0:00:02 > 0:00:04This month we have a space spectacular.
0:00:10 > 0:00:14After over a decade of chasing a comet through the solar system,
0:00:14 > 0:00:18the space probe Rosetta finally reaches its target.
0:00:24 > 0:00:27And we'll be reporting from the European Space Agency's
0:00:27 > 0:00:30mission control in Germany.
0:00:30 > 0:00:34Rosetta is one of the most exciting and ambitious missions ever
0:00:34 > 0:00:37attempted, like something straight out of science fiction.
0:00:37 > 0:00:40There's a six billion kilometre journey,
0:00:40 > 0:00:43a rendezvous with a comet and then, if all goes well,
0:00:43 > 0:00:47a landing on the surface using harpoons and grappling hooks.
0:00:47 > 0:00:50It's a wonderful scientific mission but it is also a remarkable
0:00:50 > 0:00:53feat of engineering and I'm going to meet the people
0:00:53 > 0:00:57who are in control and find out how they're going to pull this off.
0:00:57 > 0:01:00And here in the UK, we'll be discovering why comets are
0:01:00 > 0:01:04so important to study and viewing one visible in our skies right now.
0:01:04 > 0:01:07Welcome to The Sky At Night.
0:01:33 > 0:01:37Welcome to the European Space Operations Centre
0:01:37 > 0:01:39mission control in Darmstadt, Germany.
0:01:39 > 0:01:42This is where Rosetta's most critical manoeuvres are planned
0:01:42 > 0:01:44and then carried out.
0:01:44 > 0:01:47We'll be getting a tour of the spacecraft itself
0:01:47 > 0:01:49and a look at the latest images from Rosetta
0:01:49 > 0:01:52which have given scientists one or two surprises.
0:01:52 > 0:01:55And I'm here at the Open University in Buckinghamshire,
0:01:55 > 0:01:57where one of the key instruments on the Rosetta lander
0:01:57 > 0:02:01was designed and built. We'll be finding out more about comets
0:02:01 > 0:02:05and how they're helping us unravel mysteries of Earth's past
0:02:05 > 0:02:08and maybe looking into the origins of life itself.
0:02:08 > 0:02:13And there's a comet visible right now in the night sky.
0:02:13 > 0:02:15Pete Lawrence will be showing you how to find it
0:02:15 > 0:02:18and how to take a great comet photo.
0:02:29 > 0:02:32Comets are probably one of the most spectacular
0:02:32 > 0:02:35and enigmatic objects we see in our night skies.
0:02:35 > 0:02:37For millennia they have caused us to wonder,
0:02:37 > 0:02:40"What are they and where do they come from?!"
0:02:42 > 0:02:47Even 1,000 years ago we recognised their distinctive shape.
0:02:47 > 0:02:49In the 11th century Bayeux Tapestry
0:02:49 > 0:02:52Halley's Comet is carefully stitched,
0:02:52 > 0:02:54showing three main parts to a comet.
0:02:54 > 0:02:59A solid nucleus surrounded by a halo, called a coma,
0:02:59 > 0:03:01and then a long streaming tail
0:03:05 > 0:03:09With the advent of photography comets have provided breathtaking images
0:03:09 > 0:03:13and revealed features that cannot be seen with the naked eye.
0:03:14 > 0:03:17Multiple tails are often revealed on photos.
0:03:19 > 0:03:22A very straight gas tail is caused by the solar wind
0:03:22 > 0:03:27ionising gases as they are given off, making them glow.
0:03:27 > 0:03:30It always points directly away from the sun.
0:03:31 > 0:03:36The more familiar diffused, often curved tail is made up of dust
0:03:36 > 0:03:38which streams behind the comet,
0:03:38 > 0:03:40which is also slightly deflected by the solar wind.
0:03:45 > 0:03:49Recently we've been able to get an even closer look at a comet.
0:03:49 > 0:03:54In 1986, space probe Giotto took these remarkable images
0:03:54 > 0:03:57as it flew past Halley's Comet.
0:03:57 > 0:04:00In the past 30 years there have been a number of missions
0:04:00 > 0:04:02that have flown past comets.
0:04:02 > 0:04:04And what they've discovered is a central nucleus
0:04:04 > 0:04:07one to ten kilometres wide.
0:04:07 > 0:04:11Comets also are surprisingly black due to the high carbon content.
0:04:11 > 0:04:14The carbon is mixing with ice and rock,
0:04:14 > 0:04:15and as the comet approaches the sun,
0:04:15 > 0:04:20that ice vaporises, producing a coma and the glorious comet's tail.
0:04:22 > 0:04:24The tail can be very long indeed.
0:04:24 > 0:04:29Comet Hyakutake's was about 360 million miles long
0:04:29 > 0:04:31when it appeared in 1996.
0:04:33 > 0:04:36When the Earth passes through the remains of a comet's tail,
0:04:36 > 0:04:39the result is an often spectacular meteor shower
0:04:39 > 0:04:43as dust particles burn up in the Earth's upper atmosphere.
0:04:48 > 0:04:52It's only when comets approach the sun closely enough to become active
0:04:52 > 0:04:55and brightly lit that they become visible to us.
0:04:56 > 0:04:59To date we've detected over 4,000 comets
0:04:59 > 0:05:02but we know that there are billions more out there.
0:05:02 > 0:05:05We think they're the leftover detritus of the formation
0:05:05 > 0:05:09of the solar system, some 4.5 billion years ago.
0:05:09 > 0:05:12And, as such, we can use them as tiny time capsules,
0:05:12 > 0:05:15giving us a window into our distant past.
0:05:18 > 0:05:21Now we hope to get an unprecedented view of a comet,
0:05:21 > 0:05:25the snappily named 67P/Churyumov-Gerasimenko,
0:05:25 > 0:05:27was discovered in 1969
0:05:27 > 0:05:31and it's what is known as one of the Jupiter family comets,
0:05:31 > 0:05:34as they have been swung into their orbits by Jupiter's gravity.
0:05:35 > 0:05:39Picked from obscurity, it has become a scientific celebrity
0:05:39 > 0:05:42as the target for the Rosetta mission.
0:05:44 > 0:05:47And with Rosetta approaching it, we're beginning to get images
0:05:47 > 0:05:51of the comet for the first time and it's throwing up some big surprises.
0:05:51 > 0:05:55Chris is in Germany, looking at the latest images hot off the press.
0:05:57 > 0:06:00Letting me loose in ESA's mission control is a bit like letting
0:06:00 > 0:06:03a child loose in a sweet shop.
0:06:10 > 0:06:12Here, look what I've found.
0:06:12 > 0:06:15This is a model of Rosetta and it's completely accurate.
0:06:15 > 0:06:19The real thing weighed 2.9 tonnes on launch,
0:06:19 > 0:06:22this one's not quite that big but you can see these long solar panels
0:06:22 > 0:06:25which in real life are 32 metres long.
0:06:25 > 0:06:29They need to be that size to capture the faint light of the sun and so
0:06:29 > 0:06:33that Rosetta can be powered all the way out in the outer solar system.
0:06:33 > 0:06:36It's got this beautiful communications antenna here.
0:06:36 > 0:06:39This can point towards Earth so it can send its signals back to us
0:06:39 > 0:06:41and then, on the back, all of the instruments.
0:06:41 > 0:06:45This is the side that will face the comet. You can see here
0:06:45 > 0:06:49in particular the two cameras of the OSIRIS imaging system.
0:06:49 > 0:06:51Those will provide the scientific images
0:06:51 > 0:06:54and they'll help us select a landing site for Philae.
0:06:54 > 0:06:59This is the little lander that will somehow touch down on the comet.
0:07:03 > 0:07:07On August 6th Rosetta went into orbit around the comet and so now
0:07:07 > 0:07:11those cameras are providing vital images to help the team
0:07:11 > 0:07:12choose their landing spot.
0:07:12 > 0:07:16But, as Dr Holger Sierks shows me,
0:07:16 > 0:07:19those images have provided quite a surprise already.
0:07:19 > 0:07:22The early images taken, yes, the beginning of July
0:07:22 > 0:07:26when it had just barely started to resolve were a surprise
0:07:26 > 0:07:30and it looks like two bodies sticking together,
0:07:30 > 0:07:33- so that was quite obvious right from the beginning.- Yes.
0:07:33 > 0:07:34The first days in early July.
0:07:34 > 0:07:37The most recent ones I've seen make it look a bit like a rubber duck
0:07:37 > 0:07:40or something like that, or at least a small head on a body.
0:07:40 > 0:07:43Is that because it's two bodies that have stuck together
0:07:43 > 0:07:46or could this shape have appeared some other way?
0:07:46 > 0:07:48I like the rubber duck a lot.
0:07:48 > 0:07:50We don't know it yet.
0:07:50 > 0:07:54That is a surprise and we'll have to work to find out why
0:07:54 > 0:07:56the body looks like this.
0:07:56 > 0:07:58It could be two pieces right from the beginning,
0:07:58 > 0:08:02it could also be a bigger block that just had
0:08:02 > 0:08:08some eruptions sideways and just carved like the shape we see.
0:08:08 > 0:08:10So, the duck, if that's what we're calling it,
0:08:10 > 0:08:13- is about three kilometres across, something like that.- Yes.
0:08:13 > 0:08:17It must make planning what you're going to do with Rosetta harder, and
0:08:17 > 0:08:20that planning depends on the images that your cameras are providing.
0:08:20 > 0:08:24- It makes planning harder but also more fascinating.- Yes.
0:08:24 > 0:08:29And we are now in the process of laying out the mapping sequences.
0:08:29 > 0:08:31Yes, and the rest of the mission depends on
0:08:31 > 0:08:34- the quality of those maps as well? - Yes.
0:08:34 > 0:08:37And we will also remap because the shape is going to change.
0:08:37 > 0:08:42We'll watch it on the way in, so to the closest point to the sun,
0:08:42 > 0:08:45so we'll see the activity rise and the comet be more
0:08:45 > 0:08:48and more active and then die out again,
0:08:48 > 0:08:52calm down. We know that the comet is releasing dust
0:08:52 > 0:08:56and we want to study these areas where the activity is formed,
0:08:56 > 0:08:58where dust has moved away,
0:08:58 > 0:09:03and so why is it happening here in this area and not in others?
0:09:03 > 0:09:07The physics of comets is not well understood.
0:09:07 > 0:09:11So the immediate task for OSIRIS is to produce a three-dimensional map
0:09:11 > 0:09:14of the surface. Can you show us how far you've got with that?
0:09:14 > 0:09:16I can show you the current state.
0:09:16 > 0:09:18Just looking here at the shape model here,
0:09:18 > 0:09:23it's hard to understand where you would safely put down this lander.
0:09:23 > 0:09:26Is the obvious thing to go for this big flat face here?
0:09:26 > 0:09:30- That seems safest to me. - Yes, that is very obvious.
0:09:30 > 0:09:34The tricky thing is the sun is coming up
0:09:34 > 0:09:38so if you project the illumination condition into November you'll see
0:09:38 > 0:09:43that it's not so favourable on the large side, on this bottom side.
0:09:43 > 0:09:45You don't want to land in the dark.
0:09:45 > 0:09:48And you don't want to land in the dark so landing will be a challenge.
0:09:48 > 0:09:52I think that we'll do a good job, I am convinced about this,
0:09:52 > 0:09:58and find a good spot, perhaps on the back of the duck, we'll see.
0:09:58 > 0:10:01Yes, OK, well, we can shoot for the back of the duck then!
0:10:01 > 0:10:03That's excellent.
0:10:05 > 0:10:09With Rosetta now in orbit, every day we see new critical
0:10:09 > 0:10:12and stunning surface detail on the comet
0:10:12 > 0:10:15and with the lander due to be released in November,
0:10:15 > 0:10:18we'll be keeping an eye on more pictures as they come in over the
0:10:18 > 0:10:23next few months and as the landing site is chosen and confirmed.
0:10:28 > 0:10:32Rosetta and the lander module carry more than 20
0:10:32 > 0:10:36scientific instruments between them, which will be sending back data.
0:10:38 > 0:10:41Here in the UK the Open University is home to the team
0:10:41 > 0:10:44in charge of a key instrument on the Rosetta lander, that will
0:10:44 > 0:10:47actually analyse the comet's samples.
0:10:47 > 0:10:50Comets are fascinating because they give us a snapshot
0:10:50 > 0:10:53into the ancient solar system and by looking at what they're made of
0:10:53 > 0:10:57we can understand how our world was formed and maybe even how life began.
0:11:01 > 0:11:05Dr Natalie Starkey is one of the comet research team here and
0:11:05 > 0:11:09has been studying particles of dust from the Earth's upper atmosphere.
0:11:09 > 0:11:11Amongst the normal dust and pollution
0:11:11 > 0:11:14she finds particles which form the tails of comets.
0:11:16 > 0:11:19So, this is one of the most interesting particles
0:11:19 > 0:11:22I've analysed actually because it contains all sorts of material.
0:11:22 > 0:11:25We've got amorphous material up in the top and also over to the right.
0:11:25 > 0:11:28- That looks quite gloopy. - Yes, exactly, it's kind of...
0:11:28 > 0:11:30It's more organic kind of material.
0:11:30 > 0:11:32Organic? That sounds interesting.
0:11:32 > 0:11:35Yes, it's not life, so people will think of organic material as life,
0:11:35 > 0:11:39but actually what we are talking about is carbon, hydrogen, nitrogen
0:11:39 > 0:11:42oxygen bonds and it's kind of organic precursor material.
0:11:42 > 0:11:45- Right.- The rest of the particle is quite rocky.
0:11:45 > 0:11:47So what sort of analysis do you do?
0:11:47 > 0:11:49Well, we try and do everything
0:11:49 > 0:11:52because this is a sample of space and we don't get many of them.
0:11:52 > 0:11:54So how many have you done in your career so far?
0:11:54 > 0:11:58I've measured about 50 so far, maybe five that are really,
0:11:58 > 0:12:01really interesting, that can tell us a lot about the kind of time
0:12:01 > 0:12:03we're looking into, this really early material.
0:12:03 > 0:12:06- 4.5 billion years ago. - Exactly, exactly.
0:12:06 > 0:12:09So we want to throw every single instrument at them that we have,
0:12:09 > 0:12:11you know, all these really advanced techniques
0:12:11 > 0:12:13because they're precious samples
0:12:13 > 0:12:16and as we are analysing it, we are destroying it as we go...
0:12:16 > 0:12:18- Taking bits off the top. - Exactly.- Yes.
0:12:18 > 0:12:20But we are getting some numbers at the same time.
0:12:20 > 0:12:23And the next images you have here show some of the beautiful
0:12:23 > 0:12:25isotopic images we get.
0:12:25 > 0:12:27So when you say isotope, what do you mean?
0:12:27 > 0:12:30Well, an isotope is just a special type of an element really,
0:12:30 > 0:12:32it just contains a different number of neutrons in it
0:12:32 > 0:12:35so we're just looking at these very little variations.
0:12:35 > 0:12:38So those isotope distributions, what do they tell us?
0:12:38 > 0:12:41Well, what we can see from this particle is that actually
0:12:41 > 0:12:44there's quite a lot of variation in this single piece of dust.
0:12:44 > 0:12:48Actually, this allows us to trace not only time -
0:12:48 > 0:12:50so when that comet might have formed, a little bit,
0:12:50 > 0:12:53it doesn't give us a date but we can kind of relative times -
0:12:53 > 0:12:57but also processes, kind of what happened to those isotope ratios
0:12:57 > 0:13:00because they change depending on the temperature
0:13:00 > 0:13:03- and the conditions that that comet formed under.- I see.
0:13:03 > 0:13:07- So isotopes are actually giving you a location and timescale.- Exactly.
0:13:07 > 0:13:10So we start to be able to place things relatively to each other
0:13:10 > 0:13:13and what we find with particles like this really interesting one
0:13:13 > 0:13:17is that it contains pieces that are a bit mixed so it's not just
0:13:17 > 0:13:20all one composition, it didn't all form in one place,
0:13:20 > 0:13:22this piece of comet actually contains other pieces of comet
0:13:22 > 0:13:25that formed in different places all over the solar system.
0:13:25 > 0:13:27And somehow it all came together.
0:13:27 > 0:13:29It somehow came together at a later date so our understanding
0:13:29 > 0:13:32of comet formation is really led by research like this.
0:13:32 > 0:13:35When we use these particles from the stratosphere we don't know
0:13:35 > 0:13:38from which particular comet they've come from, but one time
0:13:38 > 0:13:41we've actually been into space and we've sampled a comet
0:13:41 > 0:13:44and it was the Stardust mission which landed back on Earth in 2006,
0:13:44 > 0:13:47it was a NASA mission and what they did was actually just fly through
0:13:47 > 0:13:50the tail of the comet, so all the material coming off
0:13:50 > 0:13:52they just collected this as impacting particles
0:13:52 > 0:13:55into the collectors and this mission was really groundbreaking.
0:13:55 > 0:13:58So, our very simple comet model is that they formed
0:13:58 > 0:14:01far from the sun and they only contain material that formed
0:14:01 > 0:14:04far from the sun, in the cold outer reaches of the solar system.
0:14:04 > 0:14:07Which would make sense, if they formed there, that's the material.
0:14:07 > 0:14:10Yes, but actually what Stardust showed us is that this comet called
0:14:10 > 0:14:13Wild 2 contained material that was formed in the inner solar system
0:14:13 > 0:14:16so it contained material that is very similar to what we see
0:14:16 > 0:14:19in asteroids, so it's a little bit complicated.
0:14:19 > 0:14:22We probably have asteroids at one end, comets at the other,
0:14:22 > 0:14:25but now we think there's a bit of a continuum in between
0:14:25 > 0:14:28and so we need to go and measure more comets to really find out
0:14:28 > 0:14:31what this continuum is and what's going on really.
0:14:31 > 0:14:34- So I guess that is where Rosetta comes in?- Exactly.
0:14:34 > 0:14:37In your ideal scenario, the dream wish now,
0:14:37 > 0:14:39what would you like to get out of Rosetta?
0:14:39 > 0:14:42For me it's all about the landing because I want to drill into that
0:14:42 > 0:14:45comet and get some of the samples and find out what it's made of.
0:14:45 > 0:14:48It will hopefully tell us how far from the sun potentially this comet
0:14:48 > 0:14:52formed and what kind of processes it's undergone in its lifetime
0:14:52 > 0:14:54so where all those little pieces that form that comet
0:14:54 > 0:14:56actually formed themselves.
0:14:56 > 0:14:58Whether it was in the inner solar system which will be
0:14:58 > 0:15:01a bit of a surprise or whether it was way away from the sun,
0:15:01 > 0:15:04so this is one of the things will help us
0:15:04 > 0:15:07build up that picture of the comet and its life history, basically.
0:15:07 > 0:15:10Well, very good luck for it all and I am really looking forward
0:15:10 > 0:15:13- to seeing some of this data coming out.- Thank you.
0:15:25 > 0:15:29Every decade or so we get a spectacular comet passing close by
0:15:29 > 0:15:33the sun and giving us a display that dominates the night sky.
0:15:34 > 0:15:37But there are actually comets visible much more frequently
0:15:37 > 0:15:40than that and Pete's here to show you how to see one
0:15:40 > 0:15:42that's in the night sky right now.
0:15:43 > 0:15:48Typically there are lots of faint comets visible in the night sky
0:15:48 > 0:15:51but occasionally one will get bright enough so that they can be seen
0:15:51 > 0:15:54with a small telescope, or even a pair of binoculars.
0:15:54 > 0:15:58Now, there's one of those visible this month.
0:15:58 > 0:16:01This particular comet is relatively easy to see
0:16:01 > 0:16:03as long as you know where to look.
0:16:03 > 0:16:08This newly discovered comet, called C/2014 E2 (Jacques),
0:16:08 > 0:16:11can be found by locating the bright star Capella.
0:16:11 > 0:16:14At this time of year it's the brightest star
0:16:14 > 0:16:16in the north-eastern part of the sky.
0:16:18 > 0:16:21At the start of the month the comet lies in a patch of sky
0:16:21 > 0:16:25approximately one fist width at arm's length to the right of Capella.
0:16:25 > 0:16:28By the 15th it'll have moved up the sky
0:16:28 > 0:16:31to sit left of the star Mirphak in Perseus.
0:16:31 > 0:16:36Look up from Mirphak and you'll eventually arrive at the W shape
0:16:36 > 0:16:40constellation of Cassiopeia. During August the W appears on its side.
0:16:42 > 0:16:45After the 15th the comet tracks up towards Segin,
0:16:45 > 0:16:48the star that marks the left hand end of the W.
0:16:49 > 0:16:53It's so close to it on the nights of the 22nd and 23rd of August
0:16:53 > 0:16:56that a pair of binoculars pointed at the star
0:16:56 > 0:16:59should include the comet in the same field of view.
0:17:00 > 0:17:04At the end of August E2 (Jaques) moves into the constellation of
0:17:04 > 0:17:06Cepheus and, although it should be fading,
0:17:06 > 0:17:09will hopefully remain a binocular target.
0:17:15 > 0:17:18OK, you should be able to see this comet quite easily
0:17:18 > 0:17:22with just a pair of binoculars, but if you've got a digital SLR camera,
0:17:22 > 0:17:26a decent lens, and a tripod, you can try taking a photograph of it
0:17:26 > 0:17:28to get an even better view.
0:17:30 > 0:17:32Put the ISO or sensitivity of your camera high
0:17:32 > 0:17:36and use an exposure of 30 or more seconds,
0:17:36 > 0:17:39open the lens wide and set your focus to infinity
0:17:39 > 0:17:42and take a photo of what you think is the right area of sky.
0:17:42 > 0:17:45Use a remote trigger if you can to avoid camera shake.
0:17:47 > 0:17:50Now, hopefully, if you're in the right area of sky,
0:17:50 > 0:17:53you should be able to pick out a little fuzzy blob.
0:17:53 > 0:17:55Let's have a look.
0:17:58 > 0:17:59Just like that.
0:17:59 > 0:18:01And that should be the comet.
0:18:02 > 0:18:06The comet nucleus itself is, of course, not only tiny
0:18:06 > 0:18:09but incredibly black so all we're looking at is the sun's light
0:18:09 > 0:18:13reflecting off the dust it's emitting and from glowing gases.
0:18:13 > 0:18:17The fuzzy, diffuse nature of a comet does make it quite
0:18:17 > 0:18:20difficult to find first of all because it looks much fainter
0:18:20 > 0:18:24than a star, but once you have identified it in your photograph
0:18:24 > 0:18:26the thing to do then is to centre up the frame
0:18:26 > 0:18:28so you're pointing directly at the comet
0:18:28 > 0:18:32and then use a lens with a longer focal length to get closer in.
0:18:32 > 0:18:35I'm going to use a telescope for this one.
0:18:37 > 0:18:39Now, as most comets move relative to the stars,
0:18:39 > 0:18:43if you take a long exposure shot on a tracking mount,
0:18:43 > 0:18:47which keeps up with the stars, the comet will appear blurred.
0:18:47 > 0:18:51One way around this is to take shorter exposures and,
0:18:51 > 0:18:54using image processing software, combine the images,
0:18:54 > 0:18:56using the comet's head as the reference.
0:18:56 > 0:18:59This will make the stars appear like dotted lines
0:18:59 > 0:19:02but the comet will really shine through
0:19:02 > 0:19:05and hopefully show its true colour, an astonishing green glow.
0:19:05 > 0:19:10And that's a very characteristic colour, seen in a lot of comets.
0:19:10 > 0:19:14That's due to the gases which surround the central core
0:19:14 > 0:19:16of the comet, the nucleus,
0:19:16 > 0:19:20and they're giving off this amazing green coloured light.
0:19:20 > 0:19:23It's the sun's ultraviolet light that causes the gases,
0:19:23 > 0:19:27mainly cyanogen and diatomic carbon, to fluoresce and it's one
0:19:27 > 0:19:31of the features of comets only really picked up by photography.
0:19:31 > 0:19:35Comets make fantastic photographic subjects
0:19:35 > 0:19:39and if you do manage to get a long exposure shot of it, that'll pick out
0:19:39 > 0:19:43some good detail and give you a great image to show off as well.
0:19:43 > 0:19:46If you do get a nice photo, share it via our website...
0:19:50 > 0:19:53..where you'll also find my guide on how to find E2 (Jaques).
0:20:01 > 0:20:06Dix, neuf, huit, sept, six...
0:20:06 > 0:20:09It's been more than ten years since Rosetta was blasted into space
0:20:09 > 0:20:11at the start of an epic mission.
0:20:11 > 0:20:13Decollage.
0:20:15 > 0:20:17It's taken more than £1 billion of investment
0:20:17 > 0:20:19and decades of scientific work.
0:20:21 > 0:20:25So why does visiting a comet warrant so much investment?
0:20:25 > 0:20:28And how on earth are we going to achieve the mission's objectives?
0:20:28 > 0:20:31Chris has been finding out.
0:20:33 > 0:20:36One of the questions this mission sets out to answer
0:20:36 > 0:20:37is a surprising one.
0:20:39 > 0:20:41Could this water, this precious liquid
0:20:41 > 0:20:43that makes all life on Earth possible,
0:20:43 > 0:20:47have been carried here from space on the icy asteroids and comets
0:20:47 > 0:20:50which have bombarded the Earth over millennia?
0:20:52 > 0:20:55We think of ourselves as the blue planet,
0:20:55 > 0:20:58with vast amounts of liquid water,
0:20:58 > 0:21:01but if all of our water were gathered into one place,
0:21:01 > 0:21:05well, this image shows how little there really is on Earth.
0:21:05 > 0:21:09Nevertheless, it would take perhaps 100 million comets
0:21:09 > 0:21:11to bring us all this.
0:21:11 > 0:21:15It seems ridiculous that all of Earth's water could have been
0:21:15 > 0:21:18delivered from space and yet, in the early days, Earth would have been
0:21:18 > 0:21:22a hot world - any water would have boiled off almost immediately.
0:21:22 > 0:21:26And so water must have arrived on Earth and the other rocky planets
0:21:26 > 0:21:30later and one of the leading theories is that it was delivered
0:21:30 > 0:21:34during a period of heavy bombardment nearly four billion years ago,
0:21:34 > 0:21:37as icy comets and asteroids slammed into the Earth.
0:21:41 > 0:21:44We think there might have been enough comets hitting the Earth
0:21:44 > 0:21:48to supply all of our water, but one of Rosetta's tasks
0:21:48 > 0:21:51is to look for hard evidence that they really did.
0:21:52 > 0:21:56Water can contain different kinds of hydrogen, different isotopes.
0:21:58 > 0:22:02And the ratio of these isotopes gives Earth's water a distinct signature.
0:22:03 > 0:22:06Rosetta will analyse the water on the comet to see
0:22:06 > 0:22:09whether it shares that same distinctive signature,
0:22:09 > 0:22:13real evidence that our water could have come from comets.
0:22:13 > 0:22:15But that's not all,
0:22:15 > 0:22:20Rosetta will also be looking for complex chemicals like amino acids
0:22:20 > 0:22:23which form the basis of life, to find out whether these, too,
0:22:23 > 0:22:25could have come from comets.
0:22:25 > 0:22:30These are some of the most profound questions in science today and
0:22:30 > 0:22:34that's why this particular mission is so exciting, and so ambitious.
0:22:36 > 0:22:39To answer these big questions Rosetta has to do something
0:22:39 > 0:22:43really new, land on the surface and drill down to analyse what
0:22:43 > 0:22:47lies beneath, and before you can do that you have to catch the comet.
0:22:51 > 0:22:53It's an incredible undertaking,
0:22:53 > 0:22:56challenging in just about every respect
0:22:56 > 0:23:00and it's made Rosetta a huge engineering project.
0:23:01 > 0:23:04Now the most crucial moments are finally upon the team.
0:23:06 > 0:23:09Andrea Accomazzo's been working on Rosetta
0:23:09 > 0:23:12since the earliest design stages and is the flight director.
0:23:13 > 0:23:17It is one of the most challenging space missions ever.
0:23:17 > 0:23:20Nobody has ever gone to such an irregular body,
0:23:20 > 0:23:24such an active body with the need of such a high accuracy of flying
0:23:24 > 0:23:27the spacecraft around the body so it's definitely something new,
0:23:27 > 0:23:32it's unique in the history of space flight and it's fantastic.
0:23:32 > 0:23:35How do you go about rendezvousing with the comet?
0:23:35 > 0:23:38What we wanted to do, we wanted to reach the comet and stop there
0:23:38 > 0:23:40and start orbiting the comet
0:23:40 > 0:23:43so we had to slow down the spacecraft compared to the comet and slowly
0:23:43 > 0:23:47approach it and once we were close to it then we could start our mission.
0:23:47 > 0:23:51At the end of our ten-years journey we now start exploring
0:23:51 > 0:23:54a new world and we have to characterise it completely.
0:23:54 > 0:23:56We don't know anything of this new world.
0:23:56 > 0:23:58We have to characterise the gravity field first,
0:23:58 > 0:24:00we have to characterise how it's rotating,
0:24:00 > 0:24:03we know the shape, we have taken a couple of images but we have to
0:24:03 > 0:24:07characterise it to a level such that we can then orbit and land.
0:24:07 > 0:24:09And, of course, this is a changing body as well,
0:24:09 > 0:24:12we expect the comet to become more active as it gets near the sun.
0:24:12 > 0:24:15We have already seen some activity from the comet.
0:24:15 > 0:24:17How do you have to take that into account?
0:24:17 > 0:24:20It sounds like a scary place for a spacecraft to be.
0:24:20 > 0:24:23Indeed, indeed, it is also a scary place to be with a spacecraft
0:24:23 > 0:24:25which has huge solar arrays.
0:24:25 > 0:24:29Fundamentally the comet is releasing material and gases
0:24:29 > 0:24:32so we are going to a windy place with huge sails
0:24:32 > 0:24:34and it's not easy to navigate around a body like this
0:24:34 > 0:24:36but this is the mission we have and we will do it.
0:24:36 > 0:24:39A lot of science will come from the main spacecraft
0:24:39 > 0:24:42but the lander is very, very exciting. Tell us about that,
0:24:42 > 0:24:45how is the lander going to touch down on the comet?
0:24:45 > 0:24:49The lander, for sure, is the most fascinating part of this mission.
0:24:49 > 0:24:52You can imagine we are landing on a body that is far away from the
0:24:52 > 0:24:55Earth, a body that is so irregular so it definitely is the most
0:24:55 > 0:24:59fascinating, and also technically it is the most challenging for us.
0:24:59 > 0:25:01We have to release the lander when we are flying
0:25:01 > 0:25:04in front of the comet which is a very bad region for the wind.
0:25:04 > 0:25:06The wind is expected to be very high.
0:25:06 > 0:25:09- Because that is where the sun's energy comes in.- Right, right.
0:25:09 > 0:25:11The sun is heating the surface of the comet
0:25:11 > 0:25:13and it's blowing out a lot of gases.
0:25:13 > 0:25:16We have to fly very fast in front of the comet, release the lander,
0:25:16 > 0:25:19the lander will slowly fall onto the surface of the comet...
0:25:19 > 0:25:21- Just pulled by the comet's gravity? - Right.
0:25:21 > 0:25:24It is pulled by the gravity of the comet.
0:25:24 > 0:25:27There is no active system to slow down on the lander
0:25:27 > 0:25:31and when it lands, it anchors itself, it has two harpoons underneath
0:25:31 > 0:25:35and they will be fired onto the surface, hoping to hook it there.
0:25:35 > 0:25:38And so the lander will do its thing, it will send back information,
0:25:38 > 0:25:41but the mission goes on even after the landing.
0:25:41 > 0:25:42What happens next?
0:25:42 > 0:25:47The mission itself is spending 18 months at least around the comet.
0:25:47 > 0:25:51There's much more we have to discover through the science instruments on board Rosetta.
0:25:51 > 0:25:53So taking it together, it's 18 years of work for you,
0:25:53 > 0:25:57what does it feel like to be this close to starting to get data back?
0:25:57 > 0:26:01Well, when I started working on Rosetta in 1996 it looks so far away
0:26:01 > 0:26:05the whole thing but my life has gone through, in my professional life
0:26:05 > 0:26:08and my private life, has gone through this 18 years and now we are there
0:26:08 > 0:26:12and it can't be anything better than what we are living right now.
0:26:12 > 0:26:15Well, I hope it all goes well, we look forward to seeing the results.
0:26:15 > 0:26:17- Thank you very much.- Thanks.
0:26:21 > 0:26:24The Rosetta probe is an astonishing piece of craftsmanship.
0:26:24 > 0:26:29Here at the control centre they have what's called an engineering replica
0:26:29 > 0:26:32of it, kept in pristine, space-like cleanliness
0:26:32 > 0:26:36and used to test all of the software on board.
0:26:40 > 0:26:45This engineering replica is obviously missing its solar panel wings,
0:26:45 > 0:26:47but other than that it's the perfect way to admire
0:26:47 > 0:26:49all of Rosetta's features.
0:26:56 > 0:27:00The whole thing weighed 2.9 tonnes on launch.
0:27:02 > 0:27:05But 1.6 tonnes of that was fuel.
0:27:12 > 0:27:1624 tiny thrusters give precision control.
0:27:19 > 0:27:23Rosetta itself carries 11 on-board instruments,
0:27:23 > 0:27:26which all have to share the same power supply.
0:27:28 > 0:27:32There are 12,000 separate electrical connections.
0:27:32 > 0:27:37They alone took three years to build and all of them have to work.
0:27:39 > 0:27:40Over the next three and a half months,
0:27:40 > 0:27:43Rosetta will be working its way closer to the comet,
0:27:43 > 0:27:46taking images and measurements with these instruments all the time,
0:27:46 > 0:27:49helping us to understand what's going on
0:27:49 > 0:27:52and trying to select a site for the all-important landing.
0:27:52 > 0:27:56After nearly 20 years of work, I can't imagine what the team
0:27:56 > 0:27:59here must be thinking as they get close to these historic moments.
0:27:59 > 0:28:02We're going to explore a brave new world,
0:28:02 > 0:28:05we're going to learn so much not just about this comet,
0:28:05 > 0:28:07not just about the origins of the solar system,
0:28:07 > 0:28:10but also about what happened a long time ago here on Earth.
0:28:10 > 0:28:13It's a really, really exciting time.
0:28:16 > 0:28:19Of course, we'll be following Rosetta's progress over the next
0:28:19 > 0:28:22nail-biting couple of months as it spirals down towards the comet,
0:28:22 > 0:28:25releasing the lander with its grappling hooks, ready for drilling.
0:28:25 > 0:28:28And next month we'll be looking at new worlds
0:28:28 > 0:28:31discovered on planets outside our solar system.
0:28:31 > 0:28:35In the meanwhile, get outside and get looking for comets. Good night.
0:28:37 > 0:28:41# Let's hitch a rocket to the moon
0:28:41 > 0:28:44# Open out the throttle
0:28:44 > 0:28:48# Steer towards the sun
0:28:48 > 0:28:52# Rosetta's in her stride
0:28:53 > 0:28:56# Surf the comet's tail on an astronomic trail
0:28:56 > 0:29:00# Take the world along just for the ride
0:29:00 > 0:29:02# Comet chaser! #