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00:00She has traveled nearly 4 billion kilometers,
00:12delivered a probe to the surface of a toxic moon,
00:19and produced science nine years longer than originally planned.
00:30She discovered flowing liquids where none were expected,
00:38phantasmagorical structures on a planet's icy rings,
00:44a weirdly breathing magnetosphere,
00:49and a possible abode of life on a tiny world with a startling atmosphere.
00:59Now, after 20 years in space, controllers have sent the Cassini spacecraft
01:07into a daring spiral to end her remarkable journey.
01:13Streaking along Saturn's upper atmosphere at more than 124,000 kilometers per hour,
01:20Cassini streams data and images back to Earth until heat and turbulence tear her apart.
01:323, 2, 1, and liftoff of the Cassini spacecraft on a billion-mile trek to Saturn.
01:46On the evening of October 15, 1997,
02:02We have cleared the towers.
02:04A powerful Titan 4B booster leaves Launch Complex 40 at the Kennedy Space Center.
02:10All systems go.
02:11The product of two decades of intense collaboration between NASA and the European Space Agency,
02:19in particular, the Italian Space Agency.
02:22Some on Earth have protested this moment.
02:29They fear that if the launch fails,
02:32Cassini's nuclear electric generator will spread radioactive plutonium.
02:39As she glides outward on a nearly seven-year transit to Saturn,
02:49scientists organize their investigations based on past probes' findings.
02:59Their questions nest within one another,
03:03like the giant planet's concentric rings.
03:09Does Saturn have a solid surface?
03:14Or do its clouds thicken down to extreme densities,
03:20perhaps creating exotic forms of matter,
03:25like metallic hydrogen?
03:32Is there a rocky core?
03:36Why are the rings so bright?
03:41How old are they?
03:46What's going on beneath the thick orange clouds of Titan,
03:50Saturn's largest moon?
03:55How are Saturn's moons and rings related?
04:07What will this giant planet tell us about the evolution of solar systems
04:13and of life?
04:17At its distance of nearly a billion and a half kilometers
04:25from the sun, Saturn's orbit lasts 29.5 Earth years.
04:32Over the past Saturn year,
04:36Earth has added some 2.5 billion people.
04:43Average life expectancy rose from age 64 to almost 72.
04:52The Internet has exploded.
04:55It now has almost 4 billion users,
04:59with half the world's population now online.
05:05In the time of Cassini,
05:08our world has been consumed with new ways of communicating,
05:13connecting,
05:17working,
05:20living,
05:25and seeing each other.
05:30Saturn.
05:31Saturn is the Roman name for Kronos,
05:36the Greek god of time,
05:38who ate his children in a fit of jealousy.
05:42In myth,
05:43as in the ever-changing universe,
05:46time is the devourer of all things.
05:58To catch up with Saturn,
06:00mission planners have sent Cassini on a series of flybys.
06:03Each time hitching a ride on the planet's gravity
06:10to speed her on her way.
06:16Pioneer 11 flew by Saturn in 1979,
06:23Voyager 1 in 1980,
06:30and Voyager 2 in 1981.
06:40Cassini will become the first craft to orbit Saturn,
06:44captured by Saturn's gravity on June 30, 2004.
06:52Cassini's prime mission was to be 4 years,
06:55but she will remain healthy far longer.
06:59Her assignments will be extended twice,
07:02an additional 2-year equinox mission
07:06and a 7-year solstice mission.
07:11Yet Cassini's entire exploration
07:14will span less than half a Saturn year,
07:18from late winter
07:21through early summer.
07:25The Saturn system lies 9.5 astronomical units
07:29from the Sun.
07:31That's nearly 10 times farther out than Earth.
07:38The whole grand clockworks speeds along
07:41at 34,821 kilometers every hour,
07:45more than 10 times faster than a bullet fired from a gun.
07:51The planet spins fast,
07:53rotating about its axis once every 10 hours and 39 minutes.
07:58So, while a year on Saturn lasts only 11,000 Earth days,
08:04it's about 24,500 Saturn days.
08:11Made up mostly of hydrogen and helium,
08:14Saturn is the least dense of all the planets.
08:18It's often said,
08:20if you could find a bathtub big enough,
08:22Saturn would float.
08:24That's not quite accurate,
08:27but its density is lower than that of the liquid water
08:30in Earth's oceans.
08:32And it's big.
08:35You could pour 764 Earths
08:38into the volume of Saturn.
08:40This mission is officially named Cassini-Huygens,
08:50honoring two remarkable men of 17th century science,
08:54the French-Italian Giovanni Domenico Cassini,
08:58also known as Jean-Dominique Cassini,
09:02and the Dutch Christian Huygens.
09:06Key players in the scientific revolution,
09:09they collaborated and competed throughout their lives,
09:15in the process,
09:16transforming astrology into astrophysics.
09:24As director of the Paris Observatory,
09:26Cassini built and refined long-tube refractor telescopes.
09:32But Huygens found a way to remove the cumbersome tube,
09:36inventing the so-called air telescope
09:40and its better-engineered eyepiece.
09:47In 1665,
09:49Cassini co-discovered Jupiter's Great Red Spot
09:53and used it to time the big planet's rotation.
10:00Huygens, applying Galileo's ideas,
10:04invented the pendulum clock
10:06and developed the Balanced Spring Watch,
10:09both pivotal innovations in the study of space-time.
10:16Cassini published maps of surface markings on Mars,
10:20though Huygens had actually seen them first.
10:24And Huygens pegged the length of the Martian day at 24 1⁄2 hours,
10:31just seven minutes shy of the correct figure we use today.
10:36By getting parallax observations of Mars,
10:42Cassini was the first to estimate the size of our solar system.
10:49And Cassini used Galileo's method of measuring time
10:53by watching eclipses of Jupiter's moons
10:56to lay out lines of longitude on Earth.
11:02Endeavoring to perfect the geometry of optical lenses,
11:06Huygens developed the wave theory of light,
11:09setting the stage for today's quantum mechanics.
11:15Cassini explained the so-called zodiacal light,
11:19seen by astronomers as the reflection of sunlight off dust
11:23in the plane of the solar system.
11:26Toward the end of his life,
11:28Huygens determined liquid water
11:30to be a key factor in searching for extraterrestrial life,
11:35a quest now undertaken by the Cassini spacecraft
11:39and its Huygens probe.
11:42We've known Saturn as the ringed planet since 1655,
11:57when Christian Huygens explained what Galileo had seen 45 years earlier.
12:03But if you were standing on most of Saturn's moons,
12:08you'd have a hard time actually seeing the rings.
12:13Because most moons ride in the ring plane,
12:16you could only view them edge-on.
12:20From the right,
12:21watch tiny Prometheus,
12:23just 86 kilometers across,
12:25pass behind Big Tathus,
12:281,062 kilometers wide.
12:34Little Pandora scoots through from left to right.
12:44Here, medium-sized Mimas,
12:46traveling 14 kilometers per second,
12:48glides in front of the larger Rhea
12:51at 8 kilometers per second.
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13:13When Cassini launched, 18 moons were known to orbit Saturn,
13:25and 13 more were suspected.
13:28By the end of Cassini's mission, astronomers will confirm 53,
13:35with another 9 marked as conditional.
13:40Only one of them is huge, Titan.
13:47In 1655, Christian Huygens was the first to observe Titan.
13:55Giovanni Domenico Cassini discerned Iapetus in 1671,
14:01Rhea in 1672, Dione in 1684,
14:08and Tathus in 1684.
14:12The sky-watching siblings William and Carolyn Herschel found Mimas and Enceladus in 1789.
14:23In 1848, Hyperion was spotted by the father-son team of William and George Bond in the U.S. and William Lassell in the U.K.
14:35Phoebe was the first moon to be discovered through photography by the American astronomer William Henry Pickering in 1898.
14:45Some of Saturn's moons are probably captured objects, particularly those in retrograde orbits, like Phoebe.
14:54They orbit backwards, in the opposite direction from the rotation of the planet.
15:00Each Saturnian moon is a unique jewel in the majestic planet's elaborate necklace.
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16:00Before Cassini, no one suspected Enceladus to be anything other than a dead ball of rock
16:09and ice.
16:13But scientific sleuthing led to a remarkable discovery.
16:21Enceladus is about 482 kilometers in diameter.
16:26It would fit neatly between Los Angeles and San Francisco.
16:33The first good close-up, taken by Voyager 2 in 1981, showed the globe was remarkably bright
16:39and free of craters.
16:42In fact, Enceladus is the whitest body in the solar system.
16:51The first hints of a more complex story come from Cassini's magnetometer.
16:57The moon's magnetic signature looks more like that of a comet.
17:05Field lines are bent around Enceladus's south pole.
17:08A closer flyby shows the southern polar region has been recently resurfaced.
17:15Cassini's infrared spectrometer indicates the area is about 100 degrees warmer than the rest
17:22of the moon.
17:25And that heat signature aligns with four prominent tiger stripes appearing across the moon's southern
17:31terrain.
17:34They turn out to be fissures, cracks in the icy surface, each about 150 kilometers long and
17:42about 1 kilometer wide.
17:46Scientists name them Alexandria, Cairo, Baghdad, and Damascus.
17:53From each, jets of water vapor and water ice shoot out into space.
18:09Cassini eventually locates more than 100 of these geysers.
18:17Mission planners arrange more flybys and, in October of 2015, navigate within 50 kilometers
18:23of Enceladus's south pole and right through the jets, giving the instruments a chance to
18:30taste and smell them.
18:34It's mostly water ice.
18:36There's also some ammonia, methane, and carbon dioxide, key compounds associated with life.
18:45And hydrogen gas, which microbes, if there are any, could be using as a source of energy.
18:53Some of the particles are salty, like frozen sea spray, flavored by sodium and potassium.
19:04The science team imagines that a large subsurface ocean lies beneath the icy crust.
19:12As it sloshes around, carbon dioxide makes it fizzy, like bottled soda.
19:19When it finds a path to lower pressure, through the cracks of the tiger stripes, it sprays out
19:25into space like champagne when the cork pops.
19:31Most of these salty water particles fall back to the ground as snow, decorating and repairing
19:38the surface of Enceladus.
19:43But some escape Enceladus's weak gravity.
19:50So Enceladus rides a misty ring of its own creation.
20:01Were the moon to shut off its water jets, this E-ring would dissipate completely within
20:06a few hundred years.
20:11Tracking and modeling icy tendrils made by interacting geyser jets lets researchers calculate
20:18how much mass Enceladus is pumping into Saturn's rings.
20:30Enceladus orbits in resonance with the moon Dione.
20:37Their dance is thought to heat their rocky cores.
20:42It's likely that Dione, too, has a subsurface ocean.
20:49Dione's big crater, Creusa, paints bright rays at least 500 kilometers across the moon's surface,
20:56giving researchers a marker of geologic time.
21:01Researchers younger than Creusa disturb the rays.
21:05Older ones underlie them.
21:09Water is pulled down into the hot cores of these moons, reemerging as steam through the seafloor.
21:18We know this because Cassini has detected tiny silicate particles that can only form in boiling
21:24water.
21:28In Earth's oceans, hydrothermal vents called black smokers and white smokers are oases for
21:38life.
21:41The churning hot water provides energy and sets nutrient particles swirling around.
21:53Is the same thing happening beneath the ice crystal crusts of Saturn's snow globe moons?
22:01To find out, future missions must look for amino acids, fatty acids, long carbon chain molecules,
22:10and perhaps microorganisms hitchhiking on the ice crystals blasted far from the undersurface
22:18ocean depths.
22:25Many astrobiologists are fascinated by Titan because it is very cold, about minus 180 Celsius,
22:34yet it is wet.
22:36If anything lives on or inside Titan, it is almost surely not related to life on Earth.
22:45Titan is about the same diameter and mass as the planet Mercury, and Titan's surface
22:51gravity is about the same as Earth's moon.
22:54But unlike Mercury or the moon, Titan has a thick atmosphere, even thicker than Earth's.
23:03And scientists don't yet know why.
23:09It's the second largest moon in the solar system.
23:12At 5,150 kilometers in diameter, only Jupiter's Ganymede is wider.
23:21Titan is so much larger than the rest of Saturn's moons, it may have formed from the collision
23:27of several of its siblings.
23:43By mission's end, Cassini will have flown by Titan 127 times.
24:07Each pass gives the craft a gravitational acceleration equivalent to almost 1,000 kilos
24:12of extra fuel.
24:17When the two Voyagers sailed past in 1980 and 1981, they saw only this orange, smog-enshrouded
24:25globe.
24:30American and European scientists were so intrigued, they began sketching out what would become
24:36the Cassini-Huygens mission.
24:42Twenty-three years later, an international team commands the release of the Huygens probe
24:50to land on Titan.
25:01January 14, 2005, the European-built Huygens probe aero-breaks into Titan's atmosphere
25:16with its heat shield, deploys a parachute, and floats down for over two and a half hours
25:29through a nitrogen-laden atmosphere.
25:37Its camera reveals an eerie landscape.
25:47Huygens lands softly in a slushy bank of frozen methane along the shoreline of a hydrocarbon
25:57lake.
26:01Huygens continues transmitting data for another half hour after landing, sending back images
26:08of rounded pebbles, probably made of hard, frozen water ice.
26:15Humanity has placed its imprint on yet another world.
26:21The flowing liquid on Titan is methane, which acts there as water does on Earth.
26:30In the range of Titan's temperatures, methane can exist in all three states—solid, liquid,
26:38and gas.
26:41It is not impossible that a form of life could be evolving on this moon, feeding on the constant
26:47rain of hydrocarbons—a true, second genesis, completely separate from our earthly tree of
26:55life.
26:58Since Voyager first glimpsed Titan, researchers have speculated that liquid oceans grace its
27:04surface.
27:07But dense orange smog has withheld the truth.
27:12This haze collects when the sun's ultraviolet light breaks up methane in the high atmosphere,
27:18forming long molecular chains that grow large enough to fall from the sky.
27:26These methane byproducts form snowdrifts into a huge network of dunes around Titan's equator.
27:33Cassini's camera was outfitted with near-infrared filters to peer through the orange fog to verify
27:44bodies of liquid.
27:47Images come back of relatively flat areas, but are they truly oceans?
27:55Or perhaps just methane slush?
27:59Or thick tar?
28:03The answer comes from Cassini's visible infrared mapping spectrometer.
28:08It catches a specular reflection—a bright spot of sunlight bouncing off a clearly liquid surface.
28:18With Cassini's radar, flat surfaces—lakes and seas—appear dark unless they are ruffled by waves.
28:27Titan indeed has oceans, ponds, and pools of liquid hydrocarbons—ethane, methane, and propane.
28:37Strangely, they form mostly in Titan's northern hemisphere, near the pole.
28:45Saturn's eccentric orbit is to blame.
28:49Northern summer is warmer than southern summer on Saturn.
28:53But because of the way Titan is tipped, its southern summer is more severe.
28:58So all the southern liquid methane evaporates and rains out in the north.
29:06Over time, the whole system flips.
29:10In 15,000 years, Titan's lakes will all be in the southern hemisphere.
29:17This one, named Lije Amare, is larger than Lake Superior on Earth.
29:23It's probably 150 meters deep in spots.
29:28Mysterious frothy islands appear, bubbling up from under the surface.
29:35Titan holds a store of hydrocarbons about 10 times larger than all Earth's petroleum and
29:40natural gas reserves combined.
29:49Hovering 300 kilometers over Titan's south pole, a huge, persistent, toxic cloud of frozen
29:57hydrogen cyanide rotates ominously.
30:01This vortex seems to develop when Titan's southern hemisphere enters its autumn season.
30:10Titan thrusts its methane up into space at a frightening rate.
30:15The atmospheric supply can't last longer than about 20 million years.
30:21Something must be replenishing it.
30:23But what?
30:26Cassini's radar spots the answer.
30:30Mountains, some up to a kilometer tall.
30:36These may be cryo-volcanoes.
30:41Some could be active today, spewing methane from within the Moon.
30:49Cassini's radio science tools show Titan's whole body flexing in response to Saturn's gravity.
30:57That makes it warm enough inside to melt ice.
31:02Unlike the subsurface oceans of Enceladus with its rocky ocean floors, Titan's ocean is probably
31:08sandwiched between layers of water ice.
31:13So if there's an underground marine layer, it may be sealed off from the hot chemistry of
31:19geothermal vents and any chance of nurturing life forms.
31:27Even after Cassini-Huygens, we still don't know how old Titan is, where it came from, or how long it's had an active atmosphere.
31:44Clues point to a cataclysmic event in the Saturn system perhaps a hundred million years ago
31:52that either created Titan from smaller bodies or energized a barren, frozen Titan into an active system,
32:03possibly like the primitive Earth.
32:10To find out, we'll have to go back, float longer through the haze, sail the hydrocarbon seas,
32:28and soar through the nitrogen skies of Titan.
32:51To Galileo in 1610, the ringed planet appeared as three stars, with two small ones touching one large,
33:01prompting Galileo to declare that Saturn must have ears.
33:08But in 1655, using more advanced optics, Christian Huygens unmasked the apparition as a flat ring circling a spherical planet.
33:21Twenty years later, Giovanni Domenico Cassini discerned that it was not one ring, but several, with gaps between them.
33:32The widest gap was later named the Cassini Division.
33:37We now know that it's 4,800 kilometers wide, and far from empty.
33:48In 1859, Scottish mathematician James Clerk Maxwell showed that the rings are not solid disks, but composed of many smaller granules.
34:02Each tiny fleck, pebble, and boulder revolves around the planet in its own orbit, jockeying for position among trillions of others.
34:13Though all are flying several kilometers per second, they jostle one another only very gently.
34:42The concentric rings are given letters, A through G, in their order of discovery.
34:57Material riding close into Saturn's cloud tops in the D ring whips around Saturn in about four hours.
35:05But particles in the distant F ring take at least four times longer.
35:10It wasn't until the Cassini's inspection that we learned just how flat the rings are.
35:20Incredibly, they are only 10 meters thick on average.
35:24From top to bottom, only about as tall as a three-story building.
35:31These rings are 30 million times wider than they are high.
35:39And ring material can ripple up and down, crafting temporary corrugations.
35:52Many intricate wave patterns can be seen across the broad ring plane.
35:56Each one is conjured by a specific gravitational resonance with a Saturnian moon.
36:03Though the basic physics of the ring system is simple, it's mostly the product of gravity and collisions,
36:11The intricate structure of the rings is hard to mathematically model, even after 13 years of Cassini observations.
36:23The pressure of sunlight and forces from Saturn's magnetic field can push or pull smaller, less massive ring particles around.
36:35The mission team flies a series of special orbits that put the rings between Cassini and Earth.
36:43By beaming radio signals of three different wavelengths through the ring material, researchers build up a color map of particle sizes.
36:53Red areas hold more big particles.
36:57Blue regions contain mostly smaller grains.
37:02Radio waves, shown in the bottom half of this image, reveal finer structure than photos taken in visible light.
37:11Most particles are small, from tiny crystals smaller than a dust grain, up to pebble-sized.
37:19Less common are ice rocks and large boulders, up to the size of houses.
37:25A few are the size of mountains, moons in the act of forming, or falling apart.
37:35Grabbing an average size ring particle would feel something like closing your hand around a thick layer of very cold whipped cream
37:42to find a glob of solid ice cream deep inside.
37:46The packing of particles varies between rings.
37:57Very little light gets through the B ring of crowded snowballs.
38:02An astronaut would have to dig her way through it.
38:05The A ring is less congested.
38:10And the G ring is very diffuse, like fog or smoke.
38:20The Cassini mission confirms the rings are made of almost pure water ice.
38:26But tiny quantities of simple organic compounds tint and shade them.
38:34The astronomer Carl Sagan called these colorful chemicals tholans, Greek for muddy.
38:47Crossing Saturn's dark side, Cassini's camera picks up the true colors and intricate complexity of the ring plane's variations.
39:12Subtle gravitational effects, fashioned by the many moons, sculpt the ring material.
39:22Small moons, this one's named Pan, orbit within the rings.
39:29They seem to sweep clear their lanes of travel.
39:35The moon Mimas, gravitationally combing the ring's particles, causes the large Cassini division.
39:50Other rings are herded into form by so-called shepherd moons, like Prometheus and Pandora.
39:58Tiny Daphnis, just eight kilometers across, pushes a wave of ring material, like the bow wave of a boat on a lake.
40:25Daphnis bobs up and down like a merry-go-round horse, gravitationally pulling particles into dune-like mounds three kilometers tall.
40:40It has plowed a 35 kilometer wide furrow in the ring field, called the Keeler division.
40:47The larger Pan forges the 325 kilometer Enke gap in Saturn's A-ring, giving it a wavy edge, and Pan's gravity inspires a spiral wake of particles.
41:03Based on that gap, researchers predicted Pan's existence in the late 19th century, long before it was first seen.
41:18But no one anticipated Pan's remarkable shape.
41:25And it's not unique.
41:29The slightly wider moon Atlas has a similar structure.
41:36Both wear skirts of gravitationally attracted icy crystals.
41:43Certain small satellites on eccentric orbits repeatedly crash through the F-ring,
41:50leaving behind sets of disruptive splashes as evidence of their passing.
41:58Other minuscule moonlets, too small to be seen, fashion propeller-shaped resonant waves in the snowy rings falling around Saturn.
42:23The ever-evolving complexity of these ring circles moves like a musical score, playing in silence.
42:48Once every 14 years, the ring plane lies exactly edge-on to the Sun.
42:56Cassini was present for one such equinox.
43:03In essence, the sunlight on the rings has been switched off, and they cast no shadows on Saturn.
43:11They are only visible because Saturn reflects some light on them, here digitally multiplied many times.
43:19Only the F-ring, which is slightly tilted from the others, catches any sunlight.
43:26But because the rings are so thin, any tall structure within them throws its shadow onto the ring plane.
43:40Thus, in the outermost edge of the B-ring, a surprise appears.
43:45Hundreds of long shadows mark a field of icy spikes.
43:50Geometry dictates these points must range up to a kilometer or so in height.
43:57Like icebergs growing in a sea of mostly empty space,
44:02these thorn-like clumps may be molded by the invisible fingers of a gravitational resonance with one of the moons.
44:09Or, they may be drawn out by static electricity inspired by Saturn's magnetic field.
44:21Some of Saturn's rings are constantly morphing,
44:26while others are stoically consistent year after year.
44:32How old are these bright icy rings?
44:47They may have formed in the last 100 million years,
44:52when icy moons or comets collided,
44:55or were torn apart by Saturn's gravity.
44:59Or they might be as old as Saturn,
45:03the leftover debris of the solar system's birth.
45:06Cassini may yet find the true answer.
45:18Looking down at Saturn's North Pole,
45:20Cassini gets a spectacular view of the globe's jet stream.
45:24Some resonance of the wind energies banks the stream into a six-sided shape,
45:31a hexagon.
45:34Apparently, an eastward-flowing shallow jet stream is bumped by occasional storms.
45:44The jet reacts by settling into the most stable geometric shape,
45:49six roughly equal sides.
45:58This polar monsoon is about 32,000 kilometers wide.
46:04You could fit two-and-a-half Earths into it.
46:10Its winds blow faster the closer they get to the pole.
46:17Up to 540 kilometers per hour.
46:20Up to 540 kilometers per hour.
46:49Why kill Cassini in a ball of atmospheric fire?
46:54The international scientific community has agreed to avoid any possibility
46:59of contaminating Saturn's moons, especially Enceladus and Titan.
47:08Cassini is warm inside, essentially room temperature.
47:14Any microbes that found their way in during assembly could have easily survived.
47:22And Cassini's RTG will remain hot for decades.
47:28If she was allowed to accidentally crash on Enceladus,
47:32Cassini might easily melt her way down through the ice into the underground ocean.
47:39Back in 2009, studies had showed Cassini had enough fuel to go beyond Saturn
47:46to explore the ice giants Uranus or Neptune.
47:51She could have been sent back to Jupiter,
47:56or outward to visit a population of comet-like asteroids known as the Centaurs.
48:01But to get all the science possible from the Saturn system,
48:08Cassini would have to die here.
48:14That led trajectory designers at JPL to develop a jewel of orbital dynamics,
48:20the Solstice mission.
48:23The plan optimizes repeated flybys of Titan.
48:29The route features high orbits to look at the poles and the rings,
48:35long loops to map the planet's magnetic fields,
48:40flattened equatorial orbits to check out moons,
48:47and ending at the peak of northern summer,
48:52to mirror Cassini's arrival in southern summer.
48:58Between the two, scientists can infer the full cycle of Saturn's seasons.
49:06The science based on Cassini's data will go on for decades.
49:27Nudging Cassini's speed by just eight meters per second
49:31is enough to begin her death spiral.
49:35The craft makes repeated dives between the innermost ring material
49:40and the roiling atmosphere.
49:47These maneuvers would have been far too dangerous to contemplate
49:50when Cassini was designed.
49:54Along the way, the spacecraft maps fluctuations
49:58in Saturn's gravity and magnetic fields,
50:02and samples icy particles flowing in from its rings.
50:09Until the very end,
50:11Cassini beams science data and images directly to Earth.
50:17Finally, on September 15, 2017,
50:26as the Cassini spacecraft streaks along Saturn's clouds,
50:31its high-gain antenna shifts away from Earth.
50:36the signal fades,
50:43and she is gone.
50:45the energy is gone.
50:46the energy is gone.
50:48the energy is gone.
50:52the energy is gone.