,” where the craft plunged through the planet’s rings before burning up in the atmosphere below.

Cassini’s Final Plunge

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“The relationship between the mass and age of the rings is subtle,”
Luciano said there is a flux of “contaminant particles” present around Saturn that is sprayed onto the rings at a constant rate. By measuring the mass, they were able to estimate the total amount of deposited particles—and how long it took them to accumulate: 10 to 100 million years.

Before the Cassini mission, it was impossible to distinguish the gravitational effect of the rings from the main body of Saturn. This mean the mass of the rings , which is linked to their age, could not be established.

NEW STUDY FINDS EVIDENCE OF CHANGING SEASONS, RAIN ON TITAN’S NORTH POLE

WASHINGTON — An image from the international Cassini spacecraft provides evidence of rainfall on the north pole of Titan, the largest of Saturn’s moons. The rainfall would be the first indication of the start of a summer season in the moon’s northern hemisphere.

“The whole Titan community has been looking forward to seeing clouds and rains on Titan’s north pole, indicating the start of the northern summer, but despite what the climate models had predicted, we weren’t even seeing any clouds,” said Rajani Dhingra, a doctoral student in physics at the University of Idaho in Moscow, and lead author of the new study accepted for publication in Geophysical Research Letters, a journal of the American Geophysical Union. “People called it the curious case of missing clouds.”

Dhingra and her colleagues identified a reflective feature near Titan’s north pole on an image taken June 7, 2016, by Cassini’s near-infrared instrument, the Visual and Infrared Mapping Spectrometer. The reflective feature covered approximately 46,332 square miles, roughly half the size of the Great Lakes, and did not appear on images from previous and subsequent Cassini passes.

Analyses of the short-term reflective feature suggested it likely resulted from sunlight reflecting off a wet surface. The study attributes the reflection to a methane rainfall event, followed by a probable period of evaporation.

“It’s like looking at a sunlit wet sidewalk,” Dhingra said.

Titan’s north pole as seen by the Cassini Visual and Infrared Mapping Spectrometer. The orange box shows the “wet sidewalk” region, what analyses suggests is evidence of changing seasons and rain on Titan’s north pole. The blue box shows the expanded region in the bottom panel. Bottom Panel: Pictured is an expanded view of Titan’s north pole. Dark blue arrows mark clouds. Red arrows mark the mirror-like reflection from a lake called Xolotlan Lacus. Pink arrows mark the “wet sidewalk”region. The black dot marks the actual north pole of Titan. Light blue arrows mark the edges of the largest north polar sea, Kraken Mare. Credit: NASA/JPL/University of Arizona/University of Idaho.
Titan’s north pole as seen by the Cassini Visual and Infrared Mapping Spectrometer. The orange box shows the “wet sidewalk” region, what analyses suggests is evidence of changing seasons and rain on Titan’s north pole. The blue box shows the expanded region in the bottom panel. Bottom Panel: Pictured is an expanded view of Titan’s north pole. Dark blue arrows mark clouds. Red arrows mark the mirror-like reflection from a lake called Xolotlan Lacus. Pink arrows mark the “wet sidewalk”region. The black dot marks the actual north pole of Titan. Light blue arrows mark the edges of the largest north polar sea, Kraken Mare. Credit: NASA/JPL/University of Arizona/University of Idaho.

This reflective surface represents the first observations of summer rainfall on the moon’s northern hemisphere. If compared to Earth’s yearly cycle of four seasons, a season on Titan lasts seven Earth years. Cassini arrived at Titan during the southern summer and observed clouds and rainfall in the southern hemisphere. Climate models of Titan predicted similar weather would occur in the northern hemisphere in the years leading up to the northern summer solstice in 2017. But, by 2016, the expected cloud cover in the northern hemisphere had not appeared. This observation may help scientists gain a more complete understanding of Titan’s seasons.

“We want our model predictions to match our observations. This rainfall detection proves Cassini’s climate follows the theoretical climate models we know of,” Dhingra said. “Summer is happening. It was delayed, but it’s happening. We will have to figure out what caused the delay, though.”

Additional analyses suggest the methane rain fell across a relatively pebble-like surface, Dhingra said. A rougher surface generates an amorphous pattern as the liquid settles in crevasses and gullies, while liquid falling on a smooth surface would puddle in a relatively circular pattern.

Dhingra is using the wet sidewalk effect to search for additional rain events on Titan as part of her research.

Darth Vader would be impressed , Saturn’s ‘Death Star moon’ Mimas

Saturn has dozens of moons, but one looks ominously like a Star Wars Death Star. Mimas has been hailed for its resemblance , the Death Star from Star Wars.  Cassini spacecraft caught a look at the moon in October and NASA highlighted the image on Monday.

Shadows cast across Mimas’ defining feature, Herschel Crater, provide an indication of the size of the crater’s towering walls and central peak.

Named after the icy moon’s discoverer, astronomer William Herschel, the crater stretches 86 miles (139 kilometers) wide — almost one-third of the diameter of Mimas (246 miles or 396 kilometers) itself.

Large impact craters often have peaks in their center  — see Tethys’ large crater Odysseus in PIA08400. Herschel’s peak stands nearly as tall as Mount Everest on Earth.

This view looks toward the anti-Saturn hemisphere of Mimas. North on Mimas is up and rotated 21 degrees to the left. The image was taken with the Cassini spacecraft narrow-angle camera on Oct. 22, 2016 using a combination of spectral filters which preferentially admits wavelengths of ultraviolet light centered at 338 nanometers.

The view was acquired at a distance of approximately 115,000 miles (185,000 kilometers) from Mimas and at a Sun-Mimas-spacecraft, or phase, angle of 20 degrees. Image scale is 3,300 feet (1 kilometer) per pixel.

The Cassini mission is a cooperative project of NASA, ESA (the European Space Agency) and the Italian Space Agency. The Jet Propulsion Laboratory, a division of the California Institute of Technology in Pasadena, manages the mission for NASA’s Science Mission Directorate, Washington. The Cassini orbiter and its two onboard cameras were designed, developed and assembled at JPL. The imaging operations center is based at the Space Science Institute in Boulder, Colorado.

For more information about the Cassini-Huygens mission visit http://saturn.jpl.nasa.gov and http://www.nasa.gov/cassini. The Cassini imaging team homepage is at http://ciclops.org.

Credit: NASA/JPL-Caltech/Space Science Institute