We now know the age of Saturn’s rings, and the number might surprise you

In an exciting breakthrough, a research team led by physicist Sascha Kempf from the University of Colorado Boulder has presented the most convincing evidence to date supporting the theory that the rings of Saturn are relatively young. 

This finding could potentially resolve a long-standing question that has puzzled scientists for over a century.

The research, which is set to be published in the renowned journal Science Advances on May 12, estimates the rings of Saturn to be no more than 400 million years old. 

This conclusion positions the rings as significantly younger than the planet they orbit. Saturn itself is approximately 4.5 billion years old.

Sascha Kempf, an associate professor in the Laboratory for Atmospheric and Space Physics (LASP) at CU Boulder, drew a connection between their discovery and the early days of scientific curiosity. 

“In a way, we’ve gotten closure on a question that started with James Clerk Maxwell,” Kempf remarked.

How the study was done

The researchers attained this insight by focusing on an unexpected subject: dust. As Kempf explained, the solar system is perpetually inundated with tiny grains of rocky material. 

In certain cases, these particles can deposit a thin layer of dust on various celestial bodies, including the icy rings of Saturn.

In their groundbreaking study, Kempf and his team sought to date the rings of Saturn by examining the accumulation rate of this dust layer. This method is akin to estimating the age of a house by analyzing the dust collected on its surfaces over time.

Kempf used a familiar analogy to illustrate their approach, saying, “Think about the rings like the carpet in your house. If you have a clean carpet laid out, you just have to wait. Dust will settle on your carpet. The same is true for the rings.”

Gathering evidence for 13 years

The process was complex and time-consuming. Between 2004 and 2017, the researchers employed an instrument known as the Cosmic Dust Analyzer on board NASA’s late Cassini spacecraft to study the particles of dust in Saturn’s vicinity. 

Over this 13-year period, the team gathered a mere 163 dust grains that originated from outside Saturn’s immediate neighborhood. 

Nevertheless, this modest sample was sufficient for their purpose. Based on their calculations, they concluded that the rings of Saturn have likely been accumulating dust for only several hundred million years.

In the grand scheme of cosmic time, Saturn’s rings are a recent phenomenon. They have potentially come into existence, and might even vanish, in what could be considered a cosmic blink of an eye. 

However, this discovery, as groundbreaking as it is, doesn’t answer all questions about the enigmatic rings.

“We know approximately how old the rings are, but it doesn’t solve any of our other problems,” Kempf noted. “We still don’t know how these rings formed in the first place.”

Captivating and mysterious since the time of Galileo

For over 400 years, researchers have been fascinated by the seemingly translucent rings of Saturn. The Italian astronomer Galileo Galilei first observed these features in 1610 through a telescope, although he couldn’t identify what they were. 

His original drawings depict the rings somewhat like the handles on a water jug. In the 19th century, James Clerk Maxwell, a Scottish scientist, proposed that Saturn’s rings were not a solid structure, but rather composed of numerous individual pieces.

In the present day, we know that Saturn boasts seven rings made up of innumerable chunks of ice, each no larger than an average boulder here on Earth. Altogether, this ice has roughly half the mass of Saturn’s moon, Mimas, and stretches nearly 175,000 miles from the planet’s surface.

Professor Kempf pointed out that for most of the 20th century, scientists assumed that the rings formed alongside Saturn. However, this notion raised some questions. 

For instance, Saturn’s rings are remarkably clean. Observations show that the rings consist of approximately 98% pure water ice by volume, with only a minuscule amount of rocky matter. “It’s almost impossible to end up with something so clean,” Kempf stated.

Cassini gets a closeup look

The arrival of the Cassini spacecraft at Saturn in 2004 offered an unprecedented opportunity to ascertain the age of Saturn’s rings. The spacecraft, equipped with the Cosmic Dust Analyzer, which resembled a bucket, collected data until it purposefully plunged into the planet’s atmosphere in 2017. The analyzer scooped up tiny particles as they whizzed past.

The Laboratory for Atmospheric and Space Physics (LASP) engineers and scientists have designed and built a more sophisticated dust analyzer for NASA’s forthcoming Europa Clipper mission, which is slated for launch in 2024.

The team calculated that this interplanetary grime contributes less than a gram of dust to each square foot of Saturn’s rings annually. Though a light dusting, it’s sufficient to accumulate over time. Earlier studies hinted at the youthfulness of the rings, but none provided definitive measures of dust accumulation.

In a surprising twist, these dazzling rings may already be fading. A previous study from NASA scientists reported that the ice is slowly cascading down onto the planet and could vanish entirely in another 100 million years.

The fact that these ephemeral features existed at a time when Galileo and the Cassini spacecraft could observe them seems almost serendipitous, according to Kempf. This observation raises questions about how the rings formed initially. 

Some scientists have suggested that Saturn’s gravity could have torn apart one of its moons, leading to the formation of the rings. “If the rings are short-lived and dynamic, why are we seeing them now? It’s too much luck,” said Kempf.

More about Saturn

Saturn, the sixth planet from the sun, is one of the most recognizable planets due to its extensive ring system. The planet is named after the Roman god of agriculture and wealth, which is the equivalent to the Greek god Cronus, father of Zeus. Here’s a summary of what we know about this beautiful planet.

Physical Characteristics

Saturn is the second-largest planet in the solar system, only smaller than Jupiter. It has a diameter of about 74,900 miles (120,500 kilometers), which is about 9.5 times the diameter of Earth. Despite its size, Saturn has the lowest density of all the planets, and it’s less dense than water, which technically means it would float in a sufficiently large body of water.

Saturn’s composition is primarily hydrogen and helium, similar to the sun and Jupiter. Deep within Saturn’s core, there may be a solid core composed of iron, nickel, silicon, and oxygen compounds, surrounded by a deep layer of metallic hydrogen.

Atmosphere

Saturn’s atmosphere is primarily composed of hydrogen, with small amounts of helium and methane. Saturn’s top cloud layer is mostly ammonia crystals, while the lower level clouds appear to consist of either ammonium hydrosulfide or water. The atmosphere occasionally exhibits long-lived ovals and other features common on Jupiter.

Rings

Saturn’s ring system is the most extensive and complex in the solar system, extending hundreds of thousands of kilometers from the planet. The rings are composed primarily of ice particles, with a smaller amount of rocky debris and dust. The individual rings are named alphabetically in the order they were discovered, so the sequence does not correspond to their positions.

Moons

Saturn has 82 known moons, the largest of which is Titan. Titan is larger than the planet Mercury and is the second-largest moon in the solar system. It’s the only moon that has a substantial atmosphere, which is denser and thicker than Earth’s. Enceladus, another of Saturn’s moons, has geysers that eject substantial plumes of ice particles and water vapor from below its surface, suggesting a subsurface ocean.

Exploration

Saturn has been explored only through uncrewed spacecraft launched by NASA, including the Pioneer 11, the Voyager 1 and 2 missions, and the Cassini-Huygens mission. The Cassini-Huygens mission, which arrived at Saturn in 2004, allowed detailed observations of the planet, its rings, and its moons until it ended in 2017.

Rotation and Orbit

Saturn takes about 29.4 Earth years to complete one orbit around the sun, and its day is about 10.7 hours long. It has an axial tilt of 26.73 degrees, which means it has seasons like Earth, but each season lasts over seven years.

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