A journey of nearly two decades and almost 5 billion miles will come to a dramatic end next Friday. Cold, alone, and very far from home, the Cassini orbiter will take a long last look at the pale blue dot whence it sprang and finish its 294th and final orbit of Saturn by nosing over and dropping through the gas giant’s atmosphere in one final, fatal contribution to mankind’s understanding of the planetary system in which we live.
As part of the Cassini-Huygens mission conducted jointly by NASA, the European Space Agency (ESA), and the Italian Space Agency (ASI), the Cassini orbiter made several groundbreaking discoveries since its mission began when it left Earth atop a Titan IV rocket on October 15, 1997. Following are five of the craft’s more notable findings.
Second Look at Six-Sided Storm
Though first discovered by Voyager in 1981, the hexagonal cloud pattern at Saturn’s north pole was studied in greater detail by Cassini. Over the course of its observation, the hexagon changed color, going from a sea green to a golden brown. The craft also took thermal infrared images and video of the hexagon.
Though no definitive answers have been established for why the strange cloud formation exists and persists, Cassini gathered a significant quantity of invaluable data on the oddity, possibly paving the way for future scientists to discover an explanation for the phenomenon.
Up Close and Personal with Saturn’s Rings
Saturn has been famous for its rings since Galileo first observed them in 1610 and has drawn the attention of astronomers in the centuries since. However, the complex structure of the rings makes up-close observations of them critical for learning more about them. In the spring of 2005, Cassini began an experiment to measure the size distribution of the rings’ particles by passing radio waves through the rings and measuring the nature and degree of distortion the particles cause.
In addition to experiments using radio waves, Cassini took hundreds of the most detailed photos of Saturn’s rings ever produced, leading to the discovery of previously-unknown ringlets.
Microbial Life on Enceladus?
Cassini made several passes near Saturn’s moon, Enceladus, and gathered a great deal of data that rocketed the moon to the top of the list of possible life-bearing celestial bodies. In its first passes in 2005, the craft detected anomalies in Enceladus’ magnetic field that strongly suggested the presence of an atmosphere, and discerned via other measurements that the atmosphere consisted mostly of ionized water. The probe also identified ice geysers on the moon’s south pole.
Nine years later, the probe found even more water on the planet, detecting a significant salty ocean beneath its surface that likely covered the entire body beneath its rocky crust. With this discovery, scientists declared that the distant moon is one of the most likely places in the entire solar system to find microbial life other than Earth.
Seven New Moons
Fourteen significant bodies were discovered circling Saturn by Earth-based observation since Christiaan Huygens discovered Titan with a homemade telescope in 1655. Voyager discovered another five when it flew by in 1980 and 1981, but Cassini raised the bar by detecting another seven distinct orbiting bodies between 2004 and 2009. Ranging in diameter from 300 m to 7.6 km, the Cassini mission discovered the following moons:
Einstein’s Relativity Model Tested
According to Albert Einstein’s general theory of relativity, massive objects, like the sun, affect space-time in unique ways, including by causing it to curve in significant and measurable ways. Among the methods for measuring such distortion is by beaming electromagnetic radiation near the object and observing how far the beam travels. Previous tests conducted by the Viking and Voyager crafts using radio waves supported Einstein’s theory by producing a measurable frequency shift between Earth and the probes as they passed by the sun. However, the calculations are now far more accurate thanks to experiments conducted by Cassini, improving accuracy from one part in 1,000 to one part in 51,000.
[Featured Image by NASA/JPL-Caltech/SSI via Getty Images]