A nearly seven-year journey to the ringed planet Saturn began with the liftoff of a Titan IVB/Centaur carrying the Cassini orbiter and the European Space Agency's Huygens probe. Both the orbiter and the probe were history-making triumphs of engineering and scientific discovery.
Cassini-Huygens performed a flyby of the planet Venus, getting within about 176 miles (284 kilometers) of the Venusian surface. The gravity assist accelerated the Cassini spacecraft by about 4 miles per second (7 kilometers per second) to help the spacecraft reach Saturn. (Note: Cassini is shown in this illustration without its thermal blankets).
After another trip around the sun, Cassini-Huygens flew by Venus a second time for another gravity assist, this time coming within about 370 miles (600 kilometers) of the planet.
Nearly two years after launch, Cassini-Huygens flew within about 700 miles (1,100 kilometers) of Earth, passing most closely above the eastern South Pacific. The flyby gave Cassini a 3.4-mile-per-second (5.5-kilometer-per-second) speed boost. Though Cassini was now nearly as close to Earth as it had been shortly after launch, the spacecraft was now traveling much faster.
Cassini-Huygens was the seventh spacecraft ever to fly through the asteroid belt. While the belt contains a significant concentration of asteroids, the area is not considered a hazard to spacecraft. Scientists used the spacecraft's Cosmic Dust Analyzer (CDA) to better study the region.
Cassini-Huygens made its closest approach to Jupiter at a distance of 6.2 million miles (10 million kilometers) on Dec. 30, 2000. Joining forces with the Galileo spacecraft, which was already orbiting Jupiter, the two spacecraft provided unique insight into the Jovian system.
Cassini captured this image of Saturn during a camera test 20 months before arriving at Saturn. For this shot, the spacecraft was 177 million miles (285 million kilometers) from Saturn — nearly twice the distance between Earth and the sun.
When Cassini was still three months from arriving at Saturn, the spacecraft observed two storms merging into one larger storm. It was only the second time this phenomenon had been observed on the ringed planet.
With eyes sharper than any that peered at Saturn before, the Cassini spacecraft uncovered two previously unknown moons orbiting the ringed planet. Methone and Pallene, respectively 2 miles (3 kilometers) and 3 miles (5 kilometers) in diameter, brought Saturn's total of known moons to 60.
Phoebe was the first of Cassini's many moon flybys. The spacecraft passed within about 1,200 miles (2,000 kilometers) of the dark moon. By comparison, Voyager 2 flew past in 1981 at about 1.4 million miles (2.2 million kilometers) – that’s 1,000 times farther away.
Cassini, still carrying the Huygens probe, became the first spacecraft to orbit Saturn on Thursday, July 1, 2004 at 9:12 p.m. UTC (June 30 at Cassini's home base in California).
The Cassini-Huygens spacecraft beamed back information and pictures after successfully skimming the hazy atmosphere of Saturn's moon Titan. The spacecraft came within 750 miles (1,200 kilometers) of Titan's surface.
The Huygens probe successfully detached from NASA's Cassini orbiter to begin a three-week journey to Saturn's moon Titan. The Huygens probe, built and managed by the European Space Agency (ESA), was bolted to Cassini and rode along during the nearly seven-year journey to Saturn largely in "sleep" mode.
During a flyby of Iapetus, Cassini captured images of an unexpected equatorial ridge approximately 12 miles (20 kilometers) wide and 8 miles (13 kilometers) high.
The Huygens probe successfully landed on Saturn's largest moon Titan at about 11:30 UTC on January 14, 2005. The descent lasted two hours and 27 minutes. The battery-powered probe survived another 72 minutes on the surface of Titan. This was the first and, so far, only landing on any world in the outer solar system, earning Huygens the record for the greatest distance from Earth that a spacecraft has landed.
Spectacular images captured by Huygens revealed that Titan has extraordinarily Earth-like meteorology and geology.
During this pivotal flyby, the Cassini cameras obtain new, detailed images of the south polar region of Enceladus. The images reveal a surprisingly youthful and complex terrain, almost entirely free of impact craters. The area is littered with house-sized ice boulders carved by unique tectonic patterns found only in this region of the moon. To their amazement, Cassini scientists detect a huge cloud of water vapor over the area -- and relatively warm fractures in the crust that are supplying the cloud of water vapor and ice particles that extend into space. Cassini data also confirms that this activity is the major source of material in the E ring.
Cassini scientists announced evidence of liquid water reservoirs feeding the Enceladus plume, possibly in the form of geysers. After examining high-resolution Cassini images and other data showing icy jets ejecting large quantities of particles at high speed, scientists rule out the idea that the particles are produced by or blown off the moon's surface by vapor created when warm water ice converts to a gas. Instead, they find evidence that the jets might be erupting from near-surface pockets of liquid water.
During a 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.
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.
Cassini's flyby of the odd moon Iapetus revealed new details about the moon's yin and yang surface -- a white hemisphere resembling snow, and the other as black as tar.
Scientists announce 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.
During a close flyby, Cassini's instruments sampled the plume directly, and detected a surprising brew of volatile gases, water vapor, carbon dioxide and carbon monoxide, as well as organic materials, some 20 times denser than expected. The brew was described as being "like carbonated water with an essence of natural gas." New heat maps of the surface showed higher temperatures than previously known in the south polar region, with higher-than-expected temperatures running the length of the giant fissures near the south pole.
In four years at Saturn, Cassini revealed wonder after wonder. The growing body of knowledge about Saturn, its rings, moons and magnetic environment is allowing scientists to link together clues to solve long-standing scientific mysteries and formulate many new questions.
In a feat of interplanetary sharpshooting, Cassini identifies precisely where icy jets erupt from the surface of Enceladus. Carefully targeted pictures reveal exquisite details in the prominent south polar tiger stripe fractures from which the jets emanate. The images show the fractures are about 980 feet (300 meters) deep, with V-shaped inner walls. The outer flanks of some of the fractures show extensive deposits of fine material. Finely fractured terrain littered with blocks of ice tens of meters in size and larger surrounds the fractures.
Cassini performed its closest flyby of any moon of Saturn, at only 16 miles (25 kilometers) from the surface. This pass put the spacecraft's fields and particles instruments deep into the plume, directly sampling the particles and gases.
The closer scientists look at Enceladus, the more evidence they find of geologic activity. New high-resolution images show signs that the south polar surface changes over time, including surprising evidence of Earth-like tectonics, such as spreading of the icy crust, but with an exotic difference -- the spreading is almost all in one direction, like a conveyor belt. New data on the plume show it varies over time and has a far-reaching effect on Saturn's magnetosphere.
Cassini discovered Aegaeon embedded in Saturn’s G ring. This is the smallest known moon of Saturn, with a mean radius of just 0.2 miles (0.3 kilometers). The G ring appears to be generated from material blasted off of Aegaeon by micrometeoroid impacts -- one of several Saturnian rings created by the planet's moons.
Scientists working on the Cassini mission detect sodium salts in ice grains of Saturn's outermost ring. The salty ice indicates that Enceladus, which is the primary source replenishing the ring with material from its jets, could harbor a large reservoir of liquid water -- perhaps an ocean -- beneath its surface. Scientists on Cassini's Cosmic Dust Analyzer (CDA) team conclude that liquid water must be present because it is the only way to dissolve the significant amounts of minerals that would account for the levels of salt detected.
Researchers announce that data collected during close flybys of Enceladus definitively identifies ammonia in the plume. In space, the presence of ammonia provides strong evidence for the existence of at least some liquid water.
During Saturn’s equinox, sunlight hit Saturn's rings exactly edge-on, performing a celestial magic trick that made them all but disappear. Scientists used the Cassini orbiter to look at puffy parts of Saturn's rings caught in the glare from the low-angle lighting. This allowed scientists to measure the height and breadth of vertical clumps structures sticking out of the rings.
Scientists used the Cassini spacecraft's magnetospheric imaging instrument to detect this new, temporary radiation belt at Saturn, located around the orbit of its moon Dione at about 234,000 miles (377,000 kilometers) from the center of the planet.
NASA extended the international Cassini-Huygens mission to explore Saturn and its moons through 2017. This enabled Cassini to observe seasonal changes in the Saturn system over almost half of Saturn's nearly 30-year orbit around the sun.
The highest-resolution-yet temperature map and images of Saturn's icy moon Mimas 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 made its lowest dip through the hazy atmosphere of Saturn’s moon Titan, entering the moon’s ionosphere. That upper layer of atmosphere is a shell of electrons and other charged particles, which almost entirely shielded the spacecraft from Saturn’s magnetic field and allowed Cassini to observe Titan’s magnetic signature.
The Cassini Solstice Mission extension enabled scientists to study seasonal changes in the Saturn system over almost half of Saturn's nearly 30-year orbit around the sun.and other long-term weather changes on Saturn and its moons.
Cassini detected a very tenuous atmosphere known as an exosphere, which was infused with oxygen and carbon dioxide, around Saturn's icy moon Rhea. This is the first time a spacecraft has directly captured molecules of an oxygen atmosphere -- albeit a very thin one -- at a world other than Earth
Cassini 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 found more evidence for a large-scale saltwater reservoir beneath the icy crust of Enceladus. The data came from the spacecraft's direct analysis of salt-rich ice grains close to the jets ejected from the moon.
With the artistry of a magazine cover shoot, Cassini captured this portrait of five of Saturn's moons poised along the planet's rings. From left to right are Janus, Pandora, Enceladus, Mimas and finally Rhea, bisected by the right side of the frame. The view was acquired at a distance of approximately 684,000 miles (1.1 million kilometers) from Rhea and 1.1 million miles (1.8 million kilometers) from Enceladus.
Cassini "sniffed" molecular oxygen ions around Saturn's icy moon Dione for the first time, confirming the presence of a very tenuous atmosphere. The oxygen ions are quite sparse -- one for every 0.67 cubic inches of space (one for every 11 cubic centimeters of space) or about 2,550 per cubic foot (90,000 per cubic meter) - showing that Dione has an extremely thin neutral atmosphere.
Scientists discovered strange half-mile-sized (kilometer-sized) objects punching through parts of Saturn's F ring, leaving glittering trails behind them. These trails in the rings, which scientists are calling "mini-jets," fill in a missing link in Cassini's evolving story of the curious behavior of the F ring.
Cassini changed the angle at which it orbits Saturn and regularly passes above and below Saturn's equatorial plane. This allows a better perspective to see Saturn’s rings as well as views of the poles and the atmosphere of Saturn and its moons.
Call it a Saturnian version of the Ouroboros, the mythical serpent that bites its own tail. The massive storm churned around the planet until it encountered its own tail and sputtered out. This was the first time scientists observed a storm consume itself in this way anywhere in the solar system.
Cassini took a picture of our home planet from a distance of hundreds of millions of miles. NASA invited the public to help acknowledge the historic interplanetary portrait as it was being taken -- another Cassini first.
A loop high above Saturn revealed this stately view of the golden-hued planet and its main rings. This observation was planned as one of three images for Cassini's 2013 “Scientist for a Day” essay contest. The contest challenges students to study three possible targets and write about which one they think will yield the best science.
Cassini obtained the highest-resolution movie yet of a unique six-sided jet stream, known as the hexagon, around Saturn's north pole.
Each flyby provided a little more knowledge of Titan and its striking similarities to Earth. Even with its cold surface temperatures of minus 290 degrees Fahrenheit (94 kelvins), Titan is like early Earth in a deep freeze.
Scientists using mission data from Cassini identified 101 distinct geysers erupting on Saturn's icy moon Enceladus. Their analysis suggests it is possible for liquid water to reach from the moon's underground sea all the way to its surface.
Researchers studying data from Cassini observed that Saturn's largest moon, Titan, behaves much like Venus, Mars or a comet when exposed to the raw power of the solar wind.
Cassini returned images from its final close approach to Saturn's oddball moon Hyperion, upholding the moon's reputation as one of the most bizarre objects in the solar system. The views show Hyperion's deeply impact-scarred surface, with many craters displaying dark material on their floors.
A pockmarked, icy landscape looms beneath NASA's Cassini spacecraft in new images of Saturn's moon Dione taken during the mission's last close approach to the small, icy world. Two of the new images show the surface of Dione at the best resolution ever.
On its 22nd and final close, targeted encounter with the fascinating icy moon, Cassini passed Enceladus at a distance of 3,106 miles (4,999 kilometers).
In a nod to extraterrestrial mountaineers of the future, scientists working on NASA’s Cassini mission identified the highest point on Saturn’s largest moon, Titan. Titan’s tallest peak is 10,948 feet (3,337 meters) high and is within the Mithrim Montes, a trio of mountainous ridges.
After nearly two years in high-inclination orbits that limited its ability to encounter Saturn's moons, Cassini returned to Saturn's equatorial plane. A dual view of Saturn's icy moon Rhea marks the return of NASA's Cassini spacecraft to the realm of the planet's icy satellites.
Of the millions of dust grains Cassini has sampled at Saturn, a few dozen appear to have come from beyond our solar system. Scientists believe these special grains have interstellar origins because they moved much faster and in different directions compared to dusty material native to Saturn. The research, led by a team of Cassini scientists primarily from Europe, is published this week in the journal Science.
A new study based on Cassini data finds that a large sea on Saturn's moon Titan is composed mostly of pure liquid methane, independently confirming an earlier result. The seabed may be covered in a sludge of carbon- and nitrogen-rich material, and its shores may be surrounded by wetlands.
During a recent stargazing session, NASA's Cassini spacecraft watched a bright star pass behind the plume of gas and dust that spews from Saturn's icy moon Enceladus. At first, the data from that observation had scientists scratching their heads. What they saw didn't fit their predictions.
Cassini begins a series of 22 highly inclined orbits that carry the spacecraft above the poles and wind it ever closer to Saturn. Those orbits kick off just outside Saturn’s F ring, the outermost of the main rings seen here as the thin but brightest ring, appearing to be separated from all the inward rings.”
Cassini captured raw, unprocessed images of Saturn's moon, Atlas, on April 12, 2017. The flyby had a close-approach distance of about 7,000 miles (11,000 kilometers). The images are the closest ever taken of Atlas, which orbits Saturn just outside the A ring.
Scientists announce data from the spacecraft indicates hydrogen gas, which could potentially provide a chemical energy source for life, is pouring into the subsurface ocean of Enceladus from hydrothermal activity on the seafloor.
A new image from Cassini showed planet Earth as a point of light between the icy rings of Saturn. The spacecraft captured the view on April 12, 2017, at 10:41 p.m. PDT (1:41 a.m. EDT on April 13). Cassini was 870 million miles (1.4 billion kilometers) away from Earth when the image was taken.
Cassini had its last close brush with Saturn's hazy moon Titan, making its 127th and final close approach to Titan on April 21 at 11:08 p.m. PDT (2:08 a.m. EDT on April 22), passing at an altitude of about 608 miles (979 kilometers) above the moon's surface. Cassini transmitted its images and other data to Earth following the encounter.
Cassini made contact with Earth after its successful first-ever dive through the narrow gap between the planet Saturn and its rings. NASA's Deep Space Network Goldstone Complex acquired Cassini's signal at 11:56 p.m. PDT on April 26, 2017 (2:56 a.m. EDT on April 27) and data began flowing at 12:01 a.m. PDT (3:01 a.m. EDT) on April 27.
Cassini ends its historic mission with 22 daring loops passing through the gap between Saturn and the innermost ring. During this part of the mission, termed "The Grand Finale," Cassini explores an entirely new region around Saturn, coming closer than ever before.
As NASA's Cassini spacecraft prepares to shoot the narrow gap between Saturn and its rings for the second time in its Grand Finale, Cassini engineers are delighted, while ring scientists are puzzled, that the region appears to be relatively dust-free. This assessment is based on data Cassini collected during its first dive through the region on April 26.
Cassini looked on as Saturn's solstice—that is, the longest day of summer in the northern hemisphere and the shortest day of winter in the southern hemisphere— arrived today for the planet and its moons. The Saturnian solstice occurs about every 15 Earth years. Reaching the solstice, and observing seasonal changes in the Saturn system along the way, was a primary goal of Cassini's Solstice Mission—the name of Cassini's second extended mission.
The spacecraft completed its eleventh dive (of 22) through the gap, putting it halfway through the final phase of its nearly 20-year journey in space. Cassini needs only to stay out of trouble for the next two and a half months to reach the end of its mission on Sept. 15.
Just a month shy of 20 years in space, Cassini makes a final plunge into Saturn's atmosphere. The spacecraft is crushed and vaporized by the pressure and temperature of Saturn's final embrace to protect worlds like Enceladus and Titan, moons with liquid water oceans under their icy crusts that might harbor conditions for life.
After the mission ends, scientists continue to analyze measurements sent by Cassini while it was at Saturn. One example: data from Cassini reveal complex organic molecules originating from Saturn’s icy moon Enceladus, strengthening the idea that this ocean world hosts conditions suitable for life.
First Venus Flyby
April 25, 1998