Saturn's Perfect Storms Date Saturday, October 09 @ 13:33:11 Topic Life and Giant Planets To see a hurricane grow on Earth, one's best view is from orbit. But on the windiest planet in the solar system, Saturnian clouds can gather to sizes greater than our tiny blue planet. Saturn's Perfect Storms by Astrobiology Magazine staffwriter Hurricanes are examples of planet-scale storms best seen from orbit Credit: NOAA Saturn is the windiest planet in the solar system, which is one mystery of the ringed giant. Imagine not what qualifies as a terrestrial hurricane with category five status assigned beyond one hundred miles-per-hour. On Saturn the superstorms can produce a thousand mph wind. The close-up banner view shows lots of atmospheric detail, including a dark storm and wisps of clouds. The dark spot is noticeably lighter around its perimeter than in its interior. Saturn storms brew in both the northern and southern hemispheres but take on their highest winds at the equator. The hurricanes on Saturn can begin with cloud masses nearly the size of the entire Earth. As the storms grow, it is not unusual for a single storm to grow to engulf the equivalent of thirty Earths. Storms at Saturn's equator move eastward at speeds up to 450 meters per second (1000 mph), which is about 10 times the speed of the Earth's jet streams and approximately three times greater than the equatorial winds on Jupiter. Saturn's rings are just one of the unique attractions, including moons and storms. Credit: NASA/JPL The image was taken with the Cassini spacecraft narrow angle camera on Sept. 10, 2004, at a distance of 8.8 million kilometers (5.5 million miles) from Saturn, through a filter sensitive to wavelengths of infrared light centered at 750 nanometers. The image scale is 52 kilometers (32 miles) per pixel. The image has been contrast enhanced to improve visibility of features in the atmosphere. The right images show an unscaled comparison to a terrestrial hurricane (Frances) which depend on water temperature differences rather than upper atmospheric swirling winds on Saturn. When Earth storms hit land they begin to dissipate, but on Saturn a storm can circumnavigate the entire planet. During the thirty-year Saturnian summers, heated gases rise on the sunward facing hemisphere. These warmer layers eventually become unstable at higher altitudes and ammonia rich clouds eventually produce ice-crystals. Cassini's big adventure with Saturn's moon begins in earnest at the beginning of 2005, when the Huygens probe begins to descend to the surface of the largest moon Titan. European and American scientists hope to use Huygens to get a close-up view of what might provide analogies to what a very primordial Earth might have looked like, if it never progressed beyond an ice age. Just as Saturn seems like a miniature of our larger solar system, so too may its moons give a glimpse of what might have cooked up closer to the Sun than Saturn. -------------------------------------------------------------------------------- The Cassini-Huygens mission is a cooperative project of NASA, the European Space Agency and the Italian Space Agency. The Jet Propulsion Laboratory, a division of the California Institute of Technology in Pasadena, manages the Cassini-Huygens mission for NASA's Office of Space Science, Washington, D.C. The Cassini orbiter and its two onboard cameras were designed, developed and assembled at JPL. The imaging team is based at the Space Science Institute, Boulder, Colo. Related Web Pages Build Your Own Planet Eye through the Hurricane Cassini Saturn Edition, Astrobiology Magaz. Saturn's Rings in UV Cassini Closes In on Saturn Saturn-- JPL Cassini Main Page Lord of the Rings Space Science Institute, Imaging Team Boulder, Colorado Saturn: The Closest Pass Life and Giant Planets This article comes from Astrobiology Magazine http://www.astrobio.net/news/ The URL for this story is: http://www.astrobio.net/news/modules.php?op=modload&name=News&file=article&sid=1239

Saturn Sightings: Tethys Date Friday, October 08 @ 00:01:38 Topic Life and Giant Planets The Cassini spacecraft in orbit around Saturn caught a glimpse of Tethys, a cratered, icy moon. Notable for Tethys are its split fissure and enormous crater, both of which leave the impression that its fragile surface is remaking itself slowly. Saturn Sightings: Tethys based on Space Science Institute report Saturn's icy moon, Tethys. Banner image shows artist conception from surface of Tethys Credit: NASA/JPL Cassini sighted the far-off icy moon Tethys as it headed back toward Saturn in its long, looping first orbit of the planet. A faint hint of detail on the moon's cratered surface is visible here (right). Tethys was discovered by Giovanni Cassini, for whom the spacecraft was named. Its diameter is 1,060 kilometers (659 miles) across. See Cassini image gallery and slideshow The image (right) was taken in visible light with the Cassini spacecraft narrow angle camera on Sept. 9, 2004, at a distance of 8.8 million kilometers (5.5 million miles) from Tethys and at a Sun-Tethys-spacecraft, or phase, angle of 81 degrees. The image scale is 53 kilometers (33 miles) per pixel. The image was magnified by a factor of four and contrast enhanced to aid visibility. Saturn's icy moon, Tethys with surface details revealed by JPL solar system simulator. Credit: NASA/JPL Tethys is an icy body similar in nature to Dione and Rhea. The density of Tethys is 1.21 gm/cm3, indicating that it is composed almost entirely of water-ice. Tethys's icy surface is heavily cratered and contains cracks caused by faults in the ice. The terrain is composed of densely cratered regions with a lightly cratered, dark belt that extends across the satellite. Light cratering indicates that Tethys was once internally active, causing parts of the older terrain to be resurfaced. The exact cause for the dark belt is unknown, but a possible interpretation comes from recent Galileo images of Jupiter's moons Ganymede and Callisto. Both satellites exhibit light polar caps that are made from bright ice deposits on pole-facing slopes of craters. From a distance the caps appear brighter due to a haze caused by thousands of unresolved ice patches in small craters. Tethys' surface may have been formed in a similar manner, consisting of hazy polar caps of unresolved bright ice patches with a darker zone in-between. Tethys has an enormous trench named Ithaca Chasma that is about 65 kilometers (40 miles) wide and several kilometers deep. It covers three-fourths of Tethys' circumference. The fissure is about the size scientists would predict if Tethys were once fluid and its crust hardened before the interior. Another prominent feature is an enormous 400-kilometer impact basin named Odysseus. The impact scar spans more than two-fifths of the satellite with a diameter slightly larger than Saturn's moon Mimas. When Odysseus was first created, the crater must have been deep with a high mountainous rim and towering central peak. Over time the crater floor relaxed to the spherical shape of the Tethys's surface, and the crater's rim and central peak collapsed. Tethys' surface temperature is -187° C (-305° F). Saturn's moon system: Iapetus, Mimas, Rhea and Tethys. Image Credit: NASA/JPL Cassini is conducting a four-year orbital mission, circling Saturn 77 times and cruising by more than 50 close encounters (and another dozen or so more-distant encounters) with the planet's moons. In all, Cassini will aim its instruments at 8 of Saturn's 33 or more known moons. Cassini has already discovered a few that were unknown from ground observation and an earlier Voyager flyby. Along with most of the other 33-plus satellites, the featured moons appear to have an icy crust. Condensed ices give the moons very high albedo (reflection coefficients) but some are mottled with darker regions that may be rich in organic chemicals like methane or ammonia. These building blocks for primitive biochemistry may offer insight into how a similar, but much warmer environment on Earth, might have given rise to primordial life. -------------------------------------------------------------------------------- Related Web Pages Cassini Saturn Edition, Astrobiology Magaz. Saturn's Rings in UV Cassini Closes In on Saturn Saturn-- JPL Cassini Main Page Lord of the Rings Space Science Institute, Imaging Team Boulder, Colorado Saturn: The Closest Pass Voyager Image Query Form David Seal's JPL site -Solar System Simulator Life and Giant Planets This article comes from Astrobiology Magazine http://www.astrobio.net/news/ The URL for this story is: http://www.astrobio.net/news/modules.php?op=modload&name=News&file=article&sid=1236