The Spacecraft Tarot: Cassini

The original watercolor illustration is by me, Tippy Ki Yay. The background image is Hubble imagery and the credit belongs to NASA, ESA, and J. Olmsted (STScI).

The Wheel of Fortune continuously turns.

Our current state of being — no how matter pleasant nor painful — will eventually end. The Wheel of Fortune is a symbol of the one constant in life: change. From the moment we’re born to the moment we’re laid to rest, we can count on our fortunes changing, again and again and again. If you’re feeling up, like you’re on top of the world, guaranteed it won’t stay that way forever. And when you’re at your lowest, take comfort in the knowledge that the wheel is due for another spin.

A joint-mission between NASA, the European Space Agency (ESA), and Agenzia Spaziale Italiana (ASI), the Cassini-Huygens project teams know the Wheel of Fortune all too well. The mission experienced countless ups and downs throughout its 20-year journey to explore Saturn and its moons.

Between the orbiter Cassini and the Hyugens lander, the pair endured two Venus flybys, traversed an asteroid belt, watched Saturnian storms, discovered new moons, survived computer malfunctions, and landed the first spacecraft in the outer solar system. The end of mission culminated in the Grand Finale, using the spacecraft’s impending expiration date as an opportunity to dive bomb into the planet to obtain never-before-seen data.

The Titan IVB/Centaur carrying the Cassini orbiter and its attached Huygens probe launched from the Cape Canaveral Air Force Station on October 15, 1997. Image Credit: NASA

Cassini and its attached Hyugen probe launched from Cape Canaveral Air Force Station on October 15, 1997. The trip to Saturn required four separate gravity assists — two of Venus, one of Earth, and the last of Jupiter — each time spiraling the spacecraft outward, propelling it closer and closer toward its final destination.

On the way to Jupiter, Cassini-Hyugen passed through the asteroid belt. As it did so, its Cosmic Dust Analyzer instrument scooped up dust particles in a sophisticated bucket and measured their size, speed, and composition.

Seven years after launch, on July 1, 2004, the spacecraft finally entered Saturn’s orbit. It was the first spacecraft to ever do so. The new discoveries started pouring in not long after, beginning with the discovery of two new moons — the unlocking the first of many mysteries.

Cassini captured this near-infrared, color mosaic of Titan’s north polar seas on August 21, 2014. Image Credit: NASA/JPL-Caltech/University of Arizona/University of Idaho

On December 25, 2004, the Cassini-Hyugen team received a Christmas gift in the form of the Hyugen lander separating from Cassini and beginning its 22-day coast to Titan, Saturn’s largest moon. Before Hyugen landed on Titan, scientists knew very little about it — other than the fact that it was the only known world with a dense nitrogen atmosphere other than Earth.

As the Hyugen probe descended on the hazy orange world on January 14, 2005, teams began to receive a wealth of new information, snapping pictures of the surface and measuring the atmospheric composition. Hyugen revealed Titan to be remarkably similar to Earth before life evolved — a landscape stitched together with rain, clouds, rivers, and seas. The only difference is that Titan’s liquid cycle consists of methane, and not water.

Although the batteries drained on Titan’s frigid surface about an hour after landing, Hyugen’s collected data suggested that Titan could potentially be home to the same chemical processes that led to life on our planet. The possibility inspired a new mission designed specifically to search for these building blocks: NASA’s Dragonfly, set to launch 2027.

Cassini captured this view of Saturn’s rings on August 22, 2009. Image Credit: NASA/JPL-Caltech/Space Science Institute

But the menagerie of moon-related discoveries did not stop there. Years later, Cassini observed over a hundred different geysers erupting on the moon Enceladus. On March 12, 2008, Cassini flew by and sampled a plume directly, revealing a brew of water, carbon dioxide, and organic materials. The evidence suggested the presence of a liquid water ocean hiding underneath the moon’s icy crust — increasing the possibility of microbial life to this small, bright moon.

Among the many other moon-related observations made by Cassini-Hyugen, the spacecraft pair also revolutionized our understanding of how Saturn’s moons interact with the gas giant’s rings. Orbiting the planet for over a decade, Cassini discovered that Saturn’s moons both contribute to and steal from the water ice particles that make up the dazzling rings that encircle the planet. For example, most of Saturn’s outer E-ring consists of icy particles and gas venting from Enceladus. In addition, the gravitational influence of moonlets, miniature moon-sized lumps of ring material embedded in Saturn’s rings, kick around ring particles like boat propellers in the water. The result is a rapidly changing, dynamic ring system — one more chaotic than we’ve ever observed in our solar system.

However, despite all of Cassini-Hyugen’s revolutionary discoveries, the journey was not always sunshine and roses. The spacecraft pair went through their fair share of challenges — the most notable of which resulted in the Grand Finale, which ultimately ended the Cassini-Hyugen mission.

A natural color view of the last image taken by the imaging cameras on NASA’s Cassini spacecraft on September 14, 2017. Image Credit: NASA/JPL-Caltech/Space Science Institute

After 20 years in space, Cassini’s fuel was finally depleting. Knowing that the end was near, the Cassini team decided to see this expiration date as an opportunity. Cassini performed a risky series of dives between Saturn and its rings. The close orbits allowed the spacecraft to observe Saturn’s rings more intimately than ever before, revealing new organic compounds that originate from neither Titan nor Enceladus. Scientists also discovered an electric current that connects the rings to the top of Saturn’s atmosphere, as well as a new radiation belt.

During its final orbit, Cassini plunged into the gas giant’s atmosphere at tens of thousands of miles per hour. As the spacecraft burned up in Saturn’s hot, high-pressure atmosphere, Cassini became a meteor streaking through the sky — ultimately becoming one with the planet itself.

The end of mission could have been viewed as an enormous loss — instead, Cassini’s final moments were memorialized as a bittersweet celebration of a successful adventure into the solar system, punctuated by a final blaze of glory.

The Wheel of Fortune is both a comforting and sobering reminder that everything is fleeting. Take advantage of opportunities to cherish the good chapters and learn from the challenging ones — before the moment passes.

This simulated image was constructed from the measured optical depth profiles of the Cassini Division and ring A during the first radio occultation observation of Saturn’s rings on May 3, 2005. Image Credit: NASA/JPL

Read the complete Spacecraft Tarot series.



Creator of the Spacecraft Tarot. She/her.

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