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The Huygens experience

A new rendering of Huygens descent and touchdown created using real data recorded by the probe’s instruments as it descended to the surface of Titan, Saturn’s largest moon, on 14 January 2005.
The animation takes into account Titan’s atmospheric conditions, including the Sun and wind direction, the behaviour of the parachute (with some artistic interpretation only on the movement of the ropes after touchdown), and the dynamics of the landing itself. Even the stones immediately facing Huygens were rendered to match the photograph of the landing site returned from the probe, which is revealed at the end of the animation.
Split into four sequences, the animation first shows a wide-angle view of the descent and landing followed by two close-ups of the touchdown from different angles, and finally a simulated view from Huygens itself — the true Huygens experience.
This animation was released on the eighth anniversary of Huygen’s touchdown on Titan as a Space Science Image of the Week feature.

Animation: ESA–C. Carreau/Schröder, Karkoschka et al (2012). Image from Titan’s surface: ESA/NASA/JPL/University of Arizona

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Cassini Caught in Hyperion’s Particle Beam

This stunning false-color view of Saturn's moon Hyperion reveals crisp details across the strange, tumbling moon's surface. Differences in color could represent differences in the composition of surface materials. The view was obtained during Cassini's very close flyby on Sept. 26, 2005.

This stunning false-color view of Saturn’s moon Hyperion reveals crisp details across the strange, tumbling moon’s surface. Differences in color could represent differences in the composition of surface materials. The view was obtained during Cassini’s very close flyby on Sept. 26, 2005.

Static electricity is known to play an important role on Earth’s airless, dusty moon, but evidence of static charge building up on other objects in the solar system has been elusive until now. A new analysis of data from NASA’s Cassini mission has revealed that, during a 2005 flyby of Saturn’s moon Hyperion, the spacecraft was briefly bathed in a beam of electrons coming from the moon’s electrostatically charged surface.

The finding represents the first confirmed detection of a charged surface on an object other than our moon, although it is predicted to occur on many different bodies, including asteroids and comets. Continue reading Cassini Caught in Hyperion’s Particle Beam

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Cassini Watches Mysterious Feature Evolve in Titan Sea

These three images, created from Cassini Synthetic Aperture Radar (SAR) data, show the appearance and evolution of a mysterious feature in Ligeia Mare, one of the largest hydrocarbon seas on Saturn's moon Titan. Image Credit: NASA/JPL-Caltech/ASI/Cornell

These three images, created from Cassini Synthetic Aperture Radar (SAR) data, show the appearance and evolution of a mysterious feature in Ligeia Mare, one of the largest hydrocarbon seas on Saturn’s moon Titan. Image Credit: NASA/JPL-Caltech/ASI/Cornell

NASA’s Cassini spacecraft is monitoring the evolution of a mysterious feature in a large hydrocarbon sea on Saturn’s moon Titan. The feature covers an area of about 100 square miles (260 square kilometers) in Ligeia Mare, one of the largest seas on Titan. It has now been observed twice by Cassini’s radar experiment, but its appearance changed between the two apparitions….
,,, Read more at  www.nasa.gov

NASA’s Cassini Spacecraft Obtains Best Views of Saturn Hexagon

This colorful view from NASA's Cassini mission is the highest-resolution view of the unique six-sided jet stream at Saturn's north pole known as "the hexagon." This movie, made from images obtained by Cassini's imaging cameras, is the first to show the hexagon in color filters, and the first movie to show a complete view from the north pole down to about 70 degrees north latitude. Image credit: NASA/JPL-Caltech/SSI/Hampton

This colorful view from NASA’s Cassini mission is the highest-resolution view of the unique six-sided jet stream at Saturn’s north pole known as “the hexagon.” This movie, made from images obtained by Cassini’s imaging cameras, is the first to show the hexagon in color filters, and the first movie to show a complete view from the north pole down to about 70 degrees north latitude. Image credit: NASA/JPL-Caltech/SSI/Hampton

NASA’s Cassini spacecraft has obtained the highest-resolution movie yet of a unique six-sided jet stream, known as the hexagon, around Saturn’s north pole.

This is the first hexagon movie of its kind, using color filters, and the first to show a complete view of the top of Saturn down to about 70 degrees latitude. Spanning about 20,000 miles (30,000 kilometers) across, the hexagon is a wavy jet stream of 200-mile-per-hour winds (about 322 kilometers per hour) with a massive, rotating storm at the center. There is no weather feature exactly, consistently like this anywhere else in the solar system.

“The hexagon is just a current of air, and weather features out there that share similarities to this are notoriously turbulent and unstable,” said Andrew Ingersoll, a Cassini imaging team member at the California Institute of Technology in Pasadena. “A hurricane on Earth typically lasts a week, but this has been here for decades — and who knows — maybe centuries.”

Weather patterns on Earth are interrupted when they encounter friction from landforms or ice caps. Scientists suspect the stability of the hexagon has something to do with the lack of solid landforms on Saturn, which is essentially a giant ball of gas.

Better views of the hexagon are available now because the sun began to illuminate its interior in late 2012. Cassini captured images of the hexagon over a 10-hour time span with high-resolution cameras, giving scientists a good look at the motion of cloud structures within.

They saw the storm around the pole, as well as small vortices rotating in the opposite direction of the hexagon. Some of the vortices are swept along with the jet stream as if on a racetrack. The largest of these vortices spans about 2,200 miles (3,500 kilometers), or about twice the size of the largest hurricane recorded on Earth.

Scientists analyzed these images in false color, a rendering method that makes it easier to distinguish differences among the types of particles suspended in the atmosphere — relatively small particles that make up haze — inside and outside the hexagon.

“Inside the hexagon, there are fewer large haze particles and a concentration of small haze particles, while outside the hexagon, the opposite is true,” said Kunio Sayanagi, a Cassini imaging team associate at Hampton University in Virginia. “The hexagonal jet stream is acting like a barrier, which results in something like Earth’s Antarctic ozone hole.”

The Antarctic ozone hole forms within a region enclosed by a jet stream with similarities to the hexagon. Wintertime conditions enable ozone-destroying chemical processes to occur, and the jet stream prevents a resupply of ozone from the outside. At Saturn, large aerosols cannot cross into the hexagonal jet stream from outside, and large aerosol particles are created when sunlight shines on the atmosphere. Only recently, with the start of Saturn’s northern spring in August 2009, did sunlight begin bathing the planet’s northern hemisphere.

“As we approach Saturn’s summer solstice in 2017, lighting conditions over its north pole will improve, and we are excited to track the changes that occur both inside and outside the hexagon boundary,” said Scott Edgington, Cassini deputy project scientist at NASA’s Jet Propulsion Laboratory in Pasadena, Calif.

A black-and-white version of the imaging camera movie and movies obtained by Cassini’s visual and infrared mapping spectrometer are also tools Cassini scientists can use to look at wind speeds and the mini-storms inside the jet stream.
Read more at http://www.jpl.nasa.gov/news/news.php?release=2013-350

Tides control the geysers of Enceladus

enceladusThe water geysers of Enceladus spew the most material when the small moon ventures farthest from Saturn, planetary scientists in the US have found. This discovery confirms a prediction of a theory that says the geysers’ strength depends on Saturn’s tide.
Discovered by the German-born English astronomer William Herschel in 1789, eight years after he spotted the planet Uranus, Enceladus is the sixth largest of Saturn’s 62 known satellites. The small moon is 238,000 km from Saturn’s centre, about two-thirds of the distance from the Earth to the Moon. Because Saturn is so massive, though, its gravity forces Enceladus to circle it every 1.37 days.
With a diameter of just 500 km, Enceladus is only one-seventh the size of the Earth’s Moon and it lacks the radioactive elements that heat the Earth’s core. This makes it an unlikely world for geysers or any other geological activity.

Icy spray
In 1980 and 1981 NASA’s Voyager 1 and 2 spacecraft flew past the ringed planet and found Enceladus’s surface unusually smooth. This suggested that something was erasing its craters. Then in 2005 the Cassini spacecraft discovered water vapour around Enceladus. Cassini soon found the surprising source: geysers around the moon’s south pole shoot water vapour and ice particles hundreds of kilometres above the surface. Some of this material settles on the surface of the moon, covering its craters.
Now planetary scientist Matthew Hedman of Cornell University and his colleagues have examined 252 near-infrared images from Cassini. “The brightness of the plume varied quite a bit,” says Hedman, who found it four times brighter when Enceladus is farthest from Saturn than when closest. These observations agree with a prediction made in a paper published in 2007 by Terry Hurford of the Goddard Space Science Center in Maryland, who had calculated how Enceladus would respond to Saturn’s tide.
Tides arise when gravity pulls on an extended object. For example, lunar gravity tugs strongest on the side of the Earth facing the Moon, lifting the sea. Likewise, on the opposite side of the Earth, the Moon’s gravity pulls our planet’s centre out from under the sea, producing a high tide on the far side as well. Elsewhere, tides from Jupiter power the fiery moon Io, which sports active volcanoes, and melt ice beneath the surface of the moon Europa….
Read more at http://physicsworld.com/cws/article/news/2013/jul/31/tides-control-the-geysers-of-enceladus

Read also: “An observed correlation between plume activity and tidal stresses on Enceladus and “Gravity controls icy moon Enceladus’s spew

Cassini captures spectacle in Saturn’s shadow

NASA's Cassini spacecraft has delivered a glorious view of Saturn, taken while the spacecraft was in Saturn's shadow. Image credit: NASA/JPL-Caltech/Space Science Institute

NASA’s Cassini spacecraft has delivered a glorious view of Saturn, taken while the spacecraft was in Saturn’s shadow. Image credit: NASA/JPL-Caltech/Space Science Institute

Just in time for the holidays, NASA’s Cassini spacecraft, in orbit around Saturn for more than eight years now, has delivered another glorious, backlit view of the planet Saturn and its rings.

On Oct. 17, 2012, during its 174th orbit around the gas giant, Cassini was deliberately positioned within Saturn’s shadow, a perfect location from which to look in the direction of the sun and take a backlit view of the rings and the dark side of the planet. Looking back towards the sun is a geometry referred to by planetary scientists as “high solar phase;” near the center of your target’s shadow is the highest phase possible. This is a very scientifically advantageous and coveted viewing position, as it can reveal details about both the rings and atmosphere that cannot be seen in lower solar phase.

The last time Cassini had such an unusual perspective on Saturn and its rings, at sufficient distance and with sufficient time to make a full system mosaic, occurred in September 2006, when it captured a mosaic, processed to look like natural color, entitled “In Saturn’s Shadow.” In that mosaic, planet Earth put in a special appearance, making “In Saturn’s Shadow” one of the most popular Cassini images to date.

The mosaic being released today by the mission and the imaging team, in celebration of the 2012 holiday season, does not contain Earth; along with the sun, our planet is hidden behind Saturn. However, it was taken when Cassini was closer to Saturn and therefore shows more detail in the rings than the one taken in 2006.

The new processed mosaic, composed of 60 images taken in the violet, visible and near infrared part of the spectrum, can be found at http://www.nasa.gov/cassini , http://saturn.jpl.nasa.gov and http://ciclops.org .

“Of all the many glorious images we have received from Saturn, none are more strikingly unusual than those taken from Saturn’s shadow,” said Carolyn Porco, Cassini’s imaging team lead based at the Space Science Institute in Boulder, Colo.
Read more: http://www.nasa.gov/mission_pages/cassini/whycassini/cassini20121218.html

Tiny Tethys

tethysTethys may not be tiny by normal standards, but when it is captured alongside Saturn, it can’t help but seem pretty small.

Even Saturn’s rings appear to dwarf Tethys (660 miles, or 1,062 kilometers across), which is in the upper left of the image, although scientists believe the moon to be many times more massive than the entire ring system combined. This view looks toward the unilluminated side of the rings from about 18 degrees below the ringplane. The image was taken in green light with the Cassini spacecraft wide-angle camera on Aug. 19, 2012.

The view was acquired at a distance of approximately 1.5 million miles (2.4 million kilometers) from Saturn and at a Sun-Saturn-spacecraft, or phase, angle of 63 degrees. Image scale is 86 miles (138 kilometers) per pixel.
Read more: www.nasa.gov