Cassini performed 20 ring-grazing orbits that brought it within 1000 kilometers of Saturn’s outermost edge, offering incredible close encounters.
On one of those orbits, a tiny storm ballooned into an enormous, billowing mass of cloud and gas.
This Great White Storm verified long-held theories regarding water-ice geysers on Enceladus, a moon believed to contain a salty subsurface ocean suitable for supporting life.
The Cassini Mission
Cassini orbiter and Huygens probe that landed on Titan began their voyage together on October 6, 1997. These missions, named for French-Italian astronomer Jean-Dominique Cassini (1625-1712) and Dutch physicist Christiaan Huygens (1629-1695), sought to study Saturn’s rings, magnetosphere, and icy moons during their exploration journeys.
At Saturn’s atmosphere, this spacecraft studied its polar jet stream–known as “The Hexagon,” because of its hexagonal form–mapping it like a river of winds whipping across Earth’s latitudes, with dips and wiggles caused by landmasses and oceans. Furthermore, the spacecraft studied types, distribution, ages of surface units as well as measured aerosols and heavy molecules and their properties; finally performing 22 death-defying ‘Ring Dives’ between Saturn and its rings- five of which saw it physically pass through them-a feat never accomplished before by any spacecraft.
The Voyager Missions
Voyager Missions were undertaken to explore Jovian and Saturnian systems. Each spacecraft carried 10 scientific instruments – two cameras, multiple spectrometers, magnetometers – in an advanced spacecraft equipped with propulsion system.
The craft utilized plutonium-oxide-fueled radioisotope thermoelectric generators as power sources. An attitude control system utilized star tracker error signals and small thrusters for positioning.
Both Voyagers were launched on nominal trajectories that allowed for a Jupiter flyby, close encounters with Ganymede or Callisto and Earth-Sun occultation, and an encounter with Titan. Both Voyagers produced bounties of new science; charting Jupiter’s complex cloud formations, winds, storm systems and volcanic activity on Io’s moon Io. At Saturn they explored its mysterious rings featuring braids, kinks and spokes, uncovering myriad “ringlets”. After leaving Saturn Voyager 1 went onward to Uranus where 11 hitherto unknown moons were discovered before arriving at Neptune where she exited before finally leaving our solar system before exiting from Neptune before finally exiting our solar system altogether.
The Cassini-Huygens Mission
Cassini-Huygens was an innovative effort to gain insight into Saturn and its rings and moons, including Enceladus. The mission’s objectives included studying Saturn as an entire organism; inspecting its atmosphere and rings with unprecedented detail; exploring Enceladus to understand how small ice bodies form and evolve; and researching Enceladus to gain more information on small-ice body formation and evolution.
The mission concluded with an unforgettable Grand Finale of 22 thrilling dives between Saturn and its rings from April to September 2017 that yielded rich science far beyond original plans, such as direct sampling of Saturn’s atmosphere and ionosphere, unparalleled gravity measurements, the highest resolution ring images ever captured, and an unprecedented determination of ring mass.
Discoveries made during this mission included icy jets streaming from tiny Enceladus, lakes of liquid hydrocarbons and curtains of methane raining down on Titan, and Saturn’s mysterious hexagonal storms. In order to prevent any possibility that an out-of-control Cassini would ever hit Enceladus unwittingly and cause contamination there, NASA decided to safely dispose of Cassini by dropping it into Saturn’s hydrogen-rich atmosphere instead.
The Dragonfly Mission
The Dragonfly mission seeks to study Saturn’s moon Titan. Titan is one of the largest satellites in our solar system and boasts an atmosphere rich with liquid water and methane cycles, making it one of the most intriguing locations for looking for signs of extraterrestrial life.
This spacecraft will make many flights over multiple sites on Titan, using various instruments to search for evidence of prebiotic chemical reactions that led to life arising on Earth 3.5 billion years ago. Furthermore, it will assess its planetary environment to compare with Earth during that same timeframe.
Dragonfly recently completed its critical design review and is entering its next stage of development, including fabrication and its launch onto Titan on a heavy-lift rocket. NASA confirmed its mission last November but delayed making decisions regarding cost and schedule until spring 2024.
The Galileo Mission
Galileo managed to produce more science than initially envisioned despite technical challenges with its high-gain antenna, thanks to various hardware changes and software adaptations that increased telemetry rates by over 10 times.
Galileo was successfully launched from Atlantis as part of STS-34 on October 18, 1989 with Commander Don Williams, Pilot Mike McCulley, Shannon Lucid Franklin Chang Diaz and Ellen Baker as Mission Specialists.
Galileo was powered by radioisotope thermoelectric generators, using heat generated from natural decay of plutonium to generate electricity, with sixteen scientific instruments to measure fields and particles aboard it. A separate section rotated and carried the probe, collecting data about complex bodies like Gaspra asteroid by passing close by it and making close flybys of Jupiter’s moons Ganymede and Callisto.