0:00:02 > 0:00:04Jupiter.
0:00:04 > 0:00:06The monster of the solar system.
0:00:09 > 0:00:11Huge,
0:00:11 > 0:00:12violent,
0:00:12 > 0:00:14and unforgiving.
0:00:17 > 0:00:20We have always been fascinated by it,
0:00:20 > 0:00:23and that is why, over the past 40 years,
0:00:23 > 0:00:27we've sent eight spacecraft to investigate this massive world.
0:00:28 > 0:00:32But its swirling cloud-tops still conceal many mysteries.
0:00:32 > 0:00:37And that is why we have now sent a ninth mission - Juno.
0:00:37 > 0:00:39CHEERING
0:00:39 > 0:00:45There it is! Juno's right on time, into orbit exactly as planned.
0:00:46 > 0:00:51Last Monday, Nasa's Juno probe arrived in orbit around Jupiter.
0:00:52 > 0:00:55The Sky At Night has been embedded here at mission control,
0:00:55 > 0:00:57and so tonight we bring you all the action
0:00:57 > 0:01:01as Juno completed the most dangerous and complex phase of its mission.
0:01:03 > 0:01:06We'll also be looking forward to what Juno does next,
0:01:06 > 0:01:10and how it's set to transform our understanding of the solar system.
0:01:10 > 0:01:13Welcome to The Sky At Night.
0:01:47 > 0:01:52This is the Jet Propulsion Laboratory in Pasadena, California,
0:01:52 > 0:01:54one of the iconic sights of the Space Age,
0:01:54 > 0:01:57home base for our exploration of the solar system.
0:01:57 > 0:01:59It was from right here that the world watched
0:01:59 > 0:02:02as the Voyagers and the Pioneer spacecraft
0:02:02 > 0:02:04made their first reconnaissance of the giant planets,
0:02:04 > 0:02:09and now, with Juno, we're going back to Jupiter.
0:02:11 > 0:02:16In Roman mythology, Juno was Jupiter's wife -
0:02:16 > 0:02:19the only person who could see through the clouds
0:02:19 > 0:02:21that concealed her husband.
0:02:23 > 0:02:26Juno the spacecraft's mission is exactly the same.
0:02:26 > 0:02:31Its aim is to pierce through the clouds to reveal what's going on
0:02:31 > 0:02:32inside the planet.
0:02:34 > 0:02:36The mission has three main objectives.
0:02:36 > 0:02:40To understand what drives Jupiter's violent atmosphere.
0:02:40 > 0:02:43To discover how the planet was formed,
0:02:43 > 0:02:47shedding light on the formation of the entire solar system.
0:02:47 > 0:02:52And to find out why it has such intense and spectacular aurorae.
0:03:00 > 0:03:02But first, it had to enter an orbit
0:03:02 > 0:03:06that would take it within 5,000km of the giant planet.
0:03:08 > 0:03:12The crucial manoeuvre was called Jupiter Orbit Insertion.
0:03:13 > 0:03:15And with a certain sense of theatre,
0:03:15 > 0:03:19it was set for the evening of the of 4th July.
0:03:19 > 0:03:23That morning, Juno's scientists and the world's media
0:03:23 > 0:03:25gathered at JPL to watch events unfold.
0:03:25 > 0:03:30This was to be one of the most crucial days in the whole mission.
0:03:30 > 0:03:34And the greatest fear was that the spacecraft might not make it through
0:03:34 > 0:03:37the hostile environment close to the planet.
0:03:38 > 0:03:40Can you say what we know about the ring particles
0:03:40 > 0:03:42you were worried about?
0:03:42 > 0:03:45We believe the probability's very low that we're going to hit one,
0:03:45 > 0:03:47but it's not zero.
0:03:47 > 0:03:50It's the same thing if I go through the asteroid belt, you know,
0:03:50 > 0:03:54so as we fly by very, very close,
0:03:54 > 0:03:56we look at the signal from the radio
0:03:56 > 0:03:59and can tell how it's been changed...
0:03:59 > 0:04:01I've just come out of the briefing
0:04:01 > 0:04:04with a quite nervous-looking Juno team. They're excited,
0:04:04 > 0:04:07but they're clearly worried about whether the spacecraft
0:04:07 > 0:04:10will survive the next 24 hours. But I have to show you this.
0:04:10 > 0:04:12It's the first movie we've seen from JunoCam,
0:04:12 > 0:04:15it's about two days' worth of an approach to Jupiter.
0:04:15 > 0:04:18What I love about it is you can see the main moons,
0:04:18 > 0:04:21the four Galilean moons dancing around the planet.
0:04:21 > 0:04:22You can see Jupiter growing
0:04:22 > 0:04:25as it approaches over the course of this movie.
0:04:25 > 0:04:26That means it's crunch time.
0:04:26 > 0:04:29Juno is entering the most dangerous phase of its mission,
0:04:29 > 0:04:32and what the team in the briefing there are worried about
0:04:32 > 0:04:35is dust from the rings. A single collision could end the mission.
0:04:35 > 0:04:39And the team are also worried about the radiation environment.
0:04:39 > 0:04:43That could stop Juno working and put a very premature end to the mission.
0:04:44 > 0:04:48To get into orbit, Juno had to fire its main engine,
0:04:48 > 0:04:52slowing the probe down just enough to be captured by Jupiter's gravity.
0:04:54 > 0:04:56Its trajectory had been carefully planned
0:04:56 > 0:04:59to avoid the worst of the planet's radiation belts.
0:05:01 > 0:05:03It would approach over the north pole
0:05:03 > 0:05:07before falling into an orbit that would repeatedly squeeze Juno
0:05:07 > 0:05:10between the radiation belt and the planet itself.
0:05:10 > 0:05:15No spacecraft had ever attempted such a daredevil manoeuvre.
0:05:16 > 0:05:21I spoke to Juno scientist Fran Bagenal about the dangers.
0:05:21 > 0:05:25So we're not far now from the critical moment,
0:05:25 > 0:05:28the engine burn that will deliver Juno, with any luck,
0:05:28 > 0:05:31to its desired orbit. How are the team feeling? How nervous are you?
0:05:31 > 0:05:35We're all worried and nervous and...
0:05:35 > 0:05:38I'm sure everything will go fine and I trust the engineers,
0:05:38 > 0:05:40but, yes, I've got all my fingers and toes crossed.
0:05:40 > 0:05:43We've been to Jupiter before, we had the fly-bys,
0:05:43 > 0:05:46but also the Galileo mission that went into orbit
0:05:46 > 0:05:49and explored the Jovian system. What's different about this time?
0:05:49 > 0:05:52- What is it that's dangerous? - Usually when we go to Jupiter,
0:05:52 > 0:05:54we're either getting a gravity assist
0:05:54 > 0:05:56or we stay away from the inner region.
0:05:56 > 0:05:58Or we're going in orbit and we stay on the equator.
0:05:58 > 0:06:02Now for Juno's science, we really want to get up close.
0:06:02 > 0:06:04Right around the belly of Jupiter
0:06:04 > 0:06:08there is a doughnut of very energetic charged particles -
0:06:08 > 0:06:12- ten million volt electrons whizzing around...- Which is a lot?
0:06:12 > 0:06:14Which is a lot, right? And so you're really worried
0:06:14 > 0:06:18that the electronics will be zapped by these energetic particles
0:06:18 > 0:06:22and damage the sensitive electronics you've got inside, in detectors.
0:06:22 > 0:06:26It's like taking your computer and giving it a gazillion X-rays,
0:06:26 > 0:06:28you know, you wouldn't want to do that.
0:06:28 > 0:06:30So what we're going to do is very clever.
0:06:30 > 0:06:32We're going to fly over the top of the pole,
0:06:32 > 0:06:36we're going to fly through the slot between the radiation belts
0:06:36 > 0:06:38and the clouds, through that region,
0:06:38 > 0:06:41and then out again below. And that, we hope,
0:06:41 > 0:06:45will protect us from those energetic radiation belts.
0:06:45 > 0:06:47And how small a slot is that?
0:06:47 > 0:06:50How much of a precision manoeuvre does this have to be?
0:06:50 > 0:06:52We don't really know,
0:06:52 > 0:06:55because we don't really know how far the atmosphere extends out,
0:06:55 > 0:06:58and we don't really know what the radiation belts are.
0:06:58 > 0:07:01We can map them from the ground using radio observations,
0:07:01 > 0:07:03but they're not that accurate,
0:07:03 > 0:07:07so it's not so much an issue of precision as uncertainty,
0:07:07 > 0:07:10and we don't really know what it's like. This is terra incognita.
0:07:10 > 0:07:13The other thing that makes this a little safer
0:07:13 > 0:07:16is that because of Jupiter's strong gravity
0:07:16 > 0:07:18we're moving really quickly.
0:07:18 > 0:07:21So we go in through there and get out really quickly.
0:07:21 > 0:07:29And so the spacecraft will be moving at about 165,000 miles an hour,
0:07:29 > 0:07:33and so this allows us to go from pole to pole in two hours.
0:07:33 > 0:07:36And since Jupiter is ten times the size of the Earth,
0:07:36 > 0:07:39that's equivalent to going around the Earth
0:07:39 > 0:07:43- five times in two hours.- Wow.
0:07:45 > 0:07:49It's a dangerous mission nearly two decades in the making,
0:07:49 > 0:07:52and it could end in disaster before it starts.
0:07:55 > 0:07:58So what is it that we want to know about Jupiter
0:07:58 > 0:08:00that justifies these risks?
0:08:06 > 0:08:08Jupiter dominates our solar system.
0:08:10 > 0:08:14It's 140,000km across,
0:08:14 > 0:08:17and two and a half times more massive
0:08:17 > 0:08:19than the rest of the planets put together.
0:08:21 > 0:08:25On this scale, if Jupiter were the size it appears on the screen,
0:08:25 > 0:08:27about two and a half metres across,
0:08:27 > 0:08:31then the Earth would appear the size of this basketball.
0:08:31 > 0:08:33And it would fit into Jupiter
0:08:33 > 0:08:35about a thousand times over.
0:08:37 > 0:08:40We think that Jupiter was the first planet to be formed.
0:08:40 > 0:08:43It sort of hoovered up most of the stuff left behind
0:08:43 > 0:08:45after the sun's formation.
0:08:45 > 0:08:48And like the sun, it's mostly made up of hydrogen and helium -
0:08:48 > 0:08:49about 95%.
0:08:49 > 0:08:53The other 5% is made up of heavier elements.
0:08:53 > 0:08:56And it's all spinning incredibly fast.
0:08:56 > 0:08:59This vast planet rotates on its axis
0:08:59 > 0:09:02once every ten hours.
0:09:04 > 0:09:07As it spins, the clouds of its atmosphere
0:09:07 > 0:09:09are driven into thick banks
0:09:09 > 0:09:11by the powerful winds that orbit the planet.
0:09:14 > 0:09:18Those swirling forces create giant storms
0:09:18 > 0:09:20like the famous Red Spot.
0:09:20 > 0:09:23Even though we've been studying the planet for over 400 years,
0:09:23 > 0:09:28there's still much that is quite mysterious about Jupiter.
0:09:32 > 0:09:34One of the first things Juno is aiming to discover...
0:09:36 > 0:09:39..is what powers those giant storm systems.
0:09:41 > 0:09:44To find out how it's going to do that, I went to talk to
0:09:44 > 0:09:48Jupiter expert and Juno collaborator Leigh Fletcher.
0:09:48 > 0:09:50So, Leigh, what are we seeing here?
0:09:50 > 0:09:54This is a beautiful movie that was taken by the Cassini spacecraft
0:09:54 > 0:09:58when it flew by Jupiter back in the year 2000, 16 years ago.
0:09:58 > 0:10:01You can see in this image just how dynamic the Jovian atmosphere is.
0:10:01 > 0:10:03Things are changing all of the time
0:10:03 > 0:10:06as we have these jets of wind whizzing east and west
0:10:06 > 0:10:09and separating the beautiful banded structure.
0:10:09 > 0:10:13And we think that these bright white clouds at the equator
0:10:13 > 0:10:16are regions where air is welling up from the deeper interior
0:10:16 > 0:10:20and it's dredging with it particles, or molecules, of ammonia gas,
0:10:20 > 0:10:24and those ammonia gas molecules condense and it forms ice crystals.
0:10:24 > 0:10:28Those ice crystals create these white colours
0:10:28 > 0:10:30within the equatorial zone.
0:10:30 > 0:10:32OK. What about these darker bands?
0:10:32 > 0:10:34That's an even harder question to answer.
0:10:34 > 0:10:37But what comes up must ultimately come down.
0:10:37 > 0:10:40What we believe is happening is the air that's rising over the equator
0:10:40 > 0:10:43is then sinking over the northern equatorial belt
0:10:43 > 0:10:45and the southern equatorial belt.
0:10:45 > 0:10:47Those ice crystals evaporate away
0:10:47 > 0:10:50and they reveal the natural colours of Jupiter
0:10:50 > 0:10:53deeper down within the planet. Unfortunately we still don't know
0:10:53 > 0:10:56what is actually causing the brown colour.
0:10:56 > 0:11:00What you can see here as well is that the belts look much more active
0:11:00 > 0:11:02and much more dynamic than the white regions.
0:11:02 > 0:11:07We think that all of that activity is being driven by the same molecule
0:11:07 > 0:11:10that drives atmospheric weather here on Planet Earth,
0:11:10 > 0:11:11and that's water vapour.
0:11:11 > 0:11:13You're familiar with, if you have a humid atmosphere,
0:11:13 > 0:11:16- it's more prone to thunderstorms... - Or tropical, yes...
0:11:16 > 0:11:19- Tropical storms. - Hurricanes and things. Yeah.
0:11:19 > 0:11:22Well, the same phenomena could be occurring within Jupiter.
0:11:22 > 0:11:25But if water is part of the story
0:11:25 > 0:11:29for what's driving this incredibly dynamic atmosphere,
0:11:29 > 0:11:32then we'd have to understand where the water is located
0:11:32 > 0:11:36within Jupiter and, crucially, how much is there within the planet.
0:11:36 > 0:11:38So how can we do that? Can we go any deeper?
0:11:38 > 0:11:40So Juno has got a very clever instrument
0:11:40 > 0:11:43called a microwave radiometer on board.
0:11:43 > 0:11:45And what we can see in microwave light
0:11:45 > 0:11:49is modulated by the amount of ammonia that's there
0:11:49 > 0:11:51and the amount of water that is there.
0:11:51 > 0:11:54So by building up this map - and it will take a while to build it up,
0:11:54 > 0:11:58many months of the Juno mission going over various longitudes
0:11:58 > 0:12:01to paint a complete picture of the planet -
0:12:01 > 0:12:04we'll then be able to map where the water is located
0:12:04 > 0:12:06- and where ammonia is located. - So that might give you
0:12:06 > 0:12:10- an understanding of what's driving those weather systems.- Absolutely.
0:12:10 > 0:12:13It's going to be a step-change in our understanding of
0:12:13 > 0:12:16how much water is present within the Jovian atmosphere.
0:12:17 > 0:12:20But Juno's mission is about more than
0:12:20 > 0:12:23just studying Jupiter's upper atmosphere.
0:12:24 > 0:12:28By probing the deep interior, it hopes to reveal
0:12:28 > 0:12:31how both the planet and the solar system formed.
0:12:33 > 0:12:35One of the great mysteries of Jupiter
0:12:35 > 0:12:37is understanding how it formed in the first place.
0:12:37 > 0:12:41One possibility is that it began life as a star does,
0:12:41 > 0:12:46as a collapsing cloud of gas, before becoming the planet we see today.
0:12:46 > 0:12:48Another option is that, big though it is,
0:12:48 > 0:12:51Jupiter began life in the same way that the Earth did,
0:12:51 > 0:12:54starting as nothing more than a pile of rubble,
0:12:54 > 0:12:56planetesimals that could stick together
0:12:56 > 0:13:00to eventually form a core that was maybe then times the mass of Earth.
0:13:00 > 0:13:04Big enough to grab and to hold on to a thick hydrogen atmosphere.
0:13:04 > 0:13:09Juno will tell us which of these two possibilities is the correct one.
0:13:09 > 0:13:15As it orbits the planet, Juno's path is not completely uniform.
0:13:16 > 0:13:21It's affected by tiny variations in Jupiter's gravitational field.
0:13:21 > 0:13:25By tracking these tiny wobbles over the months that it's in orbit,
0:13:25 > 0:13:28Juno will build up an incredibly detailed map
0:13:28 > 0:13:30of the planet's gravitational field.
0:13:32 > 0:13:34And that should tell us whether or not
0:13:34 > 0:13:37there's a rocky core at the heart of Jupiter.
0:13:37 > 0:13:41Either way, it's a discovery that will have profound implications
0:13:41 > 0:13:45for our understanding of how giant planets form,
0:13:45 > 0:13:47not just in our solar system,
0:13:47 > 0:13:51but also in other solar systems around other stars.
0:13:51 > 0:13:56Juno has amazing scientific potential,
0:13:56 > 0:13:58but before it could start its observations,
0:13:58 > 0:14:02the spacecraft first had to complete its orbit insertion manoeuvre.
0:14:03 > 0:14:05Back in mission control,
0:14:05 > 0:14:09while the rest of America was out celebrating the 4th of July,
0:14:09 > 0:14:11we waited for news.
0:14:12 > 0:14:15So just a few minutes ago out near Jupiter
0:14:15 > 0:14:18Juno should have started firing its main engine.
0:14:18 > 0:14:20It's the critical manoeuvre required
0:14:20 > 0:14:22to take it into orbit around Jupiter.
0:14:22 > 0:14:25The only problem is, because it's so far away,
0:14:25 > 0:14:27it'll take 48 minutes for that signal to reach us
0:14:27 > 0:14:28here at mission control.
0:14:28 > 0:14:32And only when it arrives will people start to breathe a little easier.
0:14:37 > 0:14:40We're expecting a signal from the spacecraft to say all is well,
0:14:40 > 0:14:41and then two minutes later,
0:14:41 > 0:14:44confirmation that the burn has started.
0:14:44 > 0:14:47I think it was quite jovial, but it's all gone very quiet
0:14:47 > 0:14:50and very tense. People know if this doesn't come in on time,
0:14:50 > 0:14:52something is seriously wrong.
0:14:54 > 0:14:57- Everything's looking good. - Standing by.
0:14:58 > 0:15:01We're right on the time we expected the signal.
0:15:01 > 0:15:02INDISTINCT
0:15:04 > 0:15:05Good, now?
0:15:05 > 0:15:09- Yeah, we see the expected... - Got it! They've got it.
0:15:09 > 0:15:11It's changed its velocity,
0:15:11 > 0:15:12the burn has started,
0:15:12 > 0:15:14and Juno is starting to put itself in orbit.
0:15:14 > 0:15:16- CHEERING - That's wonderful news.
0:15:16 > 0:15:18The fact that the burn has started means the engine
0:15:18 > 0:15:20is working as expected.
0:15:20 > 0:15:23But the really difficult bit is keeping it working
0:15:23 > 0:15:26as Juno travels through this most dangerous region.
0:15:26 > 0:15:30They need a burn of 35 minutes to put themselves in the desired orbit,
0:15:30 > 0:15:33so people will be keeping things crossed for a long time yet.
0:15:37 > 0:15:39In order to make all its measurements
0:15:39 > 0:15:42and probe beneath Jupiter's clouds,
0:15:42 > 0:15:46Juno has been equipped as no spacecraft ever before.
0:15:48 > 0:15:51I used to build instrumentation for spacecraft,
0:15:51 > 0:15:54but I've never been involved with anything like Juno.
0:15:54 > 0:15:58For one thing, it's huge - about 20 metres across.
0:15:58 > 0:16:00That's about the width of this hangar.
0:16:00 > 0:16:03Most of that width is made up of these huge solar panels,
0:16:03 > 0:16:05each one nine metres long.
0:16:05 > 0:16:08Now, the reason we need such large solar panels
0:16:08 > 0:16:12is cos Juno is going to sit a long, long way away from the sun.
0:16:12 > 0:16:14Out around Jupiter, the sun's intensity
0:16:14 > 0:16:18is just one 25th of what we receive here on Earth.
0:16:18 > 0:16:21It's the first time we're sending a solar-powered spacecraft
0:16:21 > 0:16:24so far into the solar system.
0:16:24 > 0:16:26The 18,700 solar cells
0:16:26 > 0:16:30will only produce around 450 watts.
0:16:30 > 0:16:33It's not much - not even enough to boil a kettle.
0:16:33 > 0:16:38But Juno's instruments have been designed to operate at low power.
0:16:38 > 0:16:41The spacecraft's brain and most of the instrument electronics
0:16:41 > 0:16:45are housed in this titanium bolt to protect it from radiation.
0:16:45 > 0:16:47But the instruments themselves
0:16:47 > 0:16:49are based on the outside of the spacecraft.
0:16:51 > 0:16:54The first instrument is Jedi,
0:16:54 > 0:16:56used to measure high-energy particles
0:16:56 > 0:16:58in Jupiter's magnetic field.
0:17:01 > 0:17:03These are the microwave detectors.
0:17:03 > 0:17:06They'll analyse water in Jupiter's atmosphere.
0:17:08 > 0:17:12And this is the only optical camera onboard, JunoCam.
0:17:12 > 0:17:16And as it was leaving the Earth, it took this magnificent picture.
0:17:16 > 0:17:18It really is quite beautiful.
0:17:18 > 0:17:21But the images JunoCam will take of Jupiter
0:17:21 > 0:17:23will be far more spectacular.
0:17:24 > 0:17:26At its closest approach to the planet,
0:17:26 > 0:17:30it will be only 4,200km above the cloud tops.
0:17:32 > 0:17:34That might sound like a lot.
0:17:34 > 0:17:38So let's use our basketball again, only this time, it's Jupiter.
0:17:38 > 0:17:42On this scale, Juno will fly less than a centimetre
0:17:42 > 0:17:45above the surface, and from that location,
0:17:45 > 0:17:49it will be able to take the highest resolution images of Jupiter
0:17:49 > 0:17:50that have ever been seen.
0:17:52 > 0:17:55This is the part of the mission we can all take part in,
0:17:55 > 0:17:57because Nasa have asked for the public's help
0:17:57 > 0:18:01in choosing the features that JunoCam will photograph.
0:18:05 > 0:18:08And as Peter's been discovering, the first step
0:18:08 > 0:18:12is that they want people to submit their own photos of Jupiter.
0:18:23 > 0:18:26Right, I'm nicely lined up on Jupiter now,
0:18:26 > 0:18:28and it's actually a pretty good view.
0:18:28 > 0:18:30The planet is getting lower in the sky,
0:18:30 > 0:18:32and it'll get even lower throughout July
0:18:32 > 0:18:34as it gets closer towards the sun.
0:18:34 > 0:18:39So what I'd say is, sort of wait 20, maybe 30 minutes after sunset,
0:18:39 > 0:18:41and then look for the brightest star-like object
0:18:41 > 0:18:44which is low down in the western part of the sky,
0:18:44 > 0:18:46and that should be Jupiter.
0:18:56 > 0:18:58OK, the view is a little bit wobbly tonight,
0:18:58 > 0:19:01but you can still make out the main features.
0:19:01 > 0:19:04You've got the two main belts running across the planet's disc,
0:19:04 > 0:19:06and you can see the gaps in between them.
0:19:06 > 0:19:09And if you look very carefully, you can see the undulations
0:19:09 > 0:19:12and other features which are along those belts.
0:19:12 > 0:19:14So what you need to do once you've got your image
0:19:14 > 0:19:16is send it up to the Juno website.
0:19:19 > 0:19:22They are processed into a composite map of Jupiter
0:19:22 > 0:19:26that's constantly updated to give the most accurate view
0:19:26 > 0:19:27of the planet's atmosphere.
0:19:27 > 0:19:30And then everyone, even those who haven't got a telescope,
0:19:30 > 0:19:31can take part.
0:19:33 > 0:19:36When Juno goes into its secure orbit,
0:19:36 > 0:19:40it will be possible to vote for the most interesting features,
0:19:40 > 0:19:44and the most popular ones will then be the target for JunoCam.
0:19:44 > 0:19:47The first really detailed images will be taken
0:19:47 > 0:19:52as Juno sweeps past Jupiter's atmosphere on August 27,
0:19:52 > 0:19:55and the first raw data will be released soon after that.
0:19:55 > 0:19:59This will give us the most detailed view we've ever had
0:19:59 > 0:20:02of Jupiter's clouds, so who knows what surprises
0:20:02 > 0:20:04and 3-D structures we're going to see?
0:20:04 > 0:20:07It's really going to be an exciting few months.
0:20:11 > 0:20:15But there's one more mystery that Juno will hope to solve,
0:20:15 > 0:20:18and that is the mystery of Jupiter's aurora,
0:20:18 > 0:20:21that blaze in ultraviolet light
0:20:21 > 0:20:23or in high-energy x-rays.
0:20:23 > 0:20:28They are like the Earth's northern lights on steroids.
0:20:28 > 0:20:30But our current understanding of the physics
0:20:30 > 0:20:33cannot explain why they are so extensive.
0:20:34 > 0:20:36Part of Juno's mission
0:20:36 > 0:20:40is to find out exactly how these aurora are generated.
0:20:41 > 0:20:44On Earth, the aurora are caused by the interaction
0:20:44 > 0:20:47of the magnetic field with the solar wind,
0:20:47 > 0:20:51the flow of particles that stream from the sun.
0:20:51 > 0:20:54Something similar must be happening on Jupiter.
0:20:54 > 0:20:56But there's a problem.
0:20:57 > 0:21:01At this distance from the sun, the solar wind is much too weak
0:21:01 > 0:21:04to generate such a bright display on its own.
0:21:04 > 0:21:08Chris tracked down planetary scientist Jon Nichols
0:21:08 > 0:21:11to find out how Juno is going to help decode
0:21:11 > 0:21:13Jupiter's remarkable aurora.
0:21:13 > 0:21:16So these are amazing images, but what exactly are we seeing?
0:21:16 > 0:21:20So we're seeing Hubble observations of Jupiter's ultraviolet auroras.
0:21:20 > 0:21:22These are the auroras here.
0:21:22 > 0:21:24Now, auroras are formed when charged particles
0:21:24 > 0:21:27trapped on a planet's magnetic field travel down the magnetic field
0:21:27 > 0:21:29and hit the atmosphere, and make it glow.
0:21:29 > 0:21:32I'm trying to imagine what it would be like looking at these aurora,
0:21:32 > 0:21:35if you could somehow stand and look up on Jupiter.
0:21:35 > 0:21:38How strong are they compared to Earth's aurora?
0:21:38 > 0:21:41So typically the auroras are about 100 times brighter
0:21:41 > 0:21:42than they are on the Earth.
0:21:42 > 0:21:46In fact, during our campaign, we've seen auroral brightness
0:21:46 > 0:21:49really increase dramatically to about 1,000 times
0:21:49 > 0:21:51what you'd see on the Earth. Now, if you could see these -
0:21:51 > 0:21:53these are obviously ultraviolet,
0:21:53 > 0:21:55taken with the Hubble Space Telescope -
0:21:55 > 0:21:57but if you could float in a balloon in Jupiter's atmosphere
0:21:57 > 0:22:00and look up at these, you'd see a curtain of red.
0:22:00 > 0:22:04It would be bright red, and it's 1,000km high,
0:22:04 > 0:22:06and it would extend from one horizon to the other.
0:22:07 > 0:22:10But auroral display of this magnitude
0:22:10 > 0:22:14requires a constant and plentiful supply of charged particles
0:22:14 > 0:22:17which can become entangled with Jupiter's magnetic field.
0:22:19 > 0:22:23Scientists think they've identified that source.
0:22:23 > 0:22:25It is Jupiter's moon, Io.
0:22:27 > 0:22:29Io is the closest large moon to Jupiter,
0:22:29 > 0:22:31and it's highly volcanic.
0:22:33 > 0:22:36Every hour, its volcanoes spew tonnes of material
0:22:36 > 0:22:39into the magnetic field that surrounds the giant planet.
0:22:42 > 0:22:45That material becomes electrically charged,
0:22:45 > 0:22:48interacting with Jupiter's magnetic field lines,
0:22:48 > 0:22:52and creating the aurora where they intersect the planet's atmosphere.
0:22:54 > 0:22:56It's an extraordinary idea,
0:22:56 > 0:22:59but it's backed up by some remarkable evidence.
0:22:59 > 0:23:02As Io orbits, it leaves its footprint
0:23:02 > 0:23:05drawn brightly in the aurora.
0:23:05 > 0:23:08I love the fact this is due to volcanoes on a moon,
0:23:08 > 0:23:10and we see it on the planet. That's quite cool.
0:23:10 > 0:23:11What about the rest of this structure?
0:23:11 > 0:23:13There's an awful lot going on here.
0:23:13 > 0:23:15Yeah, so this is the Io footprint here,
0:23:15 > 0:23:17and then we've got the main auroral oval,
0:23:17 > 0:23:19which is also driven by material from Io.
0:23:19 > 0:23:21But then we've got all this stuff in the middle,
0:23:21 > 0:23:24and we really have no idea what drives that.
0:23:24 > 0:23:27We think that it might be due to something to do with the solar wind.
0:23:27 > 0:23:29The solar wind drives the Earth's auroras.
0:23:29 > 0:23:32But we have no theories in our magnetospheric physics
0:23:32 > 0:23:34that tells us that we should see something like this.
0:23:34 > 0:23:36So we really have no idea what's causing it.
0:23:36 > 0:23:38And to understand that, you need to know what's coming in,
0:23:38 > 0:23:40you need to understand the magnetic field,
0:23:40 > 0:23:43and you need to know what's going on in the planet itself.
0:23:43 > 0:23:45- It's sort of a really complex problem.- That's right.
0:23:45 > 0:23:48And that's why Juno is the perfect spacecraft to tell us
0:23:48 > 0:23:50exactly what is going on here.
0:23:50 > 0:23:53Juno is going to fly over this region for the first time,
0:23:53 > 0:23:56and it's going to tell us what the magnetic field and the plasma
0:23:56 > 0:23:57is doing in this region,
0:23:57 > 0:23:59and it's going to reveal what's causing this.
0:23:59 > 0:24:03And if there was one thing that you could find out about Jupiter,
0:24:03 > 0:24:06you only get one answer to a question from the Juno mission,
0:24:06 > 0:24:09- what would it be?- I want to know what is causing this.
0:24:09 > 0:24:11I really want to find the answer -
0:24:11 > 0:24:15what is giving us all these sparkles and flashes and pops going off here?
0:24:18 > 0:24:22As the end of the Jupiter orbit insertion approached,
0:24:22 > 0:24:25things at mission control were increasingly tense.
0:24:26 > 0:24:28We're into the last few minutes of the burn,
0:24:28 > 0:24:30and so far everything's gone perfectly.
0:24:30 > 0:24:33Now we're waiting to hear for news that it's shut off successfully.
0:24:33 > 0:24:36If that doesn't happen, Juno only has about 10 minutes
0:24:36 > 0:24:39to recover before it plummets into Jupiter itself.
0:24:40 > 0:24:43INDISTINCT
0:24:44 > 0:24:45Almost there.
0:24:46 > 0:24:49That's the warning that the end of burn is imminent.
0:24:51 > 0:24:52Should be seconds away
0:24:52 > 0:24:55from having a spacecraft in orbit around Jupiter.
0:24:56 > 0:24:58CHEERING AND APPLAUSE
0:24:58 > 0:25:00There it is! There we go.
0:25:00 > 0:25:04Juno right on time, into orbit, exactly as planned.
0:25:04 > 0:25:07We have a spacecraft in orbit around Jupiter.
0:25:07 > 0:25:10I think people are rather pleased.
0:25:10 > 0:25:11CHEERING
0:25:15 > 0:25:17A very, very relieved team.
0:25:17 > 0:25:20I think they began to believe it was going to happen,
0:25:20 > 0:25:23but for it to happen exactly on cue
0:25:23 > 0:25:25is an astounding feat of engineering.
0:25:25 > 0:25:28Burn time was 21.02 seconds,
0:25:28 > 0:25:32only differing one second off of the pre-burn predictions.
0:25:32 > 0:25:35They were one second off their planned burn.
0:25:35 > 0:25:37To fly a spacecraft that far
0:25:37 > 0:25:40and have it work that well is an incredible feat.
0:25:45 > 0:25:47But now it's in orbit,
0:25:47 > 0:25:49it's time for the real mission to start.
0:25:52 > 0:25:55Juno's first two orbits are very long,
0:25:55 > 0:25:59allowing it time to turn its instruments back on
0:25:59 > 0:26:03and calibrate them in the hostile environment around Jupiter.
0:26:05 > 0:26:07But then the engines will burn again,
0:26:07 > 0:26:10putting it into a shorter orbit,
0:26:10 > 0:26:12just 14 days long,
0:26:12 > 0:26:14an eccentric orbit that will take it
0:26:14 > 0:26:17from over 2 million kilometres from the planet
0:26:17 > 0:26:19to less than 5,000.
0:26:20 > 0:26:24Around the middle of August, the serious science will begin.
0:26:27 > 0:26:30- Yaaaaay!- Welcome to Jupiter!
0:26:30 > 0:26:33- Congratulations!- Yaaaaaay!
0:26:33 > 0:26:35- So it went well, then? - It went great!
0:26:35 > 0:26:38It just... I mean, what were they? Like, one second off
0:26:38 > 0:26:40- or something ridiculous.- Perfect.
0:26:40 > 0:26:43It's perfect. So now the work is going to start.
0:26:43 > 0:26:45We get the data, we've got to do the work.
0:26:45 > 0:26:47But it's great. It's... Oh.
0:26:47 > 0:26:49Did you believe? Were you just sitting there relaxed,
0:26:49 > 0:26:51- or was there a...- No! I was like...
0:26:51 > 0:26:52- SHE BABBLES ANXIOUSLY - You know?
0:26:52 > 0:26:53HE LAUGHS
0:26:53 > 0:26:57- Anyway, it went well.- But the next time you fly past Jupiter,
0:26:57 > 0:27:00in less than two months' time, the instruments are on.
0:27:00 > 0:27:03So the 27th of August is the key date,
0:27:03 > 0:27:07when we do this first - all science on, engines off,
0:27:07 > 0:27:11so no distractions, and we get the data.
0:27:11 > 0:27:13And that's going to be really key,
0:27:13 > 0:27:16because we go through the aurora, we get up close,
0:27:16 > 0:27:19we look at the microwave, we try and find out the first set of water.
0:27:19 > 0:27:23We're not going to be mapping, but at least getting the first taste,
0:27:23 > 0:27:25the taste of Jupiter.
0:27:25 > 0:27:28- And we'll see what it's like.- Yeah. Well, we're looking forward to it.
0:27:28 > 0:27:31- It's going to be great. - Congratulations.- Sure.- Enjoy.
0:27:31 > 0:27:34- Come and tell us about it.- OK, I will.- Take care, well done.- OK.
0:27:34 > 0:27:35Thank you.
0:27:35 > 0:27:37What a wonderful night.
0:27:37 > 0:27:40I can hear 4th of July fireworks going off all around me,
0:27:40 > 0:27:42but up there in the sky is Jupiter,
0:27:42 > 0:27:44and we now know that there's a space probe
0:27:44 > 0:27:46orbiting that tiny point of light.
0:27:46 > 0:27:48Juno performed perfectly,
0:27:48 > 0:27:50placing itself in prime position
0:27:50 > 0:27:53to solve the mysteries of this giant planet
0:27:53 > 0:27:56and tell us lots more about the history of the solar system.
0:27:59 > 0:28:03We'll be reporting on Juno's discoveries in the coming months.
0:28:03 > 0:28:06But that's it for now, and there's no programme next month.
0:28:06 > 0:28:07We'll be back in September.
0:28:07 > 0:28:11In the meantime, go to our website to see Pete's star guide,
0:28:11 > 0:28:13and to find out more about Jupiter,
0:28:13 > 0:28:15including what we can learn about the planet
0:28:15 > 0:28:17by examining it in the infrared,
0:28:17 > 0:28:20and the strange physics at work in its core.
0:28:22 > 0:28:26But as always, get outside and get looking up.