It reads like the tear-jerking finale of a blockbuster - Titanic, Armageddon, take your pick - where our courageous hero meets their glorious, sacrificial end.

Indeed, space fans have grabbed the Hollywood trope to anthropomorphise Cassini, the plucky Nasa spacecraft that last night met its fiery destruction amid Saturn's atmosphere.

The sentiment isn't over-stated: the probe won new hearts with every mind-boggling picture it relayed from the giant planet during its 20-year mission.

It opened our eyes to one of the most Earth-like worlds we've ever encountered, with weather, climate and geology that offered new ways to understand our home planet.

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It revealed the beauty of the solar system's second biggest planet, its rings and moons, inspiring our sense of wonder and enriching our sense of place in the cosmos.

It gave us a portal to see the physical processes that likely shaped the development of our neighbourhood in space, as well as planetary systems around other stars.

The dream couldn't last forever.

As it reached the end of its propellant, Nasa scientists grew worried that an unsteerable probe might accidentally crash into one of Saturn's nearby moons and contaminate it with hitch-hiking Earthing bacteria.

Thus, they opted to safely dispose of it in Saturn's atmosphere in one final blaze of glory.
Here on Earth, there would have been some genuinely misty eyes fixed upon computer screens.

"You may think it's strange, but I feel I have known Cassini for many years," Otago Museum director Dr Ian Griffin says.

He vividly recalls watching as the craft blasted off from Florida's Cape Canaveral, in the early hours of October 15, 1997, when Elton John's Candle In The Wind was being thrashed on radio stations in the wake of Princess Diana's death.

Cassini's powerful rockets sent it curving upward into the sky, briefly turning night into day in a dazzling column of light.

Two thousand, four hundred and fifty-one days later, on July 1, 2004, the same day actor Marlon Brando died and deposed dictator Saddam Hussein went on trial, Cassini arrived at Saturn and slipped into its orbit.

It soon delivered the European Space Agency's Huygens probe to the mysterious moon Titan, marking our first descent and landing on a world in the outer solar system.

Scientists had long known Titan had an extensive, thick and opaque atmosphere that hid the moon's surface from them.

For the first time, they were able to marvel at surface lakes and rivers on Titan's surface - and record clear evidence of a liquid present on the surface of a world other than our own.

"Our new knowledge of these alien surface lakes and Titan's thick atmosphere adds vital fuel to the debate on how and where life could catch a hold on alien worlds," University of Auckland physics lecturer Dr Nicholas Rattenbury says.

And Cassini was still there above, making 127 of its own close fly-bys of Titan.

Enceladus, another moon of Saturn, had plumes of material jetting out into space.

The Cassini mission captured high-resolution images of these remarkable geyser-like, water-filled jets.

"To those of us interested in finding alien worlds on which life could emerge, water is considered as - almost certainly - the most likely medium in which life could emerge," Rattenbury said.

"However, Cassini wasn't finished there, collecting evidence that in addition to water, there was a source of energy - methane - that could be used by life."

Cassini represents a staggering achievement of human and technical complexity, finding innovative ways to use the spacecraft and its instruments, and paving the way for future missions to explore our solar system.

By the end of its mission, it had observed almost half of a Saturn year - which is 29 Earth years long.

The four seasons of Saturn's year last about seven Earth years apiece, and upon Cassini's arrival at Saturn, the planet's northern hemisphere was just beginning to emerge from winter.

Following its initial, four-year tour, Cassini's mission was extended two more years, to enable the spacecraft to observe changes - particularly in the rings - as Saturn reached equinox and the Sun shone edge-on to the rings.

The findings of the Cassini mission have revolutionised our understanding of Saturn, its complex rings, the amazing assortment of moons and the planet's dynamic magnetic environment.

"Nasa has an undoubted ability to sell a story, but the hype is not misplaced," the University of Auckland's Professor Richard Easther says.

The most distant planet easily visible to the naked eye, Saturn once marked the apparent edge of our solar system.

"Its rings are visible through even the smallest of telescopes, and seeing them this way still takes your breath away."

Since April, it's been writing the final, thrilling chapter in its 20-year saga, diving each week through the 2000km-wide gap between Saturn and its rings, and making one final close flyby of Titan.

At times, Cassini skirted the very inner edge of the rings; at other times, it skimmed the outer edges of the atmosphere.

After its orbit passed through Saturn's uppermost atmosphere, it made its final descent into the planet, breaking up just the way a meteor does.

Rattenbury says Cassini could now rightly take its place among the pantheon of other spacecraft explorers, leaving a lasting legacy of wonder and discovery.

A hero's finale, confirmed.

Swell music, sob, roll credits.