Note: Some of the statements are left as is from the original article because there was no better way I could rewrite them. All the information are from one source only - NASA. ************************************************************************** Picture courtesy: NASA The jewel of our Solar System, Saturn is the sixth planet, located at a distance of 1.4 billion km from the Sun (9.5AU), and the second largest in the Solar system. The farthest planet that can be observed without the aid of a telescope, the planet is so far away it takes 1 hour and 19 seconds for sunlight to reach it. Saturn spins at a dizzying 10.7 hours per rotation, though a bit slower than Jupiter and takes 29 Earth years to complete one orbit around the Sun. With its axis tilted at 26.73 degrees, Saturn experiences seasons like we do on Earth, though each season lasts 7 years. Nine Earths side by side would almost span Saturn’s diameter. That doesn’t include Saturn’s rings. STRUCTURE Saturn is made up of mostly hydrogen and helium. Scientists believe that center is a core of rock, and metal enveloped by liquid metallic hydrogen, which is enveloped again by liquid hydrogen. Picture courtesy: space.com Did you know that Saturn is less dense than water? If there was a pool of water large enough to hold Saturn, the planet will float!! Saturn was spotted as early as 700BC. Galileo Galilei first observed the planet’s rings but they looked like handles to him and so thought it was a triple planet system. In 1655, Christian Huygens discovered that the “handles” spotted by Galileo were actually a ring system and also discovers Saturn’s largest moon, Titan. SPACECRAFT CASSINI Pioneer 11 and Voyagers 1 and 2 conducted flybys decades earlier, taking pictures, measurements and observations as they zoomed past. These missions shed new light on Saturn’s complicated ring system, discovered new moons and made the first measurements of Saturn’s magnetosphere. But these quick encounters didn’t allow time for more extensive scientific research. The Titan IVB/Centaur rocket lifted off from Cape Canaveral, Florida, on October 15 1997 at 4:43 am carrying the Cassini orbiter and its attached probe Huygens. It took Cassini seven years to reach Saturn. Cassini orbited Saturn 294 times from 2004 to 2017. THE ROYAL CROWN When we mention “Saturn” the first image that comes to mind is its stunning massive ring system. However, there is another feature unique to Saturn. It is the spectacular jet stream at its North Pole called the “Hexagon”. While the “Hexagon” was first discovered by the spacecraft Voyager, Cassini imaged it much thoroughly from up close and front. The spacecraft first studied the feature when it was in the shadow (northern winter). It detected heat coming from within the planet. When Cassini imaged the hexagon in spring it revealed a stunningly symmetric shape, 30K km across with winds about 300 km/hour On Earth, mountain ranges and other features of the planet’s surface cause jet streams to bend and kink. On Saturn there are no such obstacles to hinder or redirect; hence the jet streams keeps flowing, orderly and hexagonal. Though scientists have created the hexagonal flow in labs, they still are not sure what drives the hexagon shape. Why not five or seven sided and why this feature is not found in the Southern Pole are questions remaining for future scientists to solve. Picture courtesy. jpl.nasa.com NORTH POLAR STORMS Cassini also observed Saturn’s North Polar storm and these were some of the observations that it recorded: The storm’s eye is 50 times wider than that of a hurricane on Earth. It is to be noted that what that these storms on Saturn’s are polar vortexes and not “hurricanes” in the true sense, because they are not caused by warm ocean waters as on Earth. They are “hurricane-like”. Picture courtesy: nasa.gov. At first Cassini sensed lightning in the form of radio waves and later in 2009 captured images of Saturn lightning with its cameras. Cassini imaged lightning on Saturn’s night side and day side, both of which had never been done before SEVEN-YEAR SEASONS AND THE MEGA STORM Just the way we on Earth experience annual weather patterns, so does Saturn. The only difference is that one year on Saturn is 29 Earth years, every 28-30 Earth years a mega storm appears on Saturn. Cassini was fortunate that Saturn’s storm arrived 10 Earth years earlier. The spacecraft could observe the storm which is also known as the “Great White Spot”. The storm was so huge it wrapped all around Saturn and spanned 300,000 km. An interesting fact is that these “Great White Spots” are always located at Saturn’s North Pole or at its equator. So far they have not been observed at Saturn’s South Pole. Why, no knows for sure yet. That’s one another thing for future scientists to solve. Scientists who analyzed data from Cassini noted that this storm is made up water and other materials from as deep as 100 kilometers that rise up to the top. The vapor freezes as it reaches the top and gives off the white color. Picture courtesy: jpl.nasa.gov. contd...
THE RING SYSTEM. We all know that the very mention of Saturn conjures images of a planet with its ring. Despite Saturn being twice as far from us as Jupiter is, the rings are so bright and so expansive that Galileo Galilei discovered the rings the same year he discovered Jupiter’s moons, in 1610. Here are few information that Cassini sent down to us after studying the size, composition, distribution, and temperature of this most magnificent and beautiful phenomenon for about ten years. The Ring system is actually seven rings with several gaps and divisions between them. They are named by the alphabets in the order they were discovered. Picture courtesy: space.com The rings are named starting from the closest to the planet - D ring, C ring, B ring, Cassini Division, A ring, F ring, G ring, and finally, the outermost E ring. The system extends up to 282,000 kilometers from the planet, and an average thickness of 10 meters. The rings are relatively close to each other, with the exception of a gap measuring 2,920 miles (4,700 kilometers) wide called the Cassini Division that separates Rings A and B. The rings are made up of billions of small chunks of ice and rock coated with another material such as dust. The ring particles mostly range from tiny, dust-sized icy grains to as large as mountains. Each ring orbits at a different speed around the planet. Some of Saturn’s moons steal ring particles, and other moons contribute particles to the rings. Water jets from the moon Enceladus, which is venting icy particles and gas into space as it orbits Saturn, provides much of the material in Saturn’s E-ring. Picture courtesy: nasa.gov Most of Saturn’s inner moons orbit within rings (some partial and some complete) made of particles blasted off the moons’ own surfaces by micrometeoroid impacts. Propellors Cassini also discovered features that look like propellers, which are sometimes several thousand miles (kilometers) long. The propellers are produced by the gravitational influence of moonlets, lumps of ring material that are estimated to be half a mile (around 1 kilometer) in diameter, which is smaller than a moon but larger than individual ring particles. Picture courtesy: jpl.nasa.gov More Propellors Image courtesy: jpl.nasa.gov Cassini studied features in Saturn’s rings called “spokes,” which can be longer than the diameter of Earth. Scientists think they’re made of tiny icy particles that are lifted by an electrostatic charge and only last a few hours. Twice every 29 and a half years the great planet Saturn appears ring-less. This is an optical illusion: Earthlings cannot see Saturn's rings when the rings are edge-on as viewed from the Earth. They are barely visible through powerful telescopes. MOONS Saturn has 53 confirmed moons and nine provisional moons. Each moon is fascinating in its own right. · Saturn’s moons contribute material to Saturn’s rings and magnetosphere, but the moons also collect material from Saturn’s rings and magnetosphere. · Saturn’s moons range in size from smaller than a football stadium to larger than the planet Mercury, and they vary in color, texture and composition. · While the larger moons are spherical, others are shaped like a sweet potato (Prometheus), a regular potato (Pandora), a meatball (Janus), and even a sponge (Hyperion). Some have a gnarled, irregular shape and texture like a dirty ice-ball (Epimetheus). One object observed in the rings (and unofficially called Peggy) may be a moon forming or disintegrating, or it might not truly be a moon at all. Titan Picture courtesy: nasa.gov · Before 2004, we knew very little about Titan other than its size and that it had a dense, nitrogen-rich atmosphere. · Rippling sand dunes, like those in Earth's Arabian Desert, can be seen in the dark equatorial regions of Titan · Data from Cassini-Huygens revealed Titan has lakes and seas of liquid methane and ethane, replenished by rain from hydrocarbon clouds. · Scientists are researching if these materials could coalesce to form cell membranes which could lead to the possibility of presence of life. · The mission also provided evidence that Titan is hiding an internal, liquid ocean beneath its surface, likely composed of water and ammonia. contd...
Encledaus Picture courtesy: nasa.gov Saturn’s moon Encledaus is the most scientifically interesting destination in the Solar System. This moon is small enough to fit within the United Kingdom. Cassini discovered that this small icy body is a very active moon that hides an ocean of liquid salty water beneath its crust. This salty water, along with other chemicals is continuously spewed out into the space from different parts of the moon in geyser-like jets. picture courtesy: jpl.nasa.gov Above is a Cassini image of Saturn's moon Enceladus backlit by the sun show the fountain-like sources of the fine spray of material that towers over the south polar region. This material gushes at 400 meters per second and forms a plume that extends hundreds of miles into space. Some of the material falls back onto Enceladus, and some escapes to form Saturn’s vast E ring. Cassini noted that the E-ring consisted not only of the icy particles but also some peculiar nano-grains that could only be generated at above 90 degree Celsius. This means that there is possibility of Earth like hydrothermal vents deep within the oceans of this moon. Scientists believe that its subsurface ocean has all the ingredients for life – liquid water, heat, and food (methane). MAGNETOSPHERE This tan colored planet has a very powerful magnetic field also; about 578 times powerful than Earth’s though this is smaller than that of Jupiter. The planet, its rings, and most of its moons lie within its magnetic field. Material blasted into space by Enceladus feeds Saturn’s giant E ring and is a major source of material (plasma) fueling Saturn’s magnetosphere. Saturn's magnetic field has north and south poles, and its magnetic field is almost perfectly aligned with the planet's rotation. In addition to their magnetic effects, magnetosphere produce radio waves. Saturn's magnetic field is far weaker than Jupiter's, and its radio signals are not powerful enough to be detected from Earth. Information courtesy: saturn.jpl.nasa.gov/science/saturn/
For fellow space buffs this is the last complete picture mosaic of Saturn captured by Cassini. Almost doesn't seem real. To think that this image exists and that I am fortunate enough to see it makes me realize how fortunate we are to live in such a time. Cassini's final moments were broadcast live on Science Channel. It is emotional viewing and definitely worth watching, especially for the people who dedicated decades of their lives to this spacecraft. Cassini’s Finale | Watch Full Episodes & More! - Science
