Category: Saturn

Long hidden behind a thick veil of haze, Titan, the only known moon with an atmosphere, is ready for its close-up on Oct. 26, 2004. This visit by the Cassini spacecraft may settle intense speculation about whether this moon of Saturn harbors oceans of liquid methane and ethane beneath its coat of clouds.

Cassini will fly by Titan at a distance of 1,200 kilometers (745 miles), with closest approach at 9:44 a.m. Pacific Time. This flyby will be nearly 300 times closer than the first Cassini flyby of Titan, on July 3.

This is one of 45 planned flybys of Titan during the four-year tour. Subsequent flybys will bring the spacecraft even closer. Scientists believe Titan’s atmosphere is similar to that of early Earth.

“Cassini will see Titan as it has never been seen before. We expect the onboard instruments will pierce the moon’s dense atmosphere and reveal a whole new world,” said Dr. Charles Elachi, director of NASA’s Jet Propulsion Laboratory, Pasadena, Calif., and team leader for the Cassini radar instrument.

One important goal of this flyby is to confirm scientists’ model of Titan’s atmosphere to prepare for the Huygens probe descent. The probe, built and managed by the European Space Agency, will be cut loose from its mother ship on Christmas Eve and will coast through the atmosphere of Titan. On the way down, the probe will sample the atmosphere with a sophisticated set of scientific instruments.

“Titan has been lying still, waiting. Cassini may finally show us if what we thought of this moon is true, and whether the Huygens probe touchdown will be a splash,” said Dr. Jean-Pierre Lebreton, Huygens project manager and project scientist for the European Space Research and Technology Center, Noordwijk, Netherlands.

Eleven of Cassini’s 12 instruments will be aimed at Titan during this encounter. Scientists hope to learn more about Titan’s interior structure, surface, atmosphere and interaction with Saturn’s magnetosphere. This first in-place sampling of Titan’s atmosphere will help in understanding the atmosphere’s density and composition, which, in turn, will help aid management of the Huygens probe. This flyby will mark the first time Cassini’s imaging radar is used to observe Titan, and is expected to provide topographical maps and show whether there is a liquid or solid surface.

“We know our instrument will see through the haze to Titan’s surface,” said Dr. Robert H. Brown, team leader for the visual and infrared mapping spectrometer, University of Arizona, Tucson. “This encounter is about digging down below the atmosphere and getting our first glimpse of Titan geology.”

Cassini’s ion and neutral mass spectrometer will taste mysterious, subtle flavors in Titan’s atmosphere. “Our instrument will scoop up a breath of Titan’s puffy atmosphere during the flyby,” said Roger Yelle, instrument team member, also with the University of Arizona. The experiment will measure how many molecules of different masses it gathers in the gulp of Titan’s mostly nitrogen, methane-laced atmosphere.

Titan is Saturn’s largest moon. It is larger than Mercury or Pluto and is the second largest moon in the solar system, after Jupiter’s moon Ganymede. Titan is a cold place thought to be inhospitable to life at 95 degrees Kelvin (minus 289 degrees Fahrenheit).

Cassini has performed flawlessly since entering orbit around Saturn on June 30. The team believes that on Tuesday night, all will proceed as planned.

“This is not the same white-knuckle situation we had during Saturn orbit insertion, but there are some things we can’t control,” said Earl Maize, deputy project manager for the Cassini-Huygens mission at JPL. “If a spacecraft anomaly should occur, or if the weather at the tracking stations does not cooperate, the science return may be limited or lost. Although this is an unlikely scenario, the possibility still exists.” Cassini will have only one opportunity to send the data back to Earth before the data are overwritten on the recorders by data from the next set of observations. The first downlink of data by NASA’s Deep Space Network occurs at 6:30 p.m. PDT.

More information on the Cassini-Huygens mission is available at http://saturn.jpl.nasa.gov and http://www.nasa.gov/cassini.

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 Science Mission Directorate, Washington, D.C.

Original Source: NASA/JPL News Release

Image credit: ESA
The sound of alien thunder, the patter of methane rain and the crunch (or splash) of a landing, all might be heard as Huygens descends to the surface of Titan on 14 January 2005.

What?s more, they will be recorded by a microphone on the probe and relayed back so that everyone on Earth can hear the sounds of Titan. Although the Russians took a microphone to Venus in the 1970s, few scientific results came out if that endeavour. A similar microphone for Mars was destroyed when NASA?s Mars Polar Lander crashed a few years ago.

The new microphone is part of the Huygens Atmospheric Structure Instrument (HASI), one of six multi-functional experiments carried on the Huygens probe. It is designed to help track down lightning by listening for the clap of thunder usually associated with such an event.

Although there is only a small chance that the spacecraft will pass near a thunderstorm, it is an extremely important investigation to carry out. It may help us to understand if thunderstorms are an important energy source for organic chemistry on Titan.

This may hold clues about how life began on Earth. Titan?s atmosphere is laced with chemicals and many scientists think these are the same as those that formed the building blocks of life on Earth, 4000 million years ago. But how did they join together on Earth to ultimately become DNA?

One possibility is that sudden discharges of energy, as occur in lightning, could have forced the simple chemicals together, making more complicated ones. So Huygens will listen for thunder and ?sniff? for chemicals that might have been produced in lightning strikes.

In fact, a second microphone experiment can also be found on Huygens. It is part of the Surface Science Package (SSP) and contributes to an experiment to measure the speed of sound in Titan?s atmosphere.

These results present an exciting possibility because if the HASI microphone does hear thunder, electrodes on the same instrument will register the lightning?s electrical discharge and scientists will be able to calculate how close Huygens passed to the storm.

If Huygens actually passes through a storm, the microphone will detect the splash of the rain onto the spacecraft casing. Unlike on Earth, this rain will not be water but probably liquid methane.

Marcello Fulchignoni, of the Universit? Denis Diderot, Paris, is the principal investigator of HASI. He says, ?Combined with the camera images, temperature and pressure profiles, and altitude data, the ?soundtrack? will provide a fascinating look at the details of the mission?s descent. We will be working hard to bring the voice of Huygens to the public as soon as we can after the descent.?

Original Source: ESA News Release

Image credit: NASA/JPL/SSI
On Jan. 14, 2005, the Huygens probe will plow into the orange atmosphere of Saturn’s moon, Titan, becoming the first spacecraft to attempt to land on a moon in our solar system since the Soviet Union’s Luna 24 touched down on Earth’s moon in 1976.

Though scientists hope that Huygens will survive the plunge, it will be flying blind through hydrocarbon haze and methane clouds to a surface that could consist of seven-kilometer-high ice mountains and liquid methane seas.

That’s the picture that emerges from a series of articles – half of them by University of California, Berkeley, researchers – published in the journal Geophysical Research Letters last month and detailing what scientists know to date about the surface, atmosphere and magnetic field of Titan. This view sets the stage for an analysis of new data soon to arrive from the Cassini spacecraft and Huygens probe.

“These (journal) papers really give a state-of-the-art picture of Titan, before Cassini goes into orbit around Saturn and the Huygens probe goes into Titan’s atmosphere,” said Imke de Pater, a professor of astronomy at UC Berkeley who wrote the introductory paper in the series and co-authored four of the nine papers. The papers came out of a meeting De Pater hosted last November at UC Berkeley to discuss what has been gleaned to date about the moon from optical, infrared and radar telescopes, including the Hubble Space Telescope and the twin Keck Telescopes in Hawaii.

Scientists expect the current sketchy picture of Titan’s surface, totally obscured by clouds and haze, will much improve when the Cassini spacecraft, which is carrying the Huygens probe, starts an intense observation of Titan later this month. While on-board infrared imaging cameras can pierce the cloud cover, however, they can only reveal bright and dark spots on the surface, which are difficult to interpret. What Huygens will encounter at Titan’s surface will remain a mystery until the probe plops into an ocean or parachutes to solid ground.

“Based upon their spectral characteristics, the bright areas imaged by various Earth-bound telescopes and the Hubble Space Telescope could be a mixture of rock and water ice,” de Pater said. Such a mixture appears relatively bright in comparison with substances like tar and liquid hydrocarbons, which absorb essentially all sunlight at these wavelengths and hence appear very dark.

“The dark areas could contain liquid hydrocarbons,” she said. “But they’re all still a mystery.”

Some scientists have suggested that one large bright area, Xanadu, is a mountain of rock and water ice that stands out because runoff (hydrocarbon rain) has washed off the dark hydrocarbon particles. UC Berkeley graduate student J. Taylor Perron and de Pater concluded in one of the papers that such an ice continent, primarily composed of water ice, could be no higher than 3 to 7 kilometers – that is, at most, 23,000 feet, about the height of Mt. Aconcagua in Argentina. That is even more impressive on a globe less than half the diameter of Earth.

The Huygens probe, which will take from two to two and a half hours to float to the surface, is aiming for a landing site in a dark area bordering a bright area near the equator, so it could land instead in a gasoline-like hydrocarbon brew of methane, propane or butane. Though the probe is designed to float, its builders expect, at most, 45 minutes of data once it sets down. A few minutes would be cause for celebration.

The Cassini/Huygens spacecraft was launched from Kennedy Space Center in 1997, the product of an international collaboration between three space agencies – the National Aeronautics and Space Administration, the European Space Agency and the Italian Space agency – involving contributions from 17 nations. It arrived at Saturn in July 2004, beginning a four-year mission to photograph and collect data on Saturn, its rings and moons. This Oct. 26, it will get within 1,000 kilometers of Titan – closer than ever before – turning its remote sensing instruments on that moon’s surface and atmosphere. Cassini will release the Huygens probe on Christmas Day, Dec. 25.

The second largest moon in the solar system and the only one with a thick, methane-rich, nitrogen atmosphere, Titan intrigues scientists because of its resemblance to a young Earth. The atmospheres of both Titan and the early Earth were dominated by nearly the same amount of nitrogen, and the chemistry discovered on Titan could provide clues to the origins of life on our planet.

De Pater and chemistry graduate student Mate Adamkovics have used the adaptive optics on the Keck Telescope in Hawaii to image the hydrocarbon haze that envelops the moon, taking snapshots at various altitudes from 150 to 200 kilometers down to the surface. In the movie they constructed from these snapshots, haze is very evident in the atmosphere at about 30-50 kilometers over the South Pole. Stratospheric haze at about 150 kilometers is visible over a large area in the northern hemisphere but not the southern hemisphere, an asymmetry observed previously. And at the southern hemisphere’s tropopause – the border between the lower atmosphere and the stratosphere at about 42 kilometers altitude – cirrus haze is visible, analogous to cirrus haze on Earth.

These observations agree with a theory of haze formation whereby sunlight creates haze particles at a high altitude – 400 to 600 kilometers above the surface – that are blown to the winter pole, where the haze accumulates as a polar “hood.” The haze particles start to settle out and are carried by a lower-elevation return flow to the summer hemisphere.

Laboratory experiments by Melissa Trainer of the University of Colorado, Boulder, reported in the journal suggest that the haze particles could be polycyclic aromatic hydrocarbons if the methane concentration in the atmosphere is high – around 10 percent – though they would be primarily long-chain hydrocarbons at low concentrations. The Huygens probe will measure gas concentrations as it plummets through the atmosphere, hopefully testing this connection between methane concentration and aerosol composition.

Cassini’s observations of Titan over the next four years should yield much more information about the atmospheric haze and surface topography, as well as raise new questions. De Pater urges ground-based astronomers to continue to observe Titan’s moon, “so the Cassini/Huygens data can be tied in with the long-term data base on Titan’s seasons,” she wrote.

De Pater herself will be peering at Titan through the Keck Telescope on Jan. 15 when the Huygens probe disappears into the atmosphere.

“I’m skeptical that we’ll see a meteor trail, as some have predicted, but our observations will give us a good image of Titan at the time of probe entry, which could be very relevant to calibrating Titan at entry time,” de Pater said.

De Pater’s research is supported by the National Science Foundation. The Nov. 17, 2003, workshop on Titan was sponsored by the Center for Integrative Planetary Studies at UC Berkeley.

Original Source: Berkeley News Release

University of California scientists working at Los Alamos National Laboratory have begun to analyze data from an instrument aboard the joint U.S.-European spacecraft Cassini. Although Cassini has only been orbiting the planet Saturn since July 1, data from the Cassini Plasma Spectrometer (CAPS) has already begun to provide new information about the curious nature of Saturn’s space environment.

CAPS had been detecting advance readings for several days before Cassini finally crossed the bow shock that exists in the solar wind ahead of the magnetosphere, a huge magnetic field bubble produced in the solar wind by Saturn’s strong magnetic field. On June 28, the spacecraft entered into the magnetosphere itself and began taking data. From this very preliminary set of measurements, it is apparent that the outer reaches of Saturn’s magnetosphere are probably populated by plasma captured from the solar wind, but closer to the planet the plasma comes primarily from the rings and/or the inner icy satellites.

According to Michelle Thomsen, the current Los Alamos CAPS project leader, “After many years of design, development and testing, and then the seven-year journey across the solar system, CAPS is finally doing the job it was built to do. We are quickly learning much, but I think we have only begun to understand what CAPS can teach us about Saturn and its space environment over the next few years.”

CAPS consists of three separate analyzers designed to measure the electrically charged particles trapped within Saturn’s magnetosphere. Los Alamos played a major role in the design and construction of two of them: an ion mass spectrometer (IMS), which incorporates a novel design developed at Los Alamos to identify the different atomic species in Saturn’s magnetospheric plasma, and an ion beam spectrometer (IBS), which is based on a design used by Los Alamos scientists on several previous solar wind research missions.

During Cassini’s first brief pass over Saturn’s rings, CAPS identified a previously unknown low-energy plasma trapped on the magnetic field lines threading the Cassini Division, the name given to the gap between the main A and B rings. With the four-year mission just beginning, including more than 70 orbits of the planet, CAPS is poised to provide scientists with a new level of understanding about Saturn’s space environment, as well as clues about some of the space physics processes that operate more universally in the solar system.

The CAPS team involves scientists and engineers from 14 institutions and six countries, including Dave Young, the Principal CAPS Investigator at the Southwest Research Institute in San Antonio, Texas. At Los Alamos, the CAPS effort was made possible by the work of numerous members of International, Space and Response Division and its predecessor organizations. The IMS was designed by Los Alamos staff member Beth Nordholt and former staff member Dave McComas. In addition to Thomsen, current members of the team include Bruce Barraclough (lead investigator for the IBS), Dot Delapp, Jack Gosling, Dan Reisenfeld, John Steinberg, Bob Tokar and summer student Brian Fish.

Los Alamos National Laboratory is operated by the University of California for the National Nuclear Security Administration (NNSA) of the U.S. Department of Energy and works in partnership with NNSA’s Sandia and Lawrence Livermore national laboratories to support NNSA in its mission.

Los Alamos enhances global security by ensuring the safety and reliability of the U.S. nuclear deterrent, developing technologies to reduce threats from weapons of mass destruction, and solving problems related to defense, energy, environment, infrastructure, health and national security concerns.

Original Source: Los Alamos News Release

In its own way, the shepherd moon Prometheus (102 kilometers, 63 miles across) is one of the lords of Saturn’s rings. The little moon maintains the inner edge of Saturn’s thin, knotted F ring, while its slightly smaller cohort Pandora (84 kilometers, or 52 miles across) guards the ring’s outer edge.

This view is a composite of nine raw images combined in a way that improves resolution and reduces noise. The final image was magnified by a factor of five. One of the component images was previously released (see PIA 06098).

The image clearly shows that Prometheus is not round, but instead has an oblong, potato-like shape. The moon was discovered during the Voyager mission, and scientists then noted ridges, valleys and craters on its surface. Hints of its varied topography are present in this view, although Cassini will likely obtain much better images of Prometheus later in the mission.

The component images were taken over about ten and a half minutes. During that time, the spacecraft’s motion caused some blurring of the F ring in the background. Cassini was below the ring plane at the time the images were obtained, and the view here is across the rings toward the distant arm of the F ring. Sunlight is coming from below left.

These images were obtained with the Cassini spacecraft wide angle camera on July 1, 2004, around the time Cassini entered Saturn’s orbit. The spacecraft’s distance from the planet ranged from approximately 181,000 to 190,000 kilometers (112,000 to 118,000 miles) during the time the exposures were taken. The image scale is approximately 11 kilometers (7 miles) per pixel.

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 Science Mission Directorate, 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.

For more information about the Cassini-Huygens mission, visit http://saturn.jpl.nasa.gov and the Cassini imaging team home page, http://ciclops.org .

Original Source: NASA/JPL/SSI News Release

Saturn’s moon Prometheus is seen shepherding the inner edge of Saturn’s F ring. Prometheus is 102 kilometers (63 miles) across and was captured in a close-up view by the Cassini spacecraft near the time of orbital insertion at Saturn PIA06098. A number of clumps are visible here along the arcing F ring.

The image was taken with the Cassini spacecraft narrow angle camera on Aug. 5, 2004, at a distance of 8.2 million kilometers (5.1 million miles) from Saturn through a filter sensitive to visible green light. The image scale is 49 kilometers (33 miles) per pixel. Contrast was slightly enhanced to aid visibility.

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 Science Mission Directorate, 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.

For more information about the Cassini-Huygens mission, visit http://saturn.jpl.nasa.gov and the Cassini imaging team home page, http://ciclops.org .

Original Source: NASA JPL News Release

Scientists examining Saturn’s contorted F ring, which has baffled them since its discovery, have found one small body, possibly two, orbiting in the F ring region, and a ring of material associated with Saturn’s moon Atlas.

A small object was discovered moving near the outside edge of the F ring, interior to the orbit of Saturn’s moon Pandora. The object was seen by Dr. Carl Murray, imaging team member at Queen Mary, University of London, in images taken on June 21, 2004, just days before Cassini arrived at Saturn. “I noticed this barely detectable object skirting the outer part of the F ring. It was an incredible privilege to be the first person to spot it,” he said. Murray’s group at Queen Mary then calculated an orbit for the object.

Scientists cannot yet definitively say if the object is a moon or a temporary clump. If it is a moon, its diameter is estimated at four to five kilometers (two to three miles) and it is located 1,000 kilometers (620 miles) from the F ring, Saturn’s outmost ring. It is at a distance of approximately 141,000 kilometers (86,000 miles) from the center of Saturn and within 300 kilometers (190 miles) of the orbit of the moon Pandora. The object has been provisionally named S/2004 S3.

Scientists are not sure if the object is alone. This is because of results from a search through other images that might capture the object to pin down its orbit. The search by Dr. Joseph Spitale, a planetary scientist working with team leader Dr. Carolyn Porco at the Space Science Institute in Boulder, Colo., revealed something strange. Spitale said, “When I went to look for additional images of this object to refine its orbit, I found that about five hours after first being sighted, it seemed to be orbiting interior to the F ring,” said Spitale. “If this is the same object then it has an orbit that crosses the F ring, which makes it a strange object.” Because of the puzzling dynamical implications of having a body that crosses the ring, the inner object sighted by Spitale is presently considered a separate object with the temporary designation S/2004 S 4. S4 is roughly the same size as S3.

In the process of examining the F ring region, Murray also detected a previously unknown ring, S/2004 1R, associated with Saturn’s moon, Atlas. “We knew from Voyager that the region between the main rings and the F ring is dusty, but the role of the moons in this region was a mystery,” said Murray. “It was while studying the F ring in these images that I discovered the faint ring of material. My immediate hunch was that it might be associated with the orbit of one of Saturn’s moons, and after some calculation I identified Atlas as the prime suspect.”

The ring is located 138,000 kilometers (86,000 miles) from the center of Saturn in the orbit of the moon Atlas, between the A ring and the F ring. The width of the ring is estimated at 300 kilometers (190 miles). The ring was first spotted in images taken after orbit insertion on July 1, 2004. There is no way of knowing yet if it extends all the way around the planet.

“We have planned many images to search the region between the A and F rings for diffuse material and new moons, which we have long expected to be there on the basis of the peculiar behavior of the F ring,” said Porco. “Now we have found something but, as is usual for the F ring, what we see is perplexing.”

Searches will continue for further detections of the newfound body or bodies seen in association with the F ring. If the two objects indeed turn out to be a single moon, it will bring the Saturn moon count to 34. The newfound ring adds to the growing number of narrow ringlets around 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 Science Mission Directorate, Washington. 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. UK scientists are playing significant roles in the mission with involvement in six of the 12 instruments onboard the Cassini orbiter and two of the six instruments on the Huygens probe.

Cassini-Huygens 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 Science and Mission Directorate, Washington. The Cassini orbiter was designed, developed and assembled at JPL. The Composite Infrared Spectrometer team is based at NASA’s Goddard Space Flight Center, Greenbelt, Md. For this image and for the latest news about the Cassini-Huygens mission, visit http://www.nasa.gov/cassini. For in-depth mission information, visit http://saturn.jpl.nasa.gov. For more information on the Composite Infrared Spectrometer, visit http://cirs.gsfc.nasa.gov.

Original Source: NASA/JPL News Release

The Cassini spacecraft has taken the most detailed temperature measurements to date of Saturn’s rings. Data taken by the composite infrared spectrometer instrument on the spacecraft while entering Saturn’s orbit show the cool and relatively warm regions of the rings.

This false-color image shows that the temperatures on the unlit side of Saturn’s rings vary from a relatively warm 110 Kelvin (-261 degrees Fahrenheit, shown in red), to a cool 70 Kelvin (-333 degrees Fahrenheit, shown in blue). The green represents a temperature of 90 Kelvin (-298 degrees Fahrenheit). Water freezes at 273 Kelvin (32 degrees Fahrenheit).

The data show that the opaque region of the rings, like the outer A ring (on the far right) and the middle B ring, are cooler, while more transparent sections, like the Cassini Division (in red just inside the A ring) or the inner C ring (shown in yellow and red), are warmer. Scientists had predicted this might be the case, because the opaque ring areas would let less light through, and the transparent areas, more. These results also show, for the first time, that individual ringlets in the C ring and the Cassini Division are cooler than the surrounding, more transparent regions.

The temperature data were taken on July 1, 2004, shortly after Saturn orbit insertion. Cassini is so close to the planet that no pictures of the unlit side of the rings are available, hence the temperature data was mapped onto a picture of the lit side of the rings. Saturn is overexposed and pure white in this picture. Saturn?s moon Enceladus is visible below the rings, toward the center.

The composite infrared spectrometer, one of 12 instruments on Cassini, will measure infrared emissions from atmospheres, rings and surfaces. This spectrometer will create vertical profiles of temperature and gas composition for the atmospheres of Titan and Saturn. During Cassini?s four-year tour, the instrument will also gather information on the thermal properties and composition of Saturn?s rings and icy moons.

Cassini-Huygens 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 Science and Mission Directorate, Washington. The Cassini orbiter was designed, developed and assembled at JPL. The Composite Infrared Spectrometer team is based at NASA’s Goddard Space Flight Center, Greenbelt, Md.

For this image and for the latest news about the Cassini-Huygens mission, visit http://www.nasa.gov/cassini. For in-depth mission information, visit http://saturn.jpl.nasa.gov. For more information on the Composite Infrared Spectrometer, visit http://cirs.gsfc.nasa.gov.

Original Source: NASA/JPL News Release

The Cassini spacecraft successfully completed a 51-minute engine burn that will raise its next closest approach distance to Saturn by nearly 300,000 kilometers (186,000 miles). The maneuver was necessary to keep the spacecraft from passing through the rings and to put it on target for its first close encounter with Saturn’s moon Titan on Oct. 26.

Mission controllers received confirmation of a successful burn at 11:15 a.m. Pacific Time today. The spacecraft is approaching the highest point in its first and largest orbit about Saturn. Its distance from the center of Saturn is about 9 million kilometers (5.6 million miles), and its speed just prior to today’s burn was 325 meters per second (727 miles per hour) relative to Saturn. That means it is nearly at a standstill compared to its speed of about 30,000 meters per second (67,000 miles per hour) at the completion of its orbit insertion burn on June 30.

“Saturn orbit insertion got us into orbit and this maneuver sets us up for the tour,” said Joel Signorelli, spacecraft system engineer for the Cassini-Huygens mission at NASA’s Jet Propulsion Laboratory, Pasadena, Calif.

The maneuver was the third longest engine burn for the Cassini spacecraft and the last planned pressurized burn in the four-year tour. The Saturn obit insertion burn was 97 minutes long, and the deep space maneuver in Dec. 1998 was 88 minutes long.

“The October 26 Titan encounter will be much closer than our last one. We’ll fly by Titan at an altitude of 1,200 kilometers (746 miles), ‘dipping our toe’ into its atmosphere,” said Signorelli. Cassini’s first Titan flyby on July 2 was from 340,000 kilometers (211,000 miles) away.

Over the next four years, the Cassini orbiter will execute 45 Titan flybys as close as approximately 950 kilometers (590 miles) from the moon. In January 2005, the European-built Huygens probe that is attached to Cassini will descend through Titan’s atmosphere to the surface.

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 Science Mission Directorate, Washington. JPL designed, developed and assembled the Cassini orbiter.

For the latest images and more information about the Cassini-Huygens mission, visit http://saturn.jpl.nasa.gov and http://www.nasa.gov/cassini.

Original Source: NASA/JPL News Release

With eyes sharper than any that have peered at Saturn before, the Cassini spacecraft has uncovered two moons, which may be the smallest bodies so far seen around the ringed planet.

The moons are approximately 3 kilometers (2 miles) and 4 kilometers (2.5 miles) across — smaller than the city of Boulder, Colorado. The moons, located 194,000 kilometers (120,000 miles) and 211,000 kilometers (131,000 miles) from the planet’s center, are between the orbits of two other saturnian moons, Mimas and Enceladus. They are provisionally named S/2004 S1 and S/2004 S2. One of them, S/2004 S1, may be an object spotted in a single image taken by NASA’s Voyager spacecraft 23 years ago, called at that time S/1981 S14.

“One of our major objectives in returning to Saturn was to survey the entire system for new bodies,” said Dr. Carolyn Porco, imaging team leader, Space Science Institute, Boulder, Colo. Porco planned the imaging sequences. “So, it’s really gratifying to know that among all the other fantastic discoveries we will make over the next four years, we can now add the confirmation of two new moons, skipping unnoticed around Saturn for billions of years until just now.”

The moons were first seen by Dr. Sebastien Charnoz, a planetary dynamicist working with Dr. Andre Brahic, imaging team member at the University of Paris. “Discovering these faint satellites was an exciting experience, especially the feeling of being the first person to see a new body of our solar system,” said Charnoz. “I had looked for such objects for weeks while at my office in Paris, but it was only once on holiday, using my laptop, that my code eventually detected them. This tells me I should take more holidays.”

The smallest previously known moons around Saturn are about 20 kilometers (12 miles) across. Scientists expected that moons as small as S/2004 S1 and S/2004 S2 might be found within gaps in the rings and perhaps near the F ring, so they were surprised these small bodies are between two major moons. Small comets careening around the outer solar system would be expected to collide with small moons and break them to bits. The fact that these moons exist where they do might provide limits on the number of small comets in the outer solar system, a quantity essential for understanding the Kuiper Belt of comets beyond Neptune, and the cratering histories of the moons of the giant planets.

“A comet striking an inner moon of Saturn moves many times faster than a speeding bullet,” said Dr. Luke Dones, an imaging team member from the Southwest Research Institute in Boulder, Colo. “If small, house-sized comets are common, these moons should have been blown apart many times by cometary impacts during the history of the solar system. The disrupted moon would form a ring, and then most of the material would eventually gather back together into a moon. However, if small comets are rare, as they seem to be in the Jupiter system, the new moons might have survived since the early days of the solar system.”

Moons surrounding the giant planets generally are not found where they originally formed because tidal forces from the planet can cause them to drift from their original locations. In drifting, they may sweep through locations where other moons disturb them, making their orbits eccentric or inclined relative to the planet’s equator. One of the new moons might have undergone such an evolution.

Upcoming imaging sequences will scour the gaps in Saturn’s rings in search of moons believed to be there. Meanwhile, Cassini scientists are eager to get a closer look, if at all possible, at their new finds. Porco said, “We are at this very moment looking to see what the best times are for retargeting. Hopefully, we haven’t seen the last of them.”

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 Science Mission Directorate, 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.

For more information about the Cassini-Huygens mission, visit http://saturn.jpl.nasa.gov and the Cassini imaging team home page, http://ciclops.org.

Original Source: NASA/JPL News Release