The Hardest NASA Mission in History

0:00 In the 1600s, a man built the most powerful telescope ever.

0:05 And on January 7th, 1610,

0:07 he used it to look further than any human being in history.

0:12 But when he did, he saw something strange.

0:15 Jupiter wasn't alone.

0:17 There were three small stars.

0:20 Over the next few days, they moved, and then there were four.

0:25 But that was impossible.

0:27 Stars didn't move like that.

0:29 For centuries, humanity believed the sky rotated us.

0:33 The sun and planets orbited Earth.

0:36 The stars were fixed on a shell.

0:38 Medieval scholars thought they were embedded in a crystalline

0:41 sphere that rotated every 24 hours around a stationary Earth.

0:46 But the man saw stars that were moving.

0:49 He thought he must have miscalculated, but his observations were consistent.

0:55 The four stars were being dragged by the big planet almost

0:58 like they were orbiting it almost as if they were moons.

1:03 The man found four bodies that shared a different

1:06 center for the first time in human history.

1:09 But that which will excite the greatest astonishment by far

1:12 and which indeed move me to call the attention of all astronomers

1:15 and philosophers is this namely that I have discovered four planets

1:20 neither known nor observed by any one of the astronomers before.

1:24 [music] These four planets would be called Io, Europa, Ganymede, and Kalisto.

1:30 The Galilean moons.

1:32 This is the story of how humanity explored the Jovian system and how it all

1:37 led to what some believe is one of the most difficult NASA missions of all time.

1:43 The mission is called Galileo, a return [music] to Jupiter.

1:51 [music] In the 1960s, [music] it was NASA's golden age.

1:59 The Apollo and Mariner missions led the [music] leaps in space exploration.

2:03 America sent probes throughout the solar system,

2:06 but its [music] golden age was ending.

2:09 NASA's budget was propped up by the Cold War.

2:12 Vietnam and social [music] reform programs from President Johnson cost money.

2:17 NASA's budget was targeted [music] when cuts were debated.

2:20 It was bad news for NASA on Earth.

2:23 But luckily, they got good news hundreds of thousands of miles away.

2:27 A pioneer [music] spacecraft passed Jupiter on its way out of the solar system.

2:31 Little was known about the conditions [music] past Mars.

2:34 Any human spacecraft could die before intended.

2:38 Maybe the asteroid [music] belt was impossible to pass.

2:41 Or Jupiter's radiation was so strong that it

2:43 fried any technology that came too close.

2:47 But the pioneer didn't just reach the king of [music] planets.

2:50 It reported back.

2:53 Studying it [music] up close was possible.

2:56 So, a plan for a thorough investigation was coming.

3:00 In 1975, [music] NASA authorizes a study for a spacecraft

3:04 that can study Jupiter and its moons, Galileo.

3:09 Jupiter is the largest and [music] closest of all the outer planets.

3:12 It is also the most similar to a star

3:14 out of any planet in [music] our solar system, 110,000th the mass of our sun.

3:20 This makes the Jovian system special.

3:22 Jupiter is a giant gravitating central body,

3:25 but it has at least four moons with only a few thousandths of its mass.

3:30 It is a mini solar system within our solar system.

3:34 Like the terrestrial planets and our sun,

3:36 Jupiter and its moons have unique features.

3:39 [music] Features they may reveal secrets about

3:41 our entire solar system waiting to be discovered.

3:46 When work began [music] on Galileo,

3:48 there were three ways to explore the outer solar system.

3:51 A deep space flyby.

3:54 The spacecraft [music] stays in interplanetary space.

3:56 It flies past one or more planets, gathering data during a short encounter.

4:01 An orbiter.

4:02 It breaks into orbit around a planet [music] or system.

4:06 And a planetary entry.

4:07 A probe probes a planet.

4:10 Each class of mission had been launched separately before,

4:13 but NASA wanted a spacecraft that could do both.

4:17 an orbiter with a probe.

4:20 Galileo would be launched on a direct path to Jupiter.

4:24 5 months before it reached the planet,

4:26 it would release its probe on a one-way journey into Jupiter's atmosphere.

4:30 The orbiter would then enter

4:31 the planet's orbit and provide long-term observations.

4:34 The orbiter and probe combined were

4:36 already at the limits of spacecraft complexity,

4:39 but NASA was going to take it a step further.

4:42 By the time Galileo was attempted,

4:44 there were only two spacecraft [music] designs

4:46 that made it to the outer planets, a Pioneer and a Voyager.

4:50 Pioneer spun around its axis.

4:52 [music] This allowed sensors to sweep the sky,

4:55 but it risk lower resolution images.

4:58 Voyager was inertially fixed that required more fuel

5:01 and made it more difficult for certain sensors,

5:03 but it did provide the camera stability [music] for good imaging.

5:07 The Galileo combined both a slow

5:09 spinning rotor for high energy physics experiments.

5:11 [music] A despun section on top for cameras and spectrometers.

5:16 Powering the machine were two radioisotopic thermmoelectric generators.

5:20 The same generator that was used for [music] other successful NASA missions.

5:24 It was an ambitious machine for an equally ambitious mission.

5:28 Proposed in 1975 and launched in 1982, [music] arrive at Jupiter in 1984.

5:35 But then things started to go very wrong.

5:38 In 1971, Torrance Johnson published a paper summarizing

5:42 our most up-to-date knowledge surrounding the Jovian system.

5:46 It showed the limits of our knowledge from Earth.

5:48 We do not know what the satellite surfaces look like.

5:51 We do not understand the composition of their atmospheres.

5:56 A the Galilean satellites are profoundly different

5:59 from the terrestrial planets the moon, Mercury, and Mars.

6:03 B.

6:03 The satellites differ among themselves greatly.

6:06 C.

6:07 Their location around a giant planet has

6:09 major importance [music] in their origin and evolution.

6:12 Io is similar in size to the moon.

6:15 Europa somewhat smaller and Ganymede and Kalisto distinctly larger,

6:19 similar [music] to Mercury.

6:21 Io and Europa have lunar-like densities while the two outer larger

6:26 satellites Ganymede and Kalisto have extraordinarily

6:31 low densities for solid planetary bodies.

6:34 These densities [music] argue strongly for significant

6:37 amounts of water in Ganymede and Kalisto.

6:40 [music] The similarities of the satellite systems

6:42 to the solar system may well go deeper.

6:45 Brightness variations [music] observed for more

6:47 than a century remain virtually unchanged.

6:50 Strong evidence that the gravitational pull of [music]

6:53 Jupiter keeps one hemisphere of each satellite toward it.

6:57 Io and Europa are [music] 5 to 10 times brighter than the moon.

7:01 Ganymede only slightly darker and Kalisto

7:04 the darkest still almost twice [music] as bright.

7:07 Such bright surfaces naturally suggested icecovered surfaces.

7:12 Io does [music] not appear to have water frost.

7:15 The answers to these and many other questions

7:17 await [music] detailed examination of the system by spacecraft.

7:21 Hopefully, the next generation [music] of orbiting spacecraft

7:23 will allow more detailed exploration of the satellite surfaces.

7:29 Barely 4 weeks after the Galileo mission officially started,

7:32 the team encountered an existential problem.

7:35 The spacecraft was too heavy.

7:37 They needed to lose weight, but the only thing they could sacrifice was fuel.

7:42 But without fuel, a direct flight to Jupiter was impossible.

7:46 Its IUS rocket wasn't strong enough.

7:49 But they did have another option.

7:51 A Centaur G Prime rocket.

7:54 It used liquid hydrogen as opposed to kerosene and packed a hell of a punch.

7:59 It could theoretically lift 40% more payload per kg at liftoff,

8:03 but there were trade-offs.

8:05 Liquid hydrogen fuel is especially explosive.

8:08 The fuel could leak through the smallest cracks.

8:11 Its low boiling point made it difficult to work with.

8:14 The rocks presented a higher risk for the shuttle and its astronauts.

8:18 The work required to make the Centaur engine safe was expensive.

8:22 Galileo was stuck between not enough power or danger.

8:25 So, the team considered a different trajectory [music] entirely.

8:29 If they had to cut fuel, maybe they could rely on a Mars gravity assist instead.

8:34 But that meant the timing had to be just right.

8:36 A 5-month delay to reach Jupiter and a stricter window to launch.

8:40 They would still only have enough fuel for Galileo

8:42 to orbit Jupiter five times [music] instead of 11.

8:46 This was their best chance, but they missed it.

8:49 Development was delayed.

8:51 They missed the Mars deadline, shattering their hopes for a 1985 launch.

8:57 Galileo was stuck on the ground.

8:59 Engineers debated splitting the ambitious plan into two.

9:02 A separate flight for the probe, another for the orbiter.

9:05 But then the delays kept coming.

9:07 The Reagan White House targeted NASA for more cuts.

9:10 Galileo was put on a hit list for potential cancellations,

9:14 but they still had one powerful option.

9:17 Crafting the Centaur engines to be safe for launch

9:20 was no longer [music] the more expensive option.

9:22 More dangerous, sure, but Galileo can make it to Jupiter with its fuel intact.

9:28 So, on December 23rd, 1985, Galileo arrived at the Kennedy Space Center.

9:34 In May 1986, it would head to the Jovian system on top of Centaur engines.

9:39 It was finally ready to launch.

9:43 In late January, NASA threw a party to introduce

9:45 Galileo's JPL staff to the Kennedy [music] Space Center personnel.

9:49 The launch was some months away,

9:51 but the Kennedy Space Center team was kept busy by [music]

9:54 the Challenger shuttle that was due to launch in 4 days.

9:57 While they celebrated at Kennedy Space [music] Center,

10:00 the warm Florida weather started to cool.

10:05 In 1979, [music] the Voyager missions did two high-speed flybys of Jupiter.

10:10 They were brief encounters,

10:11 but they were vital in updating our understanding of the Jovian system.

10:15 In 1971, [music] John S.

10:17 Lewis was the first to really publish the idea that there were oceans.

10:22 The Galilean satellites very likely have extensively melted interiors,

10:26 an extensive mantle of ammoniarich liquid [music] water,

10:29 and a relatively thin crust of ices.

10:32 If true, this meant massive subsurface oceans beneath Europa,

10:36 Ganymede, [music] and Kalisto.

10:38 The similarities of the satellite systems

10:40 to the solar system may well go deeper.

10:44 Like the hydrothermal vents that produced [music] us,

10:46 scientists saw a mini solar system with potentially

10:49 the same initial preconditions for [music] life.

10:52 Active planets spewing molten rock into water.

10:56 But it was purely theoretical.

10:58 There wasn't enough evidence, [music] and there were plenty of doubts.

11:02 Scientists RT Reynolds and Cassen said that if

11:04 any point there was liquid [music] water,

11:06 the massive ice shells on top would freeze it.

11:09 In spite of the visible evidence of our terrestrial example,

11:12 liquid water appears to be uncommon in the solar system.

11:16 Although they are comparable in size to the terrestrial planets,

11:20 they contain a considerably larger fraction of condensed H2O.

11:24 Reynolds and Cassin criticized Lewis' models directly.

11:27 A further consequence of the Lewis models [music] was the result that the bulk

11:31 of the mantle consisted of liquid water

11:33 with only a thin outer crust of solid ice.

11:37 If so, the amounts of liquid water involved

11:39 [music] would dwarf that contained in the Earth's oceans.

11:42 Thermal convection in this planetary ice layer

11:45 is efficient and will solidify an underlying liquid

11:48 shell [music] in a time that is short compared with the age of the body.

11:52 They argued that if there was ever liquid water on the three outer satellites,

11:55 the top layer of ice would eventually quickly freeze it.

11:58 The planets simply weren't hot enough

12:00 to have the massive oceans Lewis was proposing.

12:03 But there was one other possibility.

12:06 Days before Voyager 1 arrived, Reynolds and Kassen published another paper.

12:11 Theoretically, the Jovian satellites could be warmer if

12:14 Jupiter's gravitational pull caused them [music] to flex.

12:17 Flex that could generate heat.

12:19 Heat that could melt rock.

12:21 And if it could melt rock, maybe it could melt ice.

12:25 When Voyager passed Jupiter, that theory got evidence.

12:29 They received [music] visible proof of active volcanoes on Io.

12:34 In 1982, [music] David Morrison published

12:36 the most comprehensive review of the Gileian satellites.

12:40 Building on this newfound information,

12:43 the most geologically active body known in the solar system with a variety

12:47 of ongoing volcanic eruptions clearly [music] placing

12:50 this satellite in a class by itself.

12:52 The highest measured mountains rise 9 km,

12:56 giving Io the greatest topographic relief of any of the Galilean satellites.

13:00 Both Kalisto and Ganymede have crusts consisting predominantly of water ice.

13:06 Europa, the smaller sister of Io,

13:08 is presumed to be of primarily rocky composition.

13:11 This rocky interior, however, is totally invisible,

13:14 being covered by a crust of water ice

13:16 with perhaps a global ocean of liquid water underneath.

13:19 [music] There wasn't enough evidence to formally conclude

13:23 that there was liquid water on Jupiter's [music] moons.

13:26 But back in the early '7s, Lewis had suggested a signal.

13:29 An extensive electrically conducting mantle [music] forced

13:32 to convect by an input of heat

13:34 from below may be conducive to the production of a measurable magnetic field.

13:39 They needed a strong magnetometer to come

13:41 close enough to each of [music] the moons.

13:44 But there was only one spacecraft that could provide them with what

13:47 they needed and it was waiting for them at the Kennedy Space Center.

13:52 Today is a day for mourning and remembering.

13:55 Nancy and I are pained to the core by the tragedy of the shuttle Challenger.

14:00 Challenger had launched 24 times [music] already.

14:02 It was a reliable craft, but by the 25th time,

14:06 there had never been such a cold launch.

14:08 In the morning, foot long icicles were

14:10 seen hanging on structures around the [music] craft.

14:13 The lower section of Challenger's left booster was coated with sheet ice.

14:17 [music] The O-rings in the engine were stiff.

14:20 On January 28th, 1986, [music] 73 seconds in, the O-rings breached.

14:26 The shuttle's tanks failed.

14:27 Hydrogen and oxygen mixed.

14:29 Challenger was engulfed in a fireball.

14:33 The worst space [music] disaster in American history.

14:37 Engine throttling up three engines now at 104%.

14:39 [music] Challenger, go with throttle up.

14:42 Go throttle up.

14:44 [music] I've always had great faith in and respect for our space

14:55 program and what happened today does nothing to diminish it.

14:59 NASA [music] grounds its fleet.

15:01 They tell every project to provide evidence

15:03 that they can't produce a crew loss hazard.

15:06 But Galileo was set to go on top of a center G-prime rocket.

15:09 So the launch was scrapped.

15:13 But Bob Mitchell decided to give it one more chance.

15:16 With four of the best minds for trajectory mechanics at JPL,

15:20 they looked for a different path.

15:22 Most of the team had been planning for a Venus

15:24 or Earth [music] assist or some combination of the two, but that was impossible.

15:29 There was no viable trajectory that didn't fly too close

15:32 to the sun or ran out of fuel and missed Jupiter.

15:36 But Roger Deal came to Mitchell with an idea.

15:39 They could send Galileo to Venus, then back to Earth,

15:42 then back to Earth a second time.

15:44 a Venus earth gravity assist or vega ga trajectory.

15:50 It didn't give Galileo any [music] more energy, but it didn't need to.

15:54 It gave it something else,

15:56 a bend in its trajectory [music] that sent it right to Jupiter.

16:00 Galileo was fitted with new thermal blankets and shields

16:02 to protect it as it traveled closer to the sun.

16:06 On October 18th, 1989,

16:09 5 years after it was supposed to launch, it was finally ready.

16:13 Galileo left Earth and headed to the Jovian system.

16:17 But the problems [music] were just starting.

16:20 On February 10th, 1990, Galileo reached Venus.

16:24 Then it headed back.

16:26 In April, with the sun behind it,

16:27 its high gain [music] antenna could finally be opened.

16:30 It had been folded in on itself to protect against intense solar radiation.

16:35 After 2 [music] years in space,

16:36 it would finally be capable of sending and receiving data quickly.

16:40 The flight team sent commands to open it.

16:43 Its motors powered up.

16:44 They turned for 3 minutes,

16:46 but then three turned into five, and five turned into eight.

16:51 That wasn't right.

16:52 They were using way more power than what was needed to open it.

16:55 [music] The team waited, but the signal that the antenna opened never came.

17:00 In the middle of space, three of the 18 ribs of the antenna had become stuck.

17:05 The pins were held in sockets and the coatings had been worn down

17:08 by the vibrations during its long travel back

17:11 and forth on Earth caused by repeated delays.

17:14 At least three pins have been entirely worn away.

17:17 They were stuck [music] holding the cocoon in place.

17:20 The entire mission was built around that high gain antenna.

17:25 Fully operating, it could transmit 134,000 bits [music] per second.

17:29 There were still two low gain antennas,

17:31 but they could only send 40 bits [music] per second.

17:34 The mission had to produce tens of thousands of images of Jupiter and its moons.

17:38 Without the high gain antenna,

17:40 most of the data would just sit in the craft's tape recorder memory.

17:44 But they couldn't offload that data with a high gain antenna.

17:47 They had a tiny hard drive with practically no quick way of clearing it.

17:52 And they had 4 years to go before reaching Jupiter.

17:56 They pulled the motors for weeks in an effort

17:58 to free the pins some 15,000 times.

18:02 That didn't work.

18:03 They spun it while pulsing the motors in [music] an attempt

18:05 to use the centrifugal force to push the dish open.

18:09 That also failed.

18:10 They left the antenna pointing away from the sun.

18:13 The team hoped that they could make use of the thermal expansion and contraction

18:16 of the metal as it cooled and heated while pointed towards or away from the sun.

18:21 Nothing [music] happened.

18:22 They tried again a month later.

18:25 Still nothing.

18:26 But they had one last chance.

18:29 On December 13th, Galileo [music] was the furthest it would be from the sun.

18:33 The team used that chance to freeze the antenna

18:35 in an effort to finally potentially free the stuck pins.

18:38 The maneuver began.

18:40 The team waited, but the signal that the antenna opened never came.

18:48 One of its most valuable instruments was worthless.

18:51 The spacecraft could take as many pictures as it wanted.

18:54 Without a way to send it back to Earth,

18:56 they had to remain on board the tape [music] recorder.

18:59 A tape recorder with limited space and it was heading directly to the Jovian

19:04 system where it was supposed to take tens of thousands of images.

19:08 But then things started going very wrong.

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20:19 But if they couldn't make Galileo shout any louder,

20:22 maybe they could make Earth a stronger listener.

20:25 They upgraded NASA's deep space network to listen better to faint signals.

20:29 The team sent software updates to Galileo.

20:32 They modified how the craft handled data,

20:34 eliminating information from an image that wasn't valuable,

20:37 reducing the amount of storage that was needed.

20:40 After months of surgery in the vacuum of space,

20:42 the project staff announced that Galileo was capable

20:45 of completing 70% of its intended scientific goals.

20:50 It flew by Earth for its second and final time [music] on December 8th, 1992.

20:55 Then it took its last long flight to the King [music] of Planets.

21:00 Galile's approach was slow.

21:03 In 1995, the enormous planet filled [music]

21:05 more and more of the craft's horizon.

21:09 Galileo's arrival was greeted with a never-before-seen

21:11 [music] comet colliding into Jupiter.

21:13 Pillars of flame shot up 3,000 km, releasing more energy than a nuclear warhead.

21:19 It was [music] a welcome sign that the mission

21:21 was starting after such a long, painful journey.

21:24 On July 12th, 1995, Galileo severed its probe.

21:29 A cable cutter sliced through the cord that tied them to each other,

21:32 and then it spun like a bullet towards Jupiter.

21:35 It would take 5 months to reach the planet.

21:37 They'd only know it was working once it started plummeting into the atmosphere.

21:42 The orbiter [music] headed to the moons.

21:44 Two weeks after releasing, Galileo fired its engine.

21:48 It first headed to Io, Jupiter's small volcanic moon.

21:52 From afar, Galileo captured the probe signal

21:55 as it plummeted into Jupiter's thick atmosphere.

21:58 With a combination of two low antennas, an onboard tape recorder,

22:02 and a lot of optimism, the team hoped they would receive all the data.

22:06 That was a success.

22:08 They'd hoped this luck would continue,

22:10 but in August 1995, Galileo entered an interplanetary dust storm.

22:17 Peeking through the curtain of dust on October 11th, 1995,

22:21 Galileo snapped a photo of Jupiter, still some 36 million km away.

22:25 It must have been a truly awe inspiring image.

22:29 Jupiter encompassing the entire sky

22:31 with the Galilean [music] moons dwarf beneath it.

22:34 But that image would never make it to Earth.

22:36 The command to transmit the data back to Earth

22:39 sent the realtore tape recorder into a [music] panic.

22:42 Once it began to rewind, it never stopped.

22:45 For 15 hours, the [music] recorder remained stuck,

22:48 appearing to rewind endlessly.

22:51 Within hours on Earth,

22:52 a duplicate of the tape recorder suffered a catastrophic malfunction.

22:56 Faulty circuitry [music] in the recorder failed

22:58 to sense when the tape had reached its end,

22:59 and the force tore the tape clean off.

23:02 half a billion miles [music] away.

23:04 Maybe Galileo suffered the same devastating consequence

23:07 with the tape loose in the middle of space.

23:10 The mission over.

23:13 They sent new commands to stop the recorder

23:15 as the [music] team sank into despair.

23:18 They needed it to store enough images to send [music] back.

23:21 Galileo did have a small onboard computer,

23:23 but it could only store a few hundred images at best.

23:27 A week passed.

23:28 Setback after setback had played the Galileo mission since its inception.

23:33 The time had come for a final test.

23:35 Time to see if the recorder could still [music] send data.

23:38 It took more than half an hour for a signal to reach Galileo.

23:42 It took another half [music] an hour for Galileo to send a signal back.

23:45 Just a few seconds of data from the tape recorder, but it was enough.

23:51 The tape recorder [music] wasn't broken, but something had failed badly.

23:56 Capstance rotating shafts beneath the tape [music] were responsible

23:59 for controlling the rewind and playback speeds of the recorder.

24:03 A day before the failure,

24:04 Galileo had taken three snapshots of Jupiter and its major moons.

24:08 Each of the three images would be

24:10 overlaid to reconstruct a single colored photograph.

24:13 But with the new images, the recorder had reached the end of the tape

24:16 and needed to be reround back to the start.

24:19 But sitting in disuse during the long six-year voyage

24:21 had left the grease on the recorder's bearings stiff.

24:24 The reels couldn't turn easily and the capston had lost traction and slipped.

24:29 Instead of turning the tape, [music] they just spun in place like

24:32 the wheels of a car spinning uselessly on ice.

24:35 A billion dollar car.

24:37 The team needed to turn the tape back and forth to redistribute the grease.

24:41 But what if 15 hours of constant wear on a single spot had worn down the tape?

24:46 They had no choice.

24:47 The team sent Galileo commands to turn the tape.

24:50 The captains turned the myar pull tight.

24:52 The recorder pulled the tape up to 25

24:54 times around the potentially damaged section of the tape,

24:58 hopefully securing it in place.

25:01 The crisis was temporarily averted, [music] but now the rolled up sections

25:04 of the recorder were permanently off limits.

25:07 Tucked away at the end of the tape were the first

25:08 images of Jupiter and its moons during the December approach.

25:12 This was a particularly hard blow for those studying Io.

25:15 This strange little volcanic moon was not

25:17 part of the primary [music] 2-year mission.

25:19 The images lost at the end of its tape

25:21 might have been the only ones we had of it.

25:24 Finally, after an almost 6-year odyssey, the orbiter truly reached Jupiter.

25:29 On December 7th, 1995, Galileo's thrusters were finally clear to fire,

25:34 [music] and the Jupiter orbit insertion maneuver was initiated.

25:38 Galileo's trajectory was adjusted to avoid a collision course with the planet.

25:43 45 minutes into a 49minute burn, orbital insertion was achieved.

25:47 The craft was captured by the planet's gravitational field.

25:51 Jupiter [music] had many, many more moons than Galileo first observed hundreds

25:55 of years earlier through a small handmade telescope.

25:59 The four Galilean moons were just the largest of nearly 100 moons,

26:02 each of widely various sizes and shapes.

26:05 On December 7th, Galileo joined them.

26:08 It became the solar system's first man-made moon.

26:11 And on June 27th, 1996, Galileo started its first flyby.

26:17 It skimmed across the equator of Ganymede.

26:21 Ganymede is not only the largest of the Galilean moons,

26:24 but it's the largest moon in the solar system.

26:27 If it were not for Jupiter,

26:28 it could have easily earned the title of a planet for itself.

26:32 While less dense, it is larger than the planet Mercury.

26:34 Like its sister moons,

26:36 Ganymede likely formed from the leftover gas and dust which formed Jupiter

26:39 at the start of the solar system some 4.5 billion years ago.

26:44 At first glance, it appears very much like Earth's own moon.

26:48 It's tidily locked with a gray surface, [music] crowded with bright craters.

26:52 The moon resembles broken pavement, but made up of ice instead of rocks.

26:58 It was now years after the Lewis Reynolds and Cassen papers have been published.

27:02 But finally, there was a magnetometer close to one of the moons.

27:06 Dr.

27:06 Mara Kyson and her team confirmed

27:08 the detection of a large intrinsic magnetic field.

27:12 Glowing ribbons of heated electrified gas

27:14 circled the poles and produced rippling auroras.

27:18 But watching the auroras, it seemed as though the magnetic field sways.

27:22 Because Ganymede orbits close to Jupiter,

27:24 its magnetic field is embedded within the larger planet's own field.

27:28 When Jupiter's magnetic field changes,

27:30 Hubble discovered the aurora shift, rocking back and forth.

27:34 But Ganymede shifted less than expected.

27:38 Fighting back against the rocking,

27:39 scientists believe is an enormous ocean beneath the surface, 60 mi deep,

27:44 almost 30 times the average depth of the ocean on Earth,

27:47 buried under a 100 miles of icy crust.

27:50 The data sent back was remarkable,

27:52 despite the mission nearly ending a disaster multiple times.

27:56 The tape recorder could only hold so much

27:58 data before it had to be transmitted or overwritten.

28:02 But the mission continued.

28:04 By November, Galileo arrived at Kalisto.

28:07 The surface a mixture of ice and metallic rock.

28:10 As Kalisto orbited the furthest from Jupiter, it was less exposed to the immense

28:14 gravitational and tidal forces that Jupiter exerted.

28:18 However, without [music] active processes to erode

28:21 and recycle the surface of the moon,

28:22 Galileo found an ancient crittered surface which must

28:25 have taken billions of years [music] to accumulate.

28:28 Kalisto had long been considered a dead moon,

28:31 just ice and rock hanging silently in cold space.

28:34 But Galileo and its magnetometer uncovered another secret,

28:38 another possible salty ocean buried beneath its surface.

28:42 The research from decades before was validated.

28:46 But then Galileo caught a glimpse of Europa some 21,000 m away.

28:52 A month later, it was brought into proper focus.

28:55 Europa is the smallest of the Galilean moons.

28:58 Its reflective, smooth, icy surface makes it blindingly bright.

29:02 It observed a vast network of ridges and bands,

29:04 some as large as 60 km across and extending for hundreds of kilome.

29:09 Upon closer inspection, it seemed strange.

29:12 Moons are constantly under assault from space debris.

29:15 But Europa was smooth.

29:17 It also lacked mountains.

29:19 It seemed unlikely that Europa had been

29:20 spared the same punishment as its siblings.

29:23 4 billion years is a long time to be so lucky.

29:27 The smooth surface suggested constant geological activity.

29:31 Icy flows that erase imperfections on the surface.

29:34 It also had an [music] atmosphere,

29:36 albeit a thin one, containing oxygen and even water vapor.

29:40 On Earth, oxygen is [music] the result

29:42 of plants and primarily phytolanton in the ocean.

29:46 However, on Europa, the origin is likely formed

29:49 by charged particles from Jupiter impacting the icy [music] surface,

29:52 splitting the H2O of water into hydrogen and oxygen.

29:56 But then the Galileo team made another discovery.

30:00 Dr.

30:00 Kyson's [music] magnetometer team detected

30:02 measurements for an electrically conductive fluid,

30:05 a global salty ocean with twice as much water as Earth.

30:08 [music] The distance from the sun and proximity to the deadly amount

30:12 of radiation from Jupiter might have ruled out Europa as a home for life,

30:16 [music] but the ice on the surface is a double-edged sword.

30:21 On one hand, it acts as a protective barrier to the internal liquid ocean,

30:25 preventing [music] the intense radiation from irdiating

30:28 any potential life attempting to develop.

30:31 However, the surface [music] is also

30:33 where important chemical compounds are formed

30:35 by interactions with high energy particles from Jupiter that would support life,

30:40 which the shell could [music] prevent from reaching the liquid water beneath.

30:44 Moons like Ganymede and Kalisto might have had oceans beneath their surfaces.

30:47 But those are estimated to be about 100 miles down,

30:50 each hidden beneath a thick [music] crust with minimal geological activity

30:54 to transport the vital ingredients for life down to the oceans beneath.

30:58 But Europa [music] is different.

31:01 Its ocean sits closer to the surface under an icy crust only 10 or 15 mi thick.

31:07 Even without the sun to provide energy to [music] the depths of Europa's oceans,

31:10 it is possible that beneath the waves, Europa has a different source of energy.

31:16 Hydrothermal vents that spew chemical energy.

31:20 They had saved Io for last out of fear.

31:24 It's the closest moon to Jupiter.

31:26 It is also the most hazardous.

31:28 High energy electrons pelted Galileo, piercing to [music] the delicate

31:32 electronics and requiring constant staff maintenance.

31:36 When the first images of Io are relayed back, it revealed a world on fire.

31:41 The moon is under immense gravitational

31:43 stress from Jupiter [music] and nearby moons.

31:47 The tremendous strain generates the explosive

31:49 volcanic activity that riddles the surface.

31:52 The grinding of rocks melts the moon's interior where

31:55 eventually the molten rocks are forced to the surface explosively.

31:59 [music] The camera on board Galileo captured

32:02 an active volcano on the surface of the moon.

32:05 It erupted more than a mile off the surface.

32:07 [music] It is the youngest and most

32:09 volcanically active surface observed in the solar system.

32:13 Every second, [music] Jupiter's magnetic field rips 1,000 kg,

32:17 a literal ton of its mass away.

32:20 The debris is left alone in orbit.

32:22 Eventually, the charged ions entered Jupiter's upper atmosphere,

32:25 where they produce [music] auroras.

32:28 As Galileo's end drew closer and closer,

32:31 it zipped only [music] 63 mi above Io's volcanic surface.

32:35 The final flyby snap new pictures,

32:38 but the primary purpose was to put it on a final path.

32:42 Fuel was running low.

32:44 The decision was made to launch the craft into the planet.

32:47 Following its own probe, it flew forward on a one-way trip

32:51 that would guide Galileo toward its last destination.

32:54 At 11:57 a.m.

32:56 PST, September 21st, 2003,

32:59 decades after it had begun and a half billion miles from its start,

33:04 Galileo disappeared into Jupiter.

33:09 The Galileo project was led by multiple

33:11 generations of scientists and eight different project managers.

33:15 By its conclusion, it had passed through

33:17 the hands of thousands of different people.

33:20 Jupiter is an inhospitable host at the center of its

33:23 own solar system that we have only begun to understand.

33:28 More than 20 years after Galileo's death, a new craft launched.

33:32 On October 14th, 2024,

33:35 Europa Clipper left Earth as a spiritual grandchild of Galileo.

33:39 It is the first mission designed to study Europa specifically.

33:43 In the wake of the tantalizing suggestions

33:45 of subsurface oceans [music] potentially teameming with alien life,

33:49 Europa Clipper will orbit Jupiter and eventually

33:52 conduct dozens of flybys of Europa,

33:54 scrutinizing its surface and investigating its internal workings

33:58 with a vast array of [music] state-of-the-art instrumentation.

34:02 Dr.

34:03 Margaret Kyson, now in her '90s,

34:05 leads the magnetometer team to find answers to the mystery

34:08 she and her team had originally discovered decades earlier with Galileo.

34:13 Each instrument, orbiter,

34:14 or probe is a step which continues the long journey to better

34:17 understand our galactic neighbors and our own place in the solar system.

34:22 A long way from where it began when an Italian astronomer saw something he

34:26 thought were stars through the most advanced

34:28 instrument the world had at the time.

34:41 Yo, this is Alex.

34:43 I did most of the 3D in this video and uh

34:45 this project would not have been possible without Super Luminal.

34:48 Super Lumino is the render farm that our team builds and works

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34:55 I had over 100 4K space shots plus compositing waiting to render.

34:59 And uh while that would have taken weeks on my local PC,

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