NOVA; To the Moon; Interview with Robin M. Canup, Astrophysicist

fb something else declines with time but that said small things are also produced when things collide like when asteroids school i dont produce more asteroids and frightened fragments from collisions and so even today there are a lot of small impacts going on we don't have any marseilles bodies that are flying around about a clutch of the year as in the case of the giant act but of course we have one liter size parties and the occasional kilometer ten kilometer son's body which even though it's tiny compared to china impact is still fundamentally significant if you're living on the planet at the time now was what was i believe it's something like a hundred meters then as far as the end of the term

gaska type a fireball that where you have law we have something that nearly hits the ground and sent a shockwave of energy at the impact site does significant damage so what happens if a one meter chance to make them just shoots i'm not really sure exactly how much of that they sit down to be honest with you it certainly does certainly becomes a meteor in the sky you see it all through the little focus on a whole lot of water what would you rather described first what what happens after a giant vacuum and work or how you got into were probably that pride that direction inward state their

ruling on saddam will be ok well i was developing dynamical models describe the evolution of perjury brings systems that were around all of the gas giant planets and i was presenting the results a conference and bill hartman who of course is one of the originators of the giant impact theory heard my talk and talked to me afterwards and said that he thought about applying there models for how these little satellites in the brain systems accumulate to the moment because i don't think anybody's actually looked at hal the moon or creates after the impact recently it's an important point and i went into that answer enough this was that night ninety three at that time the giants had fear ie was very well accepted him as the mechanism for women and sure enough while there have been a large number of simulations byock hammer and others that model the actual collision and the jets should've to breed it were around the earth no one had looked or add or muddled the accumulation of that

debris to form of the mormons and it turns out that he was a very interesting dynamic a problem and it's placed new constraints on the type of impact its need to form them on the debris thats placed into orbit by the impact actually orbits in a very similar spot as say the rings of saturn and both cases the gravity of central planet actually i'll frustrates the accumulation of material into satellites that's why saturn's rings to accumulate into a satellite and this same process means that accumulation from an impact generated pro we're just it's actually quite inefficient and a whole series of simulations that we've been doing in the past couple years all suggests that you never end up incorporating more than half of the debris that you initially put up in orbit into the moment in fact usually the majority of the tipperary hands up being scattered or raining back down onto the earth what this meant was that the impacts that we're

placing one lunar mass worth of material in torture or get quite effectively or now no longer large enough or sufficient for mahmoud and it's turned out that even this factor of two difference the fact that we now need to enter masses in orbit set of wonderment us has been incredibly difficult to reconcile the dynamic or miles on one system well the interesting thing is it can take a very different times depending on what material looks like when you reject it if it's an extremely energetic impact on then you can have most of the material is actually in the vapor state you have a silicon vapor cloud surrounding mirrors and if that cloud is optically think it could take a long time to cool a long time being maybe a

hundred years if most of the material as instead thrown out in the form of intact trunk store magnate pieces that it would cool much more rapidly in the time scale about here one set of recalls and the particles the bodies the desk are colliding the moon accumulates extraordinarily quickly in a better year and this is just a function of the fact that the particles in orbit so close to the earth make one orbit every four five hours and so the moon accumulates once things cool in about a year which has very important implications for how hot the moon was initially because we form the moon that quickly really seems that should have been completely melted and it's not clear whether we see gee chemical evidence that we saw in iowa would be

physically impossible to be a far worse year we're going to see how well it would be a really beautiful sight because the moon is currently very far from here twenty four mitt was in very close it was ten times closer than it is now and so would be ten times larger in the night sky and is now and it might even provide enough reflected light have nighttime actually feel more like dusk so would have been a very extraordinary sight know it's a shame it's moved outward so quickly well is it moving our graduates that winter has it did it so quickly and stay there where is the nomination how will the mechanism that causes it to move our kids is its title interaction here same mechanism that gives rise to the twice a day oceanic tides that mechanism transfers and the momentum to the earth's orbit it happens very quickly when the moon's close in and then slows down

rapidly the farther out than when cats and so when the moon is close and it was moving out very rapidly at hundreds of commerce three year say whereas now the moon's only moving out about a centimeter or so three year old about how bp didn't have the breeze in your house and it's one of the things we've realized the last decade is that not only is the moon a beautiful logic intrinsically but it's had a very significant effects on the evolution of the earth and probably on the evolution of life one example of this is that the moon is massive enough relative to the earth that it actually acts to stabilize the variation of the earth's north pole with the movie on our axis tilt which of

course gives it gives us our seasonal variation varies by about a degree and half nasty remove them that fx due to the giant planets in the sun lead to a chaotic variations of the earth's north pole that is estimated to have able to use of like sixty degrees so you can imagine that if they earth were subject to that kind of variation it would be impossible to maintain a stable life supporting environment you have periods where the earth would be completely frozen over and he would certainly greatly frustrate the development of life and so now coupled in with the question of what is it take to make a terrestrial planets we've added on another condition what is it take to form a terrestrial planets with a moon like ours so that that system appears to be required in order to have a habitable planet we're very special kind of thing we're very special relative to the other trust your clients

there's one other climber system that looks a lot like a stand and actually even though it's very far away that's pluto pluto actually has a moon that it's very large relative to it also and not coincidentally we think that a planet and system formed as a result the china impacts well ok well we're finding many other planetary systems now and we've really only just begun our searches so it's looking more and more like the formation of planets as a natural consequence of stella formation many cases money may be planters systems that are very different from our own with giant planets orbiting very close to the star that might preclude having earth like planets always but it certainly looks like generally planets are common fb

why would someone who would do your work says there will be advances and computers and computer speed has of course been central to the incredible detail on the modeling were saying to this conference but yeah usually what happens is that somebody has the initial idea it's just a creative new way of looking at something and so typically even with a simple model you can make preliminary estimates to see whether the night is really gonna work on a farm like the estimates that were made the call a conference that suggested that perhaps a giant impact might just work on and then after that when it comes to working out the details year often depending on your computer resources for example and in the case of looking at how the mood forms i really had one fundamental idea and that was

the recognition that the degree after the impact was orbiting in the same place that the saturn's rings system is located now and i thought well the saturn system have rings and lots of moments and they're saying that from this debris cloud looks like that system we should get one big moment doesn't seem quite right and i was literally all it took was just the comparison arm of my models developed for the other planetary systems and extrapolation of those to the system and that and that was that i'm a half the way there fifteen years ago china comes out with to describe the way the land the interview then and now in how much change all their work basically three other theories for the origin of the time to capture co formation and fission yes yes isn't it how long ago okay

forget this that's right that's right so fifteen years ago and signed impact theory i'll was first being evaluated there were three other main theories from the origin was to capture theory the fish in theory in the coal formation theory and in fact were the scientific goals of the apollo program had been to distinguish between those theories aside which one is cracked and what ended up happening of course was that the results that we got from the moon rocks complicate the picture we had problems all three of those theories and new theory the impact theory was proposed at first it was seen as something that was an ad hoc possibly ridiculous probably unlikely and in the last fifteen years he has now evolved into the accepted theory for the origin of the earth moon system and in that time our models of how planets form have also developed and we now believe from that independent line of research that the end stage of trust a planet

formation will naturally be dominated by these large impacts between planet's size body it's and so now this tiny impact event which seemed so ad hoc an unlikely to us a decade ago we now see as a natural consequence of planet formation so it's an exciting time in your field i mean some people think it all ended in seventeen to the last apollo flight that sounds like it's getting bigger and more exciting than this is the best time to be a planetary scientist why why does one become a planetary scientist because some point you look up in the sky when you're a kid and you wonder are we alone either other planets are there other earths and we're in a generation where we are just beginning to find other planetary systems and there is fundamentally no more important finding in my opinion on that and i mean tom is the moon a part of that process we are on our understanding that the senate hoping that

future is the planets that were able to detect of course are not the earth like planets there the giant planets jupiter so the saturns and so what our theoretical understanding gives us is a way to look at a system where we can only see the jupiter and answer the question does that system have a verse and that's really the long term goals of our models to be able to extrapolate them to other systems with very different architectures of giant planets determine if those systems might have earth like planets and moons so starting on one studying our moon is fundamentally important both in understanding the evolution of the history of the earth the evolution development of life and the likelihood of earthen systems in other solar systems fifteen years ago when john was once their work what we're doing where were you were in what was an old mac and just turned thirty

so fifteen years ago on i was a high school student and the voyager results from the voyager one and two encounters with jupiter saturn and uranus were coming back and so we were getting these incredible pictures of the giant planets for the first time and i have to say that was very inspirational to me at that time we've seen some fairly young grad students here is it possible that the one geoff and iraq and yours is working on a high hope so i hope that i hope that someday young people you see here will be looking at a new lunar samples by the time i'm retiring and learning more about the history of the movie and how it formed in an ultimately threw that the history of the earth so great it's we don't

want any of this be happy paul well apollo was the primary driver of course involve the initial discoveries that depend on the nights we got from analyzing the lunar samples on a and e the origin of the moon was of course a big scientific issue before apollo and once we have the letter samples from apollo we have all sorts of nucci a chemical and time constraints on the origin the moon which led to the proposal of this new impact theory so in terms of going back and these younger students here and continuing when you say you hope it will be new samples are is important to have a manned missions humans gone well fundamentally humans are able to distinguish between things in a way that it's very difficult to imagine robotic missions ever being able to do and what it comes to picking out certain types of rocks for example rocks that might

look like they were produced from an impact event vs rocks that are the celtic in nature then the the ability to distinguish on the spot gives you an amazing invention of course humans are the best at distinguishing on the spot when all are you going to keep keep working in this new space of a future enjoy doesn't usually there are certainly hope so i hope to keep working in this field it's something that as a child i found innately fascinating i grew up thinking that by the time i was at all you would be going to mars and that was actually one of my dreams as a child was to be an astronaut and go to mars of course what's happened since then and now i'm doing just scientific research and nine astronaut but the same fundamental scientific questions that noted vaguely then still motivate me now are we alone are there other

earths could you imagine let's say you could go back in time what from what you know of the history of science we were back in the forties the fifties we've been conceived in doing this kind of work were you thinking says of all the movement what fundamentally is has been an ig to wonder to rout human civilization i'm sure i mean i've since humans walked up on earth we have to look up and wondered where the movie came from what it was doing but it's really only been the last decade or so that we've realized the extent to which the moon has directly influenced her and then that coupled with these new discoveries of all of these systems of planets around nearby stars that is it's hard to imagine that thirty or forty years ago we could've known

half the number of planetary systems we would find of their diversity that many of them will look very different from our own with large giant planets honest non circular close in orbits so we really live in a special time scientifically now how do you feel about the work and the science that work that was done all that was not the most about science and the us are not supposed to do the job well you know i actually so our talk by dave smith at one of our planetary science meetings and he described the process that they went through which involved many hours of direct interactions with geologist where they talk the astronaut sit down and meet your creator and they taught them what the various rock types were and what they need to look for and so they were actually extraordinarily well trained on and so online of the initial science is still being built upon today those

visual artist who of course yes and the initial rocks that we we have now or you know there are only clues there only remnants from age that it's very difficult to find things preserved on the earth and there there're only direct evidence of any great quantity of material from another planet her body is that whether you can actually get material placed into orbit and a few very primitive simulation and of course you know we're quibbling over what kind of impact with a reform a big enough moon but then we didn't even know if you could even get anything close to him and that's worth material into orbit with anything close to the right spin of the year and so that was really a remarkable finding enough that you remember no no

eminem and i graduated high school at sixteen so of the two million viewers yet the heart is actually the person who got it started working on the moon how i was doing our work modeling clattering dynamics in saturn's rings and neptune springs the rain ring system and he heard me give a talk at a conference he came up to me afterwards and said you know if you go beyond that taken from these models applying and because i don't think anybody is for the mill after john impact it and this was back in around ninety three american to have to work on that ever since the interview goes coming up to seventeen years

eyes in hackers to compare them with what it looks like we need for the moment but the main to be honest the main contribution i made so far it's the first thing is going because as the first person to do that this is just going to sleep imports over the years we will certainly things pete when the plants were forming and then there's a star that's right that's right that's right you take everything that's in the plant's now divided up into even a hundred pieces of a lot more intense rains and then the number of surviving things as objects to make lemonade is the climb something else declines with time but that said

small things are also produced when things collide like when asteroids school i dont produce more asteroids and frightened fragments from collisions and so even today there are a lot of small impacts going on we don't have any mars side