Saturn has been known since prehistoric times. In ancient times, it was the most distant of the known planets in the Solar System and thus a major character in various mythologies (Babylonian, Roman, Greek, Hindu and many more). Humans had been tracking Saturn’s movements since thousands of years, but it wasn’t until Galileo first pointed his telescope at Saturn in 1610, was anyone able to take a closer look at this majestic gas giant. Later, Giovanni Cassini used a more powerful telescope to observe Saturn and concluded that the protrusions around the planet were in fact rings! Although Cassini’s discovery didn’t stir up huge discussions, it was an important one. Many moons of Saturn were discovered in the 18th and 19th centuries.
But one of the most important observation was obtained in the 20th century. The twin Voyager space probes of NASA made their closest approach during their Saturn fly-by in 1980 and 1981. This was the only time after the Pioneer 11 fly-by, that humans had a very close look into the Saturn’s atmosphere.
What the Voyagers revealed to us, was so phenomenal that our idea of Saturn and its moons went upside down in a span of just few months.
Voyager’s images of the Rhea, Tethys, Dione and other moons of Saturn tantalised scientists with features very different to those expected. Perhaps the most profound insight came with the observations of Titan, Saturn’s largest moon. Images sent by Voyager showed that Titan, unlike other moons might have a thick atmosphere which made it difficult for the equipment on-board to take images of Titan’s surface.
Voyager’s findings also suggested that Enceladus, Saturn’s brightest moon might still be active with geological activity.
The findings of Voyager were game changing. The fact that Titan had a thick atmosphere indicated the potential of this moon to harbor life. At a time when Mars was considered to be the best candidate for presence of alien life, Titan shot into the limelight with Voyager’s success. Scientists began speculating the possible conditions on surface of Titan. Major space agencies all over the world were rescheduling their missions with Titan being their top priority. All eyes were on Saturn now.
Finally in 1988, NASA and ESA decided to work on a mission to Saturn. The initial idea of NASA was a Saturn orbiter, but later ESA also developed a Titan lander. Cassini became a symbol of international cooperation with contributions from over 27 countries. Finally, after 9 years of working on the project, Cassini was launched on October 15, 1997, aboard the Saturn IVB. Cassini took almost 7 years to complete the 2.2 billion miles journey to Saturn and achieved orbit on July 1, 2004, becoming the first spacecraft to orbit an outer solar system body.
On January 15, 2005, the Huygens probe descended on Titan, making most of its calculations and observations during the atmospheric entry. Huygens’ experiments provided substantial evidence for presence of liquid methane lakes on the surface. Huygens imaged Titan’s surface for the first time and the results were amazing. It worked for about an hour after landing until its batteries died off.
During the 13 years that followed, Cassini performed 295 orbits of Saturn and 162 targeted fly-bys of its moons, taking a total of 452,000 images! The most beautiful of these was of the Enceladus fly by, when Cassini captured the jet sprays of the moon into the atmosphere. Cassini imaged Enceladus and the results suggested the presence of a huge subsurface ocean, making it one of the most exciting science destinations in our solar system.
After two mission extensions, one of 2 years and the other of 7 years, Cassini was running low on its Plutonium nuclear fuel. To protect the potential life harbouring moons of the planet from contamination, NASA planned for a spectacular end to the mission, and named it the “GRAND FINALE”. Starting from 26 April, 2017, Cassini executed a series of 22 dives in the space between Saturn and its rings, braving through the unexplored region, collected a set of most detailed data and images of Saturn’s rings.
On the final orbit Cassini plunged into Saturn’s atmosphere, keeping its antenna pointed towards Earth, sending in last bits of information about the planet, transmitting its farewell.
After 13 years of travel and science, studying the huge planet, Cassini ended its mission on September 15, 2017. We bid farewell to the traveller from Earth, as Cassini became a part of Saturn itself, evaporating in its skies.
Data transmitted by Cassini will be studies for decades to come. Cassini, for sure, won’t remain as the only Saturn orbiter, but its contribution to mankind will be remembered for millennia to come.
Sai Sandeep Kumar
Second Year B.Tech