The spacecraft Cassini was tasked with investigating Saturn in more detail and undertook missions to find out more about the planet and its many moons. It officially finished its most recent mission last month (September 15th) when it plummeted into Saturn’s atmosphere. Cassini started its first mission 10 years ago, on 15th October 1997, and was launched from Cape Canaveral in Florida. On board was the Huygens probe from the European Space agency, destined to be the first probe to ever land on a moon other than our own.
Before Cassini, little was known about the moons and rings of Saturn. The only other missions that ever came close to it were Voyager 1 and 2, and the Pioneer voyages. However, these were simply fly-bys which, although revealed much about the planet, did not uncover its detailed structure or that of the atmosphere. From 1997-2004, Cassini was in interplanetary cruise, which involved swing-bys of other planets like Earth, Venus, and Jupiter in order to give enough gravity assist trajectory to reach Saturn. The Cassini mission was extended twice to create three missions in total; the original Cassini-Huygens Saga (2004-2008), the Cassini Equinox (2008-2010), and the Cassini Solstice mission (2010-2017). Cassini became the first spacecraft to orbit Saturn, which allowed a more in depth study of the planet for the first time.
The Cassini-Huygens Saga was instrumental in being able to investigate the moons of Saturn, especially Titan (the largest of Saturns moons) and Iapetus. The mission allowed a scientific insight into the geology and the compostion of Titan’s surface, as well as its clouds and atmosphere, for the first time. The Huygens probe was able to land on Titan itself, making it the first time a spacecraft has landed there, and the furthest point away from Earth where a landing has ever been successful in the outer solar system.
The Cassini Equinox was the second mission to take place around Saturn and allowed 64 orbits of the planet. The Equinox crossing took place in August 2009, an event that only occurs every 15 years due to the long solar orbit time of Saturn. This allowed Cassini an unrivalled view of the rings of Saturn as they cooled with the onset of Saturn “winter”, feeding unprecedented information back to scientists on Earth. Similarly, the Solstice mission was an opportunity to explore the spring/early summer taking place on the northern hemisphere of Saturn.
The Cassini missions drew to a close in late 2016 as the final set of manouvres were performed. Cassini dove between the innermost ring and Saturn itself to gather an immense amount of data of the gravity and magnetic fields on Saturn. Eventually, Cassini ended the 20 year long mission before falling into Saturns atmosphere.
Cassini made several discoveries, and has revealed that there are some parallels between Earth and Saturn. The moon Titan was found to have characteristics similar to Earth, with water-like bodies of lakes and seas, as well as rain. The mission also allowed the prebiotic chemistry on Titan to be monitored and studied to evaluate if it has the prerequisites to sustain life. Little was previously known about the rings of Saturn, but Cassini has unveiled that the rings are dynamic and active, and they have been imaged thoroughly, allowing the first images of their vertical structure to be taken.
The Cassini missions have been notable for the groundbreaking content they have uncovered. Cassini travelled an astounding 4.9 billion miles since its launch in 1997 and completed 294 orbits of Saturn. This in turn has created a staggering amount of research – 3948 scientific papers have been published since the missions started. The data collected from Cassini will be hugely valuable to future research, and the termination of Cassini’s mission is the end of an extraordinary chapter in our space exploration saga.
Kira Knowles
Image: NASA Jet Propulsion laboratory