Paragraph 1

"NOT everything looks lovelier the longer and closer its inspection. But Saturn does."

Explanation: Not everything becomes more beautiful the more you look at it, but Saturn does.

"It is gorgeous through Earthly telescopes."

Explanation: Saturn appears stunning through telescopes on Earth.

"However, the 13 years of close observation provided by Cassini, an American spacecraft, showed the planet, its moons and its remarkable rings off better and better, revealing finer structures, striking novelties and greater drama."

Explanation: The 13 years of close observation by the Cassini spacecraft enhanced our understanding of Saturn, revealing more details, new discoveries, and dramatic features of the planet, its moons, and rings.

"By and large the big things in the solar system—planets and moons—are thought of as having been around since the beginning."

Explanation: It is generally believed that the large celestial bodies in the solar system, such as planets and moons, have existed since the beginning of the solar system.

"The suggestion that rings and moons are new is, though, made even more interesting by the fact that one of those moons, Enceladus, is widely considered the most promising site in the solar system on which to look for alien life."

Explanation: The idea that Saturn's rings and moons are relatively new is intriguing, especially considering that Enceladus, one of Saturn's moons, is considered one of the best places in the solar system to search for alien life.

"If Enceladus is both young and bears life, that life must have come into being quickly."

Explanation: If Enceladus is young and contains life, this life must have formed rapidly.

"This is also believed to have been the case on Earth."

Explanation: The rapid emergence of life is also believed to have occurred on Earth.

"Were it true on Enceladus, that would encourage the idea that life evolves easily when conditions are right."

Explanation: If life emerged quickly on Enceladus, it would support the idea that life can evolve quickly when the right conditions are present.

Paragraph 2

"One reason for thinking Saturn’s rings are young is that they are bright."

Explanation: One reason scientists believe Saturn's rings are young is because they are bright.

"The solar system is suffused with comet dust, and comet dust is dark."

Explanation: The solar system is filled with comet dust, which is dark in color.

"Leaving Saturn’s ring system (which Cassini has shown to be more than 90% water ice) out in such a mist is like leaving laundry hanging on a line downwind from a smokestack: it will get dirty."

Explanation: If Saturn's rings, which are mostly made of water ice, are exposed to comet dust, they would get dirty, much like laundry left outside near a smokestack.

"The lighter the rings are, the faster this will happen, for the less mass they contain, the less celestial pollution they can absorb before they start to discolour."

Explanation: The lighter the rings, the quicker they will become dirty because they have less mass to absorb the comet dust before they discolor.

"Jeff Cuzzi, a scientist at America’s space agency, NASA, who helped run Cassini, told the Lunar and Planetary Science Conference in Houston that combining the mass estimates with Cassini’s measurements of the density of comet-dust near Saturn suggests the rings are no older than the first dinosaurs, nor younger than the last of them—that is, they are somewhere between 200m and 70m years old."

Explanation: Jeff Cuzzi, a NASA scientist, explained at a conference that based on the mass estimates and Cassini’s measurements of comet dust near Saturn, the rings are estimated to be between 200 million and 70 million years old, aligning with the time of the first and last dinosaurs.

Paragraph 3

"That timing fits well with a theory put forward in 2016, by Matija Cuk of the SETI Institute, in California and his colleagues."

Explanation: This age range fits well with a theory proposed in 2016 by Matija Cuk and his colleagues from the SETI Institute.

"They suggest that at around the same time as the rings came into being an old set of moons orbiting Saturn destroyed themselves, and from their remains emerged not only the rings but also the planet’s current suite of inner moons—Rhea, Dione, Tethys, Enceladus and Mimas."

Explanation: The theory suggests that at about the same time Saturn's rings formed, an older set of moons around Saturn destroyed themselves, and their remains formed the rings as well as Saturn's current inner moons, including Rhea, Dione, Tethys, Enceladus, and Mimas.

Paragraph 4

"Dr Cuk and his colleagues used computer simulations of Saturn’s moons’ orbits as a sort of time machine."

Explanation: Dr. Cuk and his team used computer simulations of the orbits of Saturn’s moons to simulate the past.

"Looking at the rate at which tidal friction is causing these orbits to lengthen they extrapolated backwards to find out what those orbits would have looked like in the past."

Explanation: They studied the rate at which tidal friction is causing the moons' orbits to expand and worked backward to determine what the orbits would have been like in the past.

"They discovered that about 100m years ago the orbits of two of them, Tethys and Dione, would have interacted in a way that left the planes in which they orbit markedly tilted."

Explanation: They found that about 100 million years ago, the orbits of Tethys and Dione would have interacted in such a way that their orbital planes would have become tilted.

"But their orbits are untilted."

Explanation: However, their current orbits are not tilted.

"The obvious, if unsettling, conclusion was that this interaction never happened—and thus that at the time when it should have happened, Dione and Tethys were simply not there."

Explanation: The conclusion, though unsettling, is clear: the interaction never occurred, meaning that at the time it should have, Dione and Tethys did not exist.

"They must have come into being later."

Explanation: Therefore, Dione and Tethys must have formed later than previously thought.

Paragraph 1 Summary

Saturn is a stunning planet, and the Cassini spacecraft's 13 years of close observation revealed remarkable features of the planet, its moons, and rings. The age of Saturn’s moons and rings is in question, especially since one moon, Enceladus, is considered a prime candidate for alien life, raising the possibility that life can evolve quickly when conditions are right.

Paragraph 2 Summary

One reason for believing Saturn’s rings are young is their brightness, as they are composed mainly of water ice, which would quickly get dirty from comet dust. Measurements suggest the rings are between 200 million and 70 million years old, aligning with the time of the dinosaurs.

Paragraph 3 Summary

This timing supports a theory that Saturn’s rings and moons were formed after an older set of moons around Saturn destroyed themselves, and their remains formed the rings and the inner moons, such as Enceladus.

Paragraph 4 Summary

Dr. Cuk and his colleagues used computer simulations of the moons' orbits to trace their history, discovering that two moons, Tethys and Dione, must have formed later than expected since their orbital interaction never occurred as predicted.