The Supermassive Podcast - 26: The Marvellous Moon

Episode Date: February 25, 2022

Who doesn’t love looking up at the moon?! Joining Izzie and Dr Becky, Professor Katherine Joy from the University of Manchester explains what past and future lunar missions can tell us, and Dr Megan Barford from Royal Museums Greenwich gives us a tour of two stunning moon maps from the 17th century. Plus, Dr Robert Massey takes on your questions and shares his top tips for moon-gazing. See the moon maps here... By Riccioli & Grimaldi, 1651: https://www.sciencephoto.com/media/1179815/view By Cassini, 1679: https://www.sciencephoto.com/media/1093522/view The Supermassive Podcast is a Boffin Media production by Izzie Clarke and Richard Hollingham. 

The moon is essentially a fossil. It's only three days away if you can get a rocket big enough to get there. And it went right up to including winged man bats. The toenail moon, unsurprisingly, is not an official name. Hello and welcome to the supermassive podcast from the Royal Astronomical Society with me, Izzy Clark, and astrophysicist Dr. Becky Smithers. Yeah, this month it's all about our mate the moon. And I feel like Izzy, I want you to put in like despicable me, like the moon, because I feel like it's only appropriate now that we're finally

on this episode. We've got lots of questions to ask. Where did it come from? What do we know about it? And what is still left to discover? I know. I mean, it's only taken us two years to get to this point, but better late than never, right? So coming up, Professor Catherine Joy from the University of Manchester will be telling us what past and future lunar missions can tell us. Plus, I spoke with Dr. Megan Barford about some of the moon maps

that we can find in the Royal Astronomical Society's library. And obviously, Dr. Robert Massey, the Deputy Director of the Royal Astronomical Society, is here with us as always as well. We talked a bit about this in our December episode, Robert, where we talked about eclipses, but you literally wrote a book about the moon. So we have the best person here. about eclipses but you literally wrote a book about the moon so we have the best person here yeah i did with my with my uh my friend alexandra loska who is an art historian and we loved this project i have to say there's so much actually that's so wonderful about it not just looking at it in the sky but also the way it resonates in culture and i think some of my favorite things connected with it are well one you can see for yourself quite soon the nebra sky disc

which is the beautiful bronze and gold disc that was discovered dates from 1600 bc so nearly 5 000 years old 4 000 years old discovered in germany in 1999 and it'll be on display in the world of stonehenge exhibition in the british museum as it happens just as this podcast goes out for about six months fantastic and I also really like the kind of wacky things like there was this moon hoax story not faking moon landings we all know those happen please don't email us about this but where the New York Sun in the 1830s ran a whole series of articles a paper that no longer exists about John Herschel who was the son of one of our founders William Herschel and he was working in southern Africa in the Cape of Good Hope observatory and he the stories

claimed he was discovering exotic life on the lunar surface using a preposterous telescope with a seven seven foot lens and it went right up to including winged man bats. Now, it's wonderful. It's a brilliant story. And then my personal favourite feature on the surface is something called the Moon Maiden, which was drawn on Cassini's first scientific map of the Moon in the second half of the 17th century. And I thought this was just an embellishment. I thought Cassini, old softy, drawing his wife and or lover on the surface of his map. But it turns out that it really does look like that. So if you get a small telescope and you look near Mare Imbrium,

which is one of the big basins, there's a feature called Prometorium Heraclides. And with a small telescope or a smartphone camera, it looks like a moon maiden. It looks like a woman with long hair. It's extraordinary. I thought this is just an embellished drawing, but no, it really does look like that. So I love looking at it. I think it's hair. It's extraordinary. I thought this is just an embellished drawing, but no, it really does look like that.

So I love looking at it. I think it's fantastic. That's amazing. I mean, I know most people would just be impressed if they get out the telescope. I'm more impressed by the fact that you could pronounce those words. I would have butchered that.

I'm looking at them in the script like, ah, no, not gonna try. But can we start with the basics though robert i mean how old is the moon and when was it formed and how do we know that it's it's a little bit younger than the earth so the the most popular the most accepted idea for the formation of the moon is it's about 4.425 billion years old that was refined by about 85 million years very recently. About 100 million years younger than the Earth. And the idea is that something the size of Mars,

this is in the era of the solar system, bear in mind with loads of stuff flying around when the planets have just formed and there's still an enormous amount of things flying around. Something the size of Mars hit the so-called proto-Earth, right? So the Earth before it was the Earth, sometimes called, and the object I think striking, it was called Theia.

And that cataclysm, that unimaginable collision, you know, planets smashing together, left behind the Earth we have today. Well, it wasn't like the Earth we have today, but it would become the Earth like today with a very dense iron core left behind. And then we get a strong magnetic field. It becomes very helpful for life, actually,

in protecting us. And then the debris that was thrown out by that the idea is the moon coalesced out of that over over you know probably over decades that you saw this cloud of debris around what was left of the earth and it coalesced together gravity pulled it together and you ended up with a much less dense moon left behind and one of the big clues for that came from the Apollo missions and the rocks they returned to the earth where the ratio of the different types of oxygen the so-called isotope ratio so imagine you've got oxygen you've got slightly heavier and slightly lighter atoms of oxygen and the ratio of those in moon rocks is the same as we find on earth so it really strongly supports the idea that the two bodies are connected it is a i mean

it's a great theory i absolutely love it and the one thing i i love the most about it is it means the earth at one point looked a little bit like saturn because it had this huge debris disc around it that then formed our moon and i'm you know i'm kind of sad it formed the moon i'd quite like instead but anyway cheers robert we'll catch up with you later in the show to take on some of those listener questions okay so that is the age and the formation of the moon covered but what else do we actually know about our rocky neighbor I spoke with lunar geologist professor Catherine Joy from the University of Manchester who started by telling me about the structure of the moon and what it was like billions of years ago. We're still asking these questions about what the interior structure of the moon is like and how it actually is similar and different to the other rocky terrestrial planets

like the Earth, Mars, Venus and Mercury. We think that the moon's core is relatively small. And this is sort of our understanding of the size is really dependent on understanding its early history. So after the moon formed, we think that the early phase of the moon's history is dominated by what we refer to as the lunar magma ocean phase. It sounds quite dramatic, but it basically means that we think that the moon was essentially a big ball of molten magma. And this molten magma cooled and as it cooled, different crystals or different phases precipitated out of this kind of early hot magmatic body. And the dense one sank to the interior to form that core and the mantle. And then the lighter material that formed kind of later on in this early phase actually floated up kind of out of the magma towards the moon's surface.

And this is the material that gives rise to those white areas on the moon we call them the lunar highlands but that's why the moon is white because it formed in this early phase of the moon's history and then if you look at the moon as i'm sure many of us have done then you see like these black patches which are what we call the seas so can you explain what those are and what do they tell us about the moon? So after the moon gained this crust, this sort of white area of the highlands, it was heavily bombarded by things hitting the moon's surface, asteroids and comets that were migrating around in the inner solar system,

striking the surface, carving out massive basins, hundreds to thousands of kilometers in diameter these created topographic lows so lowlands across the surface of the moon and then slightly later on we think that the moon's interior partially melted so we had magmas that were generated which these magmas migrated up through the moon's crust and erupted at the surface as volcanoes much like we see in places like Hawaii or Kilauea and also in places like Iceland it's a very similar type of volcanic activity fire fountaining and it's those that give rise to those black dark seas that we see

infilling these big impact craters on the moon yes so why don't we still have those today do we know what happened so we had volcanism today? Do we know what happened? So we had volcanism on the moon. We think, well, we constrain this using some of the samples that we've collected from the moon itself. And we've also looked from orbits to sort of calculate the ages of some of these surfaces. And we think that the moon's volcanic activity lasted from about 4.3 billion years ago, which is quite a long time, to as recently, certainly as 2 billion years ago. And that new age, that youngest age has been constrained by a very recent mission that China has performed to bring back some of these volcanic rocks here to Earth that we've been able to age date. But the moon may even been about as active as 1 billion years ago, which is really remarkable for such a small planetary body,

which you imagine would run out of energy and heat to kind of generate this melting in the interior. It's actually pretty recent. And so it's fascinating to ask the question, what drove the moon's heating for such a long period of time? And that's something we'd really like to understand in the context of terrestrial planets diversity so you know how does that differ from mars and venus and all these bigger bodies in the inner solar system obviously there have been missions to the moon but what have they collected and you know what have they told us that helps better our understanding of the moon yeah so the moon's fantastic is that you know it's only three days away if you can get a rocket big enough to get there um but we've sent this you know a plethora of missions to the moon

it's quite incredible all you know all the way from the earliest missions that sort of fly by missions that took photographs through to really sophisticated orbital mapping missions pointing a huge array of different experiments down at the surface where we've looked at the moon's chemistry from orbit we've looked at the topography we've looked at the moon's chemistry from orbit. We've looked at the topography. We've looked at the mineralogy. We've even taken high resolution photographs where you can see things on the moon's surface down to 50 centimetres in size. Incredible detail. So we've got this, you know, this global data set of remote sensing data, which has been, we're able to compare all of these to help generate and test our models but for me being a geologist and being a person that loves studying rock samples the best

thing is is we have the samples that have been collected from the moon and these include the nearly 400 kilograms that were returned by the Apollo missions from the six locations on the near side we have about 300 grams from the Russian emissions that visited the eastern limb of the moon. And then most recently, just a year ago, or just over a year ago, we have the new Chinese samples that returned 1.7 kilograms of moon rock from the near side. And so this collection is really valuable where we can take small pieces and put them in our machines and age date them, measure their chemistry, their isotopic history, to piece together our ideas of how the moon can evolve through time. But we're really not satisfied. You know, we really want more samples because we've

only visited the near side. We've never been to the far side of the moon with a lander mission that can bring us back moon rocks as of yet. And so that's what I'm, you know, we're really hoping that the next generation of lunar explorers is going to do for us and I think it's it's the far side of the moon that that has been spoken about quite a lot recently when we're talking about missions so what is it about the far side of the moon that we want to explore what's you know what's the attraction I suppose so the attraction is is we've just not really been there. Yeah.

Fair enough. It looks very different to the near side. So the near and far side of the moon, when you look at a picture of comparing the two hemispheres, the far side of the moon actually has very few of those mare basalts, those seas that you mentioned earlier on. It seems to mostly be white in appearance and its surface is dominated by large impact craters, one of which is huge. It's actually the biggest impact crater in the whole of the solar system, two and a half thousand kilometers in diameter. And so really what we want to do is we want to get into that impact basin, look at the rocks that are there to test whether it could have excavated down into the lunar interior, into this mantle, kind of lower material below the crust. And that can inform us about kind of the moon structure. Yeah. And, you know, with any mission and exploration in space comes the question of water.

Is that something that we're looking for on the moon or signs of it in whatever form that takes? that we're looking for on the moon or signs of it in whatever form that takes? So the water is really critical for human exploration because eventually, you know, in tens of years time, we're going to hopefully learn to live off the land wherever we go and utilise reserves and reservoirs of water to do things such as support bases that we build for sustainable living on planetary surfaces and also eventually to convert into rocket fuel to make it easier to travel back and forth between different bodies in the solar system so water is critical now on the moon we've always thought of the moon as a very very dry body and for the vast majority of areas that is true but we now know from again

some of the analysis of samples that have been returned from the moon and also from some of our orbital remote sensing data, that there's places on the moon that may have elevated water concentrations. And we even think in the polar regions, in impact craters that never see the sunlight, there could be reserves of icy material mixed in to some of the local soils. And these icy reservoirs could be really interesting places to go to but but again we we need i know you keep saying we don't know anything we really don't know how much is there and actually a lot of the the upcoming exploration is really targeted to ask that question what what is in those craters how much is there what is it made of is it all water or is it in the other form of volatiles? And then eventually, how can we tap into that to

use it in a sustainable way? Thanks very much to Catherine Joy from the University of Manchester. So there's quite a lot to unpack there. But Becky, hearing about the structure of the moon actually got me thinking, if it's had this molten core, do we know if the moon ever had a magnetic field yeah i mean it's a it's a great question because i mean theoretically if it had a molten core it's got moving electronic charges which produces a magnetic field right and so yes it it could have actually had a magnetic field at some point in the past we don't it doesn't anymore presumably that core has solidified and those charges have stopped moving around what's really cool is that you know some of the evidence that we have for it having a magnetic field in the past comes from the Apollo mission lunar rocks that were brought

back the robot was talking about earlier as well and you sort of see the alignment of various you know metals that suggest there was a magnetic field you know around about four billion years or so ago you know right after the moon formed but the big debate that's still ongoing is whether actually the moon did have a magnetic field or whether you had these sort of like little bursts of magnetic field being created from various different impacts by you know when there was this huge heavy bombardment in the early days of the solar system you know in those collisions you could generate these magnetic fields that would cause this alignment and i mean that's what's caused it rather than the moon as a whole having a magnetic field so we're not entirely sure we'd need more moon rocks to know you know we need a

bigger sample to actually study so from different places on the moon and also of different ages as well to try and pinpoint you know is this something that happens sporadically then it's probably impacts whether it was really concentrated on one happens sporadically and then it's probably impacts or whether it was really concentrated on one age of rocks, right? And then it's probably a global magnetic field. So we've got a bit of a limited picture from the Apollo moon rocks. So maybe that's the reason to go back.

Yeah, absolutely. And can studying the moon tell us anything about Earth's history as well? Yeah, I mean, the moon is essentially a fossil, right? That can tell us about earth and moon shared history because there's no plate tectonics there's no weather right to to make those older rocks disappear those older rocks are still there they've not been destroyed like they have been on earth and you know it's why the astronauts footprints will all still be there in you know

hundreds of thousands of years as well because there's no weather on the moon so because it's this sort of like almost like perfect fossil you can find out you know when the you know when we had a larger amount of impacts in the solar system when the impacts were impacting i guess you know and that'll be true for both the moon and the earth as well we one of the really cool things that we could we could do as well by studying moon rocks and studying the moon as sort of like this fossil is work out if water was brought to the earth and the moon system by comets and asteroids when did that actually arrive as well can we see that in sort of the rock history on the moon that's lost to us on earth um even there's also one possibility as well that you know if you had a lot of impacts on the early earth that would have thrown up especially there are very big impacts like ejecta out into space right if you imagine right a big impact and it throws stuff back out that

ejecta could then land on the moon so you could have very old earth rocks that no longer exist on earth because they've been destroyed in plate tectonics you know just turned back into lava or whatever um you know that are now on the moon and we could find on the moon. So people are always searching in the Apollo samples for something weird that shouldn't be there that, you know, doesn't belong with all the moon rock as well. So we're always keeping our eyes peeled because, you know, no idea what the moon could teach us really, what surprises it might have in store. Who doesn't love looking up at the moon? And in the 1600s, it was quite the thing to do. The telescope had been recently invented, and so astronomers turned their attention to study our bright neighbour.

This created various moon maps, which are great works of art that documented the craters that are etched onto the moon's surface. I spoke with Dr Megan Barford, Curator of Cartography at the Royal Museums Greenwich, who told me about some of the moon maps in the Royal Astronomical Society's archive. So today we're going to be looking at two maps, one which was published in 1651 by Jesuit astronomers Giovanni Riccioli and Francesco Grimaldi, and one that was published a bit later in the 17th century, so in 1679, by Jean-Dominique Cassini. So let's start with this first one by Riccioli and Grimaldi. So I'm looking at it now online, obviously we're doing this over

Zoom, and it's incredibly detailed from something from the 1600s talk me through it i guess one of the first things to say is that this map is part of a book um the novum almagestum so the new almagest which richioli published as a kind of new encyclopedia of astronomy and one of the really important things in the 17th century to include, one of the kind of novel things to include, was a map of the moon. The telescope had been invented in the early 17th century, so the first recorded evidence of the telescope we have is from 1608, and it very quickly spread throughout Europe.

Astronomers were fascinated by the possibilities and because the moon is bright and close it was one of the first objects that astronomers turned their telescopes to and what they saw was extraordinary. Suddenly the moon became a celestial body that had valleys and craters, it had a landscape. So what we can see here are sort of craters with shadows, we can see the kind of dark plains which Riccioli describes as seas, so we know now that these are lava plains. You'll notice that the map isn't a sort of perfect circle, that there is kind of two segments at either end. And that's because over the course of time from Earth, you can actually see slightly more than half of the surface of the moon. And that's because the moon travels at a constant speed around an elliptical orbit,

which basically means you see the kind of ears they're sometimes described as um as known as libration basically kind of apparent lunar wobble which means you can see more than half of the surface at once i love that we know that the moon has craters but it also has ears that's great so and they are detailed i mean we have what looks like a map of the moon as you say we've got this circle there are dark patches we've got craters that we know. But it's labelled and everything has a name. It's all written on here. So, you know, how long does it take to make this?

Do we know? The history of mapping is often a history of copying and compilation as well as of observation. So when Riccioli and Grimaldi make their map, they draw on work that's been done. I mean, this map is actually made and Grimaldi make their map, they draw on work that's been done. I mean, this map is actually made by Grimaldi and then Riccioli comes up with the naming system. So they draw together existing moon maps. They check them against their own observations in order to compile this map.

The system of naming which Riccioli develops for lunar features is broadly the one that we still use today so in the 17th century as astronomers start to name lunar features there are various different methods proposed for kind of how to how to set it out so one of the first moon maps that has a lot of names on uses the names of kind of Catholic nobility in Europe. A few years later, a Polish astronomer, Johannes Hevelius, does extensive observation of the moon and says, well, the lunar surface looks a little bit like the geography of the countries around the Mediterranean. the Mediterranean so we can name various of these features after the Mediterranean after islands and mountains Riccioli comes along and says well I mean it just doesn't does it and is also kind of wary of naming these lunar features after contemporary political figures that seems like asking for a whole lot of trouble right so he decides to use for sort of features so for particular

creators the names of astronomers so if you look you might see a Zofi which is named for al-Sufi a great sort of medieval Islamic astronomer Aristophanes so an ancient Greek astronomer and then you also see the sort of seas which are named after emotions or kind of weather so you have the sea of tranquility the bay of rainquility, the Bay of Rainbows, and so on. Let's look at this Cassini map because I love it. I think it's stunning. And just a reminder to listeners, we have put links to these images on the episode description. So please go and have a look at them because they are incredible. So I'm thinking this is, you said this was from 1679.

That's right. And it's an absolutely beautiful engraving you know you can see sort of the craters the valleys the plains one of the sort of fascinating things about this map is how clear Cassini was about the kind of practical function of moon mapping. Maybe someone said something a bit snide to him, right? And so he goes on a bit of a, those who do not look at things in depth think that maps of the moon are useless descriptions of an imaginary country.

And what he says is that actually there's a really practical purpose of mapping this place that people will never go, which is about establishing terrestrial longitudes so this is a bit of a complicated one but basically if two observers different places on earth measure the time during a lunar eclipse that the shadow passes over the surface of the moon over a particular lunar feature then you can establish the relative longitude between those two observers.

And that's something that a lot of 17th century astronomers emphasise, that kind of, you know, OK, this has a very distinctly practical purpose. So Cassini says that this serves to mark very precisely the places of Earth and to improve geographical and hydrographic maps without which it is impossible to make long journeys and to trade with far-off people. So his eyes are on imperial trade networks and long-distance voyages of the 17th century. How did they and these maps then influence society and what was their impact? these maps then influenced society and what was their impact? It's an absolutely fascinating subject which takes us to kind of ideas about life on other worlds and ideas about the place

of the earth in the cosmos. There had been an idea that the universe is geocentric, so earth-centred, the universe is geocentric, so earth-centred, and that everything beyond the earth was perfect and unchanging, held in spheres which kind of rotated independently of each other. Now, the idea of something being perfect and unchanging was pretty dramatically challenged, in particular by the moon observations of Galileo Galilei. If you've got craters and valleys and hills, that shows that this is a surface which isn't unchanging. If the moon is somehow analogous to the earth, that means the moon has a history of

change. That means not only does the moon have terrestrial features but it also means that the earth becomes a celestial body and this challenge to thinking about the moon and the place of the earth in the cosmos is kind of cemented by the observation that Earth's moon is not the only moon. So Galileo also sees the moons of Jupiter, at which point the Earth is no longer the only body around which things rotate. And so together, these lunar observations form a massive challenge to the way that the place of the earth is thought of and as this kind of observation of lunar landscapes develops there's sort of increasing speculation of like well if

this is a landscape does that mean there's life there and in the 17th century this is also cause for a huge amount of theological worry about sin and salvation essentially so do beings on the moon are they affected by adam's sin and a lot of theologians say no but if christ died once and for all, salvation is for all, does that extend beyond the earth? Some have, you know, these kind of incredibly complex reasonings about the possibility of growing grapes on the moon, and therefore the possibility of wine, and therefore the possibility of the Eucharist. And since the moon is too cold to grow grapes then a loving God would not allow there to be life on the moon which would remain in a state of sin because of the absence of the Eucharist this is something that Oliver Morton talks about in his book

The Moon History for the Future right and so if you want to read more about that, definitely. Oh, well, we actually do Space Book Club, so we'll put it on the list. Thanks so much to Dr Megan Barford and their book, A is for Atlas, Wonders of Maps and Mapping, will be out in May later this year. And don't forget, you can see the pictures of the moon maps that we discussed in our show notes. This is the Supermassive Podcast

from the Royal Astronomical Society with me, astrophysicist, Dr. Becky Smeathers, and with science journalist, Izzy Clark. This month, we're exploring one of our favourite topics, the fabulous moon. To be honest, I'm amazed that we've actually got this far through the episode

without you mentioning, dare I say, the toenail moon. I got toenail moon earrings in today and everything. I wore them for our moon episode. I literally saw one the other day and you were the first thing I thought of. And I was like, for goodness sake. I love this. My joy for the toenail moon has infected others. We need a hashtag.

No, no, we don't. We don't need that. I mean, Becky, do you want to explain this for our new listeners, the ongoing saga of this bloomin' toenail moon? Sure. So the toenail moon, unsurprisingly, is not an official name for this phase of the moon.

What? The phase of the moon we're talking about is the Crescent Moon. I have always loved a Crescent Moon. I think it looks the most beautiful in the sky. But I also think it happens to look a little bit like a toenail. One of the worst things that you could compare it to. I mean, maybe fingernail might have been better. No, that's right.

That's what it reminds me of. It's what i've always called it and do you know what the name has now stuck and i love the fact that people see the moon and think of me and toenails and toenails lovely such a nice image um so one thing that we actually haven't discussed yet is humans returning to the moon. Right. And there's quite a few big steps happening this year to get, you know, towards that. So what are the plans that are in motion at the moment? Well, I think one of the things that stops us from going back in the past 50 years or so

since the Apollo missions has always been money, right? And I think there's been a bit more money ploughed into this in recent years to get us back as sort of a stepping stone to get to Mars has always been the idea right so I mean we could just build another tin can right and chuck some people on it and you know keep our fingers crossed that everything was okay and sure we could do that I don't think that's probably how we'd want to do it this time and also we wouldn't want to go back just for the sake of it. We want to go back to do something new for a purpose, for science, that kind of stuff. So you need a couple of things to go back.

The Saturn V rocket is no longer in operation. So we're going to need a really, like a really heavy launch rocket, as they call them, that can launch very heavy payloads. So NASA's working on like the SLS, for example. But you've also got SpaceX's Falcon Heavy rocket as well. And then also you need something to house your astronauts and ESA's working on sort of a capsule that could house your astronauts. But also again, SpaceX have got their Dragon capsule

that's taking people to the ISS. That could be adapted for astronauts, you know, for going to the moon as well. But once those things are all in place, like what's the argument for going back to the moon what do you do well i think the argument always has to be it always has to be science motivated really so and we talked about before about getting more moon rocks to study various different things about the origins of water and the history of our own planet and what we can learn stuff like that

i think the plans and nasa's plans i think it's back in 2025 is the goal it was 2024 but it got pushed back a little bit and i think the plan is to build a space station around the moon you know the international space station has shown us for the past 20 30 years how long it's been up there that it is possible to have humans in space for that long amount of time and it's safe as well and so it can be used if you have a space station around the moon to refuel various different missions and restock various different missions. But also you could have astronauts living up there long term and then sort of just, you know, doing pops to the surface, like a pop to the shops. Right. You just pop up and pop back up. It's the idea of making perhaps that a little bit safer than, you know, an eight day round trip or something, quick trip to the moon, that kind of thing.

to the moon that kind of thing um and then obviously going forward it's then that's a launch base to get to mars because it's much easier to launch a rocket from the moon than it is from the earth because the lower gravity um and so i think that's really interesting ideas you know it's two sort of reasons science and then onward to mars and then also people talk about mining the moon and stuff like this but there's lots of you know is that the right thing to do philosophical cultural reasons about whether you should do that who owns the moon all this legal stuff around space that comes into play as well but i think you know the science motivation of uh understanding more about the moon system and then also the science motivation of wanting to send humans to mars as well to investigate further i think that's definitely the reasons that um you know we'd want to go back yeah because it

does blow my mind that only 12 people have been to the moon like you just think it's three days away yeah and there was this you know there was a rush and like now now we're done like oh yeah done that it's just like three trips to australia and loads of people yeah i think it was more of the tin can issue that uh probably held people back but um yeah it is it is a strange thing to think that but like i said i think it's just it's money you know like it costs a lot to to do this kind of space travel and you know like all science you have to apply for funding you have to justify it all that kind of stuff so yeah i think probes have been the best way of exploring in the past 50 years it's much safer it's much cheaper but there comes a point where you know there are some things that you want people on the ground for.

Yeah, absolutely. And thank you to everyone who has sent in their questions about the moon. Quite a lot of you have piled in on Twitter, which is great. So we've got some of them for you, Robert and Becky. Robert, do you want to take this one from now? I think it's Astronasurf, I think we say it with confidence. And they ask, why have NASA and other space agencies decided to return to the south pole of the moon instead of the north pole? And I guess first off, you know, what do we actually know about the moon's poles? Well, the moon's poles are one of those great coincidences in astronomy because it turns out that the tilt of the moon on its axis makes it pretty much perpendicular to the sun so because of the tilt the tilt of the moon and then the tilt of the moon's axis compared with the orbit around the earth the tilt of the

earth's orbit around the sun all of those things combine to mean that basically you don't get seasons on the moon so you imagine the axis axis of the moon is sort of sitting bolt upright compared with the sun. And if you compare that with the Earth, you know, we've got an axial tilt. We get winter and summer and so on. And what that means in turn is that there are regions, particularly the South Pole, where you have close to, not absolutely, but close to perpetual sunlight and also deep craters where you get close to perpetual darkness. to perpetual sunlight and also deep craters we get close to perpetual darkness um it's it's particularly pronounced in the south pole to answer the question from astronoser because it also

coincides with something called the achin impact basin which is an enormous feature from an from an ancient impact that is two and a half thousand kilometers across and as much as eight kilometers deep so absolutely huge and if you have deep craters in that then they're in almost perpetual darkness there's some evidence they get little bits of light and that what that in turn means is that the stuff becky was talking about earlier where you get asteroids and comets depositing water on the moon if that's been dumped into those craters there's quite a lot and when i say quite a lot you know perhaps a few percent or more of water ice mixed in with that soil so it might be an interesting place to put something like a moon base because you could access that water probably to use do things like make rocket fuel

from it break it into hydrogen and oxygen and also if you had a base there with solar power that could almost always see sunlight you could run it that way too so there's that's why there's so much interest in it and there are actually some missions coming up even this year there's a russian mission called uh luna 25 that might land near the crater boguslavsky which is in the south lunar pole region i know the pronunciation i hope i got that right and it's not the first time we've explored it. There was a mission, I think more than a decade ago now, called LCROSS, where an impactor was thrown at a, I think it was the crater Cabius, near the South Pole, kicked out a plume of material.

And by analysing that plume, the astronomers on Earth could, with the orbiter probe that was associated with it, could see that there was water ice, evidence for water ice in the plume. So it's pretty much confirmed that water is there. And there's a great deal of interest in it. If you go to the North Pole, on the other hand, it's more distributed. In the South Pole, it seems to be more concentrated in the craters.

So that's why there's so much interest in it. Did you see that exhibition they had, or it was like sort of an installation at Bath Abbey, where they had the projection of the moon on this huge sphere that they hung from the ceiling and people could walk underneath it and around it and my sister went and she said like she stood directly under it and looked up at the south pole and was like what on earth is that was that was that the museum of the moon was that yeah that's the one it's the one i think it did a

bit of a tour around the uk because i remember that it was also in Ely Cathedral as well. He has seven of those, apparently. I know him. He lives up the road from me in Bristol and he has seven of these moons travelling around the world all the time. It's so popular. Can I have one in my flat? That would be really great.

Does your flat have a seven-metre high ceiling? I surprisingly know. I don't even have seven tall ceilings. Amazing. Well, thanks, Robert. ceiling um i surprisingly know amazing well thanks thanks robert and becky siraj who's in mumbai has this question and a fundamental part to it is the fact that the moon is slowly moving away from us so he says at what speed is the moon moving away from our Earth? And what will be the consequences for our planet if that happens? Yeah, so, I mean, the moon moving away from Earth, right? It comes back to this idea of this giant impact that Robert was talking about before at the beginning of the episode, right? That the moon formed from the debris that was left over from it,

which was obviously a lot closer in than our moon is now. You know, as I was saying before, it looked like Saturn, right? That's what you should picture at the beginning i had this huge big dusty debris around it and it's been moving away from us ever since and the speed it's moving away is 3.78 centimeters per year which i think is faster than even than your fingernails grow or it's around about yeah i think i've seen that similar um and it's all to do with this gravitational tug of war between the moon and the earth right the moon it's not just that tug of war between the moon and the earth, right? The moon, it's not just that the earth pulls on the moon and keeps it in orbit.

The moon also pulls on earth. It creates these bulges in the oceans that then create our tides, right? And you have two because it's sort of like, you know, every action there's an equal and opposite reaction, right? But if you're picturing sort of that happening and you're picturing the bulges in the ocean lined up perfectly with the moon that's not actually how it happens the bulges are actually ever so slightly ahead of where the moon is and that's because the earth is also rotating as well so because they're ever so slightly ahead the moon is almost always pulling them back a little bit as well pulling on earth's rotation and so you get this exchange of energy where the moon steals a little bit of energy from the earth's rotation and so you're you slow down the earth as you sort of

speed up the moon in its orbit and so it moves ever so slightly further away from the earth and they've been doing that for four odd billion years right moving ever further and further away so it doesn't just mean the moon's further away it also means that the earth's day has been getting longer so in the past four and a half billion years or so it's gotten 19 hours longer so when the moon was first formed the earth's day was only about five hours long and we know that because we can actually study this in coral growth as well which i think is amazing that's weird i wanted to be a marine biologist this is a great crossover for me as well you can study coral growth and you can also look at the fossil records and you can see that there's you know that there's change in in the length of the day

over time and if we think about that going into the future with with what siraj said with consequences on earth it could be a bit of a big deal at least far in the future because if we think about the earth's rotation slowing down like think about when you set a like a spinning top spinning and it starts to slow down like what happens to it it starts to wobble right like all over the place so earth's rotation could become a little bit unstable around its axis like robert was talking about before right and it's our axis that give us our seasons so if you're if that axis is wobbling around we could have these really severe swings in temperature from hot to cold we could lose our seasons we could not have regularity to our seasons you know and all life on earth has evolved to cope with the seasons and so

if that changes you know it would be a huge huge concern but we're talking about you know billions of years in the future here so it's not something we should really sleep over exactly i was gonna say and do we do we even know at what point that you know a distance that it has to get to or probably not i i don't really i didn't look at it i should have done but i don't know what it is i presume it's i presume it's another four and a half billion years in the future you know in terms of uh how slow the earth's rotation has to get but um yeah yeah it's not tomorrow yeah thank goodness i've got plans um robert chris baldwin wants to know are other moons tidally locked around their host like ours yeah that's that's a really good question chris and i confess i i didn't i knew that there were some but what i hadn't appreciated was that the bulk of the bigger moons the bigger natural satellites in the solar system are indeed

tightly locked what that means i should say is that it's uh keeping the same face to their planet so like the moon more or less keeps the same face to us as it goes around so it takes as long to rotate as it does to revolve there's a really nice demonstration you can do with the spinning chair and this kind of stuff which i i can't easily convey in the podcast another time but most of the moons of the moons of mars jupiter saturn uranus and neptune are all like that and the ones that aren't where they're not tidal block tend to be smaller and further out so you've got less weaker gravitational interaction and a really interesting example of this as well is pluto the dwarf planet and its satellite sharon they are locked to each other so both the the dwarf planet and the moon going

around it always keep the same face to each other i like to picture it like two friends holding hands and spinning yeah i know i was thinking actually it's a shame this is this is probably going out after valentine's day because i thought actually that's quite, you know, we get this romantic illusion of the moon and the planet perpetually keeping the same face to each other. Yeah, well, people can bear that in mind for next year. Exactly. Card companies and so on. Becky Ashley King from Manchester asks,

Is there a link between the moon's size and its impact on Earth's tides? For example, if the moon was suddenly 50% larger would tidal levels increase 50% too yeah 100% it's it's a gravitational effect this tidal effect right so it depends on the mass and the distance what gravitational pull the oceans feel so if the moon got 50% heavier your tidal force would be twice as big if it was only half the distance as it is now if it was closer to us then the tidal forces would be four times bigger because it depends on divided by the distance squared right um let's clarify ashley's question so if the moon was suddenly 50 larger i didn't know if they meant mass or size so if it just swelled to 50 larger and got a lot

less dense but stayed the same mass like it just sort of you know like a puffer fish just blew up a little bit then that wouldn't change the tides because it's the same mass that's still pulling so i think that's good um to clarify but it does mean if we think about again the moon being closer to us in the past and now moving further away you can imagine what the tides were like on the very early earth right they were they were huge because they were you know so much stronger even at half the distance they were four times stronger so you can imagine no one was building beautiful coastal mansions back then because they would probably be wiped out by what we would call a tsunami so well thanks for

answering those guys and also just for listeners we are going to be returning back to the topic of the moon it's not over yet uh later on in the year to celebrate the 50th anniversary of the last man on the moon jean cernan but if you want to get in touch in the meantime with any questions then you can email them to podcast at ras.ac.uk or tweet at royal astros. So that's almost everything for this month. But Robert, if people want to do a little bit of moon gazing, what are your top tips? What should they look out for? Well, one thing you can say about the moon, right,

is it's the easiest thing to find in the night sky. You know, always, right, if we have a clear sky. But it turns out that in February and March, and April, actually, the moon is particularly good. It's, in the evening sky, it's high high up and the best time to look at it for seeing some of the things we've talked about is around what's called first quarter which is a quarter of the way through the lunar month when the moon is about half illuminated and in the weeks ahead that's on the 10th of March when the line will be pretty much down you know halfway so you'll have half of it lit up, half of it in darkness.

And that bit there, the so-called terminator line, is the line between sunrise. Basically, it's the sunrise line. So what you see as you look through a telescope is all these mountains and craters with very strong shadows. So they really, really stand out. So it also makes the craters look much deeper than they are. The mountains look really dramatically high. It's like golden hour for photographers. It's absolutely fantastic, exactly. And if you pick up, so look at it with your naked eye.

There's always a beautiful sight in itself. But pick up a pair of binoculars even. You'll see those mountains and the bigger craters like Copernicus, Plato and Tycho all stand out really well. If you get a small telescope, you can look at those same big craters and even see craters inside them if you're able to confirm the fact the moon has literally been pelted throughout its history you can see it for yourself so easily and at the same time you also can spot some of the more subtle features like these wrinkle ridges where lava planes contracted and and there's this famous straight wall fault which is this sort of slope and it looks like a at the right time which is a day or

so after first quarter so probably around the 11th of march you see this weird straight line which is just that the angle illuminating it sticks out so fabulous things to see i mean i loved it in the first lockdown of just really connecting with the moon and in sort of just in nature where you can just you'd get a full moon and all you need is either you know I had um I think I just used binoculars and a smartphone but just being able to take lovely pictures of the moon it's it's so easy so if anyone hasn't done it I would really recommend just doing it because it's it is amazing how much you can see with such a simple setup although with straight with a

smartphone won't work right because they're designed to mimic like your actual like what you would see with your eyes so the field of view is like like almost 180 degrees and sometimes right 90 degrees and so the moon only being half a degree across means it only fills like one 180th of your field of view which is why it looks tiny and why any smartphone picture of the moon that's, you know, not got binoculars in between or whatever it is, looks terrible. Yeah, you can cherish that moment for yourself. Hold it to a telescope. I mean, I'm always amazed, you know, how good the photos are.

You can get, if you spend a little money, you can get things that will look, smartphone holders. I did try one of those out and that's great actually makes it so easy to take pictures uh but even even in many cases i think people who are absolute experts of smartphone photography can just line up their smartphone at night on even quite faint things but definitely the moon get great pictures it's really really easy to do and you just crop it when you process it yeah exactly yeah and what about some of the other things that we can see in the night sky this month so we're now moving away a bit you know eventually from winter although it might not quite feel like it into the into the spring stars you can see all to still see those fabulous winter constellations

earlier on in the evening Orion and so on but uh I would say look out for things like Leo the lion which will be really high in the south and from later on in the evening and it's one of those constellations that actually to me at least looks a bit like a crouching lion it's got this this main this sickle of stars rising up from the star regulus at the bottom and it you know does it's very easy to imagine the lion crouching there and if you've got a dark side, you can do things like try to spot features. You probably need a small telescope for this. There's galaxies like Messier 65 and 66 just at the bottom of Leo there. And between Leo and those winter constellations, you've got the very faint constellation of Cancer.

And that includes the lovely open cluster Messier 44. Still easy to find and enjoy this time of year. And it has about 1,000 stars in in it you won't see all of those but you'll certainly find it easy to see a few tens of stars with a small telescope and finally in terms of planets in the morning sky if you're up and about even reasonably early you'll see Venus is really stunning right now it's pretty much as high as it will be this year very very very obvious if you see this bright object in the morning sky please don't write to me about a ufo it's not a ufo it's venus and if you have a telescope and you look at it you'll see that it's changing phase as it moves between around the sun and you'll see it's shrinking down it's moving away from us

the crescent it's got shrinking down but it's also fattening it's also getting rounder and it'll be about half full on the 20th of march and it's right next to mars it's also getting rounder and it'll be about half full on the 20th of march and it's right next to mars as well isn't it in a minute too it is right next to mars and mars will be really great later in the year and mars if you look at it if you want a comparison consider you know mars is about half the size of the earth right and it's uh it's significantly further away but look at the difference in brightness between the two you know relatively faint red mars next to stunning brilliant white venus those thick clouds in its atmosphere make it so bright you know i'm the sunlight so well yeah i mean i'm quite jealous of the people who are further south than us at the

minute i mean we did have suraj from mumbai earlier so i mean those who are further south you're gonna get treated to not just mars and venus but mercury and saturn too it's like the morning is just like spoiling us at the minute with I know and I didn't mention that because yeah in the UK they're really hard to see and Mercury is there are definitely times a year in the UK when you can see Mercury fairly easy but very brief fleeting periods and we will I promise to keep an eye on when it's good and I'll be mentioning that too but you're absolutely right further south I mean generally actually if you're down on the equator or getting close to the equator, you see the whole night sky. You know, we're always a little bit restricted that much further north.

I just think this means we have to do an on location podcast recording, to be honest. Absolutely. From the equator. I might be up for that. Or Australia. Well, we'll work on that. But I think that's it for this month. So we'll be back in March with a look at galaxies. My precious babies. I know, I know. Again, another topic that I'm like, okay, let's cross this off the list as well.

How have we not done an episode on galaxies? So actually we're going to do two episodes on galaxies because there's just so much. And we're also going to be back with our space book club as well. Yay. yay and remember tweet us if you try some astronomy at home it's at royal astrosoc on twitter or email your questions to podcast at ras.ac.uk and we'll try and cover them in a future episode episode what's the episode

and we'll try and cover them in a future episode until then though happy stargazing i almost just laughed all over your entire line i was like hold it in i was holding it together doing the live what's the episode that was fun