{"id":13479,"date":"2021-07-23T11:21:44","date_gmt":"2021-07-23T10:21:44","guid":{"rendered":"https:\/\/www.innovationnewsnetwork.com\/?p=13479"},"modified":"2021-07-23T11:21:44","modified_gmt":"2021-07-23T10:21:44","slug":"an-up-close-and-personal-insight-to-the-rings-of-saturn","status":"publish","type":"post","link":"https:\/\/www.innovationnewsnetwork.com\/an-up-close-and-personal-insight-to-the-rings-of-saturn\/13479\/","title":{"rendered":"An up close and personal insight to the rings of Saturn"},"content":{"rendered":"
Dr Larry Esposito from the Laboratory for Atmospheric and Space Physics at the University of Colorado, Boulder discusses Saturn\u2019s rings \u2013 from Cassini discoveries to future exploration<\/h2>\n
One of the most enduring symbols of space exploration is a planet surrounded by a ring. This symbol inspires a celestial context: nothing on Earth is like it. Earth once possessed a ring of debris that coalesced to form our own Moon. It is likely that planets around other stars also have rings. I have had the good fortune to be an investigator on the space missions Pioneer Saturn, Voyager, and Cassini that each visited the planet Saturn and studied its ring system and associated moons. It has been a wonderful surprise that Saturn\u2019s rings are just as beautiful and scientifically compelling seen close up. Furthermore, Saturn\u2019s ring system is not just an object of beauty, but a complicated physical system that provides a local laboratory and analogy for other flat cosmic systems like spiral galaxies and planet-forming disks.<\/p>\n
It is now known that planetary rings, once thought unique to the planet Saturn, exist around all the giant planets. These rings are not solid objects but are composed of countless particles with sizes ranging from specks of dust to small moons. For each planet, the rings are quite different. Jupiter\u2019s ring is thin and composed of small, dust-like particles. Saturn\u2019s rings are broad, bright, and opaque. Uranus has narrow, dark rings among broad lanes of dust that are invisible from Earth. Neptune\u2019s rings include incomplete arcs restricted to a small range of their circumference. All rings lie predominantly within their planet\u2019s Roche limit, where tidal forces would destroy a self-gravitating fluid body.<\/p>\n
The common occurrence of ring material around the planets is one of the major scientific findings of the last 40 years. The new ring systems were discovered by both spacecraft and ground-based observers, often surprising by contradicting our expectations. The rings\u2019 appearance and composition differ among the various planets, and likewise within each ring system. Most of the ringed planets have dim and relatively small ring systems. The brightest and broadest set of rings with the most active processes is found around the planet Saturn, which was scrutinised by the U.S.\/European Cassini space mission from 2004 to 2017 (see Fig. 1).<\/p>\n
The particles in Saturn\u2019s rings come in a broad range of sizes. Their size distribution extends from submicron dust to meter-sized particles to small embedded moons 100\u20131,000m in radius. The largest may be like Saturn\u2019s moons Pan and Daphnis, about 10km in radius.<\/p>\n
What are the ring particles made of? Measurements all imply that the particles of Saturn\u2019s rings are almost entirely water ice. They are bright, like the surfaces of Saturn\u2019s inner satellites. Their colour and spectral variations indicate compositional differences between different parts of the rings. Some of these differences may be primordial; others arrive from interactions with the environment, including meteoroid bombardment.<\/p>\n
We astronomers have a first-order understanding of the dynamics and key processes in Saturn\u2019s rings, much of it based on previous work in galactic and stellar dynamics. Unfortunately, the models are often idealised and cannot yet predict many phenomena in the detail observed by spacecraft. The latest Cassini data show spectacularly that the rings do not behave like a simple fluid. Many puzzles of the ring dynamics are still unsolved after three decades of study!<\/p>\n
Saturn\u2019s rings show many youthful features: these icy rings are bright and appear relatively undarkened by continually infalling meteoritic dust. In addition, the small moons discovered by Voyager could not themselves have survived the flux of interplanetary meteoroids for the age of the Solar System. In much less time, these small moons would be shattered by an impacting object.<\/p>\n
This realisation provides a potential solution to the problem of young rings. These impacts not only destroy the moons, but they can also recreate the ring systems. The new rings would gradually spread and eventually be ground to dust. Shattered moons can re-form to provide material for future rings. Moons can naturally form as the rings spread away from Saturn. Data from Cassini\u2019s observations indicate the moons not only sculpt the rings\u2019 structure; they also provide the reservoirs for past and future ring systems and possibly trigger new structures forming now. Thus, the rings may provide the material creating past and future moons.<\/p>\n
This unexpected range of phenomena seen in Saturn\u2019s rings gives some insight into the processes in other flattened astrophysical systems. The processes now observed in planetary ring systems parallel those that occurred at the time of the origin of the planets. Clearly, Saturn\u2019s rings are not now accreting to form planets, as the original planetesimals did in the birth of our Solar System. However, many processes are occurring now in rings that resemble those that occurred in the original solar nebula, particularly interactions between the disk and embedded protoplanets. Models that explain the present processes in rings can be compared in detail to Saturn ring observations, allowing testing and refinement that is no longer possible for the early Solar System.<\/p>\n
In 2009, the Cassini space mission observed the Sun setting on the rings, which occurs every 15 years, at the time of Saturn\u2019s equinox. This unique viewing perspective allowed structures never before viewed to be seen briefly (see Fig. 2).<\/p>\n