NASA’s Cassini probe gazes across the icy rings of Saturn toward the icy moon Tethys, whose night side is illuminated by Saturnshine, or sunlight reflected by the planet.
What the final days of Cassini will look like:
This includes making a detailed map of the gravity field in which the contributions from the huge world and the rings can be teased apart.Cassini is essentially trying to weigh the rings. Their mass says something about their age.The more massive they are, the older they are likely to be. Some scientists think they could even have formed with Saturn itself 4.6 billion years ago. They would certainly need a large mass to withstand the forces that might erode them over time, such as collisions from tiny meteoroids. But it is looking like the opposite may actually be true - that their mass is less than previously estimated.If confirmed it points to the rings being the remnants of some object that has broken apart around Saturn in the recent past."For younger rings, it would require a comet, or a centaur (one of a group of small, icy objects), or perhaps even a moon moving too close to Saturn. Saturn's gravity would break apart that object and then the remaining bits would go on to form rings," explained Linda Spilker, Nasa's Cassini project scientist."Perhaps that's happened more than once. Maybe some of the differences we see in the rings are from different objects that were broken apart. But if the rings are less massive they won't have had the mass to survive the micro-meteoroid bombardment that we estimate to have happened since the formation of the planet."So, we're heading in the direction of the rings being perhaps 100 million years old or so, which is quite young compared to the age of the Solar System," she told BBC News.Dr Spilker did however caution that these were early days in the analysis of the new data and the uncertainties were still large.
On Sept. 2, the 21st #GrandFinale passage between Saturn and its rings was completed successfully. One more remains. go.nasa.gov/2qcf2Vx
Staggering StructurePhotojournal: PIA21627September 6, 2017This view from NASA's Cassini spacecraft shows a wave structure in Saturn's rings known as the Janus 2:1 spiral density wave. Resulting from the same process that creates spiral galaxies, spiral density waves in Saturn’s rings are much more tightly wound. In this case, every second wave crest is actually the same spiral arm which has encircled the entire planet multiple times.This is the only major density wave visible in Saturn's B ring. Most of the B ring is characterized by structures that dominate the areas where density waves might otherwise occur, but this innermost portion of the B ring is different.The radius from Saturn at which the wave originates (toward lower-right in this image) is 59,796 miles (96,233 kilometers) from the planet. At this location, ring particles orbit Saturn twice for every time the moon Janus orbits once, creating an orbital resonance. The wave propagates outward from the resonance (and away from Saturn), toward upper-left in this view. For reasons researchers do not entirely understand, damping of waves by larger ring structures is very weak at this location, so this wave is seen ringing for hundreds of bright wave crests, unlike density waves in Saturn's A ring. The image gives the illusion that the ring plane is tilted away from the camera toward upper-left, but this is not the case. Because of the mechanics of how this kind of wave propagates, the wavelength decreases with distance from the resonance. Thus, the upper-left of the image is just as close to the camera as the lower-right, while the wavelength of the density wave is simply shorter. This wave is remarkable because Janus, the moon that generates it, is in a strange orbital configuration. Janus and Epimetheus (see "Cruising Past Janus") share practically the same orbit and trade places every four years. Every time one of those orbit swaps takes place, the ring at this location responds, spawning a new crest in the wave. The distance between any pair of crests corresponds to four years’ worth of the wave propagating downstream from the resonance, which means the wave seen here encodes many decades’ worth of the orbital history of Janus and Epimetheus. According to this interpretation, the part of the wave at the very upper-left of this image corresponds to the positions of Janus and Epimetheus around the time of the Voyager flybys in 1980 and 1981, which is the time at which Janus and Epimetheus were first proven to be two distinct objects (they were first observed in 1966). Epimetheus also generates waves at this location, but they are swamped by the waves from Janus, since Janus is the larger of the two moons. This image was taken on June 4, 2017, with the Cassini spacecraft narrow-angle camera. The image was acquired on the sunlit side of the rings from a distance of 47,000 miles (76,000 kilometers) away from the area pictured. The image scale is 1,730 feet (530 meters) per pixel. The phase angle, or sun-ring-spacecraft angle, is 90 degrees.The Cassini mission is a cooperative project of NASA, ESA (the European Space Agency) and the Italian Space Agency. The Jet Propulsion Laboratory, a division of Caltech in Pasadena, manages the mission for NASA's Science Mission Directorate, Washington. The Cassini orbiter and its two onboard cameras were designed, developed and assembled at JPL. The imaging operations center is based at the Space Science Institute in Boulder, Colorado.For more information about the Cassini-Huygens mission visit https://saturn.jpl.nasa.gov and https://www.nasa.gov/cassini. The Cassini imaging team homepage is at https://ciclops.org.
Once more unto the breach… Today we make the final #GrandFinale pass between Saturn’s rings & the planet: go.nasa.gov/1Up1oba
Colorful Structure at Fine ScalesPhotojournal: PIA21628September 7, 2017These are the highest-resolution color images of any part of Saturn's rings, to date, showing a portion of the inner-central part of the planet's B Ring. The view is a mosaic of two images that show a region that lies between 61,300 and 65,600 miles (98,600 and 105,500 kilometers) from Saturn's center.The first image (Figure A, above) is a natural color composite, created using images taken with red, green and blue spectral filters. The pale tan color is generally not perceptible with the naked eye in telescope views, especially given that Saturn has a similar hue.The material responsible for bestowing this color on the rings—which are mostly water ice and would otherwise appear white—is a matter of intense debate among ring scientists that will hopefully be settled by new in-situ observations before the end of Cassini's mission.The different ringlets seen here are part of what is called the "irregular structure" of the B ring. Cassini radio occultations of the rings have shown that these features have extremely sharp boundaries on even smaller scales (radially, or along the direction outward from Saturn) than the camera can resolve here. Closer to Saturn, the irregular structures become fuzzier and more rounded, less opaque, and their color contrast diminishes.The narrow ringlets in the middle of this scene are each about 25 miles (40 kilometers) wide, and the broader bands at right are about 200 to 300 miles (300 to 500 kilometers) across. It remains unclear exactly what causes the variable brightness of these ringlets and bands—the basic brightness of the ring particles themselves, shadowing on their surfaces, their absolute abundance, and how densely the particles are packed, may all play a role.The second image (Figure B) is a color-enhanced version. Blue colors represent areas where the spectrum at visible wavelengths is less reddish (meaning the spectrum is flatter toward red wavelengths), while red colors represent areas that are spectrally redder (meaning the spectrum has a steeper spectrum toward red wavelengths). Observations from the Voyager mission and Cassini's visual and infrared mapping spectrometer previously showed these color variations at lower resolution, but it was not known that such well-defined color contrasts would be this sharply defined down to the scale (radial scale) of a couple of miles or kilometers, as seen here.Analysis of additional images from this observation, taken using infrared spectral filters sensitive to absorption of light by water ice, indicates that the areas that appear more visibly reddish in the color-enhanced version are also richer in water ice.The third image (Figure C) is a composite of the "true" and "enhanced" color images for easy comparison.This image was taken on July 6, 2017, with the Cassini spacecraft narrow-angle camera. The image was acquired on the sunlit side of the rings from a distance of 47,000 miles (76,000 kilometers) away from the area pictured. The image scale is about 2 miles (3 kilometers) per pixel. The phase angle, or sun-ring-spacecraft angle, is 90 degrees.The Cassini mission is a cooperative project of NASA, ESA (the European Space Agency) and the Italian Space Agency. The Jet Propulsion Laboratory, a division of Caltech in Pasadena, manages the mission for NASA's Science Mission Directorate, Washington. The Cassini orbiter and its two onboard cameras were designed, developed and assembled at JPL. The imaging operations center is based at the Space Science Institute in Boulder, Colorado.For more information about the Cassini-Huygens mission visit https://saturn.jpl.nasa.gov and https://www.nasa.gov/cassini. The Cassini imaging team homepage is at https://ciclops.org.CreditNASA/JPL-Caltech/Space Science Institute
The Cassini-Huygens mission is a joint endeavour of Nasa, and the European and Italian space agencies.BBC News will have live coverage of the ending of the mission on both TV and radio. Inside Science will preview the climax this Thursday at 16:30 BST on Radio 4. A Horizon documentary will also review the mission and the final hours in a special programme to be broadcast on Monday 18 September at 21:00 BST on BBC Two. And you can still watch the Sky At Night programme Cassini: The Gamechanger on the iPlayer. This is being repeated on Thursday on BBC Four at 19:30 BST.
NASA Previews Saturn Mission EndOriginal air date: Sept. 15 at 10 a.m. PT (1 p.m. ET; 17:00 UTC/GMT) A news conference held to give a detailed review of final mission activities for NASA's Cassini mission to Saturn. It included remarks from: - Jim Green, director of Planetary Science, NASA Headquarters, Washington - Earl Maize, Cassini project manager, JPL - Linda Spilker, Cassini project scientist, JPL - Hunter Waite, team lead for Cassini's Ion and Neutral Mass Spectrometer, Southwest Research Institute, San Antoniohttp://www.ustream.tv/recorded/107896690
Quote from: catdlr on 09/14/2017 04:11 amNASA Previews Saturn Mission EndOriginal air date: Sept. 15 at 10 a.m. PT (1 p.m. ET; 17:00 UTC/GMT) A news conference held to give a detailed review of final mission activities for NASA's Cassini mission to Saturn. It included remarks from: - Jim Green, director of Planetary Science, NASA Headquarters, Washington - Earl Maize, Cassini project manager, JPL - Linda Spilker, Cassini project scientist, JPL - Hunter Waite, team lead for Cassini's Ion and Neutral Mass Spectrometer, Southwest Research Institute, San Antoniohttp://www.ustream.tv/recorded/107896690I'm confused... Original air date when? two days hence, as I read this?
The Saturn System Through the Eyes of Cassini (e-Book)Downloadable electronic book showcasing the discoveries of the Cassini-Huygens mission to Saturn.September 11, 2017This free NASA e-Book celebrates Saturn as seen through the eyes of the Cassini spacecraft. The Cassini-Huygens mission has revolutionized our knowledge of the Saturn system and revealed surprising places in the solar system where life could potentially gain a foothold—bodies we call ocean worlds.Since its arrival in 2004, Cassini–Huygens has been nothing short of a discovery machine, captivating us with data and images never before obtained with such detail and clarity. Cassini taught us that Saturn is a far cry from a tranquil lone planet with delicate rings. Now, we know more about Saturn’s chaotic, active, and powerful rings, and the storms that rage beneath. Images and data from Saturn’s moons Titan and Enceladus hint at the possibility of life never before suspected. The rings of Saturn, its moons, and the planet itself offer irresistible and inexhaustible subjects for intense study. As the Cassini mission comes to a dramatic end with a fateful plunge into Saturn on Sept. 15, 2017, scientists are already dreaming of going back for further study. Over a period of 13 years, Cassini has captured about 450,000 spectacular images within the Saturn system, providing new views of the “lord of the rings” and a plethora of iconic images. To honor the art and science of Cassini, this book was developed collaboratively by a team from NASA’s Planetary Science Division (PSD), NASA’s Jet Propulsion Laboratory (JPL), and the Lunar and Planetary Institute (LPI). While these images represent the tip of the iceberg—each telling a story about Saturn and its mysterious moons—our hope is that the mission will inspire future artists and explorers. The sheer beauty of these images is surpassed only by the science and discoveries they represent.Download and read on any device:Apple DevicesAmazon Kindle DevicesOther e-ReadersFixed Layout (Printer-Friendly)This book was developed collaboratively by the National Aeronautics and Space Administration (NASA) including NASA’s Planetary Science Division (PSD), NASA’s Jet Propulsion Laboratory (JPL), and the Lunar and Planetary Institute (LPI), operated for NASA by Universities Space Research Association.CreditNASA / Jet Propulsion Laboratory - Caltech / Lunar and Planetary Institute