Back in 1997, the National Aeronautics and Space Administration -- in partnership with the European Space Agency -- had launched their most ambitious project yet: the Cassini-Huygens spacecraft designed to reach Saturn and its moons and bring back data that will transform humanity's understanding of the gas giant and its system. Needless to say, Cassini was successful in achieving its goals plus discovering new things about the planet and its system ever since it reached the territory in 2004. Cassini made a lot of discoveries regarding Saturn's famous rings and through the spacecraft, we now know that the planet is actually 72 thousand miles in diameter and has a density lower than water. Through Cassini, we now know that the rings of Saturn are relatively young and consist of bits of water, ice, and small and gigantic grains of sand.
The Cassini mission has come to an end in 2017 after 13 years of service. Engineers behind the spacecraft decided it is best for Cassini to undergo an intentional death dive to avoid the contamination of Saturn's nearby moons which they found out contains water. Nowadays, researchers are occupied with analyzing the final data sent back by the Cassini spacecraft.
Before coming to the end of its life, Cassini was placed in a position between Saturn and its rings which allowed it to be closer to Saturn than previous flybys. Because of this, scientists were able to obtain unprecedented resolution images of the ultraviolet auroras present on the planet. The observations, which are published in Geophysical Research Letters, described how Saturn's auroras are created through interactions of the solar wind with a stream of energetic particles from the Sun and Saturn's quick-rotating magnetic field. Kind of auroras here in on Earth, Saturns ultraviolet auroras are located on Saturn's polar regions. However, unlike Earth's auroras, Saturn's ultraviolet auroras are known to be highly dynamic and known to be pulsating and flashing depending on the dynamic processes that occur in the plasma environment of the planet.
Alexander Bader, a Ph.D. student at Lancaster University and the lead author of the research explains that a lot of questions regarding Saturn's auroras are still unanswered even after the successful Cassini mission. According to him, the last set of close-up images from Cassini was able to provide highly detailed views of small-scale structures. These structures are previously undiscernable by the spacecraft. "We have some ideas about their origins but it still needs a lot of analysis."
Bader says that satellite imagery is not enough to find answers regarding these mysterious ultraviolet auroras as the origins of the energetic particles that cause these light shows are far away from the planet's surface. The first analysis of the particle measurements done by Cassini shows that like the auroras in the neighboring Jupiter, Saturn's ultraviolet auroras are generated by a lot of energetic particles (much more than Earth's) although the physical mechanisms between the auroras of Saturn, Jupiter, and Earth are quite similar.
Three years after the Cassini mission ended and it is still able to make scientists baffled with its discoveries. The researchers are optimistic that even though they do not understand the data available yet, it will soon be helpful in understanding the gas giant and its auroras and it will be more promising combined with the observations of the Juno spacecraft in the magnetosphere of Jupiter.
