SATURN: THE GAS GIANTS’ OUTER PLANET

Paige Lamping, Nelly Bablumoo

Introduction

Saturn is one of the most interesting planets in the solar system, and it is most famous for its stunning array of rings. The great ball of Saturn is made up mostly of hydrogen and helium. Since Saturn shines brighter than most stars, to the naked eye it appears yellowish. We will provide an overview of Saturn, and the development of Cassini Mission. While doing so, we will be answering the question, how do we know the size, temperature, composition and distribution about Saturn’s rings and orbit from the Cassini Mission? The discoveries of Cassini Mission lead to many specific aspects of Saturn that made it one of the most extraordinary planets in the solar system; such as its size and mass materials, its rings system, and the formation of its fabricated unique features. Cassini sent numerous images and information to the astronomers back on Earth, who were able to study these images and get a better understanding of Saturn. From these images, Saturn’s equinox will be described. The features of Saturn and its rings will be further explained and what Cassini’s data led the NASA team to discover. The surprising find will improve our understanding of where planets form around a star and explore furthermore on the interesting planet of Saturn. [2]

An Overview of the Cassini Mission

The Cassini Mission was created to conduct an in-depth, up-close study of Saturn and its orbit. Cassini was launched in October 15, 1997 and was centred on Saturn. The mission finally arrived to Saturn on June 30, 2004. The instruments on board on Cassini spacecraft sent back valuable information will help scientists to get a better understanding about the mysterious and beautiful rings. The most important part of the mission after the launch was the Saturn orbit insertion. Cassini would make six targeted insertions of the four icy moons, Iapetus, Enceladus, Dione and Rhea. The spacecraft was the largest interplanetary one to date including the probe and the orbiter. Released from Cassini a Huygens (pictured to the right passing through the gap in the rings) probe which was contributed by a European Space Agency carrying eight other projects, this probe landed on Titan. It was used to measure particle temperatures, and it was also used to examine the physical properties, chemical composition and the structure of Titans atmosphere. The astronomers also used it to study clouds, winds and particles in the atmosphere. This was a way for them to explore the physical properties of Titans surface. [11]

Although the purpose of exploring space has been debated, the Cassini Mission goals were numerous and significant, objectives that have brought answers to scientists about questions long speculated on and has raised many questions for future missions to resolve. From the Cassini Mission, scientists only begin to find answers such as where the rings come from, and the source of Titan’s abundant supply of methane. [9]

Communication between Cassini and Earth happened through an antenna subsystem, and one high-gain antenna which the function of this antenna was to support the communication, but also to conduct some scientific experiments. And two low-gain antennas were used for emergency communication if high-gain was unavailable. Cassini instruments included the Cassini Plasma Spectrometer, which was a direct sensing instrument that measured energy. A Composite Infrared Spectrometer which was a remote sensing instrument that measured infrared waves coming from any objects in order to read their temperatures. A Cosmic Dust Analyzer which measured speed, size and direction of tiny dust grains by Saturn. An Imaging Science Subsystem, which captured images of visible light and infrared and ultraviolet images. Also, an Ion Neutral Mass Spectrometer that analyzed small charged particles. And a Dual Technique Magnetometer was used to measure the strength and direction of magnetic field that surrounds Saturn. [5]

One of the differences between Saturn and Earth is Saturn’s thunderstorm patterns. Scientists found that the energy output from Saturn differs in each hemisphere, with the southern portion radiating about 17% more than the northern. One is cloud cover, which has fluctuated greatly, and the window of this energy change. It does match with the changes in the seasons as well. But when compared to Voyager 1 data from the 80s, the energy change was far greater than then, possibly hinting at a positional variance or even a solar radiance change on Saturn’s cloud cover. [10] Of course, Cassini hasn’t just examined Saturn alone. The many wonderful moons of the gas giant were also examined in earnest and one in particular especially: Titan. As the final orbits came to an end, more data was gathered. Cassini got extremely close to Saturn and on August 13, 2017 it made its closest approach at the time at 1,000 miles above the atmosphere. [2]

Outline of the seven different rings (A-G):

In this section, there will be a brief overview of the rings and their order, including a diagram labelling each of the rings. They are named alphabetically in order of discovery. From innermost to outermost: D, C, B, A, F, G and E. D is way less dense compared to the rest of the rings and appears fainter.

The rings were first seen by Galileo in 1610 through a telescope. The bright globe of Saturn surrounded by rings which may be composed of ice.  Three of these rings are visible from the Earth using a telescope.  Photographs sent back from the Voyager in the 1980s were able to identify further narrower rings “ringlets” in between the three main rings.  The main rings are labelled A, B and C, with A the outermost ring.[13]

Saturn’s moons:

In this section the moons Enceladus, Titan, Prometheus, Pan and newly discovered by Cassini, Daphnis will be discussed. Saturn has 62 discovered moons, and 53 of them are named. While exploring the surrounding of Saturn, Cassini uncovered two new moons orbiting Saturn, Methane and Polydeuces. One thing that Cassini found was about one of the many moons, Enceladus which was found to provide a large amount of the material for the E-ring because of the jets of liquid water erupting from its frozen exterior, which is thought to have a big reservoir of water beneath its surface that could in theory be a harbour for life. Cassini also discovered a global ocean with indications of hydrothermal activity within Enceladus. [6]

A discovery made about Saturn’s largest moon Titan was that it was found to be an astonishing floating rock in space, due to its methane clouds and methane rain that creates a surface filled with rivers and lakes. On April 22, 2017 Cassini did a final flyby of Titan where it began 22 dives between the planet and the rings, exploring a dangerous zone for the spacecraft, where it was possible for Cassini to be struck and destroyed by passing rocks or particles. Cassini flew between the outer part of the atmosphere and the inner zone of the rings, risking hitting particles or gas molecules, including a giant liquid methane lake. During this flyby interesting data was discovered about Titan’s organic chemistry, which was shown to be similar to the chemistry that was present on Earth before life began. The features of Titan are still not completely understood, but some features, such as the landscape are theorized as large upwellings of nitrogen bubbles. [14]

Saturn’s Rings:

Here we will discuss what was previously known about their origin and what Cassini discovered about them. The rings are made mostly of billions of water ice chunks varying in size and most are around 30 feet thick, but it is unclear exactly how they were created. To get a better understanding of the size and distribution of the rings, Cassini observed the way the light of distant stars changed when passing through the rings. Which lead to the discoveries of propellers, the material that makes up Saturn’s E ring comes from the moon Enceladus, and that the ring particles ring particles closest to Saturn move faster than the ring particles farther away from Saturn. [8]

Images from Cassini revealed that Saturn’s rings contain millions of what the NASA team call “moonlets” that are orbiting the rings. The images revealed that these moonlets were ranged in size from the size of a house to a kilometre wide. Also shown in the images were “propeller” like structures in the rings that imply a group of small moons hidden within the rings.  These propellers are gaps in the material that have a length of thousands of miles, thought to be created by the moonlets. A grainy structure that astronomers referred to as straw could also be seen from the images sent by Cassini, which were thought to be constructed temporarily by the clumping together of material, but the reason for this is still not completely understood.

While exploring the rings of Saturn, Cassini observed evidence of meteors and small bodies colliding into the rings. The countless tiny particles of rock and ice that make up the rings are continually being struck by other space particles. The observations it made included some of Saturn’s moons stealing ring particles and other moons contributing particles to the rings. Cassini’s data is consistent with the previous theory that the rings have a relatively young age due to still being bright in appearance. In relation to the rings Cassini did many things including creating maps of Saturn’s gravity and magnetic fields, estimating the amount of material in the rings, taking high-resolution pictures of the planet and its rings, and capturing images of the planet showing intense hurricanes that encircled the planet and the rings. From Nov. 30, 2016 – April 22, 2017: every week during this period Cassini made loops around Saturn’s poles getting a better look at the outer edges of the rings. Cassini also discovered that there seems to be way less dust going into Saturn’s system than initially expected. Meaning the rings could possibly be ancient and bright. Also shown was ring matter that clumped together into snowballs, which were then cleared by tiny moonlets that left propeller-shaped gaps in the rings thousands of kilometres long. Another discovery was of a large ring, 8 million miles away from Saturn, most likely made up of debris from Phoebe.[12]

Equinox:

Similar to Earth, Saturn has an axis of rotation that is tilted. This causes the planet to be tilted toward the sun for half the year, illuminating the top of the rings. For the other half of the year, Saturn is tilted the other way, causing the south pole and the bottom of the rings to be illuminated instead. Although, for two short spans of times in Saturn’s orbits around the sun, the edges of the rings point directly at the sun. During this brief period of time, the north and south poles of Saturn receive the same amount of sunlight. This occurrence, called an equinox occurs only once every 15 years. Saturn’s equinox creates shadows that caused misconception that the rings may be warped. At this angle, Cassini made it possible to see clouds of dust, called ejecta strutting up from the rings. Cassini’s NASA team was able to carefully study these clouds of dust and were able to determine that the ejecta clouds consisted of streams of meteoroids that were plummeting through the rings plane. This stream of meteoroids launches pieces of dust out of their normal orbit and pushed to create a new one. The dust will eventually settle and return to its normal orbit. This discovery will be impactful because scientists will be able to directly measure the abundance of different sized objects flying around the solar system. Saturn acts as a detector, making these measurements possible.[17]

Another discovery made while observing the equinoxes shown by Cassini was the temperature of the rings using an infrared spectrometer, which helped get a better overall understanding of all aspects of Saturn. The reason for this was because the sunlight that was hitting the rings struck the rings on their edge rather than on their flat surface. In addition, Cassini used the equinoxes to examine the poorly unknown phenomena of Saturn’s “spokes.” The name comes from their finger-like radial features in the rings that spin along with the rings, similar to the spokes in a wheel. With a length of more than 10,000 miles, these unfamiliar phenomena are thought to be composed of small ice particles that lift above the surface of the rings by an electrostatic charge.[16]

Conclusion

The Cassini probe explored many of Saturn’s characteristics from its icy rings to the magnetic field, which is a very ambitious mission. The mission also entails the first descent of a probe to a moon of another planet – the most distant landing ever attempted on another object in the solar system. These discoveries and close-ups of the exquisite characteristics of Saturn are what make this planet the most interesting and amazing of the solar system.[15]

What we gained from this project is that, we now have the knowledge of how these missions work, and what/how Saturn function/made up of. We learned about how certain parts of the spacecraft work together. All in all, we earned a lot about space/planets/space-crafts and how they work and operate in discovering/exploring the space and Saturn.

 

Works Cited

1. NASA’s Jet Propulsion Laboratory and Goddard Space Flight Center, Davis, Philips. “Science:Rings.” Cassini Science Communications Team. Retrieved from: https://saturn.jpl.nasa.gov/science/rings/
2. NASA’s Jet Propulsion Laboratory and Goddard Space Flight Center, Davis, Philips. “Solar System Overview.” Retrieved from: https://solarsystem.nasa.gov/planets/saturn/overview/
3. The Conversation. “The beauty and mystery of Saturn’s rings revealed by the Cassini mission.” Academic Journalism Society. Retrieved from: https://theconversation.com/the-beauty-and-mystery-of-saturns-rings-revealed-by-the-cassini-mission-83492
4. NASA’s Jet Propulsion Laboratory and Goddard Space Flight Center, Davis, Philips. “In Depth: Cassini.” Retrieved from: https://solarsystem.nasa.gov/missions/cassini/in-depth/
5. National Aeronautics and Space Administration. “Cassini — The Grand Finale.” Jet Propulsion Laboratory California Institute of Technology. Retrieved from:https://saturn.jpl.nasa.gov/legacy/files/Cassini_Grand_Finale_Fact_Sheet_508.pdf
6. NASA’s Jet Propulsion Laboratory and Goddard Space Flight Center, Davis, Philips. “
7. About the Mission – End of Mission Completed.” Cassini Science Communications Team. Retrieved from: https://saturn.jpl.nasa.gov/mission/about-the-mission/summary/
8. Howell Elizabeth, Space.com Contributor. “Cassini-Huygens: Exploring Saturn’s System.” September 15, 2017. Retrieved from: https://www.space.com/17754-cassini-huygens.html

12. “About Cassini-Huygens.” Retrieved from: http://m.esa.int/Our_Activities/Space_Science/Cassini-Huygens/Cassini_spacecraft
13. “About Cassini-Huygens: The Mission – Mission objectives.” Retrieved from: https://m.esa.int/Our_Activities/Space_Science/Cassini-Huygens/The_mission
14. Guardian News and Media Limited or its affiliated companies. “Saturn: What did the Cassini mission tell us about Saturn and its moons?” Retrieved from: https://www.theguardian.com/science/2017/sep/15/what-did-the-cassini-mission-tell-us-about-saturn-and-its-moons
15. Cassini Imaging Central Lab. “Icy tendrils reaching into Saturn ring traced to their source.” Astronomy.com. Kalmbach Publishing Co., 20 Apr. 2015. Retrieved from: http://www.astronomy.com/news/2015/04/icy-tendrils-reaching-into-saturn-ring-traced-to-their-source
16. Douthitt, Bill. “Beautiful Stranger.” National Geographic Dec. 2006: 50. Retrieved from:https://owlcation.com/stem/What-is-the-Cassini-Huygens-Probe
17. Goddard Space Flight Center. “Cassini Reveals Saturn is on a Cosmic Dimmer Switch.” Astronomy.com. Kalmbach Publishing Co., 11 Nov. 2010. Retrieved from: http://www.astronomy.com/news/2010/11/saturn-energy-emission
18. Guterl, Fred. “Saturn Spectacular.” Discover Aug. 2004: 36-43. Print.
19. Haynes, Korey. “Saturnian Storms Explained.” Astronomy Aug. 2015: 12. Print. JPL. “At Saturn, One of These Rings Is Not Like the Others.” Astronomy.com. Kalmbach Publishing Co., 2015. Retrieved from: https://owlcation.com/stem/What-is-the-Cassini-Huygens-Probe
20. Miriam Kramer, Space.com Staff Writer “Saturn’s Rings Bombarded by Space Rocks” https://www.space.com/20824-saturn-rings-impacts-dust-clouds.html
21. Mike Wall, Space.com Senior Writer, Cassini Snaps Dazzling Photo of a ‘Ring-Bow’ in Saturn’s Rings. https://www.space.com/37623-saturn-rings-photo-nasa-cassini.html