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Home » Page 1526

Geoengineering could be needed to halt climate change

New technologies that remove carbon from the atmosphere could be needed to combat man-made climate change, according to a report published today by the Royal Society.

Most attempts to deal with climate change involve reducing emissions of carbon dioxide – the report also calls for governments to work towards an agreement to cut carbon dioxide emission by 50% on 1990 levels by 2050 – but some scientists believe that this may not be enough to stop the planet’s average temperature rising by 2 °C by the end of the century.

Geoengineering is the deliberate intervention into the climate system to counteract man-made global warming. It could offer a solution to climate change, but some scientists are reluctant to discuss it, fearing that it could encourage complacency in cutting emissions.

Giant sunshades

The Royal Society report, Geoengineering the climate: Science, governance and uncertainty, looks at different geoengineering options for tackling climate change, including constructing giant sunshades in space that can reflect the Sun’s rays and introducing iron into the world’s oceans to rapidly increase the amount of phytoplankton that consume carbon dioxide.

The 12 authors of the report – led by John Shepherd from the UK’s University of Southampton – divide geoengineering into two types: carbon dioxide removal (CDR) that acts to removes carbon dioxide from the atmosphere and solar radiation management (SRM), which involves reflecting sunlight back into space.

Soaking up carbon

They conclude that CDR technologies would be best suited to combat climate change. These include capturing carbon dioxide from ambient air as well as using land to soak up carbon. “It is too soon to pick winners,” says Shepherd. “We need more research into several avenues to decide which technologies are most effective.”

However, they conclude that SRM methods, such as constructing giant sunshades in space and pumping aerosols into the atmosphere to reflect sunlight, would not be long-term solutions and their usage offers potentially dangerous consequences. “Using aerosols would be like taking an aspirin to cure a headache,” Shepherd told physicsworld.com. “But it might not be a long-term solution to the underlying problem.”

The report, which contains seven recommendations, calls for £10m per year to be spent by UK research councils to fund geoengineering projects. “This is still only about 10% of what the UK spends on climate change,” says Shepherd. “We must make sure that the projects are researched in a responsible manner and that they are openly discussed.”

For a detailed discussion of geoengineering schemes, see “Engineering the climate”, which appears in the September issue of Physics World.

Physicists shed light on mysterious battlefield injury

A common battlefield brain injury could originate in the blast waves of nearby explosions, even though such waves cause relatively small accelerations of a soldier’s body. That is the conclusion of physicists in the US who have used computer simulations to study the causes of traumatic brain injury (TBI), a poorly understood condition that appears to be on the increase.

According to the simulations, the blast waves of grenades, landmines and other devices can bypass a soldier’s helmet, distort the skull and inflict potentially dangerous loads on the brain. These loads may be sufficient to cause TBI, even when there has been no contact with shrapnel from the explosion.

“This is a potential new mechanism,” explains William Moss, a physicist at Lawrence Livermore National Laboratory (LLNL) in California and an author of the study. “There are so many candidate possibilities [for TBI] that have been put out by the Department of Defense and others – they’re frantically searching for an answer to this problem.”

TBI has many symptoms and can lead to disabilities or even death. It has become more prevalent as modern armour has cut the number of outright kills from explosives, but no one is sure of the cause. Physicians know that it is linked to explosions, but just which of the many effects of explosions – the impact of shrapnel, the inhalation of toxic gas, or the blast itself, perhaps – has been a mystery.

A model soldier

Moss’s group has now shown how a blast wave could result in TBI. Their simulation is a matrix with a 2.3 kg charge of C4 high explosive situated roughly 4 m from a body with a simplified head containing three layers: a skull, a layer of spinal fluid and a brain. With knowledge of how the pressure front generated by a C4 explosion travels through the air, and by characterizing the material properties of the three head layers, the researchers could calculate the brain’s response.

A normal, direct impact of an explosion damages the body through an extremely high acceleration. The US group discovered that the accelerations from blast waves are far smaller yet at the same time are able to squeeze the skull and create pressure gradients that are much larger, at several atmospheres per centimeter. These pressure gradients can deform the skull by 50 µm, which for a confined brain is enough to cause serious injury. Even with an added Kevlar helmet, the simulations exposed dangerous loads that could potentially lead to TBI.

“When we sat down and compared [the predictions] to guesses from doctors and biometricians of what stress levels they thought might be bad, we were in the same order of magnitude,” says Michael King, Moss’s colleague at LLNL.

Anthony Strong, a neurosurgeon at King’s College London, thinks the study makes “interesting reading”. “I have seen one or two teenage patients with head injuries where the inference was inescapable that their skull, at least at that age, must be more flexible than we usually assume,” he adds. “The only problem for me is that I have no way of knowing whether the assumptions made [in this study] about skull elasticity are reasonable.”

Funding required

The US group – which includes Eric Blackman of the University of Rochester – agrees that some of the materials included in the simulations, particularly the Kevlar, should ideally be better characterized. However, the researchers have not yet secured funding to continue their research. If they do get the opportunity to continue, they say they would improve the fidelity of the model and evaluate different types of armour.

In the meantime, the study may encourage the military to reconsider the design of helmets, and to focus on the type of data collected for studying battlefield injuries. Currently, the US military fits some soldiers with accelerometers and single-point pressure gauges to collect data on explosion impacts, but Moss and King suggest that more sophisticated instruments, including more pressure gauges and strain gauges, are needed to completely determine the nature of the injury.

The research will be reported in Physical Review Letters. A preprint is available at arXiv:0809.3468.

Engineering the climate

The climate change we are experiencing now is caused by an increase in greenhouse gases due to human activities, most notably the burning of fossil fuels, agriculture and deforestation. Although global warming has been around in the scientific literature since a landmark paper by Swedish physicist Svante Arrhenius in 1896, it has only been in recent decades that our scientific understanding of the climate system has made it clear that a global warming of greater than 2 °C above pre-industrial levels may be dangerous and should therefore be avoided.

While greenhouse gases include not only carbon dioxide (CO2) but also methane, nitrous oxide, ozone and CFCs, international political negotiations have focused on the need to reduce CO2 emissions. In three months’ time, the 15th Conference of the Parties (CoP15), part of the United Nations Convention on Climate Change in Copenhagen, will aim to set binding targets for emission reductions (so-called conventional mitigation). But even if global CO2 emissions are cut by 50% by 2050, this now seems unlikely to be enough to keep global warming below 2 °C this century. Indeed, since the Kyoto protocol to limit greenhouse gases was established in 1997, global CO2 emissions have continued to climb despite growing concerns over climate change. Given that conventional mitigation now appears insufficient to avoid dangerous climate change, do we have a plan B? This is the motivation for geoengineering, a term that describes deliberate intervention in the climate system to counteract man-made global warming. This can be achieved in two ways, by direct removal of carbon dioxide and by solar-radiation management, which aims to cool the planet by reflecting more sunlight out into space.

Removing carbon dioxide

The most obvious approach to CO2 removal is to plant forests, but this is relatively inefficient and requires large areas of land. A more radical suggestion is to fertilize the ocean with a limiting nutrient such as iron in the hope of enhancing the oceanic carbon sink (which currently absorbs about 25% of man-made CO2 emissions). Small-scale ocean-fertilization experiments have produced artificial phytoplankton blooms through the addition of iron, but it is questionable whether this will translate into a long-term enhancement of the carbon sink. A major risk with this approach is that ocean currents make it impossible to contain the area over which ocean ecosystems are modified by the addition of nutrients.

A safer method of removing carbon dioxide is air capture, which involves chemical or physical extraction of CO2 from the air and burial of the carbon in geological stores. The storage part of this approach is similar to conventional carbon capture and storage, which aims to remove the CO2 from the exhaust gases of fossil-fuel power stations. Air capture can in principle be carried out at any location, although it is most useful close to the geological stores. Chemical methods of air capture typically involve the reaction of carbon dioxide with sodium hydroxide to produce sodium carbonate, whereas physical capture involves ion-exchange resins that are able to filter CO2 from the air, which can subsequently be washed from the filters with water. There are major advantages to air-capture techniques because they remove the primary cause of global warming and, unlike conventional mitigation, offer the possibility of reducing CO2 concentrations below current levels. However, these techniques are currently expensive and carry the associated difficulties of finding suitable stable geological stores for the carbon.

Blotting out the Sun or brightening the planet

An alternative to the removal of carbon dioxide is solar-radiation management, which involves reducing the amount of sunlight absorbed by the Earth as a whole. The global mean temperature of the planet is determined by the balance between the solar radiation absorbed and the infrared radiation lost by the Earth to space. It is possible to cool the planet by either increasing the amount of infrared radiation lost to space (as in the CO2 removal techniques) or by reducing the amount of solar radiation absorbed by the planet. Managing solar radiation involves either blotting out a fraction of the sunlight using space-based sunshades or increasing the brightness (albedo) of the planet.

Space sunshade
Space sunshade

There are various techniques for surface-based solar-radiation management: the so-called white-roof approaches, in which human settlements, predominantly roofs and pavements, are painted with reflective materials; selection of brighter crop and pasture plant species; and even more radical plans that would involve covering the deserts with highly reflective plastics. The climate benefits of these techniques vary with the area modified. For example, white-roof approaches have a relatively small impact on global mean temperature, because human settlements still only cover about 2% of the global land area. On the other hand, large-scale modification of plant albedos could yield a global cooling sufficient to offset global warming to date, but other more urgent pressures on agricultural productivity probably make this approach impractical. Brightening of the deserts could have an even greater cooling effect, but such localized forcing of the climate system carries the risk of changing critically important atmospheric circulations, such as the monsoons that bring rainfall to significant fractions of the Earth’s population.

Similar risks are associated with techniques to brighten the clouds, since these will obviously operate only where the clouds exist. However, modifying cloud albedo is a potentially large lever on the climate that could provide a global cooling to offset a doubling of atmospheric carbon dioxide. The most advanced cloud-modification proposal involves whipping up additional sea salt to provide extra cloud-condensation nuclei that would make marine stratocumulus clouds brighter – these are the lower-altitude clouds over the coastal regions and oceans. The cloud-modification proposal has gone as far as designs for the automated ships that would deliver the extra sea salt to the stratocumulus clouds. The costs involved with this approach are unclear, but they are likely to be significantly less than a similar cooling produced by conventional mitigation.

An even cheaper technique may be to mimic the climatic impacts of major volcanic eruptions by injecting particulates or “aerosols” into the Earth’s stratosphere (upper atmosphere). These aerosols would reflect additional sunlight just as they did after the eruption of Mount Pinatubo in 1991, which led to a global cooling of about 0.5 °C. Ideas of this type probably originated with the Russian physicist Mikhail Budyko in the 1970s, who suggested using sulphur as the basis for the stratospheric aerosols as is the case for volcanic eruptions. The notion of geoengineering through stratospheric aerosols was subsequently pursued in the 1990s by physicist and H-bomb inventor Edward Teller, who envisaged more-sophisticated reflecting particles. But the discussion of geoengineering proposals remained taboo among mainstream climate scientists until 2006, when chemistry Nobel laureate Paul Crutzen reassessed the utility of injecting sulphur into the stratosphere in the light of the climatic effects of the Pinatubo volcanic eruption. Concerns remain about uncertainties in the regional response of rainfall to the combination of elevated CO2 and reduced sunlight, and in the potential impact of additional aerosols on the recovery of the hole in the ozone layer. However, the estimated costs of maintaining a sulphate aerosol shield, most likely through a small number of dedicated high-flying aircraft, are remarkably cheap compared with the costs of conventional mitigation by factors of hundreds or even thousands. For that reason, stratospheric aerosol techniques are considered by many to be the most promising alternative to conventional mitigation.

The most sci-fi of the techniques for solar-radiation management involves placing sunshades between the Sun and the Earth. The most promising sunshade position appears to be at the L1 Lagrange point, which is the position about 1.5 × 106 km from Earth towards the Sun, where the gravitational attraction of the two bodies cancel. At this point, sunshades of about 3 × 106 km2 would be required to counteract a doubling of CO2. There are formidable challenges associated with the design and manufacture of light, durable materials that could be used for the sunshades, but the primary long-term costs are likely to be associated with the launch of the elements of the sunshades and their routine repair and replacement. Even if such a geoengineering approach proved to be technologically and economically feasible, there are massive international governance issues to be negotiated before implementation. Such issues are also common to the other large-scale techniques such as desert-albedo modification, cloud-albedo modification and stratospheric aerosol injection, all of which involve cooling the global climate but will not offset all regional climate changes and could even exacerbate changes in some regions. In addition, techniques based on managing solar radiation obviously do not deal with the uncertain effects of ocean acidification due to increasing CO2.

Lifting the taboo

According to the Stern Review, which was published in 2006 and is one of the most influential documents on the economics of climate change, using conventional mitigation to avoid a potentially dangerous 2 °C global warming would cost up to 1% of global gross domestic product, about $350bn per year at current prices. The figure above summarizes the potential of the various geoengineering proposals based on an assessment published by the Royal Society this month. In addition, it compares each of the techniques against conventional mitigation, as this represents the most obvious solution to global warming and is at the heart of international climate negotiations.

Plan b
Plan b

Geoengineering alternatives can be assessed based on annual costs, benefits in terms of the reduction in global mean temperatures and the risks associated with each technique. These factors are shown schematically in the figure. While some approaches, such as ocean fertilization or white-roof techniques, can be ruled out because they are unlikely to have a significant global climate benefit, most of the geoengineering proposals appear cheap compared with conventional mitigation. More importantly, many have a higher climate benefit to annual cost ratio than conventional mitigation (i.e. they lie above the dotted line).

The benefit-to-cost ratio appears largest for stratospheric aerosol injection, although this carries the risks of regional climate change and delaying the recovery of the hole in the ozone layer. In addition, highly effective techniques for solar-radiation management such as sulphur aerosol injection carry what is sometimes called “termination risk”, that is the risk of sudden global warming in the event of failure of the geoengineering. The flip side to this termination risk is that such approaches can be deliberately switched off if unintended consequences emerge.

The safest alternative to conventional mitigation is CO2 air capture, which removes the primary cause of global warming and therefore avoids the risks associated with termination, regional climate change and ocean acidification. Currently, however, air capture appears expensive relative to conventional mitigation and very expensive relative to large-scale techniques for solar-radiation management.

The primary reason there has been so little debate about geoengineering amongst climate scientists is concern that such a debate would imply an alternative to reducing the human carbon footprint. In the worse case this might retard international climate negotiations. But there is now a growing feeling that it is time to lift the geoengineering taboo so that proper scientific research can be carried out prior to any potentially dangerous large-scale implementation on the climate system, as highlighted by this month’s Royal Society report. Research priorities should include an assessment of the impact of techniques for solar-radiation management on regional climate, using climate models and analogues such as volcanic eruptions from the Earth’s past, and accelerated development of air-capture techniques involving state-of-the-art materials science. For scientists who want to save the planet, there should be no more attractive research field than geoengineering.

At a glance: Geoengineering

  • It now seems that even a stringent reduction of 50% in carbon-dioxide emissions by 2050 may not be enough to prevent dangerous global warming
  • Geoengineering offers an alternative to the reduction of carbon-dioxide emissions, although more research needs to be done to ascertain the efficacy and risk associated with large-scale interventions in the climate system
  • There are two types of geoengineering proposals: direct carbon-dioxide removal and solar-radiation management
  • Many geoengineering proposals have a better ratio of climate benefit to annual cost than conventional mitigation

More about: Geoengineering

S Arrhenius 1896 On the influence of carbonic acid in the air on the temperature of the ground Phil. Mag. 41 237–276
P J Crutzen 2006 Albedo enhancement by stratospheric sulphur injections: A contribution to resolve a policy dilemma? Climatic Change 77 211–219
Royal Society 2009 Geoengineering the Climate (London, Royal Society)
N Stern 2006 The Economics of Climate Change: The Stern Review (Cambridge University Press)
E Teller, L Wood and R Hyde 1997 Global warming and ice ages: I. Prospects for physics-based modulation of global change Lawrence Livermore National Laboratory Preprint UCRL-JC-128715

Listen to Newton and the Counterfeiter

By Hamish Johnston

Starting today and running for the rest of the week on BBC Radio 4:

“Crawford Logan reads from Thomas Levenson’s biography of Isaac Newton and his rivalry with one of 17th-century London’s most accomplished and daring criminals, William Chaloner.”

The action starts at 09:45 BST here .

Or you can listen to Newton and the Counterfeiter at your leisure using the BBCs iPlayer facility.

Breath-testing for cancer using gold

 

Researchers in Israel have invented a new type of breath test for detecting lung cancer in patients using sensors built with gold nanoparticles. Although the analysis of breath particulates is not a new tool in cancer diagnosis, this is the first technique that could detect cancer without the need to pre-treat the exhaled breath, say the researchers.

Lung cancer accounts for more than a quarter of all cancer-related deaths with an estimated 1.3 million people dying from the condition worldwide each year. Breath testing is an established, non-invasive method that works by linking “volatile organic compounds” (VOCs) with specific forms of lung cancer. The drawback of this method at present is that it requires collecting samples and analysing them using techniques such as mass spectrometry and infrared spectroscopy.

Tiny gold nuggets

Hossam Haick at the Israel Institute of Technology and his colleagues have now developed a new device for detecting cancer in breath, which could provide an almost instant diagnosis of a patient’s health, they say. At the heart of the new device is a carbon-based sensor with embedded gold nanoparticles.

When a patient breathes into the device, particulates in the breath accumulate on the carbon layer and the sensor swells, pushing the gold nanoparticles further apart, which, in turn, alters the resistance of the film. Each type of particulate has a unique effect on the resistance, which can be measured by having a current flow through the sensor. “The user gets a figure on the device’s display panel that indicates whether the person is healthy or has cancer,” says Haick.

Having inserted the new sensor into a breath-test device, the researchers then carried out a series of tests for calibration purposes. By recruiting 96 volunteers – 40 lung cancer patients and 56 controls – the team built up a catalogue of VOCs based on the electrical signals that were present in the breath of lung cancer sufferers but not in the breath of controls.

Skip the trials

Haick and his team are currently testing their new device on a wider range of volunteers in order to consider the impact of factors like diet, alcohol and genetics. Moreover, in a break from the convention in medical innovation, the researchers claim that full clinical trials may not be necessary to take this new technology to a stage where it is hospital-ready. They believe instead that they could prove the device’s accuracy using a series of “artificial mixtures” of particulates that could simulate cancerous and healthy breath.

Tony Cass, a biomedical engineer at Imperial College, London, sees promise in the new technique but he has his reservations about the idea of bypassing clinical trials. “It has the potential, but will need a lot more clinical validation before it becomes accepted,” he says. Cass warns about the danger of oversimplifying real-life cancer diagnoses. “The use of ‘synthetic’ breath is a good way to test some aspects of the device but the nature of the approach using sensors arrays and chemometrics requires evaluation in complex – i.e. real patient – samples,” he adds.

In addition to lung cancer, this new device has also been used to promising effect in the diagnosis of other diseases including renal failure, Haick told physicsworld.com. Cass also agrees that the device has the potential to become a flexible addition to the medical toolkit. “It may find earlier use in monitoring a patient’s response to treatment and could be useful in ruling out other diseases that may present similar symptoms to lung cancer in the early stages such as chronic obstructive pulmonary disease,” he says.

This research appears in the latest edition of Nature Nanotechnology.

Plasmonic laser puts the squeeze on light

Plasmonic laser in action
Plasmonic laser in action

Researchers at the University of California at Berkeley claim to have created the smallest semiconductor laser ever. The new nanoscale device can generate light in a space just 5 nm in size, which is 100 times smaller than the spot produced by conventional lasers. The feat could pave the way for a host of applications, including optical computers that use light instead of electrons to process information, biosensors and nanometre-sized photonic circuits.

Normally, light cannot be focused to a spot smaller than half its wavelength – something known as the diffraction limit. However, in recent years, scientists have succeeded in compressing light down to the nanoscale by coupling it to the electrons that oscillate collectively at the surface of metals – called surface plasmons. The resulting excitations of light and electrons are known as “surface plasmon polaritons” or SPPs.

Previous attempts to exploit SPPs to make nanoscale plasmonic lasers failed because the inherent resistance of metals absorbs the SPPs, causing them to dissipate almost immediately after they are generated. This effect becomes worse the tighter the light is bound to the surface.

Hybrid waveguide

Experimental set-up
Experimental set-up

Now, Xiang Zhang and colleagues have overcome this problem by constructing a hybrid device consisting of a cadmium sulphide semiconductor nanowire separated by a 5 nm thick insulating layer from a metallic silver surface. This structure – dubbed a “hybrid plasmonic waveguide” by the researchers – can concentrate light into an area as much as 100 times smaller than a diffraction-limited spot. And, because it is non-metallic, it poses little resistance so that SPPs can survive for longer.

The researchers can then amplify the SPPs present by shining light onto the structure. “We are able to do this because the nanowire essentially acts an amplifier for nanoscale light,” team member Rupert Oulton told physicsworld.com. “This is something that scientists have been trying to achieve for about six years now and is an important milestone for turning the science of nanoscale light into technology.”

The result is all the more exciting because it has been demonstrated with semiconductor materials, which are fully compatible with modern electronic device engineering, he added.

Sniffing out single molecules

The most interesting applications to come out of this research will be those that take advantage of the nanoscale light produced. For example, the interactions between light and matter could be strengthened, which means that very weak effects might be observable. This could come in handy for detecting single molecules, allowing for extremely sensitive biodetection, said Oulton.

This is something that scientists have been trying to achieve for about six years now and is an important milestone for turning the science of nanoscale light into technology. Rupert Oulton, University of California, Berkeley

“We have also shown that the plasmon laser is very efficient so it could operate in a similar way to a conventional laser,” he explained. “The ultra-small size of the light would increase the speed of optical telecommunications, while the compact dimensions of the device would allow you to pack and modulate thousands of these tiny light transmitters onto a single chip.” Such schemes are promising since computers are fast reaching the speed limitations of electronics and will need to move to optics for a significant leap forward, he said.

The new device follows hot on the heels of another nanolaser, the “spaser”, developed by researchers from Purdue, Cornell and Norfolk State universities. Here, a dye coupled to gold spheres just 44 nm across immersed in solution generates surface plasmons when exposed to light.

Towards a practical device

The UC Berkeley team now plans to improve its technology by exciting its laser using electrical current instead of light so that the device is more practical to use. “This will not be that difficult – optical injection is far less efficient than electrical, so the hard part is done,” said Oulton.

“This is a nice work indeed,” commented spaser co-inventor Vladimir Shalaev of Purdue University. “And it’s interesting that the Berkeley and the NSU-Purdue-Cornell work on nanolasers both came out almost at the same time, at a moment when the community is preparing to celebrate the 50th anniversary of the invention of the laser next year. Both types of nanolaser represent important breakthroughs and we can expect many applications in nanophotonics, sensing, and other fields of science and tech.”

The research is reported in the journal Nature.

Molecules revealed in all their glory by microscope

 

Olympic gold
Olympic gold Five interlocking rings of benzene come into view

Physicists in Switzerland and the Netherlands have designed a new form of atomic force microscopy (AFM) capable of revealing the identity of individual atoms within a molecule for the first time. The result is a key breakthrough in surface microscopy and could yield important insights into chemical reactions as well as the development of single-electron devices, say the researchers.

AFM – invented some 20 years ago – gives scientists the best view for examining atoms on the surfaces of both insulators and conductors. The basic process is to scan a sharp metal tip across a sample to generate images based on the balance of tiny forces between the tip and the sample. Ongoing improvements to the technique have enabled researchers to view surfaces in unprecedented detail, including a significant breakthrough in 2007 when researchers managed to resolve isolated atoms on a material’s surface for the first time.

Focusing the issue

To improve AFM to even higher resolutions, however, researchers need to move the microscope’s tip to within 1 nm of the sample and at this range a number of technical challenges arise. The main problem is the danger of the tip being laterally displaced or even adsorbed by the sample on account of van der Waals forces – the weak electrostatic attractions between adjacent atoms or molecules that arise from fluctuations in the positions of their electrons. Moreover, as the probe edges closer to the sample, it becomes even more important to know the exact atomic composition and geometry of the AFM tip and with conventional tips this information is not always completely clear.

Now, however, a team led by Leo Gross of the IBM research laboratory in Zurich, Switzerland, has overcome these problems to resolve individual atoms and bonds within a single molecule. Gross realized that the atom or molecule at the very tip of the AFM probe governs the contrast and resolution of the microscopy. For this reason, they replaced the metal tip of conventional AFMs with a single molecule of carbon monoxide (CO), which is very stable as well as being subject to significantly smaller van der Waals forces when in close proximity to a sample.

To demonstrate their new tool the researchers applied their AFM tip to a well studied hydrocarbon known as pentacene (C22H14), which consists of five fused benzene rings and measures just 1.4 nm in length. They produced an image showing all five carbon rings as well as the individual carbon and hydrogen atoms within the molecule. The observed spacing between individual atoms was only 0.14 nm – the best resolution yet for an AFM.

Serendipitous tip

Gross revealed to physicsworld.com that there was an element of luck in discovering that carbon monoxide makes for a highly effective AFM tip because they had picked up the CO molecule by accident during routine use of their conventional AFM. The researchers were quick, however, to realize that the observed improvement in resolution made scientific sense because CO has been used in scanning tunnelling microscopy (STM), for many years, to improve resolution for the same reason.

Gross says that he and his team intend to develop their research with the short term goal of improving resolution and building up a catalogue of chemical signatures for a range of different atoms and molecules. Eventually the CO-tipped AFM could be used to determine the identity of unidentified familiar molecules for use in chemical analysis. In the longer term, new forms of AFM such as this could be applied to the study of chemical reactions and catalysis at the atomic level.

The electronics industry could also benefit from the new microscope because a better profile of molecular structure could help in the development of single electron devices. “Although we are focusing on small-scale experimental improvements, it is good to have long-term goals,” said Gross. “An improved understanding of electronic processes at the molecular scale could set the stage for electronics beyond CMOS,” he added.

This research appears in the latest edition of Science.

It's a Hard Life for Brian May

bang.jpg
Guaranteed to blow your mind

By James Dacey

As the recession trundles on and the Pound slumps to unprecedented lows against the Euro, many Brits are shying away from foreign travel this year — instead heading to the once popular tourist towns of the English South coast.

If you happen to be holidaying in Devon on 5th of September, anywhere near the town of Torbay, then why not pop along to the Torbay Bookshop. Queen guitarist turned astrophysicist Brian May will be signing copies of his popular science book BANG! The Complete History of the Universe, which has just been released in paperback.

Accompanying the guitar legend will be the book’s co-authors — and regular TV presenters of things “spacey” — Sir Patrick Moore and Chris Lintott.

I can’t make it along myself, sadly, but I wonder if Brian will be chucking in a free copy of his PhD — A Survey of Radial Velocities in the Zodiacal Dust Cloud — which was published for popular audiences around this time last year.

Is ‘hot Jupiter’ too close for comfort?

Hot Jupiter
Just one million years to go?

Astronomers have discovered an exoplanet that is ten times as heavy as Jupiter but orbits its star in less than a day. According to the current understanding of planet formation and evolution, the scientists have managed to spot the billion-year-old exoplanet about one million years before it is sucked into the star. However, such a sighting should be a relatively rare occurrence, suggesting that physicists may have to reconsider their understanding of how stars interact with their planets.

The new exoplanet is called WASP-18b and belongs to a class known as “hot Jupiters” – so-called because they are about the same size as Jupiter but orbit their stars much more closely than Jupiter orbits the Sun. Almost 375 such exoplanets (planets that orbit stars other than the Sun) have been discovered to date. Astronomers believe that hot Jupiters form far from their companion stars and then migrate inwards over time.

WASP-18b was discovered using the “transit” method – where a planet causes its host star to dim as it passes between the star and Earth – by the WASP South transit survey. The exoplanet’s orbit was then studied independently using radial-velocity observations from the Coralie spectrograph. The latter technique works out the mass and orbital period of an exoplanet from the wobble it induces in its star.

Bulges and torques

WASP-18b is about ten times the mass of Jupiter and orbits its star in 0.94 days, making it the second confirmed hot Jupiter to have an orbital period of less than a day. Because it is so big and so close to its star (it is just three stellar radii away), tidal interactions should elongate both planet and star along the line joining their centres. However, both the star and planet are spinning on their respective axes, and the resulting bulges and torques should cause WASP-18b to spiral inwards so that it is engulfed and destroyed by its star in less than a million years.

Andrew Collier-Cameron of St Andrew’s University in the UK and colleagues in Switzerland, Belgium and the US have shown that that the star is about a billion years old. Stars and their planets are believed to form at the same time, which should make WASP-18b the same age. This means that the team have either caught the exoplanet at a rare moment in its lifetime – as it is just about to be swallowed by the star – or the star is very bad at dissipating the tidal energy between it and the planet. The latter explanation would significantly increase WASP-18b’s lifetime and, if confirmed, would force astronomers to rethink their understanding of tidal interactions in planetary systems and how solar systems evolve.

Another explanation, put forward by Douglas Hamilton of the University of Maryland, who was not involved in the current study, is that WASP-18b may have interacted with another planet after reaching full size (and when it was still relatively far away from its parent star). Such a process might then have pushed WASP-18b closer to the star.

“Or, could something be holding the planet up against the inward drag of tides?” asks Hamilton. “For example, a poorly understood aspect of stellar convection or an unknown subtlety of tides themselves?” All these possibilities need to be examined more closely, he stresses.

Collier-Cameron and colleagues say that if WASP-18b is spiralling rapidly inwards, the effects should become visible to telescopes within as little as a decade and could thus be measured.

The research is reported in the journal Nature.

Engineers call for ‘artificial trees’ to reduce CO2

On the low-carbon highway
On the low-carbon highway

Constructing a forest of ‘artificial trees’ is one of the most promising technologies to remove carbon dioxide (CO2) from the atmosphere, according to a report published by the Institution of Mechanical Engineers in the UK. The report also calls for a national UK programme for research and development into “geoengineering” projects that could provide a better understanding of the risks and costs of manipulating the climate.

Most attempts to deal with climate change involve reducing emissions of CO2 and in December the United Nations Convention on Climate Change in Copenhagen will attempt to set binding targets for lowering such emissions for the first time. Yet even an agreement to cut CO2 emission by 50% by 2050 may not be enough to stop the planet’s average temperature rising by 2 °C by the end of the century.

Geoengineering – deliberate intervention into the climate system to counteract man-made global warming – offers an alternative approach. The new report, Geoengineering – Giving us Time to Act?, looks at different geoengineering options for tackling climate change, including adding iron to the oceans to produce phytoplankton blooms that then absorb CO2 and constructing giant sunshades in space that can reflect the Sun’s rays.

Absorbing carbon

The authors – led by Tim Fox, head of environment and climate change at the Institution of Mechanical Engineers – found that constructing fly-swat-shaped “artificial trees” is the most promising approach to reducing CO2. Such a tree would work by letting air pass through into the structure and then catching the CO2 via a “sorbant” material, such as sodium hydroxide. The CO2 is then removed and buried underground in a similar manner to conventional carbon capture and storage.

According to the report, constructing 100,000 such “trees” – each costing around $20,000 – would require 600 hectares of land but would be enough to remove the CO2 from the UK’s homes and transport system.

Algae to the rescue

The report also recommends coating buildings with algae, which would absorb CO2 via photosynthesis. The authors state that the algae can then be “periodically harvested from building surfaces and used as biofuel”.

The third recommendation is to make building surfaces more reflective. Although the authors claim that this method may not be as effective as the other two, “it does have the additional benefit of reducing temperatures in city centres, [which] can often be several degrees hotter than the surrounding environment”.

The report also outlines a 100 year roadmap for geoengineering in the UK, which calls for £10m per year in funding to help bring together climate scientists, economists and engineers as well as the development and deployment of “smart grids” to manage demand by communicating with electricity meters in homes.

A separate report on geoengineering by the Royal Society is due to be published on Wednesday.

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