I was only 15 years old when I saw the announcement for NASA’s upcoming exploratory mission to Saturn. At that moment in my life I had solidified my interest (sorry, “obsession”) with spaceflight. The brief article burned in my mind with NASA’s bold assertion: this new space probe would be exploring the planet Saturn from orbit. Saturn! No country had yet sent a spacecraft to study specifically the ringed gas giant.
On Friday, September 15th of this year, Cassini will descend into Saturn’s atmosphere after nearly 13 years in orbit. The spacecraft was lunched in 1997 and entered orbit around Saturn in 2004. Take a moment to think about everything that you’ve experienced for the last thirteen years. For the entirety of that period, planetary scientists from around the world have been working to study the data returned from this far-flung space probe.
The spacecraft (which is nearly as large as a bus and is powered by a nuclear radioisotope thermoelectric generator) has shown to us visions of a world alien to our senses. Photographs taken by the Cassini orbiter have allowed us to see things we are incapable of viewing from earth such as the hexagonal jets streams turning about Saturn’s poles or the faintest of the rings that encircle the planet. A magnetometer onboard has measured the first record of the planet’s magnetic field. Orbits that passed the famous ring structure made it possible to determine the nature of the matter that forms them. And imagery returned of the diminutive moon Enceladus has shown what appear to be geysers of water erupting from its surface. (The tiny world was thought to be of too little mass to feature active geothermal processes).
One of the most impactful elements of the mission was the inclusion of a lander probe, know as Huygens (Named for Christiaan Huygens.) The lander detached from the main spacecraft and entered the atmosphere of the moon Titan in 2004. Never before had humans seen what existed below the clouds that masked the surface of the largest moon in our solar system.
Everything we know about the chemistry, atmospheric makeup, geography, and geology of Titan comes from data collected by instruments on Huygens and Cassini. Here is an entire world, alien to us, yet close enough to be similar. We can see in images like the one above that Titan has hills and shorelines and most of it was formed by chemicals other than water. Instead, we know through Cassini that Titan experiences a hydrologic cycle that is made up of ethane, methane, and hydrocarbon rich nitrogen.
The longevity and audacity of the Cassini mission has, and will continue to have an impact on NASA and its affiliate s for decades to come. Unlike the Voyager and Mariner missions of the 1970s, Cassini did more than a dramatic flyby of Saturn -it persisted. The mission not only demonstrated the technological capability of deploying a separate lander, but of the extensions to the original mission profile and flexibility to change targets. In an increasingly risk-averse aerospace culture, the Cassini team proved that bold goals can still achieve results.
There’s a certain sadness than comes naturally at the end of a space mission. Years of labor and study come to a close, and in many cases, the actual hardware is lost to the cosmos forever. Additionally, trends in both science funding and politics have curtailed further proposals to study Saturn and its moons. For those who’ve dedicated their lives to the study of the outer planets, this week could be the last an American spacecraft visits Saturn in their lifetimes. It’s justified to feel bittersweet about the successes Cassini/Huygens accomplished when political changes suggest there will be no successor.
But there is hope: Every decade, the U.S. National Research Council meets and publishes a document known as the Planetary Decadal Survey . Participating scientists make suggestions, balance cost versus scientific return, and prioritize potential future exploratory planetary missions. the last decadal survey was conducted in 2011 and the report was published a year later. In the 2011 survey, strong emphasis addressed the lack of knowledge concerning Europa, one of Jupiter’s icy moons. This had impact on NASA’s decision to approve a planned orbiter probe, now known as Europa Clipper.
Saturn and it’s moons were not left out; in fact, there were seven distinct mission concepts featuring the ringed-gas giant in the 2011 survey. Listed, they are: Titan Saturn System Mission,
Saturn Atmospheric Entry Probe Trade Study, Saturn Atmospheric Entry Probe Mission Concept Study, Saturn Ring Observer Concept Study, Enceladus Flyby & Sample Return Concept Studies,
Enceladus Orbiter Concept Study, and Titan Lake Probe Concept Study. While none of these mission concepts received the priority or impetus of Europa or Mars, if offers a glimmer of hope for the researchers who wish tone day delve deeper into the study of Saturn.
For now we will have to remain satisfied with the years of data Cassini/Huygens delivered. In days, the spacecraft will descend into Saturn itself, heated by the friction of the planet’s atmosphere. What remains will be pulled deep into the gaseous abyss, eventually crushed by the immense gravity. A mission is complete. Goodbye, Cassini.
For more information about Cassini and the Grand Finale, click the link below: