Archive for cassini spacecraft

Forecast for Titan: Wild Weather Could be Ahead

By alkaon on May 23, 2013 No Comments

Vast Ligeia Mare in False Color
Ligeia Mare, shown in here in data obtained by NASA’s Cassini spacecraft, is the second largest known body of liquid on Saturn’s moon Titan. It is filled with liquid hydrocarbons, such as ethane and methane, and is one of the many seas and lakes that bejewel Titan’s north polar region. Cassini has yet to observe waves on Ligeia Mare and will look again during its next encounter on May 23, 2013. Image credit: NASA/JPL-Caltech/ASI/Cornell
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May 22, 2013

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Saturn’s moon Titan might be in for some wild weather as it heads into its spring and summer, if two new models are correct. Scientists think that as the seasons change in Titan’s northern hemisphere, waves could ripple across the moon’s hydrocarbon seas, and hurricanes could begin to swirl over these areas, too. The model predicting waves tries to explain data from the moon obtained so far by NASA’s Cassini spacecraft. Both models help mission team members plan when and where to look for unusual atmospheric disturbances as Titan summer approaches.

“If you think being a weather forecaster on Earth is difficult, it can be even more challenging at Titan,” said Scott Edgington, Cassini’s deputy project scientist at NASA’s Jet Propulsion Laboratory, Pasadena, Calif. “We know there are weather processes similar to Earth’s at work on this strange world, but differences arise due to the presence of unfamiliar liquids like methane. We can’t wait for Cassini to tell us whether our forecasts are right as it continues its tour through Titan spring into the start of northern summer.”

Titan’s north polar region, which is bejeweled with sprawling hydrocarbon seas and lakes, was dark when Cassini first arrived at the Saturn system in 2004. But sunlight has been creeping up Titan’s northern hemisphere since August 2009, when the sun’s light crossed the equatorial plane at equinox. Titan’s seasons take about seven Earth years to change. By 2017, the end of Cassini’s mission, Titan will be approaching northern solstice, the height of summer.

Given the wind-sculpted dunes Cassini has seen on Titan, scientists were baffled about why they hadn’t yet seen wind-driven waves on the lakes and seas. A team led by Alex Hayes, a member of Cassini’s radar team who is based at Cornell University, Ithaca, N.Y., set out to look for how much wind would be required to generate waves. Their new model, just published in the journal Icarus, improves upon previous ones by simultaneously accounting for Titan’s gravity; the viscosity and surface tension of the hydrocarbon liquid in the lakes; and the air-to-liquid density ratio.

“We now know that the wind speeds predicted during the times Cassini has observed Titan have been below the threshold necessary to generate waves,” Hayes said. “What is exciting, however, is that the wind speeds predicted during northern spring and summer approach those necessary to generate wind waves in liquid ethane and/or methane. It may soon be possible to catch a wave in one of the solar system’s most exotic locations.”

The new model found that winds of 1 to 2 mph (2 to 3 kilometers per hour) are needed to generate waves on Titan lakes, a speed that has not yet been reached during Titan’s currently calm period. But as Titan’s northern hemisphere approaches spring and summer, other models predict the winds may increase to 2 mph (3 kilometers per hour) or faster. Depending on the composition of the lakes, winds of that speed could be enough to produce waves 0.5 foot (0.15 meter) high.

The other model about hurricanes, recently published in Icarus, predicts that the warming of the northern hemisphere could also bring hurricanes, also known as tropical cyclones. Tropical cyclones on Earth gain their energy from the build-up of heat from seawater evaporation and miniature versions have been seen over big lakes such as Lake Huron. The new modeling work, led by Tetsuya Tokano of the University of Cologne, Germany, shows that the same processes could be at work on Titan as well, except that it is methane rather than water that evaporates from the seas. The most likely season for these hurricanes would be Titan’s northern summer solstice, when the sea surface gets warmer and the flow of the air near the surface becomes more turbulent. The humid air would swirl in a counterclockwise direction over the surface of one of the northern seas and increase the surface wind over the seas to possibly 45 mph (about 70 kilometers per hour).

“For these hurricanes to develop at Titan, there needs to be the right mix of hydrocarbons in these seas, and we still don’t know their exact composition,” Tokano said. “If we see hurricanes, that would be one good indicator that there is enough methane in these lakes to support this kind of activity. So far, scientists haven’t yet been able to detect methane directly.”

The Cassini-Huygens mission is a cooperative project of NASA, the European Space Agency, and the Italian Space Agency. The mission is managed by JPL for NASA’s Science Mission Directorate, Washington. JPL is a division of the California Institute of Technology in Pasadena, Calif.

For more information about Cassini and its mission, visit: http://www.nasa.gov/cassini and http://saturn.jpl.nasa.gov .

Jia-Rui C. Cook 818-354-0850
Jet Propulsion Laboratory, Pasadena, Calif.
jccook@jpl.nasa.gov

2013-170

Article source: http://www.jpl.nasa.gov/news/news.php?release=2013-170

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Cassini Shapes First Global Topographic Map of Titan

By alkaon on May 16, 2013 No Comments


These polar maps show the first global, topographic mapping of Saturn’s moon Titan, using data from NASA’s Cassini mission. Image credit: NASA/JPL-Caltech/ASI/JHUAPL/Cornell/Weizmann

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Using data from NASA’s Cassini spacecraft, scientists have created the first global topographic map of Saturn’s moon Titan, giving researchers a 3-D tool for learning more about one of the most Earthlike and interesting worlds in the solar system. Image credit: NASA/JPL-Caltech/ASI/JHUAPL/Cornell/Weizmann

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To create the first global, topographic map of Saturn’s moon Titan, scientists analyzed data from NASA’s Cassini spacecraft and a mathematical process called splining. Image credit: NASA/JPL-Caltech/ASI/JHUAPL/Cornell/Weizmann

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Scientists have created the first global topographic map of Saturn’s moon Titan, giving researchers a valuable tool for learning more about one of the most Earth-like and interesting worlds in the solar system. The map was just published as part of a paper in the journal Icarus.

Titan is Saturn’s largest moon – with a radius of about 1,600 miles (2,574 kilometers), it’s bigger than planet Mercury – and is the second–largest moon in the solar system. Scientists care about Titan because it’s the only moon in the solar system known to have clouds, surface liquids and a mysterious, thick atmosphere. The cold atmosphere is mostly nitrogen, like Earth’s, but the organic compound methane on Titan acts the way water vapor does on Earth, forming clouds and falling as rain and carving the surface with rivers. Organic chemicals, derived from methane, are present in Titan’s atmosphere, lakes and rivers and may offer clues about the origins of life.

“Titan has so much interesting activity – like flowing liquids and moving sand dunes – but to understand these processes it’s useful to know how the terrain slopes,” said Ralph Lorenz, a member of the Cassini radar team based at the Johns Hopkins University Applied Physics Laboratory, Laurel, Md., who led the map-design team. “It’s especially helpful to those studying hydrology and modeling Titan’s climate and weather, who need to know whether there is high ground or low ground driving their models.”

Titan’s thick haze scatters light in ways that make it very hard for remote cameras to “see” landscape shapes and shadows, the usual approach to measuring topography on planetary bodies. Virtually all the data we have on Titan comes from NASA’s Saturn-orbiting Cassini spacecraft, which has flown past the moon nearly 100 times over the past decade. On many of those flybys, Cassini has used a radar imager, which can peer through the haze, and the radar data can be used to estimate the surface height.

“With this new topographic map, one of the most fascinating and dynamic worlds in our solar system now pops out in 3-D,” said Steve Wall, the deputy team lead of Cassini’s radar team, based at NASA’s Jet Propulsion Laboratory in Pasadena, Calif. “On Earth, rivers, volcanoes and even weather are closely related to heights of surfaces – we’re now eager to see what we can learn from them on Titan.”

There are challenges, however. “Cassini isn’t orbiting Titan,” Lorenz said. “We have only imaged about half of Titan’s surface, and multiple ‘looks’ or special observations are needed to estimate the surface heights. If you divided Titan into 1-degree by 1-degree [latitude and longitude] squares, only 11 percent of those squares have topography data in them.”

Lorenz’s team used a mathematical process called splining – effectively using smooth, curved surfaces to “join” the areas between grids of existing data. “You can take a spot where there is no data, look how close it is to the nearest data, and use various approaches of averaging and estimating to calculate your best guess,” he said. “If you pick a point, and all the nearby points are high altitude, you’d need a special reason for thinking that point would be lower. We’re mathematically papering over the gaps in our coverage.”

The estimations fit with current knowledge of the moon – that its polar regions are “lower” than areas around the equator, for example – but connecting those points allows scientists to add new layers to their studies of Titan’s surface, especially those modeling how and where Titan’s rivers flow, and the seasonal distribution of its methane rainfall. “The movement of sands and the flow of liquids are influenced by slopes, and mountains can trigger cloud formation and therefore rainfall. This global product now gives modelers a convenient description of this key factor in Titan’s dynamic climate system,” Lorenz said.

The most recent data used to compile the map is from 2012; Lorenz says it could be worth revising when the Cassini mission ends in 2017, when more data will have accumulated, filling some of the gaps in present coverage. “We felt we couldn’t wait and should release an interim product,” he says. “The community has been hoping to get this for a while. I think it will stimulate a lot of interesting work.”

The Cassini-Huygens mission is a cooperative project of NASA, the European Space Agency and ASI, the Italian Space Agency. JPL, a division of the California Institute of Technology in Pasadena, manages the mission for NASA’s Science Mission Directorate, Washington. The radar instrument was built by JPL and the Italian Space Agency, working with team members from the United States and several European countries.

Jia-Rui Cook 818-354-0850
Jet Propulsion Laboratory, Pasadena, Calif.
jccook@jpl.nasa.gov

Michael Buckley 240-228-7536
Johns Hopkins Applied Physics Laboratory, Laurel, Md.
Michael.buckley@jhuapl.edu

2013-161

Article source: http://www.nasa.gov/mission_pages/cassini/whycassini/cassini20130515.html

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Seasonal plasma changes at Saturn

By alkaon on May 4, 2013 No Comments

Saturnian-plasma-sheetResearchers working with data from NASA’s Cassini spacecraft have discovered one way the bubble of charged particles around Saturn — known as the magnetosphere — changes with the planet’s seasons. The finding provides an important clue for solving a riddle about the planet’s naturally occurring radio signal. The results also might help scientists better understand variations in Earth’s magnetosphere and Van Allen radiation belts, which affect a variety of activities on Earth, ranging from space flight safety to satellite and cellphone communications.

In data collected by Cassini from July 2004 to December 2011, Tim Kennelly from the University of Iowa in Iowa City and his colleagues examined “flux tubes,” structures composed of hot, electrically charged gas called plasma, which funnel charged particles in toward Saturn. Focusing on the tubes when they initially formed and before they had a chance to dissipate under the influence of the magnetosphere, the scientists found that the occurrence of the tubes correlates with radio-wave patterns in the northern and southern hemisphere depending upon the season. This seasonal effect is roughly similar to the way Earth’s northern lights appear more frequently in the spring and autumn months.

Radio emissions have been used to measure Jupiter’s rotation period reliably, and scientists thought it also would help them determine Saturn’s rotation period. To their chagrin, however, the pattern has varied over the visits by different spacecraft and even in radio emissions originating in the northern and southern hemispheres. The new results could help scientists hone in on why these signals vary the way they do.

Article source: http://www.astronomy.com/~/link.aspx?_id=d963f2a9-bd7d-4cec-b32f-52e2c966e4f6

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NASA Probe Spies Giant Hurricane on Saturn – National Geographic News

By alkaon on May 2, 2013 No Comments

A monster-sized hurricane raging around Saturn‘s north pole has come into focus, thanks to NASA’s Cassini spacecraft, and researchers hope it will help shape our understanding of similar storms on Earth.

“Morphologically, this giant storm resembles that of hurricanes and typhoons on Earth—with an eye at its center and spiraling clouds outside—but this Saturnian hurricane is on a titanic scale,” said Kunio Sayanagi, a Cassini imaging team member at Hampton University in Virginia.

Watch a video of the hurricane on Saturn.

Just the eye of the storm is estimated to stretch 1,250 miles (2,000 kilometers) across—more than 20 times larger than hurricanes that swirl on Earth. (Related: “Colossal Storm May Rage on Jupiter-like ‘Failed Star.’”)

Scientists aren’t sure when the hurricane formed, but speculate that it could be a permanent weather feature, said fellow Cassini imaging team scientist Andrew Ingersoll at the California Institute of Technology in Pasadena.

When Cassini first arrived at the gas giant in 2004, the planet’s northern hemisphere was deep in winter, with its north pole tilted away from the sun and shrouded in darkness. But the orbiter’s two infrared cameras—which act like night-vision goggles—were able to pierce through the polar night and capture the first hints of the massive storm’s existence.

With the eye of the storm being an actual hole in the clouds, the deeper, warmer layers of Saturn’s atmosphere were exposed, showing up on the cameras as a telltale thermal emission, said Sayanagi.

“These cameras don’t have very high resolution, but still saw a [infrared] hotspot at the pole earlier in the mission, which we found interesting,” he explained.

Springtime for Saturn’s northern hemisphere arrived in 2009, but Cassini researchers weren’t able to get the spacecraft into the proper orbit to take pictures of the hurricane with optical cameras until November 2012.

A New View

The newly released batch of stunning photos, taken with the optical cameras under daylight conditions, now showcase the beauty and intricate structure of the hurricane in visible wavelengths.

Cassini scientists believe these new views will begin to shed light on the inner workings of not only this Saturnian hurricane, but also its smaller cousins here on Earth. (Learn about hurricanes on Earth.)

On Earth, hurricanes feed off of evaporated water droplets from warm tropical seas. But Saturn has no oceans, so how the ringed planet’s atmosphere drives hurricane formation is a mystery.

The hurricane’s location—locked at Saturn’s north pole—is also puzzling. On Earth, hurricane movements tend to start at tropical equatorial regions and glide northward due to forces acting on the storm as the planet rotates.

Meanwhile, color-enhanced images of Saturn’s hurricane show wispy clouds along the eye’s wall whipping around at speeds of 330 miles per hour (540 kilometers per hour). Even stronger winds are possible moving out from the wall.

A Hurricane’s Guts

Similar hurricane-like storms have been seen on other gas giants in our solar system. But what has stumped scientists is why wind speeds get cranked up the farther out we move in the solar system, said Caltech’s Ingersoll. (Related: “Saturn Lightning Storm Breaks Solar System Record.”)

This may seem counterintuitive, but it might have to do with the atmospheres on these outer planets being less turbulent than Earth’s atmosphere, he explained.

Both water vapor and less atmospheric turbulence make for more powerful hurricanes.

Like other gas giants, “Saturn has a deep hydrogen atmosphere with little water vapor in it, yet somehow it produces high winds anyway,” Ingersoll said.

The Cassini team believes that Saturn offers a unique laboratory to study hurricanes, which they hope will help unlock some of the mysteries of water’s role in powering such strong winds.

“Earth is complicated and messy because hurricanes interact with changing ocean temperatures, run into coastlines, get nudged around by jet streams, and these factors make it really hard to study the basic underlying principles that drive a hurricane,” explained Sayanagi.

In contrast, this newly discovered Saturnian hurricane does not encounter land-ocean boundaries and is stationary at the pole, allowing researchers to simply focus on the physics that govern hurricanes.

“This is the kind of setup we can really use to push our limits on our understanding of how hurricanes work, and the best part is that nobody is getting hurt by this extreme hurricane as we study it,” added Sayanagi.

Article source: http://news.nationalgeographic.com/news/2013/13/130501-saturn-hurricane-north-pole-space-science/

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NASA Probe Gets Close Views of Large Saturn Hurricane

By alkaon on April 30, 2013 No Comments

The spinning vortex of Saturn’s north polar storm resembles a deep red rose of giant proportions surrounded by green foliage in this false-color image from NASA’s Cassini spacecraft. Image credit: NASA/JPL-Caltech/SSI

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The north pole of Saturn, in the fresh light of spring, is revealed in this color image from NASA’s Cassini spacecraft. Image credit: NASA/JPL-Caltech/SSI

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This spectacular, vertigo inducing, false-color image from NASA’s Cassini mission highlights the storms at Saturn’s north pole. Image credit: NASA/JPL-Caltech/SSI

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PASADENA, Calif. – NASA’s Cassini spacecraft has provided scientists the first close-up, visible-light views of a behemoth hurricane swirling around Saturn’s north pole.

In high-resolution pictures and video, scientists see the hurricane’s eye is about 1,250 miles (2,000 kilometers) wide, 20 times larger than the average hurricane eye on Earth. Thin, bright clouds at the outer edge of the hurricane are traveling 330 mph(150 meters per second). The hurricane swirls inside a large, mysterious, six-sided weather pattern known as the hexagon.

“We did a double take when we saw this vortex because it looks so much like a hurricane on Earth,” said Andrew Ingersoll, a Cassini imaging team member at the California Institute of Technology in Pasadena. “But there it is at Saturn, on a much larger scale, and it is somehow getting by on the small amounts of water vapor in Saturn’s hydrogen atmosphere.”

Scientists will be studying the hurricane to gain insight into hurricanes on Earth, which feed off warm ocean water. Although there is no body of water close to these clouds high in Saturn’s atmosphere, learning how these Saturnian storms use water vapor could tell scientists more about how terrestrial hurricanes are generated and sustained.

Both a terrestrial hurricane and Saturn’s north polar vortex have a central eye with no clouds or very low clouds. Other similar features include high clouds forming an eye wall, other high clouds spiraling around the eye, and a counter-clockwise spin in the northern hemisphere.

A major difference between the hurricanes is that the one on Saturn is much bigger than its counterparts on Earth and spins surprisingly fast. At Saturn, the wind in the eye wall blows more than four times faster than hurricane-force winds on Earth. Unlike terrestrial hurricanes, which tend to move, the Saturnian hurricane is locked onto the planet’s north pole. On Earth, hurricanes tend to drift northward because of the forces acting on the fast swirls of wind as the planet rotates. The one on Saturn does not drift and is already as far north as it can be.

“The polar hurricane has nowhere else to go, and that’s likely why it’s stuck at the pole,” said Kunio Sayanagi, a Cassini imaging team associate at Hampton University in Hampton, Va.

Scientists believe the massive storm has been churning for years. When Cassini arrived in the Saturn system in 2004, Saturn’s north pole was dark because the planet was in the middle of its north polar winter. During that time, the Cassini spacecraft’s composite infrared spectrometer and visual and infrared mapping spectrometer detected a great vortex, but a visible-light view had to wait for the passing of the equinox in August 2009. Only then did sunlight begin flooding Saturn’s northern hemisphere. The view required a change in the angle of Cassini’s orbits around Saturn so the spacecraft could see the poles.

“Such a stunning and mesmerizing view of the hurricane-like storm at the north pole is only possible because Cassini is on a sportier course, with orbits tilted to loop the spacecraft above and below Saturn’s equatorial plane,” said Scott Edgington, Cassini deputy project scientist at NASA’s Jet Propulsion Laboratory in Pasadena, Calif. “You cannot see the polar regions very well from an equatorial orbit. Observing the planet from different vantage points reveals more about the cloud layers that cover the entirety of the planet.”

Cassini changes its orbital inclination for such an observing campaign only once every few years. Because the spacecraft uses flybys of Saturn’s moon Titan to change the angle of its orbit, the inclined trajectories require attentive oversight from navigators. The path requires careful planning years in advance and sticking very precisely to the planned itinerary to ensure enough propellant is available for the spacecraft to reach future planned orbits and encounters.

The Cassini-Huygens mission is a cooperative project of NASA, the European Space Agency and the Italian Space Agency. JPL, a division of the California Institute of Technology, Pasadena, manages the Cassini-Huygens mission for NASA’s Science Mission Directorate in Washington. The Cassini orbiter and its two onboard cameras were designed, developed and assembled at JPL. The imaging team consists of scientists from the United States, the United Kingdom, France and Germany. The imaging operations center is based at the Space Science Institute in Boulder, Colo.

For more information about Cassini and its mission, visit: http://www.nasa.gov/cassini
and http://saturn.jpl.nasa.gov .

Jia-Rui Cook 818-354-0850
Jet Propulsion Laboratory, Pasadena, Calif.
jccook@jpl.nasa.gov

Dwayne Brown 202-358-1726
NASA Headquarters, Washington
dwayne.c.brown@nasa.gov

2013-149

Article source: http://www.nasa.gov/mission_pages/cassini/whycassini/cassini20130429.html

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NASA’s Cassini spacecraft observes meteoroids colliding with Saturn’s rings

By alkaon on April 27, 2013 No Comments

Meteoroid impacts on Saturn's ringsNASA’s Cassini spacecraft has provided the first direct evidence of small meteoroids breaking into streams of rubble and crashing into Saturn’s rings.

These observations make Saturn’s rings the only location besides Earth, the Moon, and Jupiter where scientists and amateur astronomers have been able to observe impacts as they occur. Studying the impact rate of meteoroids from outside the saturnian system helps scientists understand how different planet systems in our solar system formed.

The solar system is full of small, speeding objects. These objects frequently pummel planetary bodies. The meteoroids at Saturn are estimated to range from about a half inch to several yards (1 centimeter to several meters) in size. It took scientists years to distinguish tracks left by nine meteoroids in 2005, 2009, and 2012.

Results from Cassini already have shown Saturn’s rings act as very effective detectors of many kinds of surrounding phenomena, including the interior structure of the planet and the orbits of its moons. For example, a subtle but extensive corrugation that ripples 12,000 miles (19,000 kilometers) across the innermost rings tells of a very large meteoroid impact in 1983.

“These new results imply the current-day impact rates for small particles at Saturn are about the same as those at Earth — two very different neighborhoods in our solar system — and this is exciting to see,” said Linda Spilker, Cassini project scientist at NASA’s Jet Propulsion Laboratory in Pasadena, California. “It took Saturn’s rings acting like a giant meteoroid detector — 100 times the surface area of the Earth — and Cassini’s long-term tour of the Saturn system to address this question.”

The saturnian equinox in summer 2009 was an especially good time to see the debris left by meteoroid impacts. The very shallow sun angle on the rings caused the clouds of debris to look bright against the darkened rings in pictures from Cassini’s imaging science subsystem.

“We knew these little impacts were constantly occurring, but we didn’t know how big or how frequent they might be, and we didn’t necessarily expect them to take the form of spectacular shearing clouds,” said Matt Tiscareno, a Cassini participating scientist at Cornell University in Ithaca, New York. “The sunlight shining edge-on to the rings at the saturnian equinox acted like an anti-cloaking device, so these usually invisible features became plain to see.”

Tiscareno and his colleagues now think meteoroids of this size probably break up on a first encounter with the rings, creating smaller, slower pieces that then enter into orbit around Saturn. The impact into the rings of these secondary meteoroid bits kicks up the clouds. The tiny particles forming these clouds have a range of orbital speeds around Saturn. The clouds they form soon are pulled into diagonal, extended bright streaks.

“Saturn’s rings are unusually bright and clean, leading some to suggest that the rings are actually much younger than Saturn,” said Jeff Cuzzi, a Cassini interdisciplinary scientist specializing in planetary rings and dust at NASA’s Ames Research Center in Moffett Field, California. “To assess this dramatic claim, we must know more about the rate at which outside material is bombarding the rings. This latest analysis helps fill in that story with detection of impactors of a size that we weren’t previously able to detect directly.”

Article source: http://www.astronomy.com/~/link.aspx?_id=2fc2587b-9463-4056-bc61-5bee76b6b157

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Saturn is Like an Antiques Shop, Cassini Suggests

By alkaon on March 28, 2013 No Comments

The Cassini spacecraft observes three of Saturn’s moons set against the darkened night side of the planet. Image credit: NASA/JPL-Caltech/Space Science Institute

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These two global images of Iapetus show the extreme brightness dichotomy on the surface of this peculiar Saturnian moon. Image credit: NASA/JPL-Caltech/Space Science Institute

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The effects of the small moon Prometheus loom large on two of Saturn’s rings in this image taken a short time before Saturn’s August 2009 equinox. Image credit: NASA/JPL-Caltech/Space Science Institute

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A new analysis of data from NASA’s Cassini spacecraft suggests that Saturn’s moons and rings are gently worn vintage goods from around the time of our solar system’s birth.

Though they are tinted on the surface from recent “pollution,” these bodies date back more than 4 billion years. They are from around the time that the planetary bodies in our neighborhood began to form out of the protoplanetary nebula, the cloud of material still orbiting the sun after its ignition as a star. The paper, led by Gianrico Filacchione, a Cassini participating scientist at Italy’s National Institute for Astrophysics, Rome, has just been published online by the Astrophysical Journal.

“Studying the Saturnian system helps us understand the chemical and physical evolution of our entire solar system,” said Filacchione. “We know now that understanding this evolution requires not just studying a single moon or ring, but piecing together the relationships intertwining these bodies.”

Data from Cassini’s visual and infrared mapping spectrometer (VIMS) have revealed how water ice and also colors — which are the signs of non-water and organic materials –are distributed throughout the Saturnian system. The spectrometer’s data in the visible part of the light spectrum show that coloring on the rings and moons generally is only skin-deep.

Using its infrared range, VIMS also detected abundant water ice – too much to have been deposited by comets or other recent means. So the authors deduce that the water ices must have formed around the time of the birth of the solar system, because Saturn orbits the sun beyond the so-called “snow line.” Out beyond the snow line, in the outer solar system where Saturn resides, the environment is conducive to preserving water ice, like a deep freezer. Inside the solar system’s “snow line,” the environment is much closer to the sun’s warm glow, and ices and other volatiles dissipate more easily.

The colored patina on the ring particles and moons roughly corresponds to their location in the Saturn system. For Saturn’s inner ring particles and moons, water-ice spray from the geyser moon Enceladus has a whitewashing effect.

Farther out, the scientists found that the surfaces of Saturn’s moons generally were redder the farther they orbited from Saturn. Phoebe, one of Saturn’s outer moons and an object thought to originate in the far-off Kuiper Belt, seems to be shedding reddish dust that eventually rouges the surface of nearby moons, such as Hyperion and Iapetus.

A rain of meteoroids from outside the system appears to have turned some parts of the main ring system – notably the part of the main rings known as the B ring — a subtle reddish hue. Scientists think the reddish color could be oxidized iron — rust — or polycyclic aromatic hydrocarbons, which could be progenitors of more complex organic molecules.

One of the big surprises from this research was the similar reddish coloring of the potato-shaped moon Prometheus and nearby ring particles. Other moons in the area were more whitish.

“The similar reddish tint suggests that Prometheus is constructed from material in Saturn’s rings,” said co-author Bonnie Buratti, a VIMS team member based at NASA’s Jet Propulsion Laboratory, Pasadena, Calif. “Scientists had been wondering whether ring particles could have stuck together to form moons — since the dominant theory was that the rings basically came from satellites being broken up. The coloring gives us some solid proof that it can work the other way around, too.”

“Observing the rings and moons with Cassini gives us an amazing bird’s-eye view of the intricate processes at work in the Saturn system, and perhaps in the evolution of planetary systems as well,” said Linda Spilker, Cassini project scientist, based at JPL. “What an object looks like and how it evolves depends a lot on location, location, location.”

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, Pasadena, manages the mission for NASA’s Science Mission Directorate, Washington, D.C. The visual and infrared mapping spectrometer team is based at the University of Arizona, Tucson.

Jia-Rui Cook 818-354-0850
Jet Propulsion Laboratory, Pasadena, Calif.
jccook@jpl.nasa.gov

2013-117

Article source: http://www.nasa.gov/mission_pages/cassini/whycassini/cassini20130327.html

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Saturn is Like an Antiques Shop, Cassini Suggests

By alkaon on March 27, 2013 No Comments

Bright Moons
The Cassini spacecraft observes three of Saturn’s moons set against the darkened night side of the planet. Image Credit:
NASA/JPL/Space Science Institute
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March 26, 2013

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A new analysis of data from NASA’s Cassini spacecraft suggests that Saturn’s moons and rings are gently worn vintage goods from around the time of our solar system’s birth.

Though they are tinted on the surface from recent “pollution,” these bodies date back more than 4 billion years. They are from around the time that the planetary bodies in our neighborhood began to form out of the protoplanetary nebula, the cloud of material still orbiting the sun after its ignition as a star. The paper, led by Gianrico Filacchione, a Cassini participating scientist at Italy’s National Institute for Astrophysics, Rome, has just been published online by the Astrophysical Journal.

“Studying the Saturnian system helps us understand the chemical and physical evolution of our entire solar system,” said Filacchione. “We know now that understanding this evolution requires not just studying a single moon or ring, but piecing together the relationships intertwining these bodies.”

Data from Cassini’s visual and infrared mapping spectrometer (VIMS) have revealed how water ice and also colors — which are the signs of non-water and organic materials –are distributed throughout the Saturnian system. The spectrometer’s data in the visible part of the light spectrum show that coloring on the rings and moons generally is only skin-deep.

Using its infrared range, VIMS also detected abundant water ice – too much to have been deposited by comets or other recent means. So the authors deduce that the water ices must have formed around the time of the birth of the solar system, because Saturn orbits the sun beyond the so-called “snow line.” Out beyond the snow line, in the outer solar system where Saturn resides, the environment is conducive to preserving water ice, like a deep freezer. Inside the solar system’s “snow line,” the environment is much closer to the sun’s warm glow, and ices and other volatiles dissipate more easily.

The colored patina on the ring particles and moons roughly corresponds to their location in the Saturn system. For Saturn’s inner ring particles and moons, water-ice spray from the geyser moon Enceladus has a whitewashing effect.

Farther out, the scientists found that the surfaces of Saturn’s moons generally were redder the farther they orbited from Saturn. Phoebe, one of Saturn’s outer moons and an object thought to originate in the far-off Kuiper Belt, seems to be shedding reddish dust that eventually rouges the surface of nearby moons, such as Hyperion and Iapetus.

A rain of meteoroids from outside the system appears to have turned some parts of the main ring system – notably the part of the main rings known as the B ring — a subtle reddish hue. Scientists think the reddish color could be oxidized iron — rust — or polycyclic aromatic hydrocarbons, which could be progenitors of more complex organic molecules.

One of the big surprises from this research was the similar reddish coloring of the potato-shaped moon Prometheus and nearby ring particles. Other moons in the area were more whitish.

“The similar reddish tint suggests that Prometheus is constructed from material in Saturn’s rings,” said co-author Bonnie Buratti, a VIMS team member based at NASA’s Jet Propulsion Laboratory, Pasadena, Calif. “Scientists had been wondering whether ring particles could have stuck together to form moons — since the dominant theory was that the rings basically came from satellites being broken up. The coloring gives us some solid proof that it can work the other way around, too.”

“Observing the rings and moons with Cassini gives us an amazing bird’s-eye view of the intricate processes at work in the Saturn system, and perhaps in the evolution of planetary systems as well,” said Linda Spilker, Cassini project scientist, based at JPL. “What an object looks like and how it evolves depends a lot on location, location, location.”

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, Pasadena, manages the mission for NASA’s Science Mission Directorate, Washington, D.C. The visual and infrared mapping spectrometer team is based at the University of Arizona, Tucson.

Jia-Rui Cook 818-354-0850
Jet Propulsion Laboratory, Pasadena, Calif.
jccook@jpl.nasa.gov

2013-117

Article source: http://www.jpl.nasa.gov/news/news.php?release=2013-117

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NASA craft snaps last close-up photos of icy Saturn moon

By alkaon on March 16, 2013 No Comments

NASA/JPL/Space Science Institute

This raw image of Saturn’s icy moon Rhea was taken on March 10, 2013 by NASA’s Cassini spacecraft. The camera was pointing toward Rhea at approximately 174,181 miles away.

By Mike Wall, SPACE.com

NASA’s Cassini spacecraft has snapped its last up-close photos of Saturn’s icy moon Rhea, revealing a battered satellite covered in craters from violent impacts.

Cassini took the amazing new photos of Rhea on March 9 during its fourth and final planned encounter with the Saturn moon. During the encounter, the probe flew within just 620 miles of Rhea, which is Saturn’s second-largest satellite. “Take a good, long, luxurious look at these sights from another world, as they will be the last close-ups you’ll ever see of this particular moon,” Cassini imaging team lead Carolyn Porco, of the Space Science Institute in Boulder, Colo., said in a statement accompanying the photos.

The flyby was designed primarily to measure Rhea’s gravity field, mission scientists said. But Cassini also managed to take 12 pictures of the frigid moon’s battered, pockmarked surface, including one that showcases a mysterious long, curving fracture called a graben.

Rhea is the second-largest of Saturn’s 60-odd known moons, with a diameter of 949 miles. It’s far smaller than the ringed planet’s biggest natural satellite, Titan, which at 3,200 miles across is nearly 50 percent wider than Earth’s moon.

Rhea was discovered in 1672 by the mathematician and astronomer Giovanni Domenico Cassini, who gave his name to the NASA mission currently studying the Saturn system.

In 2010, researchers determined that the moon has a wispy atmosphere dominated by oxygen and carbon dioxide. The oxygen likely was blasted free from water ice on Rhea’s surface by charged particles streaming from Saturn, scientists say, but the origin of the carbon dioxide is more mysterious.

NASA/JPL-Caltech/Space Science Institute

This image was taken on March 9, 2013 by NASA’s Cassini spacecraft. The camera was pointing toward Rhea at approximately 1,727 miles away.

The Cassini mission — a joint effort involving NASA, the European Space Agency and the Italian Space Agency — launched in 1997 and arrived at Saturn in 2004. It has been studying the ringed planet and its many moons ever since, and will continue to do so on an extended mission until at least 2017.

Follow Mike Wall on Twitter @michaeldwall. Follow us @Spacedotcom, Facebook or Google+. Originally published on SPACE.com.

Copyright 2013 SPACE.com, a TechMediaNetwork company. All rights reserved. This material may not be published, broadcast, rewritten or redistributed.

Article source: http://science.nbcnews.com/_news/2013/03/16/17340546-nasa-craft-snaps-last-close-up-photos-of-icy-saturn-moon?lite

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NASA Spacecraft Snaps Last Close-Up Photos of Icy Saturn Moon

By alkaon on March 15, 2013 No Comments




NASA's Cassini spacecraft has taken its last closeup photos of the icy Saturn moon Rhea.


This raw image of Saturn’s icy moon Rhea was taken on March 10, 2013 by NASA’s Cassini spacecraft, and received on Earth March 10, 2013. The camera was pointing toward Rhea at approximately 174,181 miles (280,317 kilometers) away.
CREDIT: NASA/JPL/Space Science Institute


NASA’s Cassini spacecraft has snapped its last up-close photos of Saturn’s icy moon Rhea, revealing a battered satellite covered in craters from violent impacts.

Cassini took the amazing new photos of Rhea on Saturday (March 9) during its fourth and final planned encounter with the Saturn moon. During the encounter, the probe flew within just 620 miles (997 kilometers) of Rhea, which is Saturn’s second-largest satellite.”Take a good, long, luxurious look at these sights from another world, as they will be the last close-ups you’ll ever see of this particular moon,” Cassini imaging team lead Carolyn Porco, of the Space Science Institute in Boulder, Colo., said in a statement accompanying the photos.

Saturn Moon Rhea's Surface

This image was taken on March 09, 2013, and received on Earth March 10, 2013, by NASA’s Cassini spacecraft. The camera was pointing toward Rhea at approximately 1,727 miles (2,779 kilometers) away, and the image was taken using the CL1 and CL2 filters. This image has not been validated or calibrated.
CREDIT: NASA/JPL-Caltech/Space Science Institute

Saturday’s flyby was designed primarily to measure Rhea’s gravity field, mission scientists said. But Cassini also managed to take 12 pictures of the frigid moon’s battered, pockmarked surface, including one that showcases a mysterious long, curving fracture called a graben.

Raw Image of Rhea

Rhea is the second-largest of Saturn’s 60-odd known moons, with a diameter of 949 miles (1528 km). It’s far smaller than the ringed planet’s biggest natural satellite, Titan, which at 3,200 miles (5,150 km) across is nearly 50 percent wider than Earth’s moon.

Rhea was discovered in 1672 by the mathematician and astronomer Giovanni Domenico Cassini, who gave his name to the NASA mission currently studying the Saturn system.

In 2010, researchers determined that the moon has a wispy atmosphere dominated by oxygen and carbon dioxide. The oxygen likely was blasted free from water ice on Rhea’s surface by charged particles streaming from Saturn, scientists say, but the origin of the carbon dioxide is more mysterious.

The Cassini mission — a joint effort involving NASA, the European Space Agency and the Italian Space Agency — launched in 1997 and arrived at Saturn in 2004. It has been studying the ringed planet and its many moons ever since, and will continue to do so on an extended mission until at least 2017.

Follow Mike Wall on Twitter @michaeldwall. Follow us @Spacedotcom, Facebook or Google+. Originally published on SPACE.com.

Article source: http://www.space.com/20171-saturn-moon-rhea-photos-cassini.html

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NASA Image of the day

The Engine Burns Blue

 
This image shows a cutting-edge solar-electric propulsion thruster in development at NASA's Jet Propulsion Laboratory, Pasadena, Calif., that uses xenon ions for propulsion. An earlier version of this solar-electric propulsion engine has been flying on NASA's Dawn mission to the asteroid belt. This engine is being considered as part of the Asteroid Initiative, a proposal to robotically capture a small near-Earth asteroid and redirect it safely to a stable orbit in the Earth-moon system where astronauts can visit and explore it. This image was taken through a porthole in a vacuum chamber at JPL where the ion engine is being tested. Image credit: NASA/JPL-Caltech
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