of an asteroid hitting earth. i'll find out why we didn't see this 10,000—tonne space rock coming. we will be hit again. i'll learn about the recent planetary defence mission that deliberately smashed into an asteroid to knock it off course. there is the potential to use a nuclear stand—off weapon. exoplaneteer george dransfield discovers the role asteroids may have played in starting life on earth. are you telling me that life on earth is extraterrestrial in origin? so wrap up warm, get outside and look up. welcome to the sky at night.

asteroids have been hitting our earth for around four billion years. most famously, the chicxulub asteroid wiped out the dinosaurs and transformed life on this planet. on 15 february 2013, a 10,000—ton asteroid entered the atmosphere over the russian city of chelyabinsk. it exploded with 30 times the energy of an atomic bomb, injuring 1,600 people. and we didn't see it coming. professor alan fitzsimmons is an expert in the observation and measurement of asteroids. he's one of the scientists trying to make sure we don't miss

the next big impact. now, i want to start with some jargon busting, because there's a lot of stuff out there. there's asteroids, there's comets. can you take us through that? sure. asteroids, like good old bennu here, are objects, rocky objects that orbit the sun. we also have comets, of course. comets have a lot of ice in them. now, if that asteroid enters the earth's atmosphere, then we see it glowing as a meteor or shooting star. if they make it to the ground, that is called a meteorite. meteorite. and here's one here. they're always far more dense than i would anticipate. so, how are you monitoring the asteroids out there? this is one of the atlas telescopes. this one is in hawaii. it's designed to pick up small asteroids that may be heading towards earth on an impact trajectory. and down below here, we can see some of the images it's taken in the past ten minutes. so this is the early—warning system — it flags up for sort of further investigation? they detect, in total, about eight new near—earth

asteroids every 2a hours. it's amazing. so far, they have found over 31,000. of these near—earth asteroids, around 1,500 have been identified as potentially hazardous. so, what asteroid should we be worried about right now? well, there's a few up there, and one that's been on the risk page for almost 20 years has been the asteroid apophis. and you can see it here. 0h, right. in fact, in 2029, on friday 13 april... it would be friday 13th! it would be. ..it�*s going to make a very close approach. we're worried about it because we know it will miss us, then. it's going to miss us when it returns in 2035. but it keeps coming back, and it's about 250m across, so that, if it hit, this would wipe out a small area of the earth. you know, something, the size of a county or even a small country would really feel those effects. wow. it's reassuring that alan

is monitoring these potential threats so closely. but what i want to know is why some harmful asteroids still get missed. one of the most recent sort of devastating impacts was chelyabinsk. now, why didn't we detect that before it actually hit? well, there's a couple of reasons. first of all, chelyabinsk itself approached on its last trajectory from roughly the direction of the sun, where our ground—based optical telescopes can't look, of course. now, we could have tried to find it on a previous orbit, but chelyabinsk was really small. it was only 18 or 19 metres across. it was just too faint for us to see. objects the size of chelyabinsk and larger, there's probably about a million, and we are still very inefficient at detecting near—earth asteroids in that range. so these small objects, although they don't wipe out whole species like happened with the dinosaurs... yes. ..they hit much more frequently. chelyabinsk — it injured 1,600 people. yes.

and we really do want to be careful to try to catalogue as many of them as possible. thankfully, the technology is catching up. in 2025, the vera rubin 0bservatory will give us the widest—ever view of our skies. and in 2025, nasa will launch a new orbiting mission, the near—earth 0bject surveyor. we hope, within about a decade, to have swept up most of the potentially hazardous asteroids in our sights. so, we should be confident? i think we should be confident, but we shouldn't relax at all. we are still finding new near—earth objects every day, and we know at some point in the future, we will be hit again. tracking these asteroids and understanding the risk they pose is hugely important. but the next step is knowing if we could actually stop one if it placed us in harm's way. and lift—off

of the falcon 9 and dart. nasa's double asteroid redirection test, or dart, was an experiment to see whether we could redirect an asteroid by intentionally smashing into it. 7,6... oh, wow. ..5, 4, 3, 2... it crashed into it at more than 13,000 miles per hour. and for the first time ever, we deliberately changed the orbit of a planetary object. i want to know whether the success of dart means that we'll be safe when an asteroid poses a real threat to life on earth. professor simon green at the open university was involved in the preparation for this mission. so, simon, what was dart trying to do? well, dart was designed to deflect an asteroid by using what's called the kinetic impactor process. so it uses a spacecraft

to hit the asteroid and change its velocity ever so slightly, so that it changes its orbit. the surface of an asteroid will look something like this. it's called regolith. it's a powdered material with larger pebbles in it. so we're hitting a rubble pile, not a solid object. yeah, yeah. and it will throw off particles that change the way in which the asteroid will respond to the impact. the composition of the asteroid determines how it will behave when the spacecraft hits it. simon tests this in his lab using different materials. this is a momentum stage, and it's essentially a bucket on springs, and it allows us to measure the momentum transfer when a spacecraft, here it is, hits an asteroid. which in that case is made of wet sand. 0k. so let's see what happens, shall we? bull's—eye! and it just sat there. yes. because the wet sand absorbed

the impact of the spacecraft. when the ball hits the target made of wet sand, it should stop dead. i'lljust give you the ball back first. so, here you go. next, simon tries a material that is much more like the composition of an asteroid like dimorphos. just make sure i get my aim right. whoa! we've got ejecta — stuff thrown up. you can see this is bouncing much more this time than it did with the sand. yeah. when the ball hits the gravel, ejecta is thrown away from the surface. physics says that the more ejecta there is, the more the target is pushed in the other direction. this is called momentum enhancement. that amount of momentum carried by the ejecta has to be balanced by extra momentum in the asteroid moving in the other direction. so, it'sjust like how a rocket works. you throw stuff out one way and the rocket goes up. exactly. and that's called the momentum enhancement, this magic beta factor that everybody wants to know. right, and that's what we saw with dart? yes. when dart hit dimorphos,

the energy from the impact led to a crater being formed, and material from the asteroid was blasted out into space. this caused momentum enhancement, also known as the beta factor, and helped to propel the target further. it's the reason that a light spacecraft, weighing only half a tonne, was able to change the orbit of dimorphos, thought to weigh around five million tonnes. simon's colleague, zoe emerland, uses a high—velocity impact gun to calculate the beta factor at higher speeds in the lab. zoe fires an impactor at a target at likm a second. so this is what we get from the gun. yes. and you can see the ejecta. oh, wow. do we know how much of an extra kick the asteroid got from this momentum? we know that it gave a significant extra kick. dart mission was an incredible success because it did...

its first objective was to demonstrate that you can target a spacecraft onto an asteroid, hit it in the place you intended to, and deflect the asteroid. the impact produced a change in the orbital period by 33 minutes. that's quite a lot. now, if there were no momentum enhancement, that would have given you a seven—minute change in the period. but though momentum enhancement is useful, accurately calculating it is hard, as you need to know the composition of the asteroid. it's good because any momentum enhancement you get means you get a bigger deflection for the size and speed of the spacecraft you hit. it's bad because you don't know how much it's going to be. when we find an asteroid that's going to hit us, we have to send a reconnaissance mission to measure its properties, so we can then adjust those models to precisely that body. and then work it out, yeah? and then when we'll know exactly what spacecraft we need to hit it, how early we need

to hit it, because we'll be able to make a much better guess at what the momentum enhancement will be. what is really, really important is that we find it early. if we get it late, we might end up in the scenario where we have to launch several dart—type missions and hit one after the other. right. but of course, that is even greater risk. if you look at movies and science fiction, people send bombs and all sorts of things. they do, they do. and i have to say that, if you don't get enough warning, the asteroid is too big, then there is the potential to use a nuclear stand—off weapon. nobody wants to do that, 0k... right. ..but if it means survival of a country from total destruction, then, you know, that has to be in our planning. but it is an absolute last resort. so nonetheless, you sound quite cheerful about where we are with planetary defence. so what i'm hearing is it's going to be ourfault, us astronomers who look at the sky, not you planetary scientists, but if we don't find the things early enough, you can't help us. we have to find them early enough, yes. i find dart really inspiring.

having realised there's a threat from asteroids, humanity has pulled together and gone a long way to solving it. it's an effort that's involved astronomers with telescopes finding the asteroids, lab work like we've seen today, complex computer simulations, and some excellent spacecraft engineering. together, it's a potentially world—saving and fabulous effort. but to really figure out the asteroids, we need to understand their origins, and — surprisingly — the role played by the largest planet in the solar system. i remember in 1994, looking atjupiter with my small back garden telescope and seeing giant bruises appear on the planet's surface. it had been hit by shoemaker—levy 9, a comet that got too close to it and had broken up. and as each fragment of comet hit the atmosphere, it sent up plumes of material, thousands of kilometres high. it was a reminder of the dangers of living

in our solar system. butjupiter also has a role to play in the major threat to us here on earth — asteroids. most of them live in the asteroid belt, a region between mars and jupiter. and while they stay there, they're no threat to us at all. why are they there? blame jupiter. when the planets were forming out of the disc of gas and dust that surrounded the young sun, the giant planet's gravity seems to have stirred up this region, so the asteroids couldn't coalesce into one large world. so instead of a new planet, we get an asteroid belt. science fiction makes asteroid belts seem like scary places, like your ship might be hit by a rock at any moment, but actually, there's plenty of space. the average distance between large asteroids is perhaps a million kilometres. if asteroids stayed in the asteroid belt, there'd be no threat to us at all. and yet we see tens of thousands of near—earth objects, asteroids whose orbits cross our own and which might one day hit us.

why are they there? blame jupiter again. its gravity is still stirring up the asteroid belt, and altering the orbit of these asteroids so that they travel into the inner solar system, where they might pose a threat. butjupiter does do one good thing for us. comets and other bodies coming in from the outer solar system are much more likely to encounterjupiter than anything else, and it almost always sends them shooting out of the solar system. so, jupiter today acts as a vacuum cleaner, keeping the solar system clean, even while it stirs up our neat and tidy asteroid belt. asteroids can pose a serious danger to life on earth, which is why they're monitored by scientists across the world. but this work isn't only carried out by experts. there's also a network of amateur astronomers helping to track the meteors in our skies. one of these meteor trackers is mary mcintyre. i love doing the meteor

science, because it's amazing to just be part of a community that arejust doing so much amazing work. it's helping with meteorite recovery. it's helping with planetary defence as well. and these cameras are basically low—cost cctv cameras, but for space. mary is part of a global network of over a50 cameras. and it's something that you can set up in your own back garden. these cameras are so accessible now. the global meteor network system is using a raspberry pi computer, which is fairly inexpensive. and the software that does all of the science is free. the best place to mount the cameras is somewhere very sturdy. so it could be the back of a house or a solid wall, or it could be a shed wall like ours. and then you kind of want the camera pointing up at about a 45—degree angle. you just never know when an interesting event is going to happen.

so never, ever turn them off. the camera's observations of a meteor automatically collate with others, onto the global meteor network. these cameras capture a huge amount of data. it will tell you how fast it was going, the angle that it came in to earth's atmosphere at. it will tell you the orbit, so you know exactly where in the solar system or even extra—solar system that these events have actually originated. the majority of meteors that we observe are seen as streaks of light that burn up in the earth's atmosphere. but sometimes we see a fireball, a really bright meteor that survives the earth's atmosphere and can land here on earth as a meteorite. i think it's just the most exciting news ever when we discover that a fireball that's been picked up on our cameras has resulted in a meteorite fall that has been recovered. amateur meteor—trackers like mary are playing a major

role in the study of how asteroids may have helped to kick—start life on earth, rather than destroy it. on 28 february 2021, a bright fireball was spotted in the skies above the uk. and it's led to new ideas in understanding the early solar system. astrophysicist and exoplaneteer george dransfield is at royal holloway to find out more. this fireball was so significant because it was caught on uk fireball alliance cameras, and they were able to track its trajectory. they could see that it was headed towards gloucestershire, specifically in and around the town of winchcombe. and crucially, this meant that scientists could get to the right place immediately, and gather up all the fragments. 600g of blackened debris was picked up from people's gardens and driveways and local fields. are you sure? yeah. it totally is, it totally is. that is very obvious. 0h!

it was a truly historic moment, the first time in three decades that a meteorite has been observed hurtling across the uk, and then recovered ready for analysis by scientists around the world, including planetary scientist dr queenie chan. why is it important and significant when we find a meteorite? asteroid are the building blocks of planets. so we get to see how the planet was formed at the beginning of our solar system. 0k. so they have, like, a fossil record of, like, early solar system. and what is particularly special about the winchcombe meteorite? over here, i've got tiny pieces of the winchcombe meteorite. it's very exciting for us, because it's been recovered really quickly after its fall. so we want a clean meteorite, not as contaminated by the earth's atmosphere, but also it's a kind of carbonaceous or carbon—rich chondritic type of meteorite, a rare type of meteorite that's

been recovered on earth. carbonaceous chondrites are some of the earliest materials in the solar system — older than the earth. they could hold the answers to what molecules were present when life on earth began. queenie has another example of this rare type of meteorite to show me. so here i've got an example of that. and it's called the murchison meteorite. it's a famous meteorite that fell on earth in 1969. the meteorite here... that's a piece of space rock! yeah. so if you look closely, can you see the white specks? yeah. and they're quite rounded. so they are called...what we call the chondrules. so, chondrules are one of the first solids that's been formed at the birth of our solar system. queenie has been analysing the winchcombe meteorite, looking for what molecules existed at the very beginnings of the solar system. her focus is on amino acids, the building blocks of life. so, you've been working away at this and scraping bits off,

and studying the winchcombe meteorite. we've found that there are a range of amino acid molecules in the winchcombe meteorite, and it's quite exciting. some of them are even protein—forming type of amino acids. so the fact that we have found amino acids in winchcombe is a big deal, because we need those molecules for life to occur. and the reason why it is so exciting is because there are two theories of where our molecules of amino acid were from. so it's either that it's been totally earth—based. so it was all created by reaction on the earth's surface, or it could be delivered by asteroid from outer space. and we know that both are possible. as well as these building blocks for life, scientists have found evidence of water in samples of the winchcombe meteorite, with a chemical composition similar to that on earth. this adds weight to the theory that asteroids could have

delivered the ingredients for life to our planet. and it means that these same ingredients could also have been delivered elsewhere in the universe. hang on a second. are you telling me that, potentially, life on earth is extraterrestrial in origin? well, it's quite an interesting topic because life on earth, i don't know whether they're extraterrestrial, but we definitely know that the ingredients that need to form life, or ingredients that life needs to exist, can become...coming from outer space. we do often think of asteroids as a bit of a threat, perhaps because of the whole dinosaurs incident. but we are learning more and more about how asteroids might have also contributed to kick—starting life on earth. and what was mad cool about this incident in particular is the way citizen scientists helped track its trajectory, so that we could collect it

and then do some in—depth science with it in our labs. hello there. the summer holiday season is in full swing, and if you have plans for the weekend, well, it looks likely that the weather is going to behave itself. it will be largely dry, sunny and pretty warm. now, we have got a little bit of rain clearing away from the south and east as we speak and this area of low pressure to the far north—west.

that's at risk of driving in a few isolated showers, chiefly to the northwest of the great glen, and here, a brisk wind with it as well. but elsewhere, a lot of sunshine. any early morning residual cloud will ease away from the kent coast. the sunshine break through and temperatures should peak between 15 and 20 degrees in the north, highs of 25 in the south. that comes at a cost if you are a hay fever sufferer. certainly, across england and wales, we are likely to see high pollen levels through friday afternoon. but as we go into the start of the weekend, we'll have clear skies across england and wales. still a bit more of a breeze and a few isolated showers to the far northwest. but that means during the early hours of saturday morning, under those clear skies, temperatures will fall away to single figures in a few spots. so a slightly fresher, more comfortable night for sleeping. but we've got high pressure building in from the south and west, quietening things down. again, that low to the far north could still drive in just one or two isolated showers, but on the whole, it's a dry picture

for many of us through the weekend. we will be chasing cloud amounts around, particularly with that southwesterly wind. some cloud lapping onto west—facing coasts. here, not quite as warm, but these temperatures are where they should be really for this time of year, ranging generally from mid—teens in the north to the mid—20s in the south. then on sunday, scattered showers are likely to be continuing into the far north and west, maybe one or two through the irish sea — very fleeting, few and far between. we keep the sunshine for most. and once again, if you are planning any outdoor activities, the weather should behave itself then into next week. there is a potential for weather fronts to push its way into the far northwest. just how much rain we'll have in the southeast corner is really subject to question. here is where we're likely to see the driest of the weather, but a little more unsettled further north and west, and as a result, not quite as warm. take care. bye— bye.

live from washington, this is bbc news. talks for a ceasefire in the israel—gaza war are expected to continue into a second day. it comes as health officials in gaza report more than 40,000 people dead after ten months of fighting. and, the kremlin plots its response to ukraine's offensive into russia's kursk region. and five people are charged in the overdose death of friends star matthew perry. hello, i'm caitriona perry. you're very welcome. talks for a gaza ceasefire and hostage—release deal will reportedly continue into a second day. high—level delegations

from qatar, egypt, and the united states are in doha trying to broker a peace agreement between israel and hamas and which they hope will prevent a wider war. a us official said thursday saw a �*constructive�* first day of talks, and that they would resume friday. 0ur middle east correspondent wyre davies is injerusalem and spoke about the significance of the talks continuing. that in itself is a sign of progress but do not expect hostages to be released overnight. do not expect there to be a ceasefire overnight. these are very much talks about talks, about the framework to move on because the one thing that everybody in the region of fears is that the talks in qatar will collapse and that will allow iran or permit iran to follow through with its vow, with its promise to follow through with military action in response to the assassinations, assumedly by israel, which took place in iran and southern lebanon of a senior hamas figure and a senior hezbollah figure.

so one of the reasons why there is so much international