Nature Podcast
Introduction
This is a transcript of the 11th June 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 on the box office-smashing, popcorn-scoffing, soda-swigging Nature Podcast:
One typhoon against all odds triggers an earthquake to end all quakes.
When planets collide... none will survive
And death shall have no dominion over the rise of the immortal nematodes. The search for extraterrestrial life comes to our planet.
This is the nature...
Adam Rutherford: Sorry about that. This is the Nature Podcast. I'm Adam Rutherford.
Kerri Smith: And I'm Kerri Smith. Yep you've guessed it. This week all our science sounds like it could be from a bad 'B' Movie. We're starting with the search for life on other planets. One team reporting their work in Nature this week reasoned that there is no sense in looking elsewhere in the Universe before you've tried out your methods, somewhere you already know harbours organic life forms. So they turned their attention to Earth. They waited for lunar eclipse and then analyzed the light passing from the sun through the earth's atmosphere and reflect it off the surface of the moon. Luckily, it worked. Here's Enric Pallé of the Canary Islands Institute of Astrophysics. Nature 459, 814–816 (11 June 2009)
Enric Pallé: The first thing we need to do before we go out there searching for life is to do look back at our own planet to see how we will look like to an extraterrestrial observer, to someone who's looking at us from an astronomical distance. So that's what we've been trying to do in this work.
Kerri Smith: So when scientists go looking for life on other planets then, which they have started to do, what do they actually look for?
Enric Pallé: To mention the characteristics when you're trying to find life is to try to search for the signatures of some atmospheric components in that planet atmosphere. In particular, if you want to be able to say that the planet is inhabited or if there's a reasonable chance that there's some biology going on, on the planet or on the surface, if you find the spectra for example CO2 and water vapour and oxygen, then you can say that there's a very large chance that this planet is inhabited because these three gasses would not coexist in an atmosphere without life.
Kerri Smith: So if a planet is outside the solar system, researchers would usually try and observe these gasses by analyzing the starlight reflected from the planet's surface, but how did you do this for the earth, given that you were on the surface at the time?
Enric Pallé: So what we did is we observed a lunar eclipse and in particular, we observed the spectra of the light that was reflected from the umbra of the moon, the dark side of the moon. Now, if you sit in the umbra of the moon when an eclipse happens you'd not see the sun. The earth and the sky would be larger than the sun and the sun will be completed blocked by the earth. Still you would receive sunlight because the ring of atmosphere around the earth would let sunlight pass through it and bend it a little bit so it'd reach you on the dark side of the moon on the umbra and this starlight that has gone through the earth atmosphere carries the signature of the transmission spectra of the earth and involve the components of the atmosphere.
Kerri Smith: So when you had analyzed this transmission spectrum then at the time of the lunar eclipse in 2008, I think it was wasn't it, did you find life on earth? Did your techniques succeed?
Enric Pallé: Yes for sure, we did find life on earth. We find the signature of water vapour, oxygen, CO2, methane, which is also a component of organic origin. We also find the signatures of nitrogen and we also find some components of the ionosphere that tell us something about the outer layers of our planet and in particularly about the magnetic field of the earth. So we did find a lot of things, interesting things, and definitively if we had these spectra for an extra solar planet, we would reach the inevitable conclusion that there is life on that planet.
Kerri Smith: That must've been a relief to find that they were working and to find that you could indeed pinpoint life on earth.
Enric Pallé: On yes, yes it was. Well, actually, it's a very positive result that we have here because it is tell us that finding life in the Universe may not be as tough as we thought. The reason is this is a typical case in which we thought how the spectra would look like when nobody actually did the observations. When we actually went and did the observations, our models told us that the signatures of all these gases should be there, but they would be very faint, but in fact they are very large because there were geometric changes and we're passing through a very long path through the atmosphere. So even the smallest components like methane, which is not very abundant in the atmosphere, has a very a broad and very deep signal, which means that if we have a planet that has little methane like our planet earth, but we observed it in transmission we will see that the methane is there.
Kerri Smith: So you must be very hopeful in that case, that we'll soon be able to look for life in other planets, you know, in a really robust way.
Enric Pallé: Yeah still need the missions to be funded because the present missions that we have now flying may be able to find a few candidates, a few planets, the size of the earth or little bit bigger around sun-like stars or smaller around M stars for example some of these planets may be within the habitable zone of the star, but to go and characterize them seriously, we need to the next level of missions.
Kerri Smith: Enric Pallé.
Adam Rutherford: More planetary movie potential coming up later in the show when Geoff finds out how likely it is that our planet will be annihilated by Mars? But before that, how one natural hazard could be protecting us from another. Charlotte Stoddart has this report.
Charlotte Stoddart: Above ground the violent swirling winds and heavy rains of a typhoon are all too obvious. But new research from the Carnegie Institution of Washington and the Institute of Earth Science is in Taiwan suggest that typhoons can also have an effect underground. Using a small network of strainmeters buried in bore holes in eastern Taiwan, the researches show that typhoons can trigger slow earthquakes lasting hours or even days. What's more, these typhoon-triggered earthquakes may be protecting the area from larger, more damaging quakes. Co-author, Alan Linde told me more about the research and this slow variety of earthquake. Nature 459, 833–836 (11 June 2009)
Alan T. Linde: What we found, much to our surprise, was that at the time of typhoons passing over the land in Taiwan, they seem to trigger these events, which we call slow earthquakes. These are events in which the strain released or stress released on force in the same way as regular earthquake would do, except that the time scale are much, much longer.
Charlotte Stoddart: How common is this variety of earthquake?
Alan T. Linde: Slow earthquakes, that's extremely difficulty to answer because unfortunately you have to be rather close to them to be able to detect them. Because the motion is slow there's a little bit acceleration, which means that we don't generate seismic waves. They have been seen in a number of places, we've seen them in California and there have been a number found in southwest Japan as well.
Charlotte Stoddart: So if I were in Japan when one of these slow earthquakes happened, would I be able to feel it?
Alan T. Linde: No. A person would have observed absolutely nothing. In fact as I mentioned, you've got to have the right instrumentation close enough to be able to see it.
Charlotte Stoddart: So you've used some very sensitive instruments to show that slow earthquakes can be triggered by typhoons. Now that sounds pretty incredible to me. How does a typhoon, which is basically a rotating column of air, trigger an earthquake?
Alan T. Linde: It sounds pretty incredible to us too when we first started looking at it. Typhoon is an area of low pressure, that's we believe is the significant thing here. So that when the typhoon passes over the land at low atmospheric pressure acting on the earth's surface that's very, very small, but it clearly is sufficient it turns out to unclamp or unfold of depth sufficiently that provided this closed to that area and that's critical in this whole concept, these things are acting as triggers in that prime forcing function. So provided the area has got forces extremely close to those areas and provided that these force are such that like they can fail in the slow manner then you can get these slow events and that's what I think quiet clearly have observed in Taiwan.
Charlotte Stoddart: How did you show that it really is these typhoons causing the earthquakes? How did you demonstrate that?
Alan T. Linde: We first noticed this several years ago. At that time, we only had a few events 4 or 5 I believe. We waited a few years and now we have approximately 20 of these events that we have seen and if half of them occur at the same time as the typhoon comes through or they come just after the low pressure on land due to the passage of the typhoon. This is then repeated several years and if you do a simple statistical test to look to say what are the chances of this happening at random, in other words this could be a coincidence, well what's the chance of that being a coincidence? Well we ran those tests and we found that the chances of being a coincidence, but no real connection, is less than 1 in 10 or a 100 million and that's vanishingly small.
Charlotte Stoddart: So you're pretty sure then that it is the typhoons triggering the earthquakes?
Alan T. Linde: We're quiet sure, well, yeah we're quiet sure that we've got a triggery effect going on.
Charlotte Stoddart: Now in your paper you suggest that these typhoon-triggered earthquakes are actually protecting us from larger more damaging earthquakes. How do they do that?
Alan T. Linde: First of all let me be very clear, that's a speculation that this area of Taiwan is undergoing tremendous deformation. It's one of the most rapidly deforming areas on earth. The Philippine Sea plate is colliding with this part of Taiwan on the southeast coast. It's colliding at about eight and a half centimetre a year and normally you'd think of that as generating quiet a lot of earthquakes. For example, if I compared with another place where the Philippine Sea plate is colliding with Japan further to the northern east and that area experiences a magnitude 8 earthquake every 100 to 150 years. So we'd expect to have at least 1 or 2 magnitude 8s by now, we haven't. There have been a few magnitude 7s, but the amount of seismicity, the amount of energy released from seismicity doesn't add up to even 1 magnitude, especially from that. So what we suggest is happening here is that these slow events are relieving the stress, the strain and the stress on a segment of the fold, so that instead of having one long fold that could be stressed, its now broken up into small stress sections and the rupture starts in one, it doesn't propagate through because there's an area without stress.
Charlotte Stoddart: This is fascinating. I was really surprised when I read the title to your paper. I thought how can a typhoon possibly trigger an earthquake?
Alan T. Linde: You're absolutely right. It is surprising. We were surprised that frankly the data is simply unequivocal. There is no arguing with it.
Adam Rutherford: That was Alan Linde talking to Charlotte.
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Kerri Smith: We've got the news review coming up later in the show with critic Mark Peplow giving us the low down on some new releases. But first: The worms that refused to die. Adam?
Adam Rutherford: Who wants to live forever? Well of all the species in the world, the nematode might be the best to ask. Much of the work on longevity is done in this millimetre-long worm because they reproduce quickly and their genetics can be easily tweaked. Gary Ruvkun from Harvard Medical School has been looking how the hormone insulin can affect the lifespan in the worm. When they looked at the insulin pathways in one of their long-lived mutants, they saw their body cells called soma, behaved more like the cells of the gonads called germline cells. These cells are effectively immortal as they're passed on from generation to generation whereas body cells can only reproduce a limited number of times. I spoke to Gary this week and started by asking him how much he can extend the life of a worm by messing with insulin. Nature advance online publication (7 June 2009)
Gary Ruvkun: So the normal life span is about 2 weeks in sort of wild type animals, and if you inactivate insulin pathway, it will go to 3 times that and other labs, not my lab, other labs that sort of combine different mutations have gotten the worms to live 6 times as long. So you can really increase the lifespan of a worm a lot.
Adam Rutherford: So you studied the insulin pathway in nematode worms and C. elegans, how does that pathway, how does insulin affect the ageing process in normal worms?
Gary Ruvkun: Well it accelerates it, so if you have insulin signalling, you live a shorter lifespan, which says that in a way the short lifespan is a kind of a program that the animal is, sort of, choosing to lead a short lifespan. And the reason that I think insulin signalling works so well is that when animals are under stressed condition, they actually turn down that hormones. So it's really a signal of being stressed and so when we genetics turned down that hormone turned down insulin. We're kind of mimicking what normally happens in the stressed state and the animal kicks in a whole program that includes cessation of reproduction and protection of its somatic cells for mutation and the expression of these RNAi components and so it's a whole repertoire of responses and that's why it works so well.
Adam Rutherford: And in your long lived mutant worms, you're saying that insulin metabolism that normally exists only in the germline cells in the gonads that transfer to the soma, which is what's making them live longer.
Gary Ruvkun: That's right. So what it says it that there are attributes of the germline that can be kind of transposed to the soma and what is, I think, important is that it happens normally. We're dealing with mutants that make this happen, but low insulin signalling is something that happens in normal physiology. It happens when an animal is starved for example and so during that stressed moment, cells will now elaborate these germline characters.
Adam Rutherford: So Gary, let me just ask, it might sound like a pretty stupid question, but diseases like cancers and neurodegenerative diseases and cardiovascular diseases, these are the diseases that kill people rather than just old age which is what we used to think of as being a source of death, but what do worms die of?
Gary Ruvkun: Good question. You know, there is not just enough worm pathologists out there to figure it out. We don't know what they die of, but what we do know is that their muscles degenerate and that's what's called sarcopenia in old humans. So there is a homology at that level.
Adam Rutherford: And so let's just say if we can transfer some of this new information onto longevity in humans. Does it mean that if you're looking at a pathway such as insulin, which is pretty well understood in higher mammals and humans does it mean that we may be close to identifying may be drug targets that could help prevent some of the ravages of ageing?
Gary Ruvkun: The finding that the worm insulin regulate ageing predicted that that would be true in mammals and that has been borne true, so in mice if you ask what's the major determinant of a lifespan of a mouse, insulin like growth factor is the major, major determinant of that and in humans, Neil's lab has been looking at a 100-year-old humans whether they have mutations in their insulin like receptor pathways and this he sees a major enrichment in 100-year-olds. So the view is that the regulation of lifespan is something that a common ancestor of worms and humans did with insulin signalling. And so again we've inherited that in common and so what one discovers in the worm could turn out to be true in mammals, but again we have not all proven that this increase in the RNAi protective pathways is what happens in humans as well but I would bet on that.
Adam Rutherford: Gary Ruvkun.
Kerri Smith: We're almost out of popcorn here in the Nature Pod Studio, but we've just enough left for one more disaster movie trailer. Here's Geoff Brumfiel.
Geoff Brumfiel: The markets are falling; greenhouse gasses are rising, sometimes it sort of feels like the end of the world doesn't it? Well that's nothing compared to what Jacques Laskar of the Paris Observatory is worried about. His orbital models are predicting a finite chance that Venus or Mars could collide with the earth. Not to panic, it won't happen for another 3-1/2 billion years or so if it happens at all, but the pod team wanted to know how to prioritize their many anxieties. So I called Laskar at his home outside Paris to find out how much worrying we all should be doing? Nature 459, 817–819 (11 June 2009)
Jacques Laskar: You probably learnt at school that the planets revolves on ellipses around the sun, but since quiet a long time, it's known that the planets perturb each other so that this ellipse is on that fix, but they change shape and thus the question is whether or not there could be collisions between the planets. So if you look only of 10 to 50 million years you will only see this small change, but then this motion on the longer time when you look at it, it is chaotic. If you take two orbits with only 15 meter difference which means you make 15 meter error in the position of years for example, after 10 million years you have 150 meter error but after 100 million years, you have 150 million kilometre error, which means that you cannot predict where the earth will be in the 100 million years. So still it doesn't mean that the earth will collide with the sun. It means you don't know whether the orbit will be elongated or circular. You don't know how it will be elongated and to go beyond that you can only look to the problem in a statistical manner and this is the subject of this paper. It was to check whether on the life time of the solar system, there could actually be collision between the planets.
Geoff Brumfiel: So what did you find I mean are we all going to die?
Jacques Laskar: Well, the first thing is the planets that is the most chaotic is Mercury and this is due to a near-resonance between Mercury and Jupiter and this can make Mercury orbit to be very elongated and thus to be able to collide with Venus, but if Mercury collides with Venus it doesn't affect much of the earth but it changes somewhat the dynamics of all the orbits in the inner solar system and if you just have close encounter with Venus without collision, then Mars could be excited, the orbit could change more and then you could have close encounter between Mars and the Earth.
Geoff Brumfiel: So what would this close encounter do, I mean what would happen?
Jacques Laskar: If there was really a close encounter of Mars with the earth, then it will be terrible on the earth because there will be huge tides eventually, you know, when I mean close encounter it could be an encounter where the two surfaces are at only 1000 kilometre apart, even 10,000 kilometre would be already, it would be devastation on the earth and on Mars.
Geoff Brumfiel: And how likely do you think this is, that something like this would happen?
Jacques Laskar: Yes there are 2 questions then. One is when could it happen? And the probability how likely it could happen? The first thing it cannot happen very rapidly. In this experiment, this collision we'll not obtain before 3 billion years because these are still small perturbations, so they take time to develop.
Geoff Brumfiel: 3 billion years that's basically double the age of the solar system almost right?
Jacques Laskar: Yeah, but the life time of this one is still off about 5 billion of years so this event is before the end of the life of the sun.
Geoff Brumfiel: Okay, so, so then what about the probability? How likely is it to happen?
Jacques Laskar: Now the probability, well the probability is low. The first think you need to have is Mercury needs to go to a very high eccentricity to be able to trigger this phenomenon because in fact its really Mercury that is able to pump some eccentricity from Jupiter basically and the probability for Mercury to go to very high eccentricity, we found it to be about 1% within 5 billion of years. The probability for Mars or Venus to collide with the earth is much smaller 1/10000 something like that.
Geoff Brumfiel: So basically it sounds like we don't need to start packing our bags just yet.
Jacques Laskar: Not yet no. We've got time. You know its more, people have always thought that the solar system was stable within its age or within its life expectancy and this really showed that it actually is not the case for the small planets.
Geoff Brumfiel: It's sort of a worst case scenario for the solar system then?
Jacques Laskar: It's a possibility; it just show's that it's possible to have such a solution compatible with our present position of the planet.
Kerri Smith: Jacques Laskar reassuring Geoff that we probably won't get obliterated anytime soon.
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Adam Rutherford: Finally this week, Mark Peplow is here with some nuggets of news for us and sticking with the disaster movie theme, we hear that the govenator is facing Judgment Day yet again.
Mark Peplow: Yeah. Hi Adam. Arnold Schwarzenegger is in big trouble. The California budget deficits is causing him a huge headache and now it's becoming clear what the knock-on effect the Universities in California is going to be.
Adam Rutherford: So how bad is it?
Mark Peplow: It's looking pretty grim actually. The California budget deficit is about 24 billion dollars, largely triggered by the economic downturn. Schwarzenegger at the end of May went to the people of California, it was a poll basically to say, I have the possible solutions including tax rises, borrowing more, lots of other measures like giving school kids longer holidays so that you can pay teachers less, things like that and basically they were all roundly rejected. There was a clear message, "no you just have to spend less." Now over the coming year, for example, the University of California system which is spread over 10 different campuses, that was going to get 3.2 billion dollars in state funding that's going to be cut now, cut by 800 million dollars.
Adam Rutherford: So it's going to be cut by a quarter, that's going to have some pretty significant knock-on effects.
Mark Peplow: Absolutely. So the University of California has raised tuition fees for its students by almost 10% that's 225 thousand students that are going to be affected by that.
Adam Rutherford: And what about the institutes themselves, what are we going to see in terms of cutbacks for research programs?
Mark Peplow: Well there is a real catalogue of stuff here. Just for example the University of California, Riverside, the campus has already halted projects totalling about 185 million dollars. That includes the genomics facility that has been built but its now not going to furnished or catered out, so that people can use it just as a way of saving money.
Adam Rutherford: So it's going to sit empty with no furniture.
Mark Peplow: Certainly in the short-term that's the way they are shaping out.
Kerri Smith: Troubling times then if you're at the University of California. Now the second story you've brought into the pod concerns the potential bias in clinical trials.
Mark Peplow: Yeah, this is really interesting actually. This is our first study published in the Journal Cancer last week showing that women are underrepresented in cancer studies. This was a research done by Reshma Jagsi at the University of Michigan, where basically she looked at hundreds of cancer clinical trials that included more than half a million participants to access just what proportion of women were involved in them and she found that basically three-quarters of the studies underrepresented women. According to the standard, you want to try and get the same percentage of women in the clinical trial but actually succumb to that kind of cancer. Now clearly this is a big problem if you don't have enough women in the trial, you'll not necessarily going to be developing a drug which is as good at treating women as in men.
Kerri Smith: So presumably then in the study are now included cancers that are gender specific.
Mark Peplow: Yeah, that's right. Jagsi's own failed which is breast cancer obviously you get a almost 100% of study participants are women, but she was looking at things like lung cancer for example where you get 45% of lung cancer diagnoses are in women, but on average only about 31% of lung cancer study participants are women.
Kerri Smith: So why is that then is the proportion of women getting these cancers is you know is not dramatically lower?
Mark Peplow: Well for a problem that's actually been known about for quite a long time, there are surprisingly few good answers to that. She thinks that one of the key problems may be that women of childbearing age are generally thought to be a "vulnerable group" and people who are setting up clinical trials are more averse to including vulnerable groups in their trial. As the researches pointed out, if you're protecting them in that research you may actually be excluding them from the potential benefits of that research in the longer term and other reasons include things which might on the face of it, appears to be quite mundane. Women tend to have more childcare responsibilities. So it's often not worth their while, actually losing time and money in order to participate in clinical trials.
Kerri Smith: So how are they addressing this, this obvious problem then?
Mark Peplow: Back in 1993, the NIH was charged with tackling this problem and there's some evidence from this survey that they maybe having some success. The meta analysis showed the studies using government funding do actually include high numbers of female participants, but again the key thing according to Jagsi at least is the more research is needed into exactly why women aren't getting into these clinical trials and how you can remove those barriers to try and even the score.
Adam Rutherford: Okay and finally we're going off world with another voyage to the moon.
Mark Peplow: Yeah, this is really exciting. Next Wednesday NASA is launching its Lunar Reconnaissance Orbiter to the moon, which is really primarily a mission about hunting for ice.
Adam Rutherford: Ice on the moon, the moon doesn't have any atmosphere, it's pretty dead, it's pretty dry out there. What exactly, where exactly are they looking?
Mark Peplow: Yeah. They're looking in the dark shadowy niches of craters, particularly at the poles of the moon where for example water-bearing comets could have left traces of ice, deposits of ice there or there is even the potential that the solar wind of hydrogen ions hitting the moon over time can actually combine with oxygen and minerals on the surface to actually build up small deposits of ice, if they are left in shadows they never get touched by the sun so they build up over time.
Adam Rutherford: That is pretty amazing, I had no idea. But specifically are they looking for signs of life within that water or is it just detecting water that's going to be amazing.
Mark Peplow: No, no... No sense of life in there at all. Just to find ice there to confirm that there is ice on the moon's surface would be interesting from a scientific point of view because its going to help us to understand well could it really have survived for a long term from say a comet impact, but potentially very useful as well. The clue of this mission is in the name Lunar Reconnaissance Orbiter. This is a reconnaissance mission. What it wants to do is to find deposits of ice. The water could be split into hydrogen and oxygen, hydrogen for rocket fuel and oxygen for astronauts to breathe in a moon base. So this is very much about scoping for resources on the moon.
Adam Rutherford: So do we think that this is the first step to return to the moon just 40 years after we first touched down there?
Mark Peplow: This is a big part actually of preparing for trying to set up a more permanent man station on the moon. This is a very early step towards that because you need to know what resources you've got.
Adam Rutherford: So this is an orbit. It's not going to land on the moon. How they are actually going to detect the ice.
Mark Peplow: Well the orbiter has a bunch of instruments that its going to be able to use for remote sensing, but one of the biggest parts of the mission involves something called LCROSS and that's a lunar impactor and its basically a massive chunk of metal which is going to crash into the moon and the way this mission is set, yes there is this orbiter, but you also have the upper stage of the Atlas V rocket on which the whole caboodle is being launched. That's stringed up with little sort of a what's called a shepherding spacecraft. Now while the orbiter gets in position to orbit around the moon, the Atlas V rocket is going to be gathering speed as it orbits the earth and then head straight for the moon. The impact is due for the 8th of October. Basically that's going to crash and its going to be followed about 4 minutes later by the shepherding craft and its going to in theory take up a huge plume of dust and ice in also sorts and you can analyze and all the stuff that comes out of the moon from that impact.
Adam Rutherford: That's very cool, who designed that?
Mark Peplow: It's amazing isn't it? So when you compare with previous things, it's not the first time that we've used this sort of lunar impact idea. You know Chandrayaan-1, the Indian spacecraft did something similar last year but this is just massive. I mean its 2-1/2 tons. It's going to create a crater about 20 meters wide 3 meters deep they estimate. So it's an order of magnitude bigger than any of those man-made impacts on the moon before.
Adam Rutherford: And totally changing the face of the moon forever again.
Mark Peplow: Yeah I mean a crater that wide you should be able to actually see that.
Kerri Smith: All right. Well thanks Mark for bringing in those 3 movie pictures. I don't about you Adam I think that last one will definitely turn into a film.
Mark Peplow: Sci-Fi-tastic.
Kerri Smith: More news available on the Nature News site at http://www.nature.com/news, funnily enough.
Adam Rutherford: That's it for now. This week's feature presentation was directed by Kerri Smith, produced by Charlotte Stoddart. Key grip was me, Adam Rutherford and Geoff Brumfiel was the best boy.
Kerri Smith: I'd like to thank my mom and my dad and my agent and also those nematode researchers and the planetary scientists and my makeup artist...
