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One of the Most Complex and Ambitious Ventures in the History of Space Exploration
Saturn Rings Moons Titan Cassini Science Huygens Resources
Latest news from the planet Saturn:
Cassini is Exploring the Saturn System
After cruising across deep space for more than 6.5 years, the Cassini spacecraft from Earth arrived in the Saturn system in June 2004. It sailed through the planet's rings on July 1, 2004, beginning a four-year tour of the giant ringed planet and its many moons. The Huygens probe landed on the giant moon Titan on January 14, 2005. Cassini will continue to explore the moons and rings of Saturn until at least July 31, 2008.

NASA artist concept of Cassini at Saturn
A NASA artist imagines Cassini at Saturn.
click image to enlarge – NASA JPL  »»

A magnificent view of Saturn pieced together from 126 images of the planet recorded by Cassini in October 2005
Magnificent Saturn view pieced together from 126 Cassini images recorded in October 2004.
click image to enlarge – NASA JPL  »»

Dragon Storm in Saturn's atmosphere
Mysterious Dragon Storm in Saturn's atmosphere.
click image to enlarge – NASA JPL  »»

Huygens first color picture of Titan from the surface
The first color picture from the surface of Titan by Huygens on January 14, 2005.
click image to enlarge – NASA JPL  »»

Huygens parachute landing on Titan
NASA artist imagines Huygens parachuting through the murky atmosphere to the surface of Titan in January 2005.
click image to enlarge – NASA JPL  »»

Cassini photo of Saturn's A Ring
Cassini sees the planet's A Ring in infrared light as it arrives at Saturn
click image to enlarge – NASA JPL  »»

Cassini photo of Saturn's B and C rings
Cassini sees the planet's B and C Rings in infrared light as it arrives at Saturn
click image to enlarge – NASA JPL  »»

NASA artist concept of Cassini orbital insertion at Saturn
NASA art concept of Cassini flying through the rings on July 1, 2004.
click image to enlarge – NASA JPL  »»

Titan in three colors
Left Cassini image of Titan surface: dark water ice, bright hydrocarbons. Middle image: dark water ice, hydrocarbons. Right image: dark icy regions, bright hydrocarbons. Bright methane particle cloud near south pole in all three means particles are large compared to haze particles around the planet, indicating active atmosphere near the pole.
click image to enlarge – NASA JPL  »»

Titan glows in false colors
While flying over the terminator, where Titan's day and night meet, on July 2, 2004, Cassini's visual and infrared mapping spectrometer recorded the glow of the gas shrouded moon. Blue shows sunlight piercing thick atmosphere to the surface. Green shows the immense size of Titan's atmosphere with methane extending out 435. Red shows Titan glows at night out to 124 miles. Purple surface inside circle at right is mixing of blue and red images.
click image to enlarge – NASA JPL  »»

Images and illustrations supplied by:
NASA, JPL, ESA, ASI, University of Arizona

Current Events at Saturn

Some Important Cassini Findings So Far  »»

» April 15, 2008: NASA has extended the international Cassini mission touring Saturn and its moons for another two years to July 2010. The unmanned probe has beamed back some 140,000 images sine 2004. Its prime mission had been slated to end in July 2008. The extension will allow Cassini to make 60 more revolutions around the ringed planet and fly by its largest moon, Titan, and four other satellites. The mission is studying Saturn's rings, atmosphere, storms and moons.

Cassini follows Saturn explorations by Pioneer 11 in 1979 and Voyager 1 and 2 in 1980 and 1981. Cassini was launched in 1997, with operations at Saturn originally scheduled for 2005 through 2008. Along its 2.2 billion mile journey to Saturn, Cassini flew by Venus in 1998 and 1999 and Jupiter in 2000. It arrived at Saturn at the end of 2004 and released the Huygens probe, which flew down to land on Titan.
Cassini significant events from 1996 to date »        Cassini recent press releases »
Photo: Densely cratered plains cover the ancient surface of Saturn's moon Rhea »

» December 1, 2006: With Cassini about halfway through its tour of the expansive Saturn system of moons, rings and planet, NASA is planning an extension of the spacecraft's work at Saturn to July 2010. After that, it may either be given a new flight plan or decommissioned. The what-to-do-next decision probably won't be made until 2009. The options might include:
  • putting the spacecraft in a harmless orbit around the Saturn system
  • crashing it into Saturn or one of the moons
  • sending it inward across the Solar System to explore Jupiter or impact on Mercury
  • sending it outward to investigate a more-distant planet or even the Kuiper Belt at the edge of the Solar System.
Cassini follows Saturn explorations by Pioneer 11 in 1979 and Voyager 1 and 2 in 1980 and 1981. Cassini was launched in 1997, with operations at Saturn scheduled for 2005 through 2008. Along its 2.2 billion mile journey to Saturn, Cassini flew by Venus in 1998 and 1999 and Jupiter in 2000. It arrived at Saturn at the end of 2004 and released the Huygens probe, which flew down to land on Titan.
Photo: Cassini looks down on Saturn's murky northern hemisphere »

» November 1, 2006: Cassini has spotted a large storm, like a hurricane on Earth, with a well-developed eye, ringed by towering clouds, at Saturn's south pole. The storm is a dark area inside a thick, bright ring of clouds. It is some 5,000 miles across, which is two thirds the diameter of Earth. The storm seems different from Earth's hurricanes because it has formed without an ocean at its base and it is locked to the south pole and does not drift around. A movie made from 14 images shot by NASA over three hours shows the swirling cloud mass centered on the south pole with winds blowing at 350 miles per hour.
Movie: a short QuickTime movie of the eye »

» October 11, 2006: Cassini has spotted two new rings around the planet and confirmed the presence of two others. The new rings are associated with one or more small moons and share their orbits with the moons. NASA scientists suspect yet another moon may be lurking near a third ring. Color variations across the giant planet's rings have indicated to scientists that natural processes sort the particles in the rings by size. With the Sun on the far side, and the rings in the planet's shadow, the entire system of rings could be seen. Microscopic particles that had not been seen before could be seen. A single, faint new ring was discovered at the orbits of two tiny moons – moonlets – known as Janus and Epimetheus. A second ring was found overlying the orbit of the tiny moon Pallene, which Cassini discovered back in 2004. A third and fourth ring were visible in the Cassini Division, which is the big gap in Saturn's main ring system. The newly-discovered rings had not been seen in images from NASA's Voyager spacecraft in the 1980s. Voyager 1 flew by Saturn in 1980. Voyager 2 flew by in 1981. Saturn's smallest moons have weak gravity so they can't hold onto loose material on their surfaces. When the moonlets are struck by fast-moving interplanetary meteoroids, the loose material is blasted off of the moonlets' surfaces and into orbit around Saturn. That creates the diffuse rings along the moonlets' orbital paths. Collisions among several moonlets, or collisions with clumps of boulder-sized rubble, also might lead to debris trails. For instance, Saturn's G ring does not seem to have any moon large enough to see, so it might have been formed by a recent breakup of a moonlet.
Photo: 165 Cassini images of rings combined into one »

» July 27, 2006: Liquid methane drizzles onto the surface of Titan – Saturn's largest moon – according to data from the European Space Agency's Huygens probe, which rode piggyback on the Cassini spacecraft to Saturn. The data shows a low, barely visible, cloud of liquid methane and nitrogen that drops rain onto the surface. Huygens collected the data January 14, 2005, as it approached and landed on the moon. The slight drizzle continues all the time, day in, day out, making the ground wet and muddy with liquid methane, according to scientists at the University of Cologne, Germany, and NASA's Ames Research Center in California. Huygens landed with a splat in methane mud. On Earth, methane is a flammable gas, but Titan has no oxygen in its atmosphere to support combustion. Also, Titan's surface temperature is so cold, at minus 300 degrees Fahrenheit (minus 149 degrees Celsius), the methane remains liquid. The rain may have carved river-like features in the landscape. In the atmosphere, there is a gap separating the liquid methane cloud from a higher methane-ice cloud. Scientists say the moon's atmosphere circulates with the downward rain of methane matched by methane gas evaporating upward from the surface. The methane rains about two inches a year on Titan. That's about the same as the amount of water rain per year in California's arid Death Valley.
NASA report: the Huygens mission to Titan »

» November 20, 2005: From some 530,000 miles away, Cassini's narrow-angle camera on September 22 recorded a striking photo of Saturn's moons Dione passing Tethys above the planet Saturn's ring system. In the visible-light image, the larger moon in the foreground is Dione, which is 700 miles wide. The smaller moon in the background is Tethys, which is 665 miles across. Cassini was 900,000 miles Tethys. Since arriving in orbit around Saturn on July 1, 2004, the spacecraft has made two flybys of Dione and five of Tethys. The dark furrow seen in the rings is known as the Cassini Division. Italian astronomer Jean Dominique Cassini first spotted the Cassini Division in 1675. The close observations of Dione in 2004-2005 exposed a cratered surface with open fractures showing bright material. Dione may be mostly water ice, with a rocky core. Tethys up close reveals a huge crater, which has been named Odysseus, and a giant fissure called Ithaca Chasma, which is about 40 miles wide and covers three-quarters of the distance around Tethys. The enormous trench may have been created if the moon's liquid crust hardened before its interior.
Photo: Saturn's F ring shepherd moon Pandora »

» November 16, 2005: Cassini snapped a close-up picture on September 5, 2005, of Saturn's F ring shepherd moon, Pandora, revealing the small moon is coated with fine dust-sized ice. Pandora is 52 miles wide. The spacecraft used its narrow-angle camera to record the image from a distance of 32,000 miles.
Photo: Dione passing Tethys above Saturn's rings »

» September 20, 2005: Fifteen months after Cassini flew through the rings of Saturn into orbit around the giant gas planet, the interplanetary probe is operating almost perfectly, delivering a torrent of data from discoveries that will fill and fulfill the lives of hundreds if not thousands of scientists and engineers for years to come.

Here are some of the highlights of the probe's work this year in that faraway system:
  • Most memorably, Cassini released the probe Huygens in January and, 11 days later, the small vehicle parachuted through a smoggy atmosphere to the surface of Saturn's largest moon, Titan, where it recorded the first clear images of that natural satellite. After that, Cassini made more passes by Titan.

    While Cassini has yet to see methane rain or methane oceans, scientists suggest Titan has a weather system based on liquid methane, rather than water. That weather seems to have carved Titan's icy cliffs into a landscape not unlike Norwegian fjords. The methane vents from Titan's interior, blows into space and rains back onto the surface as hydrocarbon dust particles. No solid body in the Solar System, other than Earth, has such a complex weather system.

  • Cassini found an equatorial mountain range twice the height of Mount Everest on the heavily cratered, icy moon Iapetus. Half of Iapetus is coated with dark material while the other half shines white.

  • Cassini sent home new evidence that Saturn's moon Phoebe is an outsider that wandered in from deep space and was captured by the planet's gravity. Phoebe's surface is more diverse than anywhere in the Solar System, except Earth.

  • Cassini discovered the three-mile-wide midget moon Polydeuces orbiting in harmony with the larger moon Dione. Saturn is the only planet known to have such companion moons, referred to as Trojan moons.

  • Cassini flew by Enceladus at just 109 miles above that moon's surface. From that close in, Cassini's instruments found a cloud of water vapor venting from fissures at the moon's south pole. That meant the tiny moon Enceladus, a mere 310 miles in diameter, ranked alongside the planet Mars and Jupiter's moon Europa as the Solar System bodies likely to have liquid water beneath their frozen surfaces. Water is thought to be necessary for life. A NASA scientists called the discovery of water vapor on Enceladus one of the most important findings ever in planetary science. Enceladus orbits Saturn at a distance of 148,000 miles.

    Known before the Cassini visit as the brightest object in the Solar System, other than the Sun of course, because of its casing of ice crystals, Enceladus now also is known as the smallest body to have active volcanism. Scientists suggest jets of gas are flowing out at high velocity from fissures to form a large column of gas above the south pole. The gas is water vapor, carbon dioxide, methane and nitrogen. While temperatures at the vents are below zero, liquid water could flash into gas when it is flushed into the vacuum of space.

  • Cassini has made several discoveries among the giant planet's rings. For instance, observations of Saturn's E ring turned up microscopic icy "smoke" particles from Enceladus's vents.

  • Cassini has found several new rings surrounding Saturn.

  • Cassini's infrared spectrometer found sharp temperature differences on the surfaces of both large and small particles in Saturn's three main rings. That meant the particles rotate slowly.

  • In the A ring, 76,000 miles from Saturn's center, Cassini found particle clusters ranging in size from, as NASA described them, "sedans to moving vans." The particle clusters are constantly combining and being torn apart by tidal forces caused by Saturn's gravity.

  • Cassini discovered that winds on the planet Saturn itself blow 170 mph faster at lower altitudes than at high altitudes.

  • Cassini also discovered huge columns of thunderstorms on Saturn producing lightning bolts 10,000 times stronger than the most powerful on Earth.
Cassini is scheduled to work around Saturn for three more years amidst the planet's system of numerous rings and nearly three dozen moons.

» September 7, 2005: Cassini's synthetic aperture radar, during a flyby of Saturn's moon Titan, revealed what appears to be a large shoreline cutting across the smoggy moon's southern hemisphere. There were hints the area was once wet, or may even currently have a liquid present.

A bright, rough region about 1,060 miles long by 106 miles wide seems to be high terrain cut by channels and bays.

NASA scientists suggested Titan may have had periods of rainfall or massive seepages of liquid, possibly liquid hydrocarbons, from the ground.

Cassini had made two other radar passes by Titan in October 2004 and February 2005. The three sets of radar images seem to show at least two distinct types of drainage channels on Titan. Some are long and deep, with angular patterns and few tributaries, suggesting that fluids flow over great distances. Others are a denser network that might indicate rainfall.

The channels cut deeply into the icy crust of Titan. Some of the channels extend more than 60 miles. While some may have been fed by springs, others likely were filled by rainfall.

Titan's environment is thought to be somewhat similar to Earth's before biological activity altered the composition of our atmosphere. The difference is Titan does not have liquid water, and Titan has a very low temperature. Titan's thick, nitrogen-rich atmosphere had led scientists to think the moon must have oceans of liquid methane. However, with Cassini orbiting there for a year, no evidence of those oceans has been found.

Unfortunately, Cassini suffered some sort of breakdown in one of its two solid-state recorders during the flyby. Some data was not recorded. Fortunately, half of the data was received.

It was the eighth of Cassini's 45 planned flybys of Titan. The next radar pass will be October 26, 2005, when the radar will be pointed down at the Huygens probe landing site close to the equator.
Radar image: Titan shoreline »


» February 24, 2005: Among new Cassini color photos of Saturn's storms, rings and moons was a thunderstorm persisting in the atmosphere that researchers named the Dragon Storm. The storm sends out bursts of radio energy and has periodic flare-ups. Researchers expect to understand the Dragon's mysterious behavior after Cassini watches it for two or three years.
Story: Dragon Storm »

» January 14, 2005: Cassini relayed signals to Earth from the European lander Huygens as the probe touched down on Saturn's largest moon, Titan. Cassini had changed its path back in December to optimize its reception of radio signals from Huygens as the 772-lb. probe descended onto Titan.

Radio signals from Cassini, which travel at the speed of light, take 1 hour 24 minutes to travel from Saturn to Earth. The exact time – between 68 and 84 minutes – depends on Saturn's position on its path around the Sun with respect to Earth. Currently, Cassini is nearly 746 million miles (1.2 billion kilometers) from Earth.

The giant ringed body Saturn is the sixth planet from the Sun. It is more than nine times as far away from the Sun as Earth at an average distance of more than 850 million miles from the Sun. The closest Saturn ever comes to Earth is 746 million miles.
Picture: Saturn on Christmas Eve »

» January 2, 2005: There are 43 close flybys of the moon Titan still ahead along Cassini's path during the four-year tour of the Saturn planetary system. In 2005, Cassini has 13 encounters planned with five of Saturn's moons. Eight of the 13 will be with Titan:
  • Titan: Jan 14
  • Titan: Feb 15
  • Enceladus: Mar 9
  • Titan: Mar 31
  • Titan: Apr 16
  • Enceladus: Jul 14
  • Titan: Aug 22
  • Titan: Sep 7
  • Hyperion: Sep 26
  • Dione: Oct 11
  • Titan: Oct 28
  • Rhea: Nov 26
  • Titan: Dec 26
» January 1, 2005: Cassini flew close to the icy moon Iapetus while the European Space Agency's Huygens probe continued on course to touch down on the surface of the moon Titan about 7:30 a.m. EST (4:30 a.m. PST) on January 14, 2005.

Iapetus is Saturn's third largest moon with a diameter of 890 miles.Its leading hemisphere is very black, while the trailing hemisphere is very white. As Cassini flew within about 76,700 miles of Iapetus at a speed of about 4,474 miles per hour, it photographed the dark surface of an area known as Cassini Regio in Iapetus' dark leading hemisphere.

The only previous close-up photos of Iapetus were recorded by Voyager 1 in 1980 and Voyager 2 in 1981. Voyager 2 passed by the moon at a distance of 564,800 miles. The resolution of the Cassini pictures will be six times better than the Voyager 2 pictures. The next close flyby of Iapetus by Cassini will be in 2007.

Jean-Dominique Cassini, the person for whom the spacecraft is named, had discovered Iapetus in 1672, but from Earth was able only to see the moon's brighter trailing hemisphere.
Picture: Iapetus looks brown »
Map: Cassini Iapetus flyby »

» December 27, 2004: Cassini changed its path to keep from following Huygens into Titan's atmosphere. The change also optimized the spacecraft's path for receiving radio signals from Huygens as the probe descends onto Titan.

» December 24, 2004: Cassini flew by Saturn's giant moon Titan and released the European Space Agency's Huygens probe to fly to Titan where it will touch down on the surface about 7:30 a.m. EST (4:30 a.m. PST) on January 14, 2005.

As it moves toward Titan, Huygens will remain dormant until an onboard timer wakes it up just before it reaches Titan's upper atmosphere on Jan. 14. Then the probe will plunge through Titan's murky atmosphere, examining its chemistry as it descends to the surface. Data gathered during the 2.5-hour descent will be transmitted up to Cassini, which in turn will point its antenna toward Earth and relay the data through NASA's Deep Space Network to JPL, which then will send it on to the European Space Agency's Space Operations Center in Darmstadt, Germany, where ESA engineers will process the data from Huygens' six science instruments.
Illustration: Huygens departs »

» December 14, 2004: Cassini photographed the crater-covered moon Dione from a distance of 1.6 million miles. Dione is 695 miles in diameter.
Picture: the pocked moon »

» October 26, 2004: Cassini flew by Titan in the closest approach ever to Saturn's giant moon. The spacecraft passed within 746 miles of the icy surface of the smog-shrouded natural satellite of the ringed planet. The flyby was one of 45 planned for Cassini over four years. Titan is larger than the planets Pluto and Mercury and the only Moon known to have an atmosphere. It may have a nitrogen atmosphere and oceans of liquid methane and ethane on its frozen surface. Cassini has 12 science instruments, including spectrometers, infrared cameras and radar. It also is carrying the European Space Agency's Huygens probe, which will be dropped to Titan's surface in January 2005. The Cassini imaging systems targeted the planned Huygens landing site.
Picture: Titan's first closeup »
Picture: Titan continent Xanadu »
Picture: Titan purple haze »

» September 9, 2004: A British scientist at Queen Mary College, University of London, looking at Cassini data has discovered a new ring around Saturn and, possibly, one of two more new moons of the giant planet. The ring is associated with Saturn's moon Atlas in the area of the F-ring. Meanwhile, the two moon discoveries – by researchers at Queen Mary College, University of London, and the Space Science Institute, Boulder, Colorado – could elevate the number of moons known to be orbiting Saturn to 35. Previously, 33 natural satellites of Saturn had been verified. Just before Cassini arrived at Saturn, the spacecraft photographed a small object near the outside edge of the F-ring inside the orbit of the moon Pandora. The F-ring is Saturn's outermost ring. If the tiny object is a moon, it's probably only two to three miles in diameter. If it's not a moon, it could be a clump of the muddy material seen by Cassini near the rings. Whatever it is, the small body is just 620 miles from the F-ring and 86,000 miles from the center of Saturn and within 190 miles of the orbit of the moon Pandora. The object, labeled S/2004 S3, may not be alone. A nearby object has been seen and labeled S/2004 S4. The newly discovered ring near the moon Atlas has been labeled S/2004 1R. The 190-mi.-wide ring is 86,000 miles from the center of Saturn in the orbit of the moon Atlas between the A-ring and the F-ring. It's too early to tell if the ring extends all the way around the planet.
Animation: the new moon S2004 S3 »
Picture: the new ring S2004 1R »

» September 1, 2004: Here's some of the vital equipment on board Cassini as it tours the Saturn system:
  • Two spacecraft engines – one is a back-up.
  • Thrusters used for small changes of direction or speed.
  • Radioisotope thermoelectric generators supply 750W of electrical power.
  • Two cameras that record more than 300,000 pictures of the planet.
  • Antennas for communication with Earth.
  • A long boom holding an instrument to measure magnetic fields.
  • An infrared spectrometer to analyze Saturn's temperature and composition.
  • A plasma spectrometer to measure charged particles and solar winds.
And most importantly, Cassini is carrying the Huygens probe, which will touch down on Saturn's largest moon, Titan, in four months.
Fact Sheet: Cassini and Huygens at a glance »

» August 16, 2004: Cassini has spotted two previously unknown moons, the smallest bodies seen so far around the ringed planet. They are about 2 miles and 2.5 miles in diameter. That's smaller than the city of Boulder, Colorado. Previously, the smallest moons seen around Saturn were are about 12 miles across. The moons are 120,000 miles and 131,000 miles from the center of planet Saturn between the moons Mimas and Enceladus. For now they are called S/2004 S1 and S/2004 S2. Later, they will be given names. The JPL team isn't sure whether S/2004 S1 might not be an object called S/1981 S14 after it turned up in a 1981 Voyager image.
Animation: the new moons »

» August 9, 2004: On Earth, static can be heard on an AM radio during a thunderstorm. It works the same way on Saturn. Cassini's radio receiver heard lighting at Saturn. Only this time it sounded different from 20 years earlier when Voyager had passed by the ringed planet and heard the static. Voyager had recorded the crackle of lightning that was pretty much the same day to day from a big wide storm at low latitudes. Cassini, on the other hand, found lightning that came and went from day to day. Sometimes there were a lot of static crashes and sometimes none or almost none. The NASA JPL team thought that, unlike Voyager, the electrical bursts Cassini received might be coming from short-lived storms at mid-latitudes.
Illustration: lightning radio »

» July 21, 2004: Once it became an artificial satellite of Saturn, Cassini recorded images of the ringed planet's natural satellites including Dione, Rhea, Iapetus and Tethys.

The dark side of the icy, cratered moon Dione is seen vaguely in Cassini's July 2, 2004, photo of the sunlit side. At left, the crescent moon shows large craters. An enhanced version, at right, reveals the dark side of the 695-mi.-diameter Dione lit faintly by reflected light from Saturn. This is something like the view from Earth when the Moon's dark side is visible due to so-called earthshine. The crater near the top of the photo has a sunlit central peak, which was a common characteristic of craters on Dione in Voyager images. Voyager 1 and Voyager 2 flew by Saturn in 1980 and 1981, but, unlike Cassini, did not go into around around the huge planet. Variations in brightness on Dione's dark side in the Cassini picture hint at the bright curved linear streaks, seen by Voyager. These streaks may be water ice.
Picture: Dione from 860,000 miles »
The 950-mi.-wide Rhea is Saturn's second largest moon. An unmagnified view of Rhea as a crescent moon on July 2, 2004, shows a heavily cratered surface. That means it is ancient. Many of the craters have central peaks. Like Dione, Rhea has one of its hemispheres covered with bright, wispy streaks which may be water frost. Cassini will look for clues to help unlock the moon's geologic history when it flies by Rhea at a distance of only 311 miles on Nov. 26, 2005.
Picture: Rhea from 615,000 miles »
Iapetus seems to be a two-faced moon. One hemisphere looks very dark, while the other is very bright. Scientists wonder if the natural satellite has been coated by some material arriving on the surface from elsewhere, or else is being resurfaced by material welling up from within the moon. At 892 miles, Iapetus is only a third of the diameter of Earth's moon, which is 2,160 miles wide. The brightness variations in a July 3, 2004, photo of Iapetus are not shadows; they are real. Iapetus is pronounced eye-APP-eh-tuss.
Picture: Iapetus from 1.8 million miles »
Looking like a half-full moon, the cratered moon Tethys, the Sea Goddess, is seen in a visible light photo on July 3, 2004, hanging in space one million miles ahead of Cassini. The spacecraft will investigate the cratered, 659-mi.-diameter natural satellite during two planned flybys with the first on September 24, 2005. Cassini will be looking for the 470-mi.-long crack on Tethys that was seen in Voyager images. Voyager 1 and Voyager 2 flew by Saturn in 1980 and 1981, but, unlike Cassini, did not go into around around the huge planet.
Picture: Tethys from 1 million miles »

» July 12, 2004: Cassini was behind the Sun, hidden from Earth from July 5-12. Just before Cassini began its transit behind the Sun, it snapped pictures of Saturn's moons Iapetus, Mimas, Rhea and Tethys.
Picture: Iapetus from 1,552,897 miles »
Picture: Mimas from 888,662 miles »
Picture: Rhea from 613,872 miles »
Picture: Tethys from 1,071,904 miles »
Picture: Titan from 489,495 miles »

» July 9, 2004: Saturn's magnetosphere reaches beyond the rings. It is an invisible magnetic bubble of charged particles similar to the one enveloping Earth. Cassini's Magnetospheric Imager has shown us Saturn's magnetosphere for the first time. It appears to be a huge blob of gas sweeping along with Titan as the large moon orbits Saturn. The NASA JPL team thinks the cloud results from highly energetic particles from Saturn's radiation belt exciting neutral gas as it bombards Titan.
Story: At The Edge of an Alien World »

» July 6, 2004: Cassini images of Saturn's rings in ultraviolet light show composition varies across the A, B and C rings. The ring system begins from the inside out with the D, C, B and A rings followed by the F, G and E rings. Red in an image indicates sparser ringlets likely made of dirty particles that are smaller than in the icier turquoise ringlets. There appears to be more ice toward the outer part of the rings, than in the inner part. Looking at the A Ring from the inside out, the Cassini Division is in faint red, left, followed by the entire A ring. The Cassini Division, left, contains thinner, dirtier rings than the turquoise A ring, indicating a more icy composition. The red band roughly three-fourths of the way outward in the A ring is the Encke gap. The A Ring image was taken with the Ultraviolet Imaging Spectrograph, which is capable of resolving the rings to show features up to 60 miles across. That's about 100 times better resolution in ultraviolet than images by the Voyager 2 spacecraft.
Picture: A Ring from inside out »
An image of rings B and C also was recorded by the Ultraviolet Imaging Spectrograph. Left to right are the outer portion of C Ring and the inner portion of B Ring. The B ring begins a little more than halfway across the image. The general pattern is from dirty particles indicated by red to cleaner ice particles shown in turquoise in the outer parts of the rings.
Picture: C and B Rings from inside out »

» July 4, 2004: While trying to photograph the large moon Titan, Cassini was blocked from seeing visible light passing through the huge cloud of gas surrounding the planet-sized moon. Fortunately, the spacecraft's infrared mapping spectrometer was able to look through the smog and record surface details including a crater. Cassini recorded its observation at a distance of 210,600 miles from Titan.
Photos: Titan in three colors »
The moon's dense atmosphere is opaque at most wavelengths. In visible light, it looks like a dull orange ball. The visible-light camera saw an odd surface with indistinct straight, round and curvy features. Astronomers found those first visible-light pictures bland and hard to interpret.
Photos: Titan orange ball »
On the other hand, scientists were pleased with the images from the visible and infrared mapping spectrometer, intended to map mineral and chemical features of the moon. The spectrometer saw an exotic surface bearing a variety of materials in the south and a circular feature that may be a crater in the north.
Photos: Titan surface colors combo »
There were dark regions of relatively pure water ice and brighter regions with a much higher amount of non-ice materials, such as simple hydrocarbons. A methane cloud visible near the south pole may be composed of unusually large particles compared to the typical haze particles surrounding the moon. That suggests a dynamically active atmosphere.
Photos: Titan surface in yellow green »
Cassini's magnetosphere imager recorded a vast swarm of hydrogen molecules surrounding Titan beyond the top of the moon's atmosphere. The huge cloud sweeping along with Titan as it orbits around Saturn is so big that the big planet and its rings would fit within it. Titan is losing material gradually from its atmosphere and that is being dragged around Saturn.
Illustration: gas cloud around Titan »
Later, the orbiter will fly by Titan 45 times at various distances as close as 590 miles. On those flybys, high-resolution mapping of the moon's surface with an imaging radar will pierce the gloom and see through the opaque haze of Titan's upper atmosphere. In January 2005, Cassini will send the Huygens probe down through Titan's atmosphere to the surface.
Illustration: Huygens landing »

» July 2, 2004: Cassini photographed the large moon Titan, one of the prime targets of the entire mission. The last previous photo recorded by Cassini was on June 10 at a distance of 8.2 million miles.
Photograph: Titan on June 10 »
Tucked away securely on the Cassini spacecraft, in a shallow aluminum box with two plates around it to protect it from micro-meteoroids, is a DVD disc imprinted with 616,400 electronic signatures and paw prints of people, dogs and cats from 81 countries on Earth. These are real signatures, not just a printed list of names. Human writing, as well as inky footprints from cats and dogs, were scanned into a computer and burned into the DVD.
Background: 616,400 signatures »

» July 1, 2004: Cassini orbits Saturn. The Cassini spacecraft successfully entered orbit around Saturn at a distance of 934 million miles from Earth. The NASA JPL flight control team received radio signals at 0412 UTC confirming that the spacecraft's engine had completed its burn, pushing Cassini through Saturn's rings and on to four years of work studying the giant planet and its system of 31 known moons.

The scientific survey of the planet's gravitational and magnetic fields conducted during the fly-through of the rings was the closest measurement of Saturn ever.

As Cassini crossed through the rings, its radio and plasma wave science instrument measured puffs of plasma produced by dust impacts. The spacecraft was bombarded by some 100,000 total dust hits in less than five minutes. There were as many as 680 dust hits per second of particles about the size of particles in cigarette smoke. When converted to audible sounds, the dust hits sounded like hail hitting a tin roof. The spacecraft was not damaged and performed flawlessly.

The engine burn for entering orbit went off so well that the JPL team decided to forgo an orbital-adjustment maneuver scheduled for July 3. All of this after Cassini had traveled more than 6.5 years along a 2.2 billion-mile route to reach Saturn after its launch from Cape Canaveral Air Force Station, Florida, on Oct. 15, 1997.

During the next four years, the spacecraft will carry out 52 close encounters with seven of Saturn's 31 known moons. Cassini will spend 15 hours a day observing and saving information on its recorder, which has a capacity about the same as a music CD. At the end of most days, Cassini will send 500 images home to Earth.
Photo: Saturn rings and moons »

» June 30, 2004: After 6.5 years chugging 2.2 billion miles across the Solar System, Cassini is just a few hours out from Saturn.
Photo: Saturn from 17.6 million miles »
At 2:36 a.m. July 1, 2004 Universal time [That's 10:36 p.m. EDT and 7:36 p.m. PDT June 30, 2004.] Cassini will begin executing a series of commands to enter orbit around the ringed planet. The spacecraft will fire its main engine for a crucial 96 minutes to slow down and be captured in orbit about Saturn.
Background: what is UTC? »
Radio signals, which travel at the speed of light, take 1 hour 24 minutes to travel from Earth to Saturn. That means the NASA JPL team had to send their final orders to Cassini before the spacecraft arrived at Saturn. Upon arrival, Cassini must execute the plan on its own. Orbit insertion is a critical event in the spacecraft's lifetime.

"Everything has to go just right. The burn must occur for all 96 minutes, the turns must occur at the right time, the computers must keep the sequence going even in the event something unexpected should happen," said Robert T. Mitchell, Cassini-Huygens program manager at JPL.

At 85 minutes before the engine burn, Cassini will rotate to point its Italian-built main antenna dish forward. The 13-ft.-diameter antenna will shield the spacecraft against dust particles it might hit as it crosses a gap in the planet's rings. So there is no break in tracking from Earth, the spacecraft will use a secondary antenna to transmit a continuous monotone carrier signal.

As it enters orbit, Cassini will pass twice through a known gap between the planet's F and G rings, first while ascending shortly before the burn, then while descending shortly after the burn.

Cassini will fly closer to Saturn than at any other time during its coming four-year tour of Saturn. The spacecraft will be able to study the planet and rings at close range, passing a mere 12,427 miles above Saturn's cloud tops. That's closer than any other spacecraft to date. It will be about 10 times closer to the planet's rings than at any other time in the four-year mission.

The engine burn will slow the spacecraft by 1,400 miles per hour. Five of Cassini's 12 science instruments will be on during the burn. The others will be used shortly after the engine cuts off.
  • The magnetometer will measure the strength and direction of the magnetic field to understand the physics of Saturn's magnetic dynamics. Lightning may also be detected.
  • Another instrument will provide a record of the dust hits as the spacecraft flies through the ring plane. These observations may tell scientists the size of these tiny particles and the thickness of that ring region.
  • The remote sensing instruments will assess the rings' composition, temperature, and structure.
After descending through the rings, Cassini will turn to look back at the sunlit face of the rings to record more data. Then it will turn toward Earth to transmit its data.
Illustration: orbit insertion »

» June 28, 2004: Cassini measured the rhythm of radio signals generated naturally by Saturn and found the planet has a longer day than previously thought. A day is the period of time a planet takes to rotate one time on its axis. Voyager 1 and Voyager 2, flying by Saturn in 1980 and 1981, found a day six minutes shorter than the day measured by Cassini in 2004. That would suggest a one percent increase across two decades. Cassini found Saturn completes one rotation in about 10 hours 45 minutes 45 seconds. Scientists doubt that the big gas-bag planet actually has changed its rotation speed much. They wonder if the apparent difference has anything to do with Saturn's rotational axis being nearly identical to its magnetic axis.
Sound: Saturn's radio heartbeat »

» June 27, 2004: Cassini is reporting that Saturn's magnetic field is not like Earth's. The planet's poles seem to be on either side of its equator. That's different from Earth and other planets such as Jupiter where the magnetic poles are located at the northern and southern extremes. Data from two Cassini instruments showed the field is aligned with Saturn's axis of rotation. The poles are on either side of the equator, rather than the northern and southern extremes. While magnetic fields of Earth and Jupiter are generated by rotating cores of iron at their centers, gaseous Saturn is not known to have an iron core.

» June 26, 2004: In just a few days, Cassini will fire its main engine on for 96 minutes to start its Saturn orbit insertion maneuver. The burst of propulsion on July 1 will reduce Cassini's speed and allow it to be captured into orbit as a satellite of Saturn. The spacecraft will pass through a gap between two of Saturn's rings – the F and G rings. Cassini then will swing close to the planet and begin the first of 76 orbits around the Saturn system. During Cassini's four-year mission, it will execute 52 close encounters with seven of Saturn's 31 known moons.

Cassini has a backup engine in case the main engine fails. Particles in the ring plane too small to be seen from Earth could be fatal to the spacecraft, so Cassini will turn to use its high-gain antenna as a shield against small objects.

» June 11, 2004: Cassini flew within about 1,285 miles of the tiny dark moon Phoebe on June 11. Spacecraft photos recorded during the flyby showed Phoebe has a scarred, heavily cratered, very old surface with a great deal of variation in brightness.

Phoebe is almost four times farther from Saturn than its nearest major neighbor, Iapetus, and substantially larger than any of the other moons orbiting at comparable distances. It's only about 140 miles in diameter. Phoebe rotates on its axis every nine hours and 16 minutes and it completes a full orbit around Saturn in about 18 months. All of Saturn's moons, except for Phoebe and Iapetus, orbit very nearly in the plane of Saturn's equator. Phoebe's orbit is highly eccentric and retrograde; it orbits backwards with respect to the direction of the other moons.

Phoebe has been known by astronomers since 1898, when it was thought to be Saturn's outermost moon. That theory changed with the discovery of numerous smaller moons in 2000. Astronomers wonder if Phoebe, the largest of Saturn's numerous outer moons, might be parent to the much smaller retrograde outer moons that orbit Saturn. The the moon's pockmarked surface makes them suspect that objects striking Phoebe in the past might have kicked off chunks that now are the smaller moons of Saturn.
Photo: views of the dark moon Phoebe »

» June 3, 2004: Cassini is just a month out from Saturn with its seven majestic rings and 31 known moons. After a journey of 6.5 years, Cassini is scheduled to enter orbit around Saturn at 2:30 a.m. July 1, 2004 Universal time. [That's 10:30 p.m. EDT and 7:30 p.m. PDT June 30, 2004.]
Background: what is UTC? »

» June 1, 2004: Cassini was launched Oct. 15, 1997, on a journey covering 2.2 billion miles. It has been described as the most highly-instrumented, scientifically-capable interplanetary spacecraft ever flown. A Titan IVB/Centaur rocket carried Cassini/Huygens aloft from Cape Canaveral, Florida.
Picture: Cassini launch on a Titan IV »

Cassini stands more than two stories tall. It weighs more than six tons.

Cassini has 12 science instruments plus six more on its piggyback rider, the Huygens probe. Some 260 scientists from the United States and 17 European nations are involved in the project.

For four years, Cassini will study Saturn's rings, icy satellites, magnetosphere and Titan, the planet's largest moon.
Illustration: orbital insertion »

Earth is the third planet and Saturn is the sixth planet from our Sun. Saturn is the second largest planet in our Solar System, after Jupiter.

The planet and its ring system serve as a miniature model for the disc of gas and dust surrounding the early Sun that formed the planets.

Astronomers hope greater knowledge of how Saturn's rings and moons interact will increase our understanding of how each of the Solar System's planets evolved.
Photograph: Saturn moons and rings »


» January 15, 2005: The first color image of Titan revealed a surface darker than scientists had expected. It seems to be a mix of water and hydrocarbon ice. What had been thought in the black-and-white version of the image to be rocks or ice blocks now appears to be pebbles. The two just below the middle of the photo are about 6 inches across (left) and 1.5 inches across (center) and about 33 inches from Huygens. It looks like there might have been erosion at the base of the pebbles, possibly indicating water had flowed in the area sometime in the past.
Picture: Titan in color »

An ESA, NASA and University of Arizona image is marked with sizes to indicate the scale of the pebbles.
Illustration: pebble scale »

The surface appeared pale orange in color and covered by a methane haze. What may be a nearby sea, possibly of methane or even tar, looks like it has islands and a coastline shrouded in mist.
Picture: coast and islands? »

Starting with its descent through the atmosphere, Huygens sent back about 350 images. That was half the number expected because one channel of its two-channel radio didn't work. On the other hand, Huygens worked for hours on the surface, rather than the expected 30 minutes. That probably was due to its thermal design which kept the lander's instruments warmer than expected amidst temperatures of –290° Fahrenheit (–179° Celsius) in the environment outside the small probe.

A composite image produced from several descent images at about 5 miles altitude shows a full 360-degree panoramic view around Huygens. On the left, behind Huygens, is a boundary between light and dark areas. The white streaks near that boundary could be ground fog. As the probe descended, it drifted over a plateau. center of image, and headed toward its landing site in the dark area at right. From the drift of the probe, ESA calculated the wind speed must have been around 4 mph.
Picture: panorama from 5 miles up »

A image from an altitude of about 5 miles shows a boundary between dark lower areas and a light upper terrain carved with what look like drainage channels.
Picture: high and low terrain »

» January 14, 2005: Huygens has landed on Titan. After a seven-year journey of 2.2 billion miles across the Solar System, the European lander Huygens touched down on Saturn's largest moon.

The probe landed on Titan's surface 350 years after the moon was discovered on March 25, 1655 by the Dutch astronomer Christiaan Huygens, and just 48 years after mankind's first foray into space in 1957.

Data and photos transmitted by Huygens during the descent and landing, relayed to Earth by the orbiting Cassini spacecraft, reached Earth hours later. Cassini had changed its path back in December to optimize its reception of radio signals from Huygens as the probe descended onto Titan. Radio signals from Cassini, which travel at the speed of light, take 1 hour 24 minutes to travel from Saturn to Earth.

The European Space Agency (ESA) reported the Robert C. Byrd Green Bank Telescope at the U.S. National Radio Astronomy Observatory in West Virginia, part of a global network of radio telescopes tracking Huygens, detected the tone of the probe's carrier radio signal indicating the back cover of Huygens had been ejected on time, the main parachute had been deployed, and the probe had begun to transmit in Titan's atmosphere. The extremely feeble carrier signal, something like a telephone dial tone, was transmitted by Huygens continuously through its descent. It was a beacon only and not intended to contain science data. The Green Bank Telescope used a Radio Science Receiver supplied by NASA's Jet Propulsion Laboratory (JPL).

Among the first pictures received later on Earth was one transmitted during Huygens' descent at about ten miles altitude. It may show short drainage channels leading to a shoreline.
Picture: from 10 miles altitude »

Also among the first pictures was one transmitted at about five miles altitude. It may show shorelines between raised ground and flooded plains.
Picture: from 5 miles altitude »

Among the first pictures transmitted by Huygens after the probe landed may show ice blocks strewn around the surface of Titan.
Picture: from Titan's suface »

Additional NASA and ESA information:
NASA Huygens on Titan »
JPL Saturn »
JPL Huygens Descent »
NASA Lewis Cassini-Huygens »
ESA Cassini-Huygens »
ESA Huygens »

» January 1, 2005: The Huygens probe continued on course to touch down on the surface of the moon Titan about 7:30 a.m. EST (4:30 a.m. PST) on January 14, 2005.

» December 24, 2004: Cassini sent Huygens toward Titan where it will touch down on January 14, 2005. Huygens will remain dormant until it reaches Titan's upper atmosphere. Then the probe will plunge down through the murky atmosphere to the surface. Data gathered during the 2.5-hour descent will be transmitted to Cassini, which will relay the data through NASA's Deep Space Network to JPL, which then will send it on to the European Space Agency's Space Operations Center in Darmstadt, Germany, where ESA engineers will process the data from Huygens' six science instruments.
Illustration: Huygens departs »

» October 26, 2004: Huygens continues to ride through the Saturn system on the Cassini main spacecraft. Cassini will send Huygens off toward Titan on December 25, 2004. Twenty days later, Huygens will enter Titan's atmosphere on January 14, 2005.
Picture: Titan surface »

» September 19, 2004: Huygens' five lithium batteries were turned on and checked out. They worked well. Prior to separation from Cassini, the probe gets its electrical energy from Cassini. The next checkout will be November 23.
Movie: Titan at 5-9 million miles »

» July 15, 2004: Huygens has successfully completed an important health check-up. The Titan lander's ride through Saturn's rings aboard the Cassini main spacecraft on July 1 proved harmless for all of the six science instruments on board Huygens. Since the Cassini launch on October 15, 1997, proper working of the probe and its scientific instruments has been verified fourteen times. The last previous check-out was in March 2004 before Cassini and Huygens arrived at Saturn.

Although Saturn's rings appear solid from a distance, they actually are millions of tiny frozen dust particles and ice blocks ranging from the size of a grain of sand to as big as a house. To minimize any risk that ring particles would hit and damage spacecraft systems and science instruments, the JPL navigators sent Cassini-Huygens through a gap between rings. The gap had been known to be relatively safe since NASA's Pioneer 11 spacecraft, the first to explore the planet Saturn, passed safely through it on September 1, 1979. Pioneer 11 passed Saturn at a distance of 13,049 miles above Saturn's cloud tops.

As Cassini crossed between the rings, it created a shield for itself by pointing its 13-ft.-wide, high-gain antenna forward. The spacecraft was barraged by more than 100,000 very small particles in less than five minutes. Attached to Cassini, Huygens was well protected by its own thick heat shield.

The next Huygens check-outs by the European Space Operations Centre in Darmstadt, Germany, are scheduled for September 14 and November 23, 2004. Cassini then will send Huygens off toward Titan on December 25, 2004. Twenty days later, Huygens will descend through Titan's dense atmosphere on January 14, 2005.
Picture: Huygens before launch »

» July 4, 2004: Huygens continues to ride through the Saturn system on the Cassini main spacecraft. Cassini will send Huygens off toward Titan on December 25, 2004. Twenty days later, Huygens will enter Titan's atmosphere on January 14, 2005.
Movie: Titan at 5-9 million miles »

» July 1, 2004: Huygens is orbiting Saturn, riding piggyback on Cassini, which is touring the moons. On Christmas day, Huygens will detach from Cassini to fly down toward Titan. Huygens will enter Titan's atmosphere 20 days later.
Photograph: Titan on June 10 »

» June 28, 2004: Cassini will release the Huygens probe on its journey toward Titan on December 25, 2004 Universal time (Dec. 24 in U.S. time zones).
Background: what is Universal time? »
Shaped like a wok, the round bottomed Chinese pan used for stir frying, Huygens will be the first probe to descend to the surface of a moon of another planet. It also will make the most distant descent by a robot probe ever attempted on another object in the Solar System.
Illustration: Huygens flying to Titan »
After a 20-day ballistic freefall, Huygens will enter Titan's atmosphere on January 14, 2005. In the atmosphere, the probe will deploy parachutes and begin 2.5 hours of intensive scientific observations. The data from Huygens will be transmited up to the Cassini spacecraft, which will relay the information to Earth.
Illustration: Huygens landing »

» June 3, 2004: Huygens continues to ride into the Saturn system on the Cassini main spacecraft. The study of Titan, Saturn's largest moon, is one of the major goals of the Cassini mission. Titan may have in deep-freeze many of the chemical compounds that preceded life on Earth. Titan is the only moon in the Solar System to have a dense atmosphere and resembles the early Earth in deep freeze.
Illustration: Titan's surface »
Cassini will execute 45 flybys of Titan, coming as close as some 590 miles above the moon's surface. That will permit high-resolution mapping of the Titan's surface with an imaging radar, which can see through the opaque haze of the upper atmosphere.
Photograph: smog shrouded Titan »

» June 1, 2004: The European-built probe, Huygens, rode piggyback on the Cassini spacecraft for more than 6.5 years across deep space to the Saturn planet system. To reach Saturn, Cassini and Huygens used a series of gravity assist maneuvers to gain speed by swinging by planets:

1998 Apr 27Venus
1999 Jun 24Venus
1999 Aug 18Earth
2000 Dec 30Jupiter

The Huygens probe will fly away from Cassini on December 25, 2004, to land on the big moon Titan on January 14, 2005.
Illustration: arriving at Saturn »

The Cassini project is managed by the Jet Propulsion Laboratory (JPL) at Pasadena, California, for NASA's Office of Space Science, Washington, D.C. JPL is a division of the California Institute of Technology in Pasadena. JPL designed, developed and assembled the Cassini orbiter.

The European Space Agency (ESA) managed the development of Huygens and is in charge of operations of the probe from its control center in Darmstadt, Germany.

The Italian Space Agency (ASI) provided the high-gain antenna, much of the radio system and elements of several of Cassini's science instruments.

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