At 6:32 on Friday morning, Sept. 15, the Cassini exploratory satellite plunged into the Jovian planet Saturn, completing its fifth and final mission around the ringed planet in its 13-year survey of the planet, its picturesque rings, and its 62 moons.

As we say our goodbyes to this little explorer over a billion miles from home, we look back on Cassini’s history and significance, as well as some of its biggest discoveries of the past two decades.

The Cassini spacecraft, the product of 17 different nations working in tandem, was one of the most effective and productive interplanetary missions ever launched, spending seven years en route surveying Venus, Earth and Jupiter  before arriving for its 13-year tenure around Saturn.

The 5,000 pound probe took off from Cape Canaveral over 20 years ago on Oct. 15, 1997. Thus began 20 years of exploration and discovery.

After completing two flyby’s of Venus, one of Earth, and another of Jupiter, Cassini headed for the ringed giant, Saturn. On June 30, 2004, the probe, named for Giovanni Domenico Cassini (head of the Paris Astronomical Observatory and discoverer of four of Saturn’s moons), arrived in orbit around Saturn to begin 13 years of observations and experiments.

Included in this was the Huygens lander, sent to smack into Saturn’s largest moon, Titan. During its’ descent, the lander took detailed pictures of the surface and measurements of the atmosphere. This was humanity’s first glimpse beneath the vaporous red curtain of Titan’s thick atmosphere. The pictures it sent back revealed the existence of lakes and rivers of liquid methane on the surface, as well as the only documentation of rain on a celestial body other than Earth.

One of the most exciting of Cassini’s many discoveries lies on the medium-sized moon of Enceladus. Previously considered scientifically uninteresting, this ball of ice has become one of the most exciting celestial bodies in our solar system for astronomers and biologists alike. As Cassini flew into the shadow of Enceladus, the brief eclipse showed a shocking scene: dozens of geysers shooting miles off of the surface from the moon’s southern pole.

Further inspection revealed the nature of the discovery that the composition of the geysers was, in fact, water. The geysers showed that the water beneath Enceladus’s surface was partially in liquid form – the only liquid water ever observed somewhere other than earth.

The presence of the moon’s internal heat, the water it warmed, and the presence of organic molecules shown by Cassini’s further observations showed that Enceladus was the strongest candidate for primordial life outside of Earth.

The cameras of Cassini were then turned towards Saturn’s iconic rings. What we got back were by far the clearest images of Saturn’s rings to date in an attempt to discern the composition, age, and origin of the massive ring system.

Among Cassini’s survey of the rings was a host of never-before observed phenomena including what are colloquially termed “pinwheels” by the scientists who first observed them. These streaks in the rings are caused by larger objects in the rings pulling the particles and pebbles that make up the rings into a two-tailed pinwheel shape ahead and behind the main mass.

The fringes of the rings held another oddity. The rings had previously been observed to be of uniform thickness throughout their enormity that was no more than a couple tens of meters. When Cassini turned its camera towards the outer edges however, an odd pattern of shadows was observed on the outer edges. Upon closer inspection, it turned out that the smallest outer fringe of the rings contained a veritable wall of boulders that sometimes stretched in excess of two miles above their surroundings.

Aside from its rings, Saturn is known for its great red spot – a massive storm swirling in the upper hemisphere of the planet. In the past 120 years, only four storms of this magnitude have roiled across the surface of Saturn. Cassini had the good fortune of being present during the most recent one that erupted in 2010. Scientists had a front seat to the storms as it circled across the entire planet, creating a whole new segment to add to Saturn’s characteristic colorful bands that cross its surface.

The flashiest of Cassini’s observations of the storm has to be the little four-second clip of lightning shattering the otherwise dim and cloudy atmosphere during the storm. This lightning is a thousand times more powerful than anything on earth and dwarfs any electrical phenomena seen elsewhere in the solar system. This is the first time that Saturn’s electrical discharges have been observed.

Flying over the northern pole of the planet, Cassini shed light on one of the greatest mysteries of the ringed planet: its rotating hexagonal storm. The storm, itself larger than earth, rotates once every ten hours, and changes color seasonally – another recent discovery of Cassini. When Cassini first observed the storm, it was its wintertime blue-green color. As the storm entered its final dive, the hexagon was a golden brown color, a result of the atmospheric gasses interacting with sunlight.

The end of Cassini’s propellant (and mission, albeit 12 years later than expected) caught up with the craft. One final gravity slingshot around Titan flung the probe into a slow collision course with Saturn. In the interim, the probe made 22 close passes between Saturn and its closest rings through what is commonly called “The Big Empty.”

All of this work has culminated in the 76,000 mph death dive into the upper echelons of Saturn’s atmosphere.

NASA scientists feared contaminating moons like Enceladus with terrestrial stowaways aboard Cassini and decided to make the spacecraft a permanent fixture of the planet that it studied for over a decade.

The final dive took Cassini closer to Saturn than we have ever been. The probe disintegrated and vaporized in the atmosphere, sending back signals from its instruments until it was no longer able. The data sent back will be pored over for decades to come, shedding light on the composition of Saturn’s atmosphere and the planet itself with a closer look than we will get for decades.

The poetic closure of sending the craft into Saturn gives a little bit of sweetness to the sad ending to this two-decade-long story of exploration and unprecedented revelations.