This is the BBC. This podcast is supported by advertising outside the UK. This podcast is supported by advertising outside the UK. This podcast is supported by advertising outside the UK. This podcast is supported by advertising outside the UK. This podcast is supported by advertising outside the UK. I hope you enjoyed the programme. I hope you enjoyed the programme. I hope you enjoyed the programme. I hope you enjoyed the programme. What did we know about Mercury?
I mean, it is a ledge that Copernicus never saw Mercury himself, but he used the fact that Mercury and Venus were always seen close to the Sun to infer that they actually revolved around the Sun and not around the Earth. And the fact that you never saw them on the opposite side of the sky like Mars Jupiter and Saturn to the Sun meant that their orbits were within the Earth's orbit. So it is part of the lines of evidence for building up this new model of the Solar System.
And out of that you get two predictions to do with Mercury and Venus. One is that they should show phases. So like the Moon shows a phase depending on how much the Sun lit side of the Moon you see. It is the same for the Sun and Mercury. They should show phases. And also sometimes they would line up between the Earth and the Sun. And you would see what is known as a transit where they are seen in silhouette against the Solar Disk.
So those are the predictions that came from Copernicus. And later on, so beginning of the 17th century, Kepler was refining this model, choosing to use elliptical orbit. And was able to make the predictions of the transit in much more detail. And he said the next transit will be one of Mercury on the 7th of November, 1631. And people with telescopes all across the Western Europe tried to look for it. And as usual with these phenomena it was cloudy.
There was one person Pierre Gassandien Paris who apparently saw the transit of Mercury on the appointed day. But it threw up a few surprises. First it appeared really small, much smaller than anybody had expected. In fact he had to observe it for a while to realise it wasn't a Sun spot. And the Sun that he was observing, it's more like a hundredth of the diameter of the Sun, rather than the tenth that they were expecting.
Observing the phases of Mercury didn't happen to a lot later, Galileo when he looked through telescopes. He saw the phases Venus. He couldn't see the phases of Mercury. They didn't happen to later on in the 17th century when telescopes were more advanced. Gabe, Dave Rothrie, it's 50 years since the space probe Mariner 10 reached Mercury. What did you tell us about the terrain?
Well, it was our first close-up view of the planet. I saw Mercury from my back garden on Easter Saturdays. It's nice to feel I maybe went one better than Copernicus. But you cannot see any details of the surface by observing from Earth. Mariner 10 flew past Mercury. And because its trajectory was quite cunning, it was put in an orbit around the Sun where Mariner 10's closest point to the Sun was a Mercury's furthest point from the Sun.
And it's all bit took twice as long as Mercury's orbit. So every time Mariner 10 went round the Sun once, Mercury had gone round twice and they met each other again. So we had three flybys of Mercury from one spacecraft before it ran out of maneuvering thrust of gas and couldn't work anymore. So we got our first close-up views. Unfortunately, of the same side of Mercury each time, because the same face of Mercury was lit up by the Sun.
But we saw wonderful details. It looked deceptively moon-like, there's no atmosphere. Creators everywhere, some densely crater, some less densely cratered areas. It's actually rather dark planet. It reflects less than 10% of the Sun light. It's actually a bit darker than the Moon. What it lacks is the bright areas. When you look at the Moon, you see bright areas and dark areas. Everyone Mercury is equivalent to the dark areas. There's no bright crust form to those Feltzbar minerals.
Which tells us something about Mercury's early history. The Feltz bars didn't float and rise to the top of the early magmarotion. But it's an ancient surface heavily cratered. One thing we didn't expect to find is great fault scarves crossing the surface. But the cratered areas are cut through by a scarament slope. Sort of linear, but they snake around a bit. They're called low-bate scarves.
This is where we think a thrust fault has cut up towards the surface. The scarament is the front of the thrust sheet. This is showing us that Mercury is contracting. We think this is because it's cooling down. It's all planets. The Earth is cooling down. But we don't see these contractional faults on the Earth. The Earth's whole outer shell is being shunted around by plate tectonics. But Mercury's got these scaraments. Two kilometres high.
Hundreds, several hundred kilometres long, snaking across the surface. So if you stood on the surface at the right place, you'd see this magnificent scarament going horizon to horizon. They're not cliffs, they're not that steep. But it still be quite a landscape feature. And it's very heavily cratered.
And if you remember views that we saw from the Apollo astronauts stomping around on the moon, they were stomping around in dust. For living footprints in the lunar dust, it would be just the same on Mercury. Almost no bedrock exposed because it's been pummeled by impacts. And as I understand it, Mariner showed us something of a giant impact crater. Caloris. What was exciting about that?
Caloris is the biggest impact basin that Mariner saw on Mercury. It's still the biggest impact basin on Mercury. It's about 1,500 kilometres across when Mariner flew past each time, only the eastern half of it was lit up by the sun.
And it's got a rampart around the edge. And inside it's got a relatively smooth area with relatively few craters are formed inside Caloris itself. So the floor is younger than the rim. It's been floored over by something that's moved out the original rough nature of the crater floor and loads of cracks in it.
And it's at the point on Mercury that gets hottest because the longer it should wear the caloris basin is where the sun is overhead at noon when Mercury is closest to the sun. Hence the name Caloris meaning hot. Are we any time preampal caloris? Yes we do. It's used as the benchmark for one of the age systems on Mercury. We think caloris formed about 4 billion, maybe 3.8 billion years ago.
4 billion years is half a billion years after the birth of the solar system. So half a billion years after Mercury itself formed. At that time on Earth there may have been very primitive single-celled life. But of course life on Earth didn't really get going until about 600 million years ago. So caloris is extremely ancient. But most of Mercury's history is in this time period longer than 3 billion years ago at least.
There's a lot of ancient history on Mercury heavily pummeled by impacts for same, impacting bodies that form the crater's visible on the Earth's moon but not preserved on the Earth because the Earth has been resurfaced by active geological processes. Emma Emma bonds, 50 years ago what did Mariner reveal to us about the magnetic field of Mercury?
So Mariner Tennis Davis already explained undertook 3 flybyes of Mercury over the space of about a year in the mid 1970s. And we really didn't know very much about Mercury's magnetic or environment or space environment. So during those 3 flybyes scientists were very surprised to see evidence for an internally driven magnetic field during that first flyby.
So most of the terrestrial planets, the four inner planets, there's the Earth obviously we know we have a magnetic field but Mars does not have an internally driven magnetic field today. It has the remnants of one that probably existed long ago. Venus doesn't have an internally driven magnetic field. And so I don't think anyone was expecting little Mercury very close to the Sun to have its own internally driven field.
Well there are some interesting consequences of that. So as the spacecraft flew past it saw this magnetic signature increased to a maximum when the spacecraft got closest to Mercury. So that was the evidence for a magnetic field being driven within the planet. And knowing that that planet has an internal magnetic field then tells you something about the interior of Mercury.
It tells you that there must be a liquid part in the iron core that can actually convect and allow electrical currents to flow in order to sustain a magnetic field for a long time. It forms a sort of protection around the planet to some extent. We have a magnetic field and that extends far out into space and protects us from the Sun's radiation.
For example and and possibly protects our atmosphere from being stripped away. But what Mariner found is that Mercury does not have a very strong magnetic field. In fact it's it's about 1% of the strength of the Earth's magnetic field. So very weak indeed which is interesting in itself. But what also happens then is that as the spacecraft flew past on those flybys it saw the evidence for the wider space environment which we call the magnetosphere.
So this is the sort of protective space environment that extends out far beyond the planet itself and into space around Mercury. And it contains and is controlled by Mercury's magnetic field and that magnetosphere forms in the flow of solar wind that leaves the Sun and flows throughout the solar system past all the planets.
And if those planets have a magnetic field there is an interaction between the solar wind carrying the Sun's magnetic field and the planets internally driven field to create this magnetospheric bubble protecting the planet. And then this century there was the messenger mission. What did that set out to do that was different from Mariner. So following the Mariner 10 flyby mission in the 1970s we then had to wait 30 years until the next spacecraft headed out to Mercury.
Well it takes a long time for any planetary missions to be established, to be accepted, to be built and to actually travel to their destination. So it can take a surprisingly long time. It also takes quite a long time for a spacecraft like messenger to arrive at Mercury because it actually has to spend quite a lot of time slowing down in order to get into orbit around Mercury.
So Mariner 10 was a series of flybys it didn't orbit the planet that messenger actually wanted to go into orbit around Mercury. So that's the key difference between those missions. And to get into orbit the spacecraft has to spend a long time going around the inner solar system using Venus and Earth and Mercury itself to actually slow the spacecraft down, put the brakes on and get into orbit around Mercury.
And that difference between those missions is it really allows a huge amount of extra science to be obtained because messenger went into orbit. It took four years to orbit around Mercury before the end of the mission so it was there between 2011 and 2015. And once you're in orbit the amount of science that you can do substantially increases compared to the Mariner 10 mission.
Sorry, you were too close. We got so much science from messenger because we were in orbit and we saw the whole globe for the first time. We saw the other half of a caloric basin. But another reason for why it took so long to get a mission to Mercury is it's a very hostile environment to operate it.
And often working out how to slow down and get into orbit when you get there you've got to survive the temperatures. When you're on the day side of Mercury you've got some 10 times as strong as it is here Earth because you're that much closer. And below you've got a planetary surface at 450 degrees. So your spacecraft's being cooked from both sides. And it's very hard to keep the electronics at a working temperature. So it's very complex designing a mission to get into orbit at Mercury and that will stay cool enough for the instruments to keep working.
And it's the smallest planet and the fastest. Can you tell us about Mercury's days and years? You're right, it's the fastest. It travels around its orbit at an average of 48 kilometers per second. And it only takes it 88 Earth days to go once around its orbit.
And it's worth mentioning that it doesn't travel in a nice sort of circular path around the Sun. It's quite is quite elliptical. It's a squash circle. And the distance between Mercury and the Sun ranges between about 46 million kilometers out to 70 million kilometers.
So that's the year 88 days. What is interesting is when you try and determine the rotation of Mercury, the planet itself, which defines things like the day. And as Dave has already said, when you look from Earth through telescope, you can't really see much in the way of surface features.
And it was always assumed that Mercury was what is known as tidally locked to the Sun. This is when you've got a very massive object like the Sun and something much smaller in orbit around it like Mercury and the Sun, like the Moon around the Earth. There's the way the gravitational tidal forces act to sort of slow down or accelerate the spin of the smaller body, such that it then synchronizes that the day and the year are the same length of time.
So with the Moon, that's why it always has its face towards us because it goes once on its axis in the same time it takes to revolve once around the Earth. So it was assumed that Mercury was tidally locked to the Sun and it was only in the mid 1960s that they determined how fast it was rotating. They did that by bouncing radar signals on the planet and receiving the signal back in the echo and seeing that the signal had been smeared out.
And this is due to the Doppler effect and due to the fact it was bouncing off a rotating surface and from the amount of that broadening of the signal they could work out, it was rotating once every just short of 59 days. Now 59 days is shorter than 88 days so it is not tidally locked to the Sun to always show the same face but it's got a different kind of resonance.
In that every two times it goes around the Sun, it orbits exactly three times on its axis so it's called a three to two resonance and it's just quite a peculiarity of Mercury in the Sun's system. Thank you, David Eberlary. Messenger revealed volcanic activity which was surprising. Why was it surprising? It was surprising. I'm Mercury is a small world, you don't expect it to retain a lot of heat. The outer core is still liquid, tells you something about heat inside.
It's not volcanic activity today as far as we can tell but there are two kinds of volcanic activity that we can see traces of. There's vast plains of lava, the smooth infill of the Chloris basin whose nature wasn't apparent really from the Mariner data but we see smooth plains all over the globe now and we're pretty convinced those are vast fields of lava. Just like the vast lava fields on the Moon that form the dark areas. So that's lava plains from big, enormous, really lava flows.
But there are also holes ripped up through these lava plains which are not impact craters then, they're near circular. It's rather irregular in shapes and sometimes they're overlapping and we're very sure that these are volcanic vents, volcanic explosions have ripped up through the surface rocks. So there's a lot of these surrounding these big holes which are tens of kilometres across and up to 3.5 kilometres deep.
Surrounding these to a distance of the order of 100 kilometres you've got these bright red, relatively bright red deposits with diffuse edges and that's material that's been flung out explosively by this explosion. The volcanic explosion is not only ripped to hold in the ground, the flung material out and the only way to do that is to have gas interacting with the hot rock with the magma and expanding with sufficient violence to fling out the fragmented rock.
So we didn't expect mercury to have volatile materials but it clearly has. So either the magma is coming up from depth bringing gases in it which come out of solution when the magma nears the surface just like conducts, I don't water come out in volcanoes on earth and drive explosions. Or else you've got volatile free magma reaching a volatile rich layer in the shallow crust as the magma nears the surface. So this is a piece of early evidence that mercury is rich in volatiles.
As far as we can tell these explosive volcanic eruptions were mostly 3 billion years ago but there are some that appear to be younger. It's very hard to date features on mercury surface but if you look at the impact craters the younger they are, the crisper they are, but less have been smeared out by debris being flung over them for other craters and so on. So some of the freshest impact craters have small volcanic pits ripping through them.
So those volcanic eruptions have to be younger but these relatively young impact craters said that most recent explosive volcanic eruptions could be as young as 1 or 200 million years and that was a surprise.
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Emma Emma buns at the heart of this we don't know how murky is formed. No we don't and we would like to because... I don't think I should guess not my field of expertise but we do want to know the answer to that question because mercury is the sort of most extreme one of the most extreme end of the planets in our solar system so close to the sun such a small planet and with some really interesting features.
So messenger has made some measurements which really challenge formation theories confirming for example that 85% of mercury's radius is iron core which is a much more substantial fraction of the interior compared to the how an earth did it form in order to to be like that. As well as the iron core being a substantial fraction of the radius as Davis just mentioned there are also volatile elements in abundance on the surface which was unexpected for a planet so close to the sun.
So those challenge the formation theories and the theories sit in a couple of different categories. One of sort of chaotic events that occurred so for example was mercury impacted by another large objects like itself in early in its formation phase so we're talking back at the very beginning of the formation of the solar system.
And was it hit by something which actually stripped off part of its mantle leaving it behind with a large core but there are problems with that theory because then you would not expect to see for example volatiles on the surface given given the energy involved in a collision like that.
And there are other theories that suggest mercury could have been in a sort of hit and run type incident with a very large object mercury being much smaller that could have actually knocked it towards the inner solar system and could explain its unusual characteristics in terms of its interior.
Or there are some theories that suggest there's more orderly things that occurred at the beginning in this formation. So for example that the hot solar nebula that mercury would have been embedded within actually evaporated part of the outer regions but again how do we see these volatiles on the surface.
Or was mercury embedded within a proto planetary disk that was already sort of sorted into being very metal rich and it just happened to form in a very metal rich environment creating that iron core.
So fundamentally at this point in time the data that we have so far really challenges the formation theories that exist and so we need more data more detail that messenger wasn't able to obtain for a number of reasons partly because it was in an elliptical orbit with the closest part of its orbit in the northern part of mercury's hemisphere.
And so it could only really obtain close measurements of the surface in the northern hemisphere and so we have yet to see all of the details on the composition for example of mercury surface which should really help us to understand and to rule out what some of those theories might tell us. Thank you Carl and can we come back to earth for a second.
How did Einstein make use of mercury before we get to Einstein we go back to Newtonian mechanics which were very successful at explaining everything in the solar system and indeed in the 19th century urban a very and John Kutcher Adams used the Newtonian mechanics the effect of the gravity of this undiscovered planet Neptune acting on Uranus and perturbing orbit to show that there was another planet there.
And the trouble was Newtonian mechanics explained everything the solar system except for the motion of mercury knows we said mercury goes around in a very elliptical orbit and that orbit pivots slightly about the sun with time that means that mercury never goes around in exactly the same orbit each time.
And if you measure this by looking at what we call perihelion it's where mercury is closest to the sun in its orbit it's just a little bit for it advances a little bit each time and it advances too much to be explained by Newtonian mechanics now all the planets do this in their orbits and it's because of the gravitational effect of not just the sun but all the planets combined.
The trouble is that mercury's advancement was too high it was a big anomaly that could not be explained so urban LaValle in 1859 I mean boyd with the success of discovering Neptune and predicting where it was tried the same trick of mercury said okay maybe these orbital variations are due to another planet which was tentatively called Vulcan and which would lie closer into the sun and would perturb mercury's orbit.
And so people went and looked for this tentative planet Vulcan some people claim to see it but it was difficult to know whether there may be a scene a transit of the planet or maybe some tiny sun spots crossing the surface of the sun but more importantly there was a whole succession of total solar clips is the end of 19th century beginning of 20th century when the glare of the sun is blotted out you can see all the interior planets there was no sign of this planet Vulcan.
So it was discredited but nobody could still explain the anomaly of this procession of mercury until Einstein combined gravity and special relativity in 1915 and one of his major successes was to be able to reproduce mercury's procession exactly and this success was one of the first ways that his work came to be accepted. David what way does the geology of mercury appear to be similar to other rocky planets in what ways is very different from other planets.
Well I spent a long time saying to people mercury is not the moon but actually it's most similar object to the moon is not a planet but to a geologist it's a planetary body lots of craters lots of areas formed organically but it has no atmosphere so it's not like Mars or Earth or Venus.
But in all the rocky bodies in the solar system we see the same process is blended together in different proportions and mercury's got these big faults we've already talked about with one slab of crust being thrust over another but the movement there is just a few kilometers whereas on the earth because of plate tectonics it goes on for thousands of kilometers and never really stops.
And then we have lots of erosion on the earth so ancient features are destroyed we don't see the ancient impact grades on the earth have been eroded by wind and water or by the action of plate tectonics mercury preserves the ancient record we don't understand the inner solar system unless we look at the evidence that's on all the planets in total we have to compare everything to understand what's what's going on.
What's just going to say is it fair to say that mercury is like the moon on the surface only though because from what Emma was saying earlier about the interior structure of mercury that is in itself more like the earth. Well yeah, mercury is a much thinner rocky carapace than the earth does but it's only superficially lunar only superficially moon like as well because everywhere on mercury's surface we think now has formed volcanically.
It was pretty clear from the detailed observations by messenger but everywhere on the surface has been flooded by lava flows. We can see ancient craters have been partly flooded and so on. At mercury doesn't have the contrast between the dark areas and the light areas that the moon has.
The reason on is but on the moon when the moon was very young the way out of part was molten we call it a magma ocean and as that cooled down some light colored crystals I'm in a called felt spa was able to rise bob towards the surface because it was buoyant and that's the bright lunar highlands but were later flooded by by lava flows on mercury mercury is rocky part is deficient in iron all the iron has gone into the core and that meant that mercury's magma ocean.
The ocean was lower in density than the moon's magma ocean so when these felt spa crystals crystallized out the magma ocean they couldn't float face sank and the only thing that would float on mercury that we can think of is graphite carbon so mercury's dark as of carbon that rose towards the surface. Fascinating have these properties get blended together in different proportions to me as a geologist you should never look at just one planet you should always consider the others as well.
So what's been learned since messenger what can you say about mercury's magnetosphere and its magnetic field. The first thing that messenger found about mercury's internally driven magnetic field which is unusual is that it is offset towards the north so you would normally expect the magnetic field to be generated sort of centrally in the core of the planet but for mercury the data suggested that the
field is actually the center of the field is offset by 20% of the radius of mercury so that that's unusual and again leads to some scratching of heads around how that magnetic field is being generated in the core. The second thing that messenger was able to find by spending four years in orbit is just really to measure the magnetosphere and how it behaves over time and what what was found is that
mercury's magnetosphere is extremely dynamic in some ways perhaps this is no huge surprise mercury is very close to the sun compared to the earth and therefore the solar wind and the interplanetary magnetic field is much more intense and mercury is sitting in a strongly varying pressure of solar wind and also strength of magnetic field and those are important factors for the magnetosphere.
So a key process that occurs in the earth's magnetosphere is as a cycle of opening and closing of magnetic fields of the planet and connecting out into the solar wind and that circulation at the earth takes about 10 hours but at mercury it takes one minute so it's a sort of extreme version of driving of the magnetosphere.
And then the other thing that was also found was that this large iron core actually also plays a really interesting role so what messenger discovered was that as the solar wind gets stronger in intensity during for an example the passage of a coronal mass ejection from the sun as that pressure pushes on the magnetosphere it actually generates through electromagnetic induction an additional magnetic field within the core of the planet that pushes back and holds off the solar wind.
Thank you. Carlin there may be water on mercury we understand why might that be and what does it mean? Well first of all it's interesting there's a water I seen on mercury at all I mean there are indications of this from radar signals but it was really confirmed when messenger was an orbit around mercury.
And the thing about mercury's rotation is that the axis it rotates about is perpendicular to its orbit so it's not tilted like the earth it doesn't have seasons and that means you can have regions around the poles and we're here we're talking mainly about the deep craters around the North Pole that are in perpetual shadow they never get that blast of sunlight
and it's quite possible that you can have water ice despite this being an enormously hot surface to the planet that you've got the sheltered regions deep North Pole craters where it has been we don't know how long it's been then perhaps it was delivered by ice rich asteroids and comet stream the early heavy bombardment period so billions of years ago it's just curious that it's there at all.
Does it lead to anything? Well it's another strange fact about mercury in terms of going there it's hard enough getting as Dave said earlier it's hard enough getting spacecraft to function in that hostile environment the last thing you do is send any people there. Dave what do we learn from the hollows that seem to cover the base of mercury these great craters we've just talked about one of the biggest what's going on there?
Well the hollows were another part of a volatile story you shouldn't really think of them as craters hollows are areas on the floors mostly of craters when we flew past with messenger before we got into orbit we saw these bright regions on crater floors when we got into orbit we had enough detail to see that actually in these bright regions what you've got in detail is steep sided flat bottom depressions only about 10 or 20 meters deep and hundreds of meters across
where the surface level is just dropped down materials being eaten away and they're surrounded by these bright halos we saw could see them from a distance and it's as if the top 10 or 20 meters of the surface is just dissipated away into space somehow and that's very hard to explain you can't turn rock into vapor without breaking all the chemical bonds and letting it drift away element by element you know atom by atom and so what happened?
Well it seems to happen in lower latitudes rather than pole latitudes it's slightly concentrated at areas where it's known when mercury is at its closest to the sun so there's a link to temperature or sunlight it's only a weak link though so the contenders are it's just heat from the sun it's for sun's radiation ultraviolet photons can break chemical bonds or it's some it's for solar wind now
as Emma said the solar wind is held off by mercury's magnetosphere but in times of solar storm it is depressed down to the surface and magnet of pause is down below the surface and the solar wind can impinge upon the surface sometimes we think so it could be charged particles from the sun breaking chemical bonds or it could be micrometer rights because even tiny objects don't get slowed down as they arrive at mercury because there's no atmosphere so there's all kinds of ways where you could break chemical bonds and that stuff drift away
but we still don't understand ever whole top 10 or 20 meters has gone without leaving a residue behind it's very mysterious and we think hollows are still growing today this is the active geological process on mercury the slow recession of each cliff like edges of these hollows at rates of you know a millimeter per thousand years or something but it's still going on today
thank you Emma there are x-rays coming from the dark side mercury what I'd use as a cell running they've mentioned earlier some measurements that messenger made from the x-ray spectrometer which help us to understand the composition of the sunlit side of the planet so that's where we would expect to see an x-ray emission and that's a process that we can use to work out the elemental composition of the surface of a body that's illuminated by the sun
on the dark side of the planet though you would not necessarily expect to see an x-ray emission coming from the planet however messenger measured x-rays coming from the surface of mercury and when we looked at all of those x-ray emissions from the surface at the end of that mission and put them all together in a map we found that the x-ray emissions were coming from bands in the northern and southern hemisphere that were centered on that offset magnetic field that I that I mentioned earlier
so bands of x-ray emission that appear to be in the north and in the south but shifted towards the north just like the magnetic field is so that tells us that that x-ray emission must be organised by the magnetosphere and by mercury's magnetic field so it's likely to be the result of charged particles probably electrons impacting the surface and producing x-rays that messenger has measured
now this is interesting because if we think about the Earth when the magnetosphere interacts with our planet it interacts with the top layers of the atmosphere the ionised part of our atmosphere known as the ionosphere and charged particles from the magnetosphere move in electric currents that run parallel to magnetic field lines
and accelerate charged particles into the atmosphere and cause it to glow and that we know as the aurora but we don't have an atmosphere at mercury we don't have an ionosphere so the particles it seems are interacting directly with the surface of mercury and producing this strange x-ray emission which I can only describe as a raw roll like
I think describe it as an aurora because there is no atmosphere but this tells us something quite unusual in the solar system about a magnetosphere interacting directly with the surface of the planet thank you Dave, I'll throw the moment is the Bebid Colombo emission and what is that and why is it so significant?
Bebid Colombo is a joint European Space Agency, Japanese Space Agency, mission to mercury it's had three flybys of mercury already one more coming up in September two more flybys at the end of the year and then the next time we come to mercury we'll be going slowly enough to get into orbit
and we separate the Japanese orbit of flys-free the European orbit of flys-free and we can really start doing science there's a British led instrument on there which embers the principal investigator which will look at the x-rays will get the elemental abundances at the surface
I said we don't know what the volatiles are in the hollows or what the volatiles are in the explosive volcanic vents we don't know what minerals these elements are bonded in we'll get that from the thermal infrared spectrometer and the visible light spectrometers
we'll get compositions of the surface and stereoscopic images and more detailed finer resolution images will really understand the geology of mercury and its compositions much much better we'll understand the magnetosphere I mean Emma you've got wonderful things from magnetosphere yeah I think one of the things to say about Bebid Colombo in terms of the progression of our exploration we go from fly by mission and 50 years ago to the first orbiter messenger between 2011 and 2015
and now Bebid Colombo's days just described is a two spacecraft mission so this allows two vantage points within the system one orbiting close to mercury one in the larger elliptical orbit so there's no compromise between surface measurements which will be able to get equally in the north and south of the planet surface and a spacecraft that is dedicated to studying the wider space environment and magnetosphere
and that solar wind interaction so we expect our knowledge to hugely increase in terms of using those two spacecraft together to study those the solar wind and magnetosphere interaction and those induction magnetic fields that we see when there's strong solar wind driving of the system there's never been a spacecraft measuring the magnetic field the planet into places at the same time before Bappy will be absolutely groundbreaking with that yeah Karlin would you hope we'll come from this
this mission is going to just expand on a lot of the questions we have that we've alluded to in this program did it have this chaotic event early in its formation or is it a byproduct of where it wasn't the solar nebula right at the beginning the formation of the solar system and what Dave said is right you never learn anything from just studying one planet
you need different types of planets to look at to contrast with the mercury is certainly a case of extremes that will allow us to understand our own Earth moon system and other planets in the solar system better I'm personally looking forward to the fact that we have built an instrument which is on the payload it's the only UK instrument called the mercury imaging x-ray spectrometer and we're going to be able to make a significant contribution to understanding both the geochemistry of mercury
working out what that surface is made of in the greatest detail that we've been able to see because it is an imaging instrument specifically and we're also going to be able to look at this night side interaction between the magnetosphere and the surface and these auroral-like x-ray missions so there's a lot of exciting data to come from that mission well thank you all very much thanks Emma Bunce, Dave Rothery and Karlin Crawford and our studio engineer Bob Nettles next week
it's Thomas Wyatt and I'm basit up a Henry VIII and the alleged lover of Ann Bullin and sometimes called the father of English poetry thank you for listening and the in our time podcast gets some extra time now with a few minutes of bonus material from Melvin and his guests well I'd like to be doing an exp section is to ask what you would like to say to do enough time to say would you like to kick off that Karlin?
well one thing that would be nice to say is the name Beppy Columbo of this mission is actually named for an Italian scientist Giuseppe Columbo who in 1970 was the person who first showed it was feasible to reach the inner planets using this gravitational assist mechanism that Emma described
and this was first proven to be the case for Marinor 10 so it's sort of celebrating his achievement because the difficulty is to break the spacecraft enough in order to fall in but not get captured by the sun if you didn't do this gravitational assist it would require an awful lot of fuel
so this made a very economical way of sending missions into the inner solar system that worked not only getting to Mercury but having repeated flybys of Mercury Giuseppe Columbo also said if you do this right once your spacecraft has gone round the sun once
Mercury will have gone round twice and you can meet it again and get fly by after fly by and that was great and did you know that the messenger's trajectory to Mercury was designed with similar cunning by Chen Wang Fan from JPL who said what you need to do to get into orbit around Mercury
and have repeated flybys of Mercury and first of all you have the same kind of relationship with Mercury that Marinor did with a spacecraft goes round the sun once and Mercury goes round twice that's a 2-1 resonance when you slow down into a 3-2 resonance
then a 4-3 resonance but eventually when you creep up on Mercury the relative speed difference is so slight that you can easily get into orbit and that's what messenger did and it's kind of what theppe Columbo is doing as well and Ion drive helping it slow down a lot of the time as well
but Chen Wang Fan is in the tradition of Giuseppe Columbo in designing trajectories which get you very cheaply because you can't fill the spacecraft with rocket fuel and switch to a halt if you do that you've got no mass-free of scientific payload and you won't learn anything It is fascinating that to get to a planet that is so relatively close to us in the solar system it's actually a very complicated process to do it successfully Is that because of the separate speeds involved?
It's because you've got Earth going round at 30 km per second you have to lose that optical velocity so you're breaking the spacecraft and then speeding it up whilst also maneuvering it into the right position it's a very complex journey And of course you've got the sun at the center and the gravitational pull of the sun is overwhelming when you get close to Mercury So that's a real challenge but it is a surprise isn't it?
It takes approximately the same time for Beppe Columbo to get to Mercury as it is going to take the Jupiter system in the outer solar system So for different reasons, obviously in that case, in the juice case that spacecraft needs to speed up to get out to Jupiter but coming into the inner solar system it's all about slowing down and making sure that you don't go straight past your target Why are you too short-long?
So that Beppe Columbo was launched in 2018 and it has a seven and a half year journey to the inner solar system If it went in a perfectly straight line to go between the Earth and Mercury it would take just a few months to get there Trouble is, it wouldn't stop
and it would just keep going and be accelerated into the sun which would be very disappointing for everybody involved So what you have to do is actually send your spacecraft on a bit of a circuitous route around the solar system multiple times
doing actual gravity assist flybys of the Earth, then Venus, and then Mercury six times actually using those bodies and their motion about the sun to slow the spacecraft down enough that it can get captured weekly captured into orbit around the smallest planet in the solar system
which is very close to the star within our solar system so it's extremely challenging We are going to have a lot of new features on Mercury that are going to need names I mean we're making geological maps of Mercury at the moment across the whole of Europe using messenger data to get the best geological maps we can to set the context for what Beppe Columbo will see but a lot of places that are going to need names which is all controlled by the International Astronomical Union
Creators for example are named after artist painters musicians people that have made their name in the arts and a lot of the names were given half the planet when Mariner 10 flew by and then the rest feel half of the globe in the past 15 years since messenger
but if you look at the statistics, mostly cis white males there's only less than 20% of the creators on Mercury are named after female artist painters and musicians so we'll have to try to redress the balance there and I've got PhD students taking upon herself to look into that
and it's taken the IOU to task so but we're naming it a serious business because we want people to feel included, we want to see that they're represented out there Do you think that learning more about Mercury gives you access to a wide of your about the creation and development of the universe?
It certainly gives you a more flexible view about the kind of planets that are out there I mean we're now discovering planets around other stars in the hundreds and their thousands and there's a huge diversity in them
and actually understanding some of the diversity just within our own solar system is a stepping stone to really appreciate in what kind of variations there are in planets out there A lot of the exo-planets, planets around other stars that we've been discovering over past couple of decades
are really close to their stars even closer to Mercury's but nonetheless Mercury is the closest example we have to a star so we can learn quite a lot by studying it I mean we've got planets with atmospheres made of rock basically which are really really close to the Sun but Mercury's the best analog we've got And the easiest to study?
The easiest to study, yeah I always think the nice thing about the solar system is that you actually can go to your target of interest and make observations in situ rather than only being able to make observations remotely
so whilst we are in a solar system which could be completely unique and different to every other planetary system out there it is the one that we're in and therefore the one that we can use as a scientific laboratory to study all of these interesting different things that we've been talking about
How likely do you think it is that there are other systems like the solar system around this multi-million representation of stars etc that you've alluded to We're finding Earth like planets in terms of mass, aren't we now? Solar system doesn't have water worlds bodies for five times Earth's mass I don't know, just many Neptune's but we've found there's quite a diversity of planetary systems that most planetary systems around red dwarves aren't they?
There are an awful lot of them around red dwarves and a lot of the exoplanets we find look nothing like ones we've got on our solar system but there is a bias because up to now it's been easier to find the bigger, more massive planets that are closer to their Sun so we were biased planetary systems that didn't look anything like our own just by our detection methods and I think now the modern trance of instruments are going to start finding smaller objects, more Earth-like objects
maybe even one day mercury sized objects and get a bit more of a sort of representation of the range of stuff out there How's your cope with the idea that the what's out there might be infinite?
I don't think about it very often That's one way to go It's just some, well maybe you two have a different view but it is something you just take on board and accept and if that you're a scientist you learn not to think in linear terms but in logarithmic terms and I think that is one way of appreciating the scales involved When we're looking for exoplanets we are really restricting observations to quite a small part of our own galaxy
Let the whole galaxy let alone all the other galaxies out there so planetary scientists don't have to grapple with the infinite in quite the same way but other kinds of astronomers do Dave do you think it's possible now or ever to land on mercury?
Oh eventually it will be, we've talked about how difficult it is to get to mercury travelling slowly enough to get into orbit about mercury If you want to land you've got to touch the surface of mercury travelling now more than two or three meters per second when you get there
so that's even more slowing down So it's difficult to do, you've got to be very careful with it and carry plenty of fuel to retro rockets to slow you down and you've also got the land in the right spot If you land on mercury in the daytime this spacecraft is going to fry
If you're doing a surface of 400 degrees and you can't dump your heat it's hard enough to keep cool when you know it when you're on the surface it's worse There are desk studies being made of how to get a lander onto mercury and choosing where to land maybe on mercury's most ancient crust If you were to land at sunset you would have 88 Earth days of darkness before the sun rose and it then became very hot So what you need to do is have a spacecraft that can land, operate during the mercury night
keep yourself warm with battery pack because the temperature will drop to well below minus 100 centigrade by night on mercury It's easier to keep yourself warm and keep yourself cool So you've got three months that you can work on mercury during one more mercury night before the sun rises and cooks your spacecraft Choose your spot carefully and choose a science you can get done in three months before you die Another complication is that mercury doesn't have an atmosphere
When you think of landing probes and Mars which comes quite commonplace nowadays the atmosphere plays an important breaking effect You can slow the spacecraft down so it can land on the surface You can't use parachutes to land on mercury Silent illness and the producer is about to make his entrance Does anyone want to go to your coffee?
Tea please Tea please I'll have a tea, yes please Thank you very much In our time with Melvin Bragg is produced by Simon Tillerson and it's a BBC studio's audio production I'm Helen Lewis and I have a question What links? Family WhatsApp dramas I flounced off after someone made a particularly ignorant comment Russian State propaganda It's very good platform for spreading all this propulsion position And a woman who married an AI 100% I would never go back to humans ever, ever again No idea?
Well, that all examples of how instant messaging has changed the world Find out more by joining me for my new BBC Radio 4 series Helen Lewis has left the chat on BBC Sales We wondered the same thing So we made Biharth, a better formula for formula Learn more at biharth.com Now for 20% off-site wide