Nature Podcast

This is a transcript of the 24th March edition of the weekly Nature Podcast. Audio files for the current show and archive episodes can be accessed from the Nature Podcast index page (http://www.nature.com/nature/podcast), which also contains details on how to subscribe to the Nature Podcast for FREE, and has troubleshooting top-tips. Send us your feedback to mailto:podcast@nature.com.

Kerri Smith: This week journey to the middle of the earth.

Damon Teagle: The eventual goal would be to drill all the way through the crust and in a significant distance some hundreds of metres into the upper mantle.

Geoff Marsh: Making sperm in the lab.

Marco Seandel: One could go back to the frozen samples and then carry out the procedure described in this paper in order to produce sperm.

Kerri Smith: And detecting cancer before it gets started.

Lizzie Buchen: So for early detection the goal was to detect the cancer in women who look healthy, who are not showing symptoms of cancer but then later go on to develop cancer.

Kerri Smith: Plus a tricky type of chemical reaction cracked. This is the Nature Podcast. I am Kerri Smith.

Geoff Marsh: And I am Geoff Marsh.

Geoff Marsh: Sperm cells start off their life as a very immature type of cell that look nothing like the swimmers that they'll become. This transformation is called spermatogenesis, a process for which the inside of a testicle is perfectly seated, but replicating this process in the lab has so far eluded sperm scientists. Now a Japanese group has managed to do just that with mouse sperm. I called Marco Seandel, the author of an opinion article about this paper to first of all walk us through the naturally occurring steps of spermatogenesis in a testicle. Nature 471, 453–455 (24 March 2011)

Marco Seandel: You start out with something that we describe as a stem cell or some would call a progenitor and this is a type of cell that can simply maintain itself over time and then a decision is made in the body for the cell to begin to mature and that maturation process in humans takes a very, very long time. It actually takes over two months and that is accompanied by massive changes in virtually all aspects of the cell from the shape of the cell to the structural components, it gains a tail, the programming within the cell is completely rearranged and eventually this cell gets to the point where it can participate in fertilization.

Geoff Marsh: Right so this, this complete shift in morphology of the cell from its progenitor to its kind of final destination as a swimming sperm cell, does that also explain why a cell had to make its transition happen in a Petri dish.

Marco Seandel: Yes, absolutely and one of the critical features to make this happen in a petri dish is to provide a very critical cell type called the Sertoli cell, because we know that the Sertoli cell is essential in vivo, in the animal and the Sertoli cell has its amazing ability to at the same time provide the proper signals for both the stem cells and the more mature cell that actually lead to the final product which is the sperm.

Geoff Marsh: Right, so rather than trying to work out the complicated ingredients of all the chemicals that you might need to add to just the stem cells, you just take off a chunk of the testicular tissue and that orchestrates the whole process for you.

Marco Seandel: Exactly and it's even more complicated than just one or two cell types, there are at least 3 or 4 cell-types that we think are important. The challenge if you were to try and reconstitute that with chemicals you know would be enormous.

Geoff Marsh: Now presumably this has been done before, what problem have researchers in this field come up against before, what's been stopping us doing spermatogenesis properly in the dish?

Marco Seandel: Well there's really two things, one relates to what we were just discussing which was how do you really provide all the signals that are present in the body and equally important one needs to have a way to assess whether the system is working and the study in this case came up with a very clever way to provide a readout that they were actually getting the sperm-forming cell to be produced.

Geoff Marsh: And what was that?

Marco Seandel: Well what they did was they used the system that's becoming more common which is to engineer animals in which a fluorescent signal would get turned ON when the cells are actually maturing the way they want them to. With such a system, they could test many different types of conditions and score them for their efficiency and it's only in that sort of iterative manner that one can slowly whittle down the right recipe so to speak to make this process happen.

Geoff Marsh: And so that was the first part of the experiment. Then the researchers went on to check if these swimmers were the real deal, right, and injected them into lady mice. Tell us about that part of the experiment.

Marco Seandel: Well it's in some ways very similar to what is used in the human fertility clinics. The sperm are extracted and then directly injected into the egg and using that system you can form an embryo and the embryos are then transferred into a surrogate mother.

Geoff Marsh: I'm told that the offspring fare up.

Marco Seandel: They were actually half fertile. So, that's a good indication at least as a first step that these sperm are of reasonable quality, now I would say that there are other things that need to be done to really prove that.

Geoff Marsh: Now that's all well and good that they formed fertile offspring, but if we were to make useful application of this we probably want to be able to freeze this sperm and they also did that, right. They preserved the sperm, they froze the sperm and they thawed them and they tried again.

Marco Seandel: They did and they similarly had good results but I think that more work certainly will need to be done to show that the offspring from sperm produced from frozen tissue are truly normal.

Geoff Marsh: And that's basically you want to check the offspring's offspring.

Marco Seandel: Exactly and I mean you know with humans I think the bar is pretty high in terms of demonstrating that these are really normal.

Geoff Marsh: Yeah, you said it yourself the question on everyone's lips is, is this going to work in man?

Marco Seandel: Well I think there's certainly a need for it, it's a fairly specific situation. One can envisage a child having chemotherapy after being diagnosed of cancer and then undergoing a testicular biopsy. The tissue would then be frozen and then in the event that he later had trouble conceiving children, one could go back to the frozen sample and then carry out the procedure described in this paper in order to produce sperm.

Geoff Marsh: That was Marco Seandel of Weill Cornell University in New York.

Kerri Smith: Coming up later in the show….Movie clip runningIt's unthinkable but it must be true, a man took some tools and went where no human beings had ever set foot, alone.

Kerri Smith: Stay tuned for our very own journey into the inner of the earth.

Geoff Marsh: Time now for an update on the situation in Japan, joining me on the line from Washington DC is US news editor Ivan Semeniuk. Hi Ivan.

Ivan Semeniuk: Hello Geoff.

Geoff Marsh: Now it's been over a week since the earthquake and the subsequent tsunami, what is the latest on our coverage of Japan?

Ivan Semeniuk: Well this week we are focusing on some extent on the nuclear accident and of course we know that radiation is beginning to trickle out into the environment so we're just looking at what people are saying about that radiation, what it's telling us about the accident and also what the health risks may be, although before going any further I have to say that whatever the cost, the human cost of this radiation leak will be, it pales in comparison obviously to the, you know, the incredible catastrophe, the tsunami and the earthquakes. That's important to put that in perspective.

Geoff Marsh: Okay, so it's not having as much of a catastrophic effect but it is being picked up in very far reaching areas right?

Ivan Semeniuk: Yeah, so radiation is escaping the plant as vapor and probably as particles as well being lofted into the air, carried out to sea and also across land, carried right across the Pacific, in fact, we've talked to researchers in the US who have detected the radiation plume in the Pacific Northwest. They're finding that radiation is extremely low levels, but it does actually tell us some interesting things about the accident. For one thing some of the isotopes that are being detected are short-lived and what that indicates is that it can't just be from the spent fuel that's being stored near the plant, the short-lived isotopes almost certainly come from inside one of the reactor cores, so somehow there's been a breach of a containment vessel, that's probably what that indicates.

Geoff Marsh: Okay, and should the people across the Pacific and elsewhere be worried about these low levels of radiation?

Ivan Semeniuk: These are actually lower than what people would call as normal background exposure, where it's more of a concern is sort of in the geographic regions around the plant, that's where we've been hearing about warnings about food and water. There are indications of iodine and cesium isotopes in sea water as well. So potentially we'll hear some warnings about seafood perhaps, but certainly leafy green vegetables or shipment of those has been stopped and also milk from Fukushima province. The issue there is and this sort of harkens back to what happened at Chernobyl although this is much more serious than Chernobyl. There is iodine in the milk and this isotope of iodine 131 has an 8 day half life, so it's quite radioactive over a short term and of course the thyroid gland in humans absorbs the iodine very readily. The levels for the most part are within allowable limits, in some cases they are not, some reports seem to suggest in some cases they are not but certainly the prudent thing is to avoid consuming these products and so at the moment you know we are trying to see that happening in the area around the plant.

Geoff Marsh: And you mentioned the iodine isotopes have these very short half life, but there are some isotopes with much longer half-lives, you know with thousands of people losing their homes, is there a worry for the future of food production for the rest of Japan?

Ivan Semeniuk: That's a very interesting question, not just for food production but just the environment in general, so cesium the other isotope I mentioned has a 30-year half life, so even though it would be at very low levels it could be in the environment for centuries and there's still a lot of uncertainty and in fact a lot of debate over exactly what's the impact is on human health of a kind of persistent low doses like that, some people would say there's no safe dose of radiation, so there will always be some kind of a bump up in cancer rates when there's been a release like this, others would say that well maybe that bump wouldn't even be statistically significant and that there isn't enough information and it's going to be hard to predict the effects.

Geoff Marsh: Okay Ivan, thank you.

Ivan Semeniuk: Thank you very much.

Geoff Marsh: As always our news coverage is free to access at http://www.nature.com/news and in this week's magazine we've dedicated four pages to the situation in Japan. You can also keep up to date by following @NatureNews on Twitter.

Kerri Smith: For more highlights in Nature's world this week, here are the headlines.

Jingle

Kerri Smith: For a male mouse, there is nothing like the sweet smell of a female but scientists want to know what happens in the brain to make males choose to mate the females. Now researchers in China have found that the brain chemical serotonin underlies sexual preference in mice and maybe in all mammals. The researchers engineered male mice to lack serotonin and then tested their sexual preference. The serotonin-deficient mice didn't distinguish between males and females and tried to mate willy-nilly. This is the first time a brain chemical has been linked to sexual preference in mammals. Nature advance online publication (23 March 2011)

Geoff Marsh: Three papers report some of the first fruits of an ambitious project to map all the genetic building blocks of the fruit fly. This is the modENCODE The first draft of the fruit fly genome was completed 10 years ago, but that doesn't mean that all its genes have been marked and understanding how the genes control things like development and disease require knowledge of their structure as well as just their sequence. The three papers turn up thousands of new genes and parts of the genome that control them, but they are just the beginning of the quest to discover the function of every single fly gene and how those genes interact. Nature 471, 473–479 (24 March 2011) , Nature 471, 527–531 (24 March 2011) , Nature 471, 480–485 (24 March 2011)

Kerri Smith: People with a mutation in just one gene can neither feel pain nor smell odors finds a Nature paper this week. Several families around the world are known to be insensitive to pain because of a mutation in a gene called SCN-9A. When researchers tested three of these people it turned out that they didn't have a sense of smell either. The team next studied a mouse lacking the same gene and the same was true. The gene in question produces a channel that sits on nerve cells and lets sodium in. The researchers say that they're surprised to find that one gene controls both of these two crucial senses. Nature advance online publication (23 March 2011)

Jingle

Geoff Marsh: All those articles and more at http://www.nature.com/nature and you can also find an extra audio delight on the Nature Podcast pages. Theoretical physicists Brian Greene drops into the studio this week to tell us about multiple universes.

Brian Greene: There may be and continue to be Big Bangs in various and distinct locations throughout this larger cosmos with our universe being the outgrowth of just one of those bangs. Our universe being like one expanding bubble and a big cosmic bubble bath that has other bubbles, other universes.

Geoff Marsh: Mind boggling stuff. Find the full interview at http://www.nature.com/nature/podcast.

Jingle

Kerri Smith: In just a minute the quest to find early warning signs of cancer. But first a bit of chemistry for you. Chemists use a reaction called metathesis to make everything from plastics to pharmaceuticals. Metathesis means re-arrangement and joining me in the studio to talk about an important new form of this re-arrangement is Nature editor Andy Mitchinson. Hi Andy. Nature 471461–466 (24 March 2011)

Andy Mitchinson: Hi there.

Kerri Smith: So this is a chemistry paper about a reaction called metathesis, so I suppose we should run people through what metathesis actually is.

Andy Mitchinson: Yeah, metathesis is a catalytic reaction and it's used to make new double bonds between carbon atoms. What it really does in fact is rearrange carbon-carbon double bonds in molecules; you can kind of think of it as an atomic barn dance, so if you can imagine two dancing couples who start of holding hands and then they swap partners so they end up holding hands with someone else. Well, that's basically what the carbon atoms are doing in metathesis reactions. The double bonds between two pairs of atoms are broken and the new bond forms and the atoms end up bound to a new partner. The mechanism is more complicated than that, but overall that's what happens.

Kerri Smith: What exactly is this useful for this reaction?

Andy Mitchinson: And well the reaction has been around for a long time but initially it was used as a way of making polymers but then the development of new catalysts for metathesis in the 1990s created an explosion of interest among synthetic organic chemists and they found that it was an extremely versatile reaction for making carbon-carbon double bonds and they really used it to push the boundaries of what molecules they could make. As a result of that the importance of the reaction was recognized with a Nobel Prize in chemistry a few years ago. Nowadays, it's widely used by medicinal chemists working in drug discovery as they make and develop candidate molecules and it's fair to say that it really is one of the most widely used reactions today.

Kerri Smith: And there are different types of this reaction, aren't there?

Andy Mitchinson: Yeah there are lots; so we've just been talking about something called alkene metathesis which involves carbon-carbon double bonds but there are also variants that involve making single and triple carbon-carbon bonds and then there are lots of different ways that actually using alkene metathesis itself. So I mention polymerization before, so there's a reaction known as Ring Opening Metathesis Polymerization which ravels in the glorious acronym of ROMP and that's used to make plastics. Then you've got ring closing metathesis and that was the reaction that really got the attention is synthetic organic chemists in the 90s' and that involves reacting together carbon-carbon double bonds at the ends of bond long molecule to make a cyclic molecule; but then there's also cross metathesis which is likely to be the most important version and because it doesn't actually involve any special molecules such as polymers or cyclic molecules, it simply involves making a new single carbon-carbon bond between two different molecules and but that's actually been the most difficult metathesis reaction to develop.

Kerri Smith: And that's where this new paper fits in and I have to say Andy, when you volunteered to come to the studio to talk about chemistry, I didn't expect barn dancing or romping but we've been through both of these things but we should move on to the actual paper, so this week in the Journal Amir Hoveyda and his colleagues based at Boston College in Massachusetts released a sort of new take or basically an advance in metathesis.

Andy Mitchinson: Yeah that's right, so they report a cross metathesis reaction that allows them to make so called Z-alkenes; if you remember alkenes are just organic molecules that contain carbon-carbon double bonds and Z-alkene are a particular isomer of those molecules in which two groups attach to the carbon-carbon double bond or on the same side of that bond. Metathesis reactions generally however yield E-alkenes in which the groups are on opposites sides of the bond and that's obviously a problem that he wants to make the Z-alkenes and lots of people do.

Kerri Smith: And that was why it was difficult then to make these Z-alkenes previously?

Andy Mitchinson: Half the problem is that the E-alkenes tend to form in metathesis reactions preferentially but the other problem is that metathesis reactions are reversible and the Z-alkenes are particularly prone to the reverse reaction so even if you do get a Z-alkene forming in a metathesis reaction the chances are that it will fall apart pretty quickly but this is where Hoveyda and colleagues have come in and they've devised metathesis reactions that get around these problems, part of the solution to this involved devising a new catalyst and which was able to force the reaction to form Z-alkenes and then the other part of the solution is to find classes of starter materials that reacts particularly well or particularly controllably in these reactions and then the final piece of the jigsaw was just to find exactly the right condition to optimize the use of the products and to prevent unwanted side products from forming. It's an incredibly difficult problem to crack, loads of chemists have been trying to make Z-alkenes to be used in metathesis for a long time and it's generally recognized as one of the big outstanding problems in organic chemistry.

Kerri Smith: Now obviously chemists are going to be excited about the method that's been used and the fact that these that alkenes have been made, but what did the team actually do with the new technique, what thy have made and what would then it be possible to make in future with these?

Andy Mitchinson: Well what they did to prove how useful the reaction is, they made a couple of compounds. The first of which was something called an anti-oxygen phospholipid which is a naturally occurring compound that's been implicated in Alzheimer's disease; so obviously if you can some of this stuff that's useful for further studies and they also made an anti-tumour reagent which is the name KRN7000. By making these two compounds, this was a great demonstration of how the reaction will go on to be used in the future, so I would anticipate that these reactions would be widely used by medicinal chemists on drug discovery programs in the future.

Kerri Smith: So obviously lots of applications in future but fundamentally this is really a staggering find, isn't it?

Andy Mitchinson: Yeah, there is a guy I know an organic chemist called Phil Baranand he has described reactions as being like molecular sand storms. So you can imagine there are these trillions of molecules all flying around and around and batting into each other, interacting rebounding. When you look at reactions like that, it's astonishing that you can actually get anything useful from this at all; so to get the precise level of control that Hoveyda and colleagues have got to give you Z-alkene products, well that's just mind boggling.

Kerri Smith: Andy Mitchinson, thank you very much.

Andy Mitchinson: You're welcome.

Jingle

Geoff Marsh: Biomarkers as the name suggests, are biological markers that can indicate when a patient has got a disease like cancer for example. They include such things as mammograms for breast cancers and proteins circulating in the blood. For patients already showing symptoms, these markers have come a long way, but spotting cancers before the symptoms crop up has proven much more difficult. There's a feature about this problem in Nature this week. Natasha Gilbert spoke to its author Freelance reporter Lizzie Buchen. Nature 471, 428–432 (2011)

Lizzie Buchen: What this feature focuses on our biomarkers for the early detection of cancer; that type of biomarker has been very difficult to find and that's the type of biomarker that people think would be the best magic bullet to really decrease deaths from cancer.

Natasha Gilbert: So are there many biomarkers for the early detection of cancer in use?

Lizzie Buchen: There are a few, the best known are prostate specific antigen which is PSA for prostate cancer and then the mammograms for breast cancer but they are pretty problematic because they miss a lot of cancers and the bigger problem is they result in a lot of false-positive and so that result in over treatment and results in anxiety for people who don't actually have cancer and so they're really far from ideal.

Natasha Gilbert: So why are these biomarkers for early detection of cancer proving to be so tricky?

Lizzie Buchen: Well there's several reasons, one reason it's so difficult is just simply the biology what a lot of people want is to be able to a simple blood test and find some protein floating in there that indicates cancer in a specific organ and it's unclear such proteins even exist which is why all the potential biomarkers discovered so far are really just what people think are cancer specific levels of proteins as opposed to cancer specific proteins themselves. And there's also a bit of a paradox because the protein needs to be produced by cancer that is so small but it doesn't cause any symptoms but of course it has to be big enough that it's secreting enough of these proteins that they can be detected amongst all the other proteins already floating in the blood.

Natasha Gilbert: Do scientists have any ideas of what would make a good biomarker?

Lizzie Buchen: Yeah, there are some people who are starting to look at biomarkers that are specific to cancer to get around this false-positive issue, and so there's some people who are looking for mutated DNA specific to cancer, it's unlikely that they are going to find that in the blood but people have found potential DNA biomarkers in the stool that could indicate colorectal cancer or in urine that could indicate bladder cancer.

Natasha Gilbert: Do any of the researchers that you spoke to for the future feel that there was a particularly, you know, strong way forward for biomarkers for the early detection of cancer?

Lizzie Buchen: Yeah, again the biggest issue is really the false-positives and making these biomarkers specific to cancer and so what a lot of people think is going to be more promising would be to do serial testing, so even for PSA people think that if you can detect PSA regularly and then you can detect when it is rising and that could indicate prostate cancer as opposed to just taking one sample and finding high levels and thinking that it's cancer.

Natasha Gilbert: Is research in the field speeding up or people getting tired and they're slowing down?

Lizzie Buchen: Well, one of the issues is that the research has been going really quickly, a lot of people are getting into the field because it's such an exciting field with so much promise, but that's been a problem because there are lot of people who for example come into the field with a lot of experience in basic cancer biology and they don't have experience in translational work which is really what biomarker research is. You have to be thinking exactly how it's going to be used in the clinic.

Geoff Marsh: Lizzie Buchen talking to Natasha Gilbert. And now 60-Second Science.

Steve Mirsky: This is Scientific American's 60-Second Science. I am Steve Mirsky. Got a minute? Want to get out of the hospital alive? Well, the nursing staff has a lot to do with it. Now a study finds that a patient's risk of dying goes up along with a number of work shifts that a hospital is understaffed in nurses. The research was published in the New England Journal of Medicine. The study included almost a 198,000 patients drawing nearly 177,000 eight-hour nursing shifts. The research team originally reported that hospital nurse staffing was tied to patient's outcomes a decade ago. That study was challenged because data were collected at several institutions and thus had numerous possibly confounding variables and the current study all data were collected at a single large academic medical centre in the US. The researchers found that a patient's risk of death increased by about 2% for each work shift that was what the researchers categorized as understaffed. Patients in the study averaged three such shifts which meant that their risk of dying increased by more than 6% compared with patients with access to fully staffed nursing teams. So when it comes to nurses it's about quality and quantity. Thanks for the minute. For Scientific American's 60-Second Science I am Steve Mirsky.

(Music)

It's unthinkable, but it must be true. A man took some tools and went where no human being had ever set foot alone. Went into the interior of the earth.

Kerri Smith: In the 1959 film version of Jules Verne's book Journey to the Centre of the Earth, Professor Oliver Lindenbrook sets off with his trusty assistants to find a path to the earth's insides.

Don't you see what's at stake here? The ultimate aim of all our plan is to penetrate the unknown, do you realize we know less about the earth we live on than about the stars and the galaxies of outer space. The greatest mystery is right here, right under our feet.

(Music)

Kerri Smith: Sounds a bit too Sci-Fi, well there's a real scientific project that isn't too far away from this goal. Scientists have drilled into the earth's crust before but now they want to break into the upper mantle, the large belt of flowing rock under the crust and before the earth's molten core. Most of what we know about the earth's insides comes from observations of its magnetic field and measurements of seismic waves which tells us about its density, but it would be invaluable to have a piece of the mantle to study. The first attempts to extract some took place 50 years ago this month, an article this week talks about them and about a new plan to drill in to the mantle. I spoke to one of the article's author, Damon Teagle. Nature 471, 437–439 (24 March 2011)

Damon Teagle: Actually drilling into the mantle would be, or will be extremely ambitious and that's because we would be drilling through very hard rocks down to a depth of probably about six kilometre or so within the oceans and of course at six kilometre depth we would encounter very high pressures but also significant temperatures and we're probably talking about 300 degrees,

Kerri Smith: But nonetheless that's what your project aims to do, right?

Damon Teagle: Eventually yes, I mean the eventual goal would be to drill and try core samples all the way through the crust and in a significant distance some hundreds of meters into the upper mantle to actually collect samples to look at the nature of the boundary between the crust and the mantle which is known as the Moho and also to maybe to install instruments or place experiment within the hole to look at the physical properties of the upper mantle.

Kerri Smith: Now there's some history to this, isn't there? There's obviously a couple of film versions of Journey to the Centre of the Earth which are kind of fictional history, but it's also the 50th anniversary this year of project Mohole, people starting to try to get a piece of the mantle 50 years ago.

Damon Teagle: Yeah, and so this is in some way a really inspirational act of a relatively few individuals in the United States of the late 1950s. So, they decided that they knew about the Moho this seismic boundary between the crust and the mantle, but they didn't really understand what that meant and actually in the late 1950s this is before the acceptance and really the complete development of the theory of plate tectonics. It really wasn't to be understanding of what the ocean crust was and why it was only six kilometer thick rather than much thicker in the continent. So a small group under the guides of an organization known as the American Miscellaneous Society had this idea that we would basically go into the oceans and try and drill a hole to the crust and then to the mantle.

Kerri Smith: And how did they get on?

Damon Teagle: Well, it was actually a truly transformative experiment through the engineering efforts of an engineer called Willard Bascom they established a dynamically positioned drilling rig, they invented all sorts of new technology that didn't exist at that stage and they actually succeeded in recovering a few meters of core from the Eastern Pacific. Now this few meters of core might sound not much of a return but they actually had showed that the oceans were actually underlined by basalt, so magnetic rocks that were formed from the cooling of magma as opposed to as some people might have thought back in the 1950s that there was going to be a full history of the earth's sedimentation all the way through in the ocean basements.

Kerri Smith: What has happened to the project since the late 50s?

Damon Teagle: The actual project Mohole itself got somewhat entrenched burdened down by politics and eventually was canceled by the House of Congress in the Untied States. The main impact it had was to actually inspire a wider group of scientists to establish what was initially the Deep sea Drilling Project and that has since led on to the Ocean Drilling Program and the currently running Integrated Ocean Drilling program in the early days of that they are led to the proof of plate tectonics and development of the whole science of paleo-oceanography and paleo-climatology.

Kerri Smith: Fast forwarding to the present time then, or at least a few years into the future when you estimate you might have a sample of the mantle from your current project.

Damon Teagle: Ah, , a thousand-dollar question, a million dollar question. First we have a cruise going out next month where we will hopefully start core into the lower part of the ocean crust, however that hole and that site is probably not ideal for drilling all the way to the mantle. So what will happen though for the next few years is that there are a number of seismic and other sort of geophysical type of cruises going out to try and identify a location where mantle drilling might be possible. Once the site has been chosen what we will then need to have is that scientists and engineers will need to work together to actually develop the engineering required to drill that specific site.

Kerri Smith: Damon Teagle of the University of Southampton.

Geoff Marsh: And that's your lot. Come back next time for a surprising finding from the Kepler mission and a radical new proposal for the US's National Institutes of Health. Till then I am Geoff Marsh.

Kerri Smith: And I am Kerri Smith.Filmed in the incomparable magic of cinemascope.