A seven-year journey to the ringed planet Saturn began at 4:43 a.m. EDT with the liftoff of a Titan IVB/Centaur carrying the Cassini orbiter and its attached Huygens probe from the European Space Agency.
The Saturn-bound Cassini spacecraft successfully performed a flyby of the planet Venus, coming to within about 176 miles (284 kilometers) of the Venusian surface. The flyby gave the Cassini spacecraft a boost in speed of about 4 miles per second (7 kilometers per second) to help the spacecraft reach Saturn on June 30, 2004 PDT.
Cassini will make four flybys of planets -- two of Venus and one each of Earth and Jupiter -- to gather the speed it needs to reach Saturn.
The Cassini spacecraft, marking the 617th day of its voyage to Saturn, successfully completed its second flyby of the planet Venus, once again on time and on target.
As planned, Cassini came within about 370 miles (600 kilometers) of the planet at 1:30 p.m. PDT, with Venus' gravity giving the spacecraft a boost in speed to help it reach Saturn more than 1 billion kilometers away. Most of Cassini's scientific instruments were set to make observations during the Venus flyby.
Earthlings bid farewell to the Cassini spacecraft as the Saturn-bound mission successfully completed a highly accurate pass of Earth at 8:28 p.m. PDT (3:28 a.m., Aug. 18 UTC). The flyby gave Cassini a 5.5-kilometer-per-second (about 12,000-mile-per-hour) boost in speed, sending the spacecraft on toward the ringed planet more than 1 billion kilometers (almost one billion miles) away.
Engineers at NASA's Jet Propulsion Laboratory confirmed that the spacecraft flew past Earth at an altitude of about 1,171 kilometers (727 miles), passing most closely above the eastern South Pacific at -23.5 degrees latitude and 231.5 degrees longitude. Cassini may have been visible from small islands in that area, such as Pitcairn Island or Easter Island.
NASA's Cassini spacecraft, which made its closest approach to Jupiter at 2:12 a.m. PDT on Dec. 30, is providing ways to make invisible features visible, to track daily changes in some of the planet's most visible storms, and to hear the patterns in natural radio emissions near the edge of Jupiter's magnetic environment.
In collaboration with NASA's Galileo spacecraft, which has been orbiting Jupiter since 1995, Cassini is also beginning to provide new insight into how the solar wind of particles speeding away from the sun affects a huge magnetic region surrounding Jupiter.
Large storms on Jupiter, which can be larger than Earth and last for centuries, gain energy from swallowing smaller storms, preliminary analysis of Jupiter movies from the Cassini spacecraft suggests. The smaller storms pull their energy from lower depths, according to information collected by Galileo.
With its flyby of Saturn's moon Phoebe, the Cassini spacecraft completed the first satellite flyby in the Saturn system. Cassini came within approximately 2,068 kilometers (about 1,285 miles) of the dark moon. The Voyager 2 flyby in 1981 was from 2.2 million kilometers, (about 1.4 million miles), 1,000 times farther away.
First images from the flyby revealed Phoebe to be a scarred, cratered outpost with a very old surface and a mysterious past, and a great deal of variation in surface brightness across its surface.
Analysis revealed that Phoebe has more planet-like qualities than previously thought. Objects like Phoebe are thought to have condensed very quickly. Hence, they represent the building blocks of planets. They give scientists clues about what conditions were like around the time of the birth of planets and their moons.
Cassini images suggest that Phoebe originated in the far-off Kuiper Belt, the region of ancient, icy, rocky bodies beyond Neptune's orbit. Data show Phoebe was spherical and hot early in its history, and has denser rock-rich material concentrated near its center. Its average density is about the same as that of Pluto, another object in the Kuiper Belt. Phoebe likely was captured by Saturn's gravity when it somehow got close to the giant planet.
The international Cassini-Huygens mission's spacecraft successfully entered orbit around Saturn. At 9:12 p.m. PDT, flight controllers received confirmation that Cassini had completed the engine burn needed to place the spacecraft into the correct orbit. This began a four-year prime mission to study the giant planet, its majestic rings and 31 then-known moons.
The Cassini spacecraft beamed back information and pictures tonight after successfully skimming the hazy atmosphere of Saturn's moon Titan. NASA's Deep Space Network tracking station in Madrid, Spain, acquired a signal at about 6:25 p.m. PDT (9:25 p.m. EDT). As anticipated, the spacecraft came within 1,200 kilometers (750 miles) of Titan's surface.
At the time, Cassini was about 1.3 billion kilometers (826 million miles) from Earth. Numerous images, perhaps as many as 500, were taken by the visible light camera and were transmitted back to Earth.
Titan is a prime target of the Cassini-Huygens mission because it is the only moon in our solar system with an atmosphere. It is a cosmic time capsule that offers a look back in time to see what Earth might have been like before the appearance of life.
The European Space Agency's Huygens probe was successfully detached from NASA's Cassini orbiter today to begin a three-week journey to Saturn's moon Titan. NASA's Deep Space Network tracking stations in Madrid, Spain, and Goldstone, Calif., received the signal at 7:24 p.m. PST. All systems performed as expected and there were no problems reported with the Cassini spacecraft.
The Huygens probe, built and managed by the European Space Agency, was bolted to Cassini and has been riding along during the nearly seven-year journey to Saturn largely in a "sleep" mode.
After its seven-year journey through the solar system on board the Cassini spacecraft, ESA's Huygens probe successfully descended through the atmosphere of Titan, Saturn's largest moon.
The first scientific data arrived at the European Space Operations Centre (ESOC) in Darmstadt, Germany, at 17:19 CET.
Huygens reached Titan's outer atmosphere after 20 days and a 2-million-mile (4- million-kilometer) cruise following release from the Cassini orbiter. The probe started its descent through Titan's hazy cloud layers from an altitude of about 1270 km at 11:13 CET. During the following three minutes Huygens had to decelerate from 11,000 to 870 mph (18,000 to 1,400 kilometers per hour).
A sequence of parachutes then slowed it down to less than 200 mph (300 kilometers per hour). At a height of about 100 miles (160 kilometers) the probe's scientific instruments were exposed to Titan's atmosphere. At about 75 miles (120 kilometers), the main parachute was replaced by a smaller one to complete the descent, with an expected touchdown at 13:34 CET. Preliminary data indicate that the probe landed on a solid surface.
The probe began transmitting data to Cassini four minutes into its descent and continued to transmit data after landing at least as long as Cassini was within the beamwidth of Huygens’ antenna. The certainty that Huygens was alive came already at 11:25 CET today, when the Green Bank radio telescope in West Virginia, USA, picked up a faint but unmistakable radio signal from the probe. Radio telescopes on Earth continued to receive this signal well past the expected lifetime of Huygens.
Huygens data, relayed by Cassini, were picked up by NASA's Deep Space Network and delivered immediately to ESA's European Space Operations Centre in Darmstadt, Germany, where the initial scientific analysis took place.
Starting at about 90 miles (150 kilometers) altitude above the surface of Titan, six multi-function instruments on board ESA's Huygens probe recorded data during the descent and on the surface.
Spectacular images captured by Huygens revealed that Titan has extraordinarily Earth-like meteorology and geology. Images have shown a complex network of narrow drainage channels running from brighter highlands to lower, flatter, dark regions. These channels merge into river systems running into lakebeds featuring offshore "islands" and "shoals" remarkably similar to those on Earth. Titan's rivers and lakes appeared dry at that moment, but rain may have occurred not long ago.
Heat generated by Huygens warmed the soil beneath the probe and the probe detected bursts of methane gas boiling out of surface material, reinforcing methane's principal role in Titan's geology and atmospheric meteorology -- forming clouds and precipitation that erodes and abrades the surface.
In addition, surface images show small rounded pebbles in a dry riverbed. Spectral measurements were consistent with a composition of dirty water ice rather than silicate rocks. However, these are rock solid at Titan's temperatures.
Titan's soil appeared to consist at least in part of precipitated deposits of the organic haze that shrouds the planet.
Investigations by the Cassini orbiter have built upon these data.
The Cassini spacecraft's two close flybys of Saturn's icy moon Enceladus on Feb. 16 and March 9 revealed the presence of some unidentified substance above the surface in the vicinity of the south pole. Scientists, using Cassini's magnetometer instrument for their studies, said the source may be volcanism, geysers, or gases escaping from the surface or the interior.
The observations showed a bending of the magnetic field, with the magnetospheric plasma being slowed and deflected by the moon. In addition, magnetic field oscillations were observed. These are caused when electrically charged (or ionized) molecules interact with the magnetic field by spiraling around the field line. This interaction creates characteristic oscillations in the magnetic field at frequencies that can be used to identify the molecules. The results from the Enceladus observations were believed to be due to ionized water vapor.
Subsequent analysis of Enceladus images showed jets of fine, icy particles streaming from the moon's south polar region. The images provided unambiguous visual evidence the moon was geologically active.
NASA's Cassini spacecraft found lakes on Saturn's moon Titan.
The lakes are most likely the source of hydrocarbon smog in the frigid moon's atmosphere. Finding the source of the complex soup of hydrocarbons in Titan's atmosphere has been a major goal for the Cassini mission and is a significant accomplishment.
Numerous well-defined dark patches resembling lakes are present in radar images of Titan's high latitudes taken during the July 22 flyby. At Titan's frigid temperatures, about minus 290 degrees Fahrenheit (minus 180 degrees Celsius), the liquids in the lakes are most likely methane or a combination of methane and ethane.
This area of Titan has been in winter's shadow since before Cassini arrived, and the spacecraft had not flown over it before. During the flyby, Cassini's radar spotted several dozen lakes as small as 0.6 miles (1 kilometer) wide, with some nearly 20 miles (30 kilometers) wide. The biggest lake is about 62 miles (100 kilometers) long and may be only partly wet.
With giant Saturn hanging in the blackness and sheltering Cassini from the sun's blinding glare, the spacecraft viewed the rings as never before, revealing previously unknown faint rings and even glimpsing its home world.
A marvelous panoramic view was created by combining a total of 165 images taken by the Cassini wide-angle camera over nearly three hours on Sept. 15. The mosaic images were acquired as the spacecraft drifted in the darkness of Saturn's shadow for about 12 hours, allowing a multitude of unique observations of the microscopic particles that comprise Saturn's faint rings.
Ring structures containing these tiny particles brighten substantially at high phase angles: i.e., viewing angles where the Sun is almost directly behind the objects being imaged.
During this period of observation Cassini detected two new faint rings: one coincident with the shared orbit of the moons Janus and Epimetheus and another coincident with Pallene's orbit.
Interior to the narrowly confined ring known as the G ring and above the brighter main rings is the pale blue dot of Earth. Cassini viewed its point of origin from close to 1 billion miles (over 1 billion kilometers) away in the icy depths of the outer solar system.
Cassini completed its closest flyby of the odd moon Iapetus, passing about 1,000 miles (1,640 kilometers) above Iapetus' surface. Among the hundreds of images returned, scientists saw pictures of the moon's yin and yang -- a white hemisphere resembling snow, and the other as black as tar.
Images also showed a surface that is heavily cratered, along with the mountain ridge that runs along the moon's equator. Many of the close-up observations focused on studying the strange 12-mile (20-kilometer) high mountain ridge that gives the moon a walnut-shaped appearance.
An analysis of images from NASA's Cassini spacecraft provides conclusive evidence that the jets of fine, icy particles spraying from Saturn's moon Enceladus originate from the warmest spots on the moon's "tiger stripe" fractures that straddle the moon's south polar region.
Members of Cassini's imaging team used two years' worth of pictures of the geologically active moon to locate the sources of the most prominent jets spouting from the moon's surface. They then compared these surface source locations to hot spots detected by Cassini on Enceladus in 2005.
The researchers found that all of the jets appear to come from the four prominent tiger stripe fractures in the moon's active south polar region and, in almost every case, in the hottest areas detected by Cassini's composite and infrared spectrometer.
NASA scientists concluded that at least one of the large lakes observed on Saturn's moon Titan contains liquid hydrocarbons, and have positively identified the presence of ethane. This makes Titan the only body in our solar system beyond Earth known to have liquid on its surface.
Scientists made the discovery using data from an instrument aboard the Cassini spacecraft. The instrument identified chemically different materials based on the way they absorb and reflect infrared light. Before Cassini, scientists thought Titan would have global oceans of methane, ethane and other light hydrocarbons. More than 40 close flybys of Titan by Cassini show that no such global oceans exist, but hundreds of dark, lake-like features are present. Until this analysis, it was not known whether these features were liquid or simply dark, solid material.
The Oct. 9 flyby was Cassini's closest flyby yet of any moon of Saturn, at only 16 miles (25 kilometers) from the surface. This pass put the spacecraft's fields and particles instruments deeper into the plume than ever before, directly sampling the particles and gases. The emphasis here was on the composition of the plume rather than imaging the surface.
NASA scientists marveled over the extent of ruffles and dust clouds revealed in the rings of Saturn during the planet's equinox crossing last month. Scientists once thought the rings were almost completely flat, but new images revealed the heights of some newly discovered bumps in the rings are as high as the Rocky Mountains.
On Aug. 11, sunlight hit Saturn's rings exactly edge-on, performing a celestial magic trick that made them all but disappear. The spectacle occurs twice during each orbit Saturn makes around the sun, which takes approximately 10,759 Earth days, or about 29.7 Earth years. Earth experiences a similar equinox phenomenon twice a year; the autumnal equinox will occur Sept. 22, when the sun will shine directly over Earth's equator.
For about a week, scientists used the Cassini orbiter to look at puffy parts of Saturn's rings caught in white glare from the low-angle lighting. Scientists have known about vertical clumps sticking out of the rings in a handful of places, but they could not directly measure the height and breadth of the undulations and ridges until Saturn's equinox revealed their shadows.
The highest-resolution-yet temperature map and images of Saturn's icy moon Mimas obtained by NASA's Cassini spacecraft revealed surprising patterns on the surface of the small moon, including unexpected hot regions that resembled "Pac-Man" eating a dot, and striking bands of light and dark in crater walls.
Cassini collected the data on Feb. 13, during its closest flyby of the moon, which is marked by an enormous scar called Herschel Crater and resembles the Death Star from "Star Wars."
Scientists working with the composite infrared spectrometer, which mapped Mimas's temperatures, expected smoothly varying temperatures peaking in the early afternoon near the equator. Instead, the warmest region was in the morning, along one edge of the moon's disk, making a sharply defined Pac-Man shape, with temperatures around minus 294 degrees Fahrenheit (92 kelvins). The rest of the moon was much colder, around minus 320 degrees Fahrenheit (77 kelvins). A smaller warm spot -- the dot in Pac-Man's mouth -- showed up around Herschel, with a temperature around minus 310 degrees Fahrenheit (84 kelvins).
NASA's Cassini spacecraft took its lowest dip through the hazy atmosphere of Saturn's moon Titan on the evening of June 20 PDT (early morning June 21 UTC).
Titan's atmosphere applies torque to objects flying through it, much the same way the flow of air would wiggle your hand around if you stuck it outside a moving car window. Cassini mission planners and the NASA Engineering and Safety Center in Hampton, Va., analyzed the torque applied by the atmosphere in detail to make sure the spacecraft could fly safely at an altitude of 880 kilometers (547 miles) above the surface.
For Titan scientists, this was one of the most anticipated flybys of the whole mission. They wanted to get as close as possible to the surface with the magnetometer for a one-of-a-kind scan of the moon. Flying at this low altitude marked the first time Cassini was below the moon's ionosphere, a shell of electrons and other charged particles that make up the upper part of the atmosphere. As a result, the spacecraft found itself in a region almost entirely shielded from Saturn's magnetic field and able to detect any magnetic signature originating from within Titan.
NASA's Cassini spacecraft tracked the growth of a giant early-spring storm in Saturn's northern hemisphere that stretched around the entire planet. The monster tempest, which extended north-south approximately 9,000 miles (15,000 kilometers), was the largest seen on Saturn in the past two decades and is the largest by far ever observed on the planet from an interplanetary spacecraft.
Cassini's radio and plasma wave science instrument first detected the large disturbance's electrical activity on Dec. 5 and amateur astronomers tracked its emergence in December 2010. A Cassini image from Dec. 5 revealed the storm to be a tiny spot. Appearing at approximately 35 degrees north latitude, the storm completely encircled the planet by late January 2011.
The storm's core developed into a giant, powerful thunderstorm. The storm produced a 3,000-mile-wide (5,000-kilometer-wide) dark vortex, possibly similar to Jupiter's Great Red Spot, within the turbulent atmosphere. The storm shot plumes of gas high into the planet's atmosphere. Data from Cassini's radio and plasma wave science instrument showed the lightning flash rate as much as 10 times more frequent than during other storms monitored since Cassini's arrival at Saturn.
The storm's active convection phase ended in late June, but turbulence in the atmosphere lingered afterward.
Images from NASA's Cassini spacecraft showed a concentration of high-altitude haze and a vortex materializing at the south pole of Saturn's moon Titan, signs that the seasons were turning on Saturn's largest moon.
The structure inside the vortex was reminiscent of the open cellular convection that is often seen over Earth's oceans. But unlike on Earth, where such layers are just above the surface, this one was at very high altitude, a possible response of Titan's stratosphere to seasonal cooling as southern winter approached.
Cassini first saw a "hood" of high-altitude haze and a vortex, which is a mass of swirling gas around the pole in the moon's atmosphere, at Titan's north pole when the spacecraft first arrived in the Saturn system in 2004. At the time, it was northern winter. Multiple instruments kept an eye on the Titan atmosphere above the south pole for signs of the coming southern winter.
While the northern hood remained, the circulation in the upper atmosphere was moving from the illuminated north pole to the cooling south pole. This movement appeared to be causing downwellings over the south pole and the formation of high-altitude haze and a vortex.
Cassini's visible light cameras saw the first signs of hazes starting to concentrate over Titan's south pole in March, and the spacecraft's visual and infrared mapping spectrometer (VIMS) obtained data on the south polar atmosphere on May 22 and June 7. False-color images made with VIMS data show a concentration of aerosols forming about 200 miles [300 kilometers] above the surface of Titan's south pole.
Starting in November 2016, Cassini will begin a series of orbits that wind it ever closer to Saturn. Those orbits kick off just outside Saturn's F ring, the outermost of the main rings.
In April 2017, one final close encounter with Titan will put Cassini on a trajectory that will pass by Saturn inside its innermost ring, a whisper away from the top of Saturn's atmosphere. There will be 22 of these close passes.
On Sept. 15, 2017, after entry into Saturn's atmosphere, the spacecraft will be crushed and vaporized by the pressure and temperature of Saturn's final embrace to protect worlds like Enceladus and Titan, with liquid water oceans under their icy crusts that might harbor conditions for life.