Mars Had Liquid Water in Recent Past, Rover Finds

Even while snared in a sand trap, NASA's Mars rover Spirit has hit "wet" pay dirt: evidence of relatively recent groundwater activity on the red planet. For almost six months the rover has been precariously perched on the edge of a shallow crater in an equatorial region of Mars. The area is filled with cooled lava flows pitted by meteorite impacts.

While on a routine drive, Spirit broke through a thin crust of hard soil that capped a filled-in impact crater, and its wheels became half buried in the soft sand.

During one of these rescue attempts, Spirit churned up the soil and uncovered an intriguing layer of bright, fluffy soil. Mission managers had the rover take a closer look, and they discovered that the layer is in sulfates, minerals known to form on Earth only in the presence of liquid water.

Spirit and its twin rover Opportunity have discovered sulfate-rich soil in other regions of Mars before, said Ray Arvidson, a planetary scientist at the Washington University in St. Louis and a member of the rover science team.

But because most missions are scheduled in advance, the latest discovery marks the first time one of the robots has been stationary long enough to study sulfates in detail.

Snow on Mars

Spirit's data revealed that the newfound sulfates are likely evidence of past "wet eruptions" on Mars, when lava and sulfur-rich steam spewed from volcanic vents dotting the landscape billions of years ago.

But the crater contains a clue that liquid water continues to be active on Mars, at least in the long term: The soil is full of iron sulfate covered with a thin crust of calcium sulfate.

Sea urchins 'bulldozing' Tasmanian reef

A combination of overfishing and climate change are triggering catastrophic overgrazing of reefs by sea urchins in eastern Tasmania, say researchers.

Professor Craig Johnson of the University of Tasmania and colleagues report their findings today in the Proceedings of the National Academy of Sciences.

"When you get the two things happening together, it enables the urchin populations to build up to the point where they destructively graze," says Johnson.

Scientists believe climate change is causing stronger winds in the Southern Ocean, which speeds up the rotation of the ocean system that drives the East Australian Current.

The faster current has caused warmer water to spread further south, to the waters off eastern Tasmania, says Johnson.

He says this is causing the water in the area to warm nearly four times faster than the global average.

Northern invaders

The current is also carrying with it invaders from the north - the long-spined sea urchin (Centrostephanus rodgersii) from New South Wales waters.

"It is a really aggressive grazing species and it can just completely chew out the seaweeds and many of the other associated animals growing on the seafloor," says Johnson.

He says this can create a habitat called a "sea urchin barren".

"The analogy is like taking a bulldozer to a rainforest - you clear it back to bare earth," says Johnson.

"About 50% of the New South Wales coast looks like that right now."

Johnson says he and colleagues have previously found that the sea urchins are starting to form barrens in Tasmania and the race is on to stop these from spreading.

Research team member Dr Scott Ling also previously discovered that a key predator of the sea urchins is the spiny lobster (Jasus edwardsii), which is worth $50 million to the fishing industry.

The team's latest research looks at the impact on reefs of the interaction between climate change and the decline in the number of lobster predators due to overfishing.

Past decade set to be warmest on record

New research from the World Meteorological Organisation shows that the past decade has been the warmest since records began 160 years ago.

The United Nations weather agency and Britain's Met Office presented their findings at the Copenhagen climate change summit.

The figures show a steady rise in temperatures over the past four decades, with 2009 listed as likely to be the fifth warmest year since records began in 1850.

"In the last decade we have seen that the temperatures haven't gone up very much, but they are clearly a lot warmer then they were in the previous decade," says Dr Vicky Pope, head of climate change advice at the Met office.

Some of the UN's weather data was provided by Britain's University of East Anglia which is at the centre of a row over leaked emails which appear to suggest that the theories around man-made climate change are not solid.

The secretary-general of the WMO, Michel Jarraud, also observed that Australia has so far had its third warmest year on record.

"There were above-normal temperatures in most parts of the continents, and only in USA and Canada there were significant areas with cooler-than-average conditions," he says.

"But in large parts of Southern Asia, Central Africa, these regions are likely to have the warmest year on record."

Jarraud says the year has also been notable for extreme weather events.

"China with the third warmest year in the last 50 years, heat waves in Italy, UK, France, Belgium, Germany, an extreme heat wave in India, and Australia the third warmest year on record with three exceptional heat waves," he said.

Those heatwaves hit south-eastern Australia in January, February and November and the sub-tropical east in August.

Dark questions remain over dark energy

The recent discovery of a new kind of type 1A supernovae has raised fresh questions about their use in identifying the mysterious force known as dark energy.

Dubbed 'type point 1A' supernova, they are thought to be white dwarfs which have exploded at lower mass. They emit one-tenth the energy of other type 1A supernovae and have different chemical signatures.

It's an important discovery as all type 1A supernovae were previously thought to explode with similar mass and energy levels, allowing scientists to use them to measure distances in the universe.

Professor Brian Schmidt of the Research School of Astronomy and Astrophysics at the Australian National University in Canberra, has been investigating supernovae for more than a decade.

In 1998, he was part of a team that discovered the rate of the expansion of the universe was increasing by measuring the distance to supernovae events.

Schmidt says he realised "some force now called dark energy is causing space-time to expand at an ever accelerating rate".

'Biggest mistake'

Dark energy was first proposed by Albert Einstein, who like most scientists of his day, assumed the universe was stable.

His own equations showed that in such a universe, gravity would be the dominating force crushing everything together.

To counter this, Einstein 'invented' an expansion force to counter gravity, which he called the 'cosmological constant'.

When Edwin Hubble discovered a few decades later that the universe really was expanding, Einstein tore up his cosmological constant describing it as his greatest ever mistake.

So if type 1A supernovae aren't all the same can they still be trusted on issues as important as dark energy?

According to Schimdt, the answer is yes.

"Point 1A supernovae aren't an issue, because they're so much fainter, very rare, hard to find and only seen in nearby galaxies, making them different from usual type 1A supernovae".

The 'big rip'

A more extreme version of dark energy called 'phantom energy' could see forces increase so much, that it would lead to what some astronomers refer to as a 'big rip'.

The big rip would see the expansion of space-time occur not just on the cosmic scale of relativity theory, but on the subatomic scale of quantum mechanics.

It would tear apart atoms into protons, neutrons and electrons, even overcoming gluons to rip off quarks.

"For that to happen, dark energy needs to be created a little faster than space is created," says Schmidt. "As near as we can tell, both are created at exactly the same rate."

"Still if it did happen a hundred billion years or so in the future, it would be dramatic and quick, the stars would go out in the sky and minutes later we would be ripped to shreds.'

LHC Gets First Results; Step Toward "God Particle"?

Protons are positively charged subatomic particles found in the nuclei of atoms. Colliders such as the LHC are designed to crash such particles together so that they break apart into even more basic components, offering scientists a glimpse of the fundamental building blocks of matter.

For the Large Hadron Collider's first result, ALICE found that a proton-proton collision recorded on November 23 created the precise ratio of matter and antimatter particles predicted from theory.

The collision occurred at the lowest energy possible in the LHC—each beam had just 450 billion electron volts (GeV), creating a 900 GeV collision.

"Collisions at 900 GeV have only been measured with protons and antiprotons. They've never been measured with two protons," said David Evans, a physicist at the U.K.'s University of Birmingham and head of the ALICE project.

The results show "that we understand our detector," Evans said, "so when we go to higher-energy collisions where we don't know what the answers should be, we can better trust our results."

LHC Gets Closer to "God Particle"

At the Large Hadron Collider's current rate of activity, higher-energy collisions should occur before February 2010 and perhaps even before Christmas, Evans said.

The LHC is capable of collisions at 14 trillion electron volts (TeV), but some of the machine's most extraordinary discoveries could be made at much lower energy levels.

For example, scientists predict that the long-sought Higgs boson, sometimes called the God particle, could be discovered in the one to three TeV range.

"If we go to higher energies in February, there is a good chance the Higgs will be found," Evans said.

But after months of delay due to the LHC's electrical malfunction last year, Evans and his colleagues are greeting the collider's first scientific results with cautious optimism.

"It's a great step forward, and I think people are now allowing themselves to get excited," he said.

"If I was a nervous flyer, I would say we've taken off safely. But the trip isn't over."

Atom transistor to speed up computers

An international team of scientists have created a tiny transistor that could one day help quantum computers process impossibly large amounts of information.

The researchers are the first to make a transistor's electrical current pass though a single atom in a controllable way, another step towards the quantum computer chip.

Their research is published online in the journal Nano Letters.

Powerful computers

Although still a couple of decades away, quantum computers have the potential to solve calculations faster than all current computers working at once, says one of the research leaders, Professor Andrew Dzurak of the University of New South Wales.

"They could revolutionise society by doing things like developing more accurate climate change models and predicting how new medicines will work, reducing the time needed for lengthy lab experiments".

But in order to create these computers, researchers first need to develop quantum units of information called 'qubits' - and this can only be done with single-atom transistors.

The research team, involving scientists from the University of Melbourne, the University of New South Wales and Helinski University of Technology in Finland, are the first to successfully create these tiny devices on a silicon computer chip.

Quantum tunnelling

Scientists have struggled to create single-atom transistors until now because it's extremely difficult to control the placement of atoms at such a small scale, according to Dzurak.

"Transistors work almost like a sink - electrons pass like water from a source electrode to a drain electrode - and there's a gate that turns the flow on and off," he says.

By placing the single atom close enough to the source and drain, the team made electrons pass through it in a controllable way using a phenomenon known as quantum mechanical tunnelling.

The chance of this quantum mechanical effect occurring on a large scale is almost impossible, but at a nano-scale it's common and results in an object at the edge of a barrier suddenly passing to the other side, explains Dzurak.

Virgin Galactic Unveils First Tourist Spaceship

Aspiring space tourists got a first look at their future ride late Monday, when Virgin Galactic unveiled the first of its long-awaited SpaceShipTwo planes (pictured with wings folded upward, suspended from the middle of its twin-fuselage launch vehicle).

After years of teases, the world's only commercial spacecraft rolled out onto the tarmac at the Mojave Air and Space Port in California. There, California Governor Arnold Schwarzenegger and New Mexico Governor Bill Richardson christened the Virgin Galactic craft with the customary smashing of champagne bottles.

Virgin Galactic leader Sir Richard Branson's daughter, Holly, announced the first SpaceShipTwo plane's name: V.S.S. Enterprise, short for Virgin Space Ship Enterprise, said Virgin Galactic President Will Whitehorn.

Virgin Galactic chose "Enterprise" for its long tradition in maritime and aviation history, he said.

"It was the name of the first [NASA] space shuttle, and it has dominated science fiction as a kind of watchword for human spaceflight in the future," Whitehorn said.

Virgin Galactic Holds a Wedding

V.S.S. Enterprise is based on SpaceShipOne, a reusable manned spacecraft designed by aviation designer Burt Rutan, which won the U.S. $10-million Ansari X Prize in 2004. (Related: fast facts on Virgin Galactic's SpaceShipOne.)

Whitehorn said the Enterprise had recently been "married" to EVE, the twin-fuselage mother ship that will ferry it to launch altitude, about 50,000 feet (15,200 meters)—the space shuttle, by contrast, separates from its booster rockets at about 150,000 feet (45,700 meters). (See pictures of Virgin Galactic's Richard Branson unveiling EVE last year.)

Enterprise is the first of five planned SpaceShipTwo planes. It measures 60 feet (18 meters) long and is intended to carry two pilots and six passengers, who will pay handsomely for two-and-a-half-hour flights into suborbital space, where they'll experience weightlessness and see the curvature of the Earth.

Monday's unveiling was attended by some of the 300 or so potential passengers who have already put down at least a deposit on a U.S. $200,000 Virgin Galactic ticket.

Lightning network nears completion

A network of lightning listening stations, which promises to improve our ability to monitor thunderstorms and predict cyclone strength, should be complete next year says its director.

Every second around the world, about 63 lightning bolts flash through the sky.

Since 2002, the World-Wide Lightning Location Network (WWLLN) has been ramping up its capability to listening in on Earth's electrical tumult.

Currently 46 monitoring stations dot the globe, detecting close to 30% of all lightning strokes and locating nearly every single storm on the planet in real time.

When completed next year, WWLLN will be even more impressive. Its 60 stations could pick up all lightning activity on earth, allowing scientists to better forecast hurricanes, detect far-flung volcanic eruptions, and unravel the mysteries of how and why our planet crackles with electricity.

"Any subject you can imagine that has an association with lightning stands to benefit from WWLLN," says director Professor Robert Holzworth of the University of Washington.

For example, airlines can use data from the network to reroute their planes and avoid dangerous storm systems. Researchers are also investigating how lightning affects air quality by producing small amounts of nitrogen oxides, chemicals also common in car exhaust.

Planes and volcanoes

Spaced out approximately every 3000 kilometres, each station listens to a band of radio waves between 1 and 25 kHz. At these frequencies, pulses of radio waves from lightning travel great distances, allowing the network to pick up signals from a cyclone far out at sea or a newly-erupted volcanic ash cloud.

"When Mount Redoubt erupted last year in Alaska, we got hundreds of lightning strikes from its cloud," says Holzworth. "We might be able to develop a global warning system for volcanic eruptions that way - you just draw a circle around a known volcano, and when WWLLN picks up lightning, you know you have an ash cloud."

Undetected ash plumes have damaged dozens of commercial airplanes over the years, particularly in remote northern reaches of the volcanically active Pacific 'Ring of Fire'.

The network also holds great promise for improving cyclone forecasting. In recent years, scientists have noticed that lightning activity inside a hurricane spikes before the storm strengthens or weakens. So far, case studies of Hurricanes Emily, Katrina, and Rita in 2005 all show the same tendency.

Researchers are still trying to understand exactly why this happens, but the hope is that lightning data from WWLLN can help predict changes in hurricane strength, especially in places where weather forecasting is otherwise lacking.

"The United States is the only country in the world that does regular airplane fly-throughs of tropical cyclones," says Assistant Professor Jeremy Thomas of Bard High School Early College. "They're expensive, and in places like southeast Asia, which gets hit by lots of storms, they can't afford that kind of monitoring. Using lightning data could be very useful there."

Dark power: Grand designs for interstellar travel

He wasn't exaggerating. Even our nearest star Proxima Centauri is a staggering 4.2 light years away - more than 200,000 times the distance from the Earth to the sun. Or, if you like, the equivalent of 50 million trips to the moon and back.

Such vast distances would seem to put the stars far beyond the reach of human explorers. Suppose we had been able to hitch a ride on NASA's Voyager 1 the fastest interstellar space probe built to date. Voyager 1 is now heading out of the solar system at about 17 kilometres per second. At this rate it would take 74,000 years to reach Proxima Centauri - safe to say we wouldn't be around to enjoy the view.

So what would it take for humans to reach the stars within a lifetime? For a start, we would need a spacecraft that can rush through the cosmos at close to the speed of light. There has been no shortage of proposals: vehicles propelled by repeated blasts from hydrogen bombs, or from the annihilation of matter and antimatter. Others resemble vast sailing ships with giant reflective sails, pushed along by laser beams.

All these ambitious schemes have their shortcomings and it is doubtful they could really go the distance. Now there are two radical new possibilities on the table that might just enable us - or rather our distant descendants - to reach the stars.

In August, physicist Jia Liu at New York University outlined his design for a spacecraft powered by dark matter ( Soon afterwards, mathematicians Louis Crane and Shawn Westmoreland at Kansas State University in Manhattan proposed plans for a craft powered by an artificial black hole (

No one disputes that building a ship powered by black holes or dark matter would be a formidable task. Yet remarkably there seems to be nothing in our present understanding of physics to prevent us from making either of them. What's more, Crane believes that feasibility studies like his touch on questions in cosmology that other research hasn't considered.

Nuclear fuel: are we heading for a uranium crunch?

AS THE world prepares for the largest investment in nuclear power in decades, owners of uranium mines last week raised the prospect of fuel shortages. To make things worse, the reliability of estimates of the amount of uranium that can be economically mined has also been questioned.

Volatile oil and gas prices, along with the threat of global warming, have pushed governments to reconsider nuclear energy, partly because it is a low-carbon technology and partly because uranium supplies seem plentiful.

Mined uranium caters for about 60 per cent of the global demand for nuclear fuel. The rest comes from secondary sources, including stockpiles left over from the 1970s and 1980s, reprocessed fuel and the conversion of old Russian nuclear warheads - the so-called Megatons to Megawatts programme.

But the supply may not be as secure as first thought. The price of uranium has plummeted from a peak of around $130 per pound of uranium oxide ($286 per kilogram) in 2007 to $45 today (see graph). Some of this decline is due to slumping fossil fuel prices and some from the uncertainty surrounding the industry.

For example, investors do not know how many of the world's older reactors will be decommissioned and when. They are also unsure about the supply of secondary uranium. For instance, the Megatons to Megawatts programme, which accounts for 10 per cent of the US electricity supply, ends in 2013 and it is unknown what, if anything, will replace it.

This uncertainty is stifling investment in new mines, which could lead to future shortages, says Jean Nortier, chief executive of Uranium One, a mining and exploration company based in Vancouver, Canada. "Current prices are much too low to provide the incentive needed to meet the medium and long-term demand for uranium," he says.

Added to this are concerns that uranium resources may have been overestimated. The International Atomic Energy Agency and the Nuclear Energy Agency (NEA) publish biennial estimates of global uranium resources in the so-called Red Book. Michael Dittmar, a particle physicist at CERN in Geneva, Switzerland, last week released a critical analysis of the figures and argued that the reasons behind the fluctuation in estimated resources in recent years are unclear (

The 2007 Red Book estimates that there are 5.5 million tonnes of uranium that can be mined for less than $130 per kilo, up from 4.7 million tonnes in 2005. The uranium resources that make up these estimates are split into two categories: reasonably assured and inferred. In the normal process of geological discovery, Dittmar says, increases should be to both categories. But "almost all the increase comes from this second category", he says.

Race is on to use embryonic stem cells in humans

TISSUE grown from human embryonic stem cells, the most prized, and most controversial, cells ever grown in a lab, could at last make it into the human body.

After a decade of scientific and political wrangling, several therapies are now edging towards human trials. Which will be first?

A decade ago the medical possibilities seemed limitless. Human embryonic stem cells are unique in their ability to grow into all 200 types of human tissue. The idea was to create a range of hESC lines and to implant into people tissues and organs derived from the lines that best matched their existing tissue to prevent immune rejection.

A big hurdle came in 2001 in the US when then-president George Bush restricted federally funded researchers to working on just a dozen or so hESC lines, to please those who object to hESC research on religious or ethical grounds. Research continued in other rich countries, however, and President Barack Obama has now overturned the Bush restrictions.

But another challenge looms: stem cells' prized versatility makes their behaviour in the body unpredictable. This has led regulatory bodies like the US Food and Drug Administration (FDA) to view tissue created from hESCs with extreme caution. If a few hESCs fail to differentiate into the desired tissue they may move away from the target site and disrupt other bodily processes or turn cancerous.

Back in January, it looked likely that biotech firm Geron of Menlo Park, California, would be first to implant hESC-derived neural cells into the human body when it won FDA approval to treat people with spinal cord injuries. But the trial is now on hold after cysts formed in some treated animals.

Now, although Geron says it hopes to implant its neural cells into people by September 2010, it could be pipped to the post. Last week, Advanced Cell Technology of Worcester, Massachusetts, applied to the FDA for permission to treat a rare inherited eye condition with cells grown from hESCs.

ACT chief scientific officer Robert Lanza cites several reasons why these cells might raise fewer safety concerns than Geron's therapy (see opposite), as does a French team planning to apply next year to treat people who have burns with layers of human skin made from hESCs. Treatments for diabetes and heart disease are also on the horizon.

How to wind snail shells up the wrong way

Prod a snail embryo with fine glass rods and you can make its shell coil in the opposite direction to normal.

This gives an insight into how and when bodily symmetry is controlled through a mixture of genetic programming and physical forces. "The onset of left-right symmetry in vertebrates is still unknown, and our work may shed light on this," says Reiko Kuroda, who led the team at the University of Tokyo, Japan, that reversed snail "handedness".

Kuroda and her colleagues worked with a snail species whose cone and bodily symmetry can be either right or left-"handed", depending on the action of a gene in the mother snail called nodal.

By prodding embryos gently with glass rods at the eight-cell stage, they could reverse the genetically determined handedness of each snail.

From that point on, all the symmetry of the snail was completely reversed from what would be expected from its ancestors, including the bodily position of organs such as the heart or anus, and the direction of coiling in the conical shell.

First osmosis power plant goes on stream in Norway

Sited on the banks of the Oslo fjord in southern Norway, it generates electricity using the natural process that keeps plants standing upright and the cells of our own bodies swollen, rigid and hydrated.

Osmosis occurs wherever two water solutions of different concentrations meet at a semi-permeable membrane. The spontaneous passage of water from dilute to concentrated solutions through the membrane generates a pressure difference that can be harnessed to generate power.

"The potential is huge," said Terje Riis-Johansen, the Norwegian minister for petroleum and energy, speaking at the new plant's opening ceremony in Tofte, near Oslo, on Tuesday.

Statkraft, the renewable-energy giant running the project, estimates the total global potential of osmotic power to be around 1700 terawatt-hours per year – about 10 per cent of the world's current electricity consumption.

Rainbow trapped for the first time

Oh, to catch a rainbow. Well, it's been done for the first time ever – and with just a simple lens and a plate of glass at that. The technique could be used to store information using light, a boon for optical computing and telecommunications.

All-optical computing devices promise to be faster and more efficient than current technology, but they suffer from the drawback that signals have to be converted back and forth from optical to electrical. The ability to "slow" light to a crawl or even trap it helps, as information in the light can then be manipulated directly.

In 2007, Ortwin Hess of the University of Surrey in Guildford, UK, and colleagues proposed a technique to trap light inside a tapering waveguide, which is a structure that guides light waves down its length. The waveguide in question would use metamaterials – exotic materials that can bend light sharply.

The idea is that as the waveguide tapers, the components of the light are made to stop in turn at ever narrower points. That's because any given component of the light cannot pass through an opening that's smaller than its wavelength. This leads to a "trapped rainbow".

While numerical models showed that such waveguides would work in theory, making them out of metamaterials remained a distant dream. Now Vera Smolyaninova of Towson University in Baltimore, Maryland, and colleagues have used a convex lens to create the tapered waveguide and trap a rainbow of light.

They coated one side of a 4.5-millimetre-diameter lens with a gold film 30 nanometre thick, and laid the lens – gold-side down – on a flat glass slide which was also coated with film of gold. Viewed side-on, the space between the curved lens and the flat slide was a layer of air that narrowed to zero thickness where the lens touched the slide – essentially a tapered waveguide.

When they shone a multi-wavelength laser beam at the open end of the gilded waveguide, a trapped rainbow formed inside. This could be seen as a series of coloured rings when the lens was viewed from above with a microscope: the visible light leaked through the thin gold film.

Welcome to the high-carbon future

CARBON is a dirty word. We burn too much of it, producing billions of tonnes of carbon dioxide that threatens to wreck our planet's climate for generations to come. Before that it was the villain of the piece in the guise of the soot that poured from factory chimneys and turned cities black. It has a lot to live down.

Now our long-time enemy could be on the brink of becoming our high-tech best friend. As we learn to shape carbon on the nanoscale - into tubes and sheets, balls and ribbons - entirely new and unexpected vistas are opening up. The carbon atoms that were forged in the furnace of the universe's stars can be woven together into materials that may help gather energy from our own star. Similar materials promise to make our electronic world run with unprecedented efficiency, and may even hold the secret to eking out precious reserves of oil.

Carbon's potential stems from the fact that it is multitalented. Collections of carbon atoms will happily assemble themselves into a multitude of structures, from diamond to graphite, but these familiar forms are just the beginning. In the past few decades we have learned about the soccer-ball-shaped spheres called buckyballs, soon followed by the microscopic rolls of chicken wire we know as carbon nanotubes. Now they have been joined by graphene, sheets of carbon that are just one atom thick.

Of these many intriguing structures, graphene is causing the biggest stir. This is partly because of its unusual combination of properties: its two-dimensional honeycomb lattice of carbon atoms combines fantastic electrical conductivity with a strength tens of times that of steel in a material that is transparent to visible light. Best of all, we have finally learned how to make it.

This last breakthrough came in 2004, when Andre Geim and Kostya Novoselov at the University of Manchester, UK, discovered they could produce graphene sheets from a fleck of graphite by simply peeling it off with a strip of sticky tape (Science, vol 306, p 666). It has been followed by a flood of improved methods, including a technique reported earlier this year by Jing Kong and her team at the Massachusetts Institute of Technology, which involves growing graphene on top of crystals of other materials and then chemically stripping the supporting crystal away (Nano Letters, vol 9, p 30). After just five years of development, making graphene is easier than anyone ever thought possible, and ramping up to industrial scale production is just a question of demand. "It doesn't even require minor breakthroughs; it's just polish and precision now," says Geim.

After Geim isolated the first few flakes, it was quickly apparent to theorists that this material should have some pretty special properties. At the time there was too little of the material available to experiment on. "Now it's very different," says Vitor Pereira of Boston University. "There are more experimental than theoretical papers... That's really exciting because it's out of experimental results that the true breakthroughs come."

Energetic gamma rays spotted from 'microquasar'

After decades of searching, astronomers have confirmed that a gluttonous stellar remnant that glows brightly in X-rays can create high-energy gamma rays as well. The tiny powerhouse could serve as a nearby laboratory to study how particles are accelerated in the universe's biggest black holes.

Cygnus X-3, a pair of objects that sit some 30,000 light years from Earth, has long been a puzzle. The system is thought to contain the dense remnant of a star – either a black hole or a neutron star – that is feeding on a disc of material stolen from a companion star.

The pair orbit each other once every 4.8 hours, shining in X-rays and occasionally sending jets of material, or flares, outwards at close to the speed of light. Because of these flares, Cygnus X-3 has been dubbed a "microquasar", since it resembles quasars, the flaring supermassive black holes at the centres of some galaxies.

Interest in Cygnus X-3 has grown since the flares were first discovered by radio telescopes in 1972. In the following decades, astronomers have found hints that gamma rays – the universe's highest-energy photons – could be coming from Cygnus X-3 with energies as high as trillions or even quadrillions of electronvolts (eV).

But these detections remained tentative, in part because the flares, which occur every year or so, are unpredictable. Until now, no one has found gamma rays stemming from Cygnus X-3 that had energies higher than 300,000 eV, gamma rays that are only slightly more energetic than the highest-energy X-rays, says Marco Tavani of the Space Astrophysics and Cosmic Physics Institute in Rome, Italy.

"People claimed to have detected high-energy emission from Cygnus X-3 on many occasions, but these reports were never confirmed," Tavani told New Scientist. "For many years, people thought it was a sort of damned object."

Lava Cave Minerals Actually Microbe Poop

The discovery could offer clues in the search for life on Mars and beyond, researchers said in October at a meeting of the Geological Society of America.

"We're finding that you need to look at things you might write off as not being biological—they might be biological," said Penelope Boston, a cave scientist at the New Mexico Institute of Mining and Technology in Socorro.

The microbes were found on the walls of lava tubes in Hawaii, New Mexico, and the Portuguese Azores islands, a volcanic archipelago in the Atlantic Ocean (see map).

The finds include "a lovely blue-green ooze dripping out of the [cave] ceiling in Hawaii; a vein of what looks like a gold, crunchy mineral in New Mexico; and, in the Azores, amazing pink hexagons," said Diana Northup, a geomicrobiologist at the University of New Mexico.

"That's the waste—the bug poop, if you will."

Clues to Life on Mars?

Lava tubes form when molten lava seeps out beneath a solidifying flow from an active volcano, leaving long caves in its wake.

Since 1994 Northup and colleagues have been seeking out unusual deposits in caves, including lava tubes, and putting them under a microscope or testing them for DNA.

Her team's discoveries add to a growing body of evidence that lava tubes on other planets might be the best places to look for signs of extraterrestrial life, said Saugata Datta, a geochemist from Kansas State University who was not involved in the work.

(Related: "Could Jupiter Moon Harbor Fish-Size Life?")

In 2007, pictures from a Mars orbiter showed dark holes that appear to be places where lava-tube roofs have collapsed.

"Caves [are] a unique environment where we think that [minerals precipitating out of liquids] and microbial growth are enhanced by stable physical and chemical conditions," Datta said.

On Mars, water could have percolated into subterranean caves long ago, possibly bringing with it a banquet of minerals that could have fed ancient microbes.

Also, the insides of such caves would have remained sheltered from harsh surface conditions, giving any possible Martian fossils a better shot at long-term survival.

Evolution vs. Intelligent Design: 6 Bones of Contention

Some of evolution's most vocal critics are proponents of "intelligent design," arguing that many structures in plants and animals bear the unmistakable signature of design by a supernatural intelligence.

Intelligent design proponents say the eyes of vertebrates--including humans and the common snapping turtle seen above--could not have evolved in a stepwise fashion. That's because the eye is made of several interacting parts, and the removal of any one part will cause the entire system to cease functioning. Thus, the argument goes, the eye must have been produced in one fell swoop.

"If you look at these [evolutionary] schemes, they often very abruptly add a lens or a cornea," said Casey Luskin, a spokesperson for the Discovery Institute, a Seattle-based organization that advocates intelligent design. But things don't just appear suddenly in evolution, Luskin said. "You need to evolve things in a step-by-step fashion.

Martian "Lake Michigan" Filled Crater, Minerals Hint

Hundreds of Martian craters have been identified as possible fossil lakes, based on the presence of now dry channels or sediments deposited at former deltas, said lead study author James Wray of Cornell University.

But new pictures from NASA's Mars Reconnaissance Orbiter have revealed that Columbus crater has alternating layers of hydrated minerals—clays and sulfates known to form only in the presence of water.

"Some lakes in western Australia that are relatively acidic and pretty salty show similar minerals to what we see in Columbus crater," Wray said.

What's more, the crater is one of the few proposed fossil lakes thought to have been fed entirely by groundwater, Wray added.

"If [the water] had come from rain, we would expect to see channels," Wray said. "But we don't."

Mars Crater Lake Born of Volcanic Warping?

Columbus crater dates back to Mars's Noachian epoch, a warm, wet period that lasted from about 4.6 to 3.5 billion years ago. (See pictures of what it might look like if we terraform modern Mars.)

Previously, researchers had thought another Noachian impact basin, Gusev crater, was the best example of a fossil lakebed, based on the crater's nearby channels and layered outcrops.

But when the Mars rover Spirit started exploring Gusev crater in 2004, the probe didn't find hydrated minerals, only volcanic basalt, Wray said.

Nano-nickel makes cheap self-cleaning surface

Australian scientists have developed a simple and inexpensive method to make water repellent nanocarpets using nickel.

The technology could be used to make self-cleaning surfaces on ships and buildings or for the manufacture of stain-proof clothing.

Physical chemist and lead author Dr Chiara Neto, of the University of Sydney and colleagues, report their research in the journal Physical Chemistry Chemical Physics

Neto says self-cleaning nano surfaces have been around for several years, but they are often expensive and difficult to make.

She says the inspiration for the technology came from the lotus leaf.

"If you've seen a lotus leaf come out of a muddy pond, its leaves will be completely clean."

Neto says it's well understood that the water repellent properties of the leaves, known as superhydrophobicity, come from their physical structure.

"The surface is covered with micro-scale bumps, and these bumps are covered with much smaller hairs."

According to Neto, the combination of the waxy exterior of the leaf and the physical structure gives it its water repellent properties.

She says when water comes in contact with these surfaces it rolls off carrying with it any dirt or dust, cleaning it in the process.

"If you have a droplet on a non-hydrophobic surface it would slide off it and displace the dust, [but it does] not clean it."

Simple and cheap

Neto and her team developed their version of a superhydrophobic surface using a template that allows nickel nanowires to self-assemble.

"We then remove the template leaving behind a special surface that we call a nanocarpet."

She says each nanowire, which is about 250 times thinner than a human hair, is then coated with a special hydrophic chemical.

The combination of the nanowire structure and the hydrophopic chemical causes a layer of air to become trapped on the surface of the nanocarpet, says Neto.

"The trapped air makes the carpet superhydrophobic."

Water droplets that come in contact with the air roll off "just like [off the] the lotus leaf," she says.

A potential use of nickel nanocarpets is as an 'anti-fouling surface' on the hull of a ship, says Neto.

"A pillow of air would exist between the boat and barnacles or proteins. It's like a shield."

She says this anti-fouling technology is currently being trialed to make stain-proof clothing.

Our Atmosphere Came From Space Gases, Study Says

The new theory came about after scientists discovered that pristine samples of the elements krypton and xenon, recently collected from deep within the Earth, have the same chemical makeup as ancient meteorites.
The discovery has squelched the volcano theory, said project leader Chris Ballentine of the U.K.'s University of Manchester.

Most of the gases in the air we breathe originated in the solar nebula, the cloud of gas and dust that formed the sun and planets, the study says.

The gases became gravitationally bound to a young Earth and were then transported in the Earth's interior—leaking out over the eons through volcanic belches and cracks in the Earth's crust.

It's still true that volcanoes spewed out some gases, "but [that] contribution was insignificant" for the creation of Earth's atmosphere," Ballentine said.

Comet Bombardment

Ballentine and colleagues studied krypton and xenon because they're noble gases, so called because they don't mix chemically with most other elements.

As a result, most of Earth's krypton has remained unchanged since its arrival on our planet—allowing scientists to precisely study the conditions of early Earth.

Based on their research, Ballentine and colleagues claim that our atmosphere likely formed when gas and water-rich comets bombarded Earth, shortly after its formation 4.54 billion years ago.

Our Atmosphere Came From Space Gases, Study Says

The new theory came about after scientists discovered that pristine samples of the elements krypton and xenon, recently collected from deep within the Earth, have the same chemical makeup as ancient meteorites.
The discovery has squelched the volcano theory, said project leader Chris Ballentine of the U.K.'s University of Manchester.

Most of the gases in the air we breathe originated in the solar nebula, the cloud of gas and dust that formed the sun and planets, the study says.

The gases became gravitationally bound to a young Earth and were then transported in the Earth's interior—leaking out over the eons through volcanic belches and cracks in the Earth's crust.

It's still true that volcanoes spewed out some gases, "but [that] contribution was insignificant" for the creation of Earth's atmosphere," Ballentine said.

Comet Bombardment

Ballentine and colleagues studied krypton and xenon because they're noble gases, so called because they don't mix chemically with most other elements.

As a result, most of Earth's krypton has remained unchanged since its arrival on our planet—allowing scientists to precisely study the conditions of early Earth.

Based on their research, Ballentine and colleagues claim that our atmosphere likely formed when gas and water-rich comets bombarded Earth, shortly after its formation 4.54 billion years ago.

Marsupial soaks up sun like a lizard

A small Australian marsupial is taking a lesson from the reptile world and basking in the sun to conserve energy and improve its chances of survival, a researcher has found.

The fat-tailed dunnart, one of Australia's smallest and most widespread marsupials, basks in the sun to reduce its need for food and water in the desert - a strategy traditionally associated with 'cold-blooded' animals.

Dr Lisa Warnecke of the University of New England found that dunnarts bask to warm their body while arousing from torpor - a short hibernation that some mammals can go into for a few hours each day.

The findings appear online in the Journal of Comparative Physiology B.

Basking in combination with torpor has so far only been identified in two other mammals, both small Australian marsupials.

Adapting to change

Warnecke believes basking may be used by many more mammals that go into torpor and could help species cope with climate change.

"It appears this is a really good strategy to increase an animal's chance of survival in harsh conditions, which is going to become more important as climate change begins to negatively impact on habitats."

"If we find out that more species can do this, it will give us hope that small native mammals have a better chance of surviving," says Warnecke.

The research, which Warnecke undertook as part of her PhD, reveals that combining basking with torpor can allow dunnarts to survive on a quarter of the food and water they would normally require.

Survival strategy

Torpor on its own has already been proved a valuable survival strategy.

Earlier this year Warnecke's supervisor at the University of New England, Professor Fritz Geiser, found that more than 90% of mammals that have became extinct in the past 500 years didn't use torpor.

During torpor, an animal's body temperature drops - a dunnart will go down to around 15°C - meaning a lot less food and water is required to keep it functioning.

But rewarming from low body temperatures requires a lot of energy and is often thought of as the downside to the process, adds Geiser.

"Using the sun to passively warm the body saves up to two-thirds of the arousal energy costs," he says.

Warnecke observed the basking in the deserts of Kinchega National Park in New South Wales and in the laboratory, where she could more closely monitor the dunnarts' metabolic rates during torpor and arousal.

Brain power: 'size isn't everything'

When it comes to brain power, it's the complexity of neuronal connections, rather than the size of the brain itself, that is most important, say scientists.

Dr Lars Chittka of the Queen Mary University of London and Dr Jeremy Niven of the University of Cambridge lay out their arguments in the journal Current Biology.

According to a growing number of studies, some insects can count, categorise objects, even recognise human faces - all with brains the size of pinheads.

Despite many attempts to link the volume of an animal's brain with the depth of its intelligence, scientists now propose that it's the complexity of connections between brain cells that matters most.

Studying those connections - a more manageable task in a little brain than in a big one - could help researchers understand how bigger brains, including those of humans, work.
Bigger isn't necessarily better

Figuring out how a relatively small number of cells work together to process complex concepts could also lead to "smarter" computers that do some of the same tasks.

"The question is: If these insects can do these things with such little brains, what does anything need a big brain for?" says Chittka. "Bigger isn't necessarily better, and in some cases it could be quite the opposite."

Because we are intelligent animals with big brains, people have long assumed that big brains are smarter brains. Yet, scientists have found scant evidence to support that view, says Chittka.

Studies that have made those connections are fraught with problems. "If you try many measurements," he says, "Eventually you will find one that shows a correlation."

There's a lot of evidence, on the other hand, that overall size is irrelevant when it comes to brain power.

Among humans, individuals with larger noggins don't have higher IQs.

Whales, with brains that weigh up to 9 kilograms, are no smarter than people, with our measly 1.4-kilogram brains.

Instead of contributing intelligence, big brains might just help support bigger bodies, which have larger muscles to coordinate and more sensory information coming in.

Like computers, says Chittka, size might add storage capacity but necessarily speed or usefulness. At the same time, it takes a lot of energy to support a big brain.

Atlantis takes off to supply space station

Space shuttle Atlantis and six astronauts have blasted off on one of the last supply runs to the International Space Station before the shuttle fleet is retired next year.

The shuttle roared off from the Kennedy Space Center in Florida on Monday (19:28 GMT), punching through a thin layer of clouds as it soared over the Atlantic Ocean heading toward an orbital linkup with the space station on Wednesday.

Atlantis carries nearly 13,610 kilograms of pumps, gyroscopes and tanks of nitrogen, ammonia and oxygen, as well as other gear too big to be carried by the Russian, European and Japanese cargo ships that will keep the station supplied after the shuttles are retired.

"It's been the workhorse of just getting the big parts up," Atlantis commander Charles Hobaugh said of the shuttle in a prelaunch interview. "The station itself right now is an incredible vehicle. We just need to provide its sustainment."

Following Atlantis' mission, which is scheduled to last 11 days, NASA plans five more flights to complete the station.

The shuttle is being replaced by a capsule-style spacecraft called Orion that can travel to the moon and other places in the solar system in addition to the station, which orbits about 360 kilometres above Earth.

The station, a US$100 billion project of 16 nations, has been under construction for more than a decade.

Safety concerns

NASA plans to end the 30-year-old space shuttle program next year, bowing to long-standing concerns about safety and the expense associated with maintaining and flying Atlantis and its two sister ships, Discovery and Endeavour.

The shuttle program costs NASA about US$5 billion a year, and has claimed the lives of 14 astronauts. The first crew of seven perished during a launch accident in 1986 and the second died during a landing attempt in 2003 due to a heat shield breach.

Atlantis will bring home station flight engineer Nicole Stott, the last station crew member to fly on the shuttle. She spent three months living and working on the space station.

During its planned 11-day mission, the Atlantis crew is scheduled to conduct three spacewalks to install antennas, replace an oxygen tank on the US airlock and other tasks.

NASA built four pallets to hold spare pumps, gyroscopes, tanks of oxygen, nitrogen and ammonia, as well as other gear.

Two will fly on Atlantis and will be mounted outside the station during the shuttle's weeklong visit. The final two pallets will fly on the last two shuttle flights next year.

"We're going to warehouse parts that only the shuttle can deliver in large volume," said Mike Sarafin, NASA's lead flight director.

GFC does little to stem global emissions

Despite the global financial crisis, carbon emissions from fossil fuels rose 2% last year, leaving the Earth on a worst-scenario track for global warming, according to a new report.

The report, in today's issue of the journal Nature Geoscience, comes in the run-up to December 7-18 UN talks in Copenhagen aimed at crafting a pact to combat climate change from 2013.

The report authors also voiced concern for the world's oceans and forests, saying the capacity of these fabled "sinks" to soak up dangerous greenhouse gases was fading.

And they placed the spotlight on surging emissions by China and developing countries, explaining that a huge chunk of this carbon comes from exporting goods that are consumed in rich nations.

Global emissions from fossil fuels in 2008 amounted to 8.7 billion tonnes of carbon, an increase of 2% over 2007, say the report authors, a group of 30 climate specialists, working under the banner of the Global Carbon Project (GCP).

The average annual increase in emissions since the start of the decade has been 3.6%, and the lower annual rate of increase last year can be pinned to the start of the world financial crisis, they say.

Emissions in 2009 are predicted to fall by 2.8% in response to the financial crisis, signalling a return to 2007 levels, say the researchers, but they warn against complacency.

"Although that sounds like good news, we must remember that CO2 emissions are very tightly linked with economic activity," says Australian co-author Dr Michael Raupach of CSIRO Marine and Atmospheric Research in Canberra.

"A return to rapid emissions growth is likely as the world recovers from the GFC."

"If the recovery follows current predictions, the effect of the GFC will be as if all burning of fossil fuels had been stopped for a period of just 6 weeks," adds Raupach. "The GFC has not bought us much time."

Leonid Meteor Shower: Best Sky Show Tuesday Predawn

In those regions, sky-watchers are advised to venture out away from bright city lights between 2 a.m. and 4 a.m. on the 17th, when they should see 30 to 50 meteors an hour.

(Find out how light pollution has changed our views of the night sky.)

But in Asia, the peak happens during predawn hours, so observers there will have a front row seat for this year's display. (See a NASA map of the 2009 Leonids' peak visibility.)

"Thanks to advances in computer power, since the 1990's we have been able to predict these upswings in activity," said William Cooke, head of NASA's Meteoroid Environment Office.

"This year there is going to be a Leonid strong outburst [during the peak], where the rates may race up to 300 per hour," Cooke said.

"But it may have a surprise in store, as well, and bring an unpredicted short peak at some point, so it's worth it for everyone [all around the world] to go out and look."

Leonids Shower a Temperamental Rock Star

The Leonids are so named because they seem to radiate from the constellation Leo, the lion, which rises above the northeastern horizon between 1 a.m. and 3 a.m., depending on your location.

Like other meteor showers, such as the Perseids and the Orionids, the Leonids happen when Earth plows through a trail of debris left in the wake of a comet orbiting the sun.

When a comet gets close to the sun, melting ice releases pieces of dust, most no larger than grains of sand. Earth annually crosses paths with the orbiting debris from some comets, and the grains burning up in our atmosphere create meteors.

(See pictures of the 2009 Perseids.)

Among the annual sky-shows, the Leonids shower is like a temperamental rock star: In most years it delivers a modest show, with rates of about 15 shooting stars an hour.

In other years, however, the Leonids can suddenly erupt in spectacular meteor storms, with rates of more than a thousand meteors an hour.

That's because the trail of comet debris that creates the Leonids is uneven. The parent comet, Tempel-Tuttle, nears the sun every 33 years, leaving behind fresh clumps of material.

"In exceptional cases, the Earth will dive right through a very fresh trail lain down by the comet, and rates will be truly astronomical." said Geza Gyuk, an astronomer at the Adler Planetarium in Chicago.

The Leonids shower of 1833, for example, saw as many as a hundred thousand meteors an hour—equal to an average of 30 meteors a second, Gyuk said.

Could Jupiter Moon Harbor Fish-Size Life?

And the extraterrestrial ocean is currently being fed more than a hundred times more oxygen than previous models had suggested, according to provocative new research.

That amount of oxygen would be enough to support more than just microscopic life-forms: At least three million tons of fishlike creatures could theoretically live and breathe on Europa, said study author Richard Greenberg of the University of Arizona in Tucson.

(Related: "Did Rising Oxygen Levels Fuel Mammal Evolution?")

"There's nothing saying there is life there now," said Greenberg, who presented his work last month at a meeting of the American Astronomical Society's Division for Planetary Sciences. "But we do know there are the physical conditions to support it."

In fact, based on what we know about the Jovian moon, parts of Europa's seafloor should greatly resemble the environments around Earth's deep-ocean hydrothermal vents, said deep-sea molecular ecologist Timothy Shank.

"I'd be shocked if no life existed on Europa," said Shank, of the Woods Hole Oceanographic Institution, who was not involved in the new study.

Right-Handed Chimps Provide Clues

Uncovering another link between chimpanzees and humans, a new study found chimps gesture mainly with their right hands. This indicates the chimp brain's left side is used in communication, as in people.

Unedited Transcript:

A new study shows chimpanzees seem to use the left half of their brain when communicating with other chimps, just like humans use the left side of the brain for most language skills.

The findings suggest another link between humans and one of the species most closely related to us.

This video of chimpanzees in the wild is from the National Geographic archives.

The study was conducted with captive chimps at Yerkes National Primate Research Center in Atlanta. The findings are published in the January issue of the research journal: Cortex.

The scientists studied hand-use in 70 captive chimpanzees over 10 months. They recorded a variety of communicative gestures specific to chimpanzees produced in different social contexts.

Study supervisor William Hopkins of Agnes Scott College, says they found a predominance of the right hand for gestures, indicating use of the left side of the brain.

Researchers also believe that the finding gives additional support to the idea that speech evolved from gestures in our ancestors. They say the gestures in apes share key features with human language, including intentionality, referential properties and flexibility of learning and use.

Scuba diving to the depths of human history

KITTED out with the latest scuba gear, Garry Momber peers through the murky water to the seabed below. It's dark - Momber is 11 metres below the water's surface and the black peat of the seabed absorbs what little light reaches the bottom. Then the tide turns, and as clearer water flows in from the open seas, the decaying remains of an ancient forest emerge from the gloom. Working quickly, he records details of the exposed material before the strengthening current forces him away from the site.

This is all in a day's work for Momber, who is director of the Hampshire and Wight Trust for Maritime Archaeology in Southampton, UK. His job is to search for clues to a prehistoric world lost beneath the waves in the channel that separates the Isle of Wight from the south coast of England - to be precise, at a location 300 metres off the port of Yarmouth.

Momber's work is just part of a growing trend for searching the deep for clues to our distant past. The field of underwater archaeology is perhaps best known for unearthing relics from more recent history, like Henry VIII's ship the Mary Rose, yet the seabed is stuffed with clues to prehistory too - especially a murky period 11,500 years ago, at the end of the last ice age, when early Europeans were slowly changing from being nomadic hunter-gatherers into settled farmers.

Back then, sea levels were 50 metres lower than today, and the vast majority of early societies would have lived on fertile land by the coast. But as the ice sheets melted, millions of square kilometres of coastal territory would have been flooded. By 4000 BC, when the coastline had stabilised to roughly its current form, 40 per cent of prehistoric Europe was submerged - along with much of the evidence for their way of life.

"Anybody who was doing anything on the shore more than 6000 years ago was doing it below present sea levels," says Nic Flemming of the UK's National Oceanography Centre in Southampton.

The result is that remains found on land today are not going to tell you much about these early societies. "If you leave out 40 per cent of the data, you're going to make some serious mistakes," says Flemming.

What's more, finds from the sea floor are well preserved. Indeed they are often in better condition than similar discoveries on land, since the low-oxygen conditions in mud and peat sediments slow the decay of organic material. Underwater sites can therefore provide unparalleled insights into the lifestyles of our ancestors as the ice age ended. "Underwater archaeology can open the door to how societies evolved and developed," says Momber.

Ripples in space divide classical and quantum worlds

WHY can't we be in two places at the same time? The simple answer is that it's because large objects appear not to be subject to the same wacky laws of quantum mechanics that rule subatomic particles. But why not - and how big does something have to be for quantum physics no longer to apply? Ripples in space-time could hold the answer.

The location of the boundary between the classical and quantum worlds is a long-standing mystery. One idea is that everything starts off as a quantum system, existing in a superposition of states. This would make an object capable of being, for example, in many places at once. But when this system interacts with its environment, it collapses into a single classical state - a phenomenon called quantum decoherence.

Brahim Lamine of Pierre and Marie Curie University in Paris, France, and colleagues say that gravitational waves may be responsible for this. These waves in the very fabric of the universe were generated by its rapid expansion soon after the big bang, as well as by violent astrophysical events such as colliding black holes. As a consequence, a background of ripples at very low amplitudes pervades space-time.
Lamine and colleagues calculated how this fluctuating space-time might contribute to quantum decoherence. They found that for systems with very large mass, such as the moon, decoherence induced by the gravitational waves would have caused any quantum superposition to dissipate immediately. At the other end of the scale, such waves would have a negligible effect on massless photons.

To test whether gravitational waves do in fact cause the decoherence seen in large objects, the researchers suggest using a set-up called a matter-wave interferometer in which molecules are made to pass through multiple gratings. The wave-like nature of the molecules causes them to diffract, and the diffracted waves interact to give rise to an interference pattern. Quantum decoherence destroys this pattern, so in principle this could provide a test for whether the decohering effect of background space-time fluctuations matches predictions. Such a system would have to be completely isolated to rule out other effects.

This is, however, impossible in practice - with today's interferometers, at least. Experiments pioneered by Anton Zeilinger, Markus Arndt and colleagues at the University of Vienna, Austria, have been able to generate interference with beams of 60-atom carbon buckyballs, but even with molecules of this size the effect of gravitational waves would be too small to be observed.

Crohn's blamed on lazy immune cells

A MYSTERIOUS bowel disease thought to be caused by an over-exuberant immune system may paradoxically be triggered by immune cells that don't do enough in the early stages of bacterial infection.

Since some treatments for Crohn's disease aim to suppress the immune system, it's possible these drugs could be making things worse. The discovery by Anthony Segal of University College London and his colleagues is causing a stir among immunologists. Caetano Reis e Sousa at Cancer Research UK calls it "provocative", while Jean-Laurent Casanova at The Rockefeller University in New York says it is "a major breakthrough".

A similar mechanism may be at the root of a host of other "autoimmune" disorders, in which immune cells turn on the body's own tissue. Underactive immune cells could also explain why some of us are more prone to infectious diseases.

About 1 in 1000 people in the US and Europe have Crohn's. Symptoms include swollen, painful intestines and diarrhoea. Inflamed sections of gut often have to be surgically removed.

Segal and his colleagues got their first clue when they noticed a weaker immune response in people with Crohn's than in healthy people after both groups were injected with heat-killed Escherichia coli. The team reasoned that this lukewarm response might allow an infection to build up and eventually trigger a debilitating secondary immune response, resulting in Crohn's.

If this is the case, though, why does Crohn's only manifest itself in the intestine? After further experiments it became clear that the immune weakness only revealed itself when large numbers of killed E. coli were injected. As the bowel is one of the few places in the body where bacteria exist in huge numbers, Segal concluded that this is where the weakened immune response has its biggest impact. "It's only in the bowel that you routinely get massive loads of bacteria - and if these breach the intestinal wall it will cause an infection."

It still wasn't clear, however, what caused the weakened immunity in the first place. So Segal's team focused on cells called macrophages, the immune system's whistle-blowers. In people with Crohn's disease, they found that macrophages secrete lower levels of cytokines, the chemicals that rally other immune cells to infection sites (Journal of Experimental Medicine, DOI: 10.1084/jem.20091683).

The team concluded that ineffectual rallying of immune cells in people with defective macrophages is what allows intestinal bacteria to run amok in the early stages of an infection, setting in motion the series of events that leads to Crohn's disease.

Ink breakthrough puts the shine into printed images

The difference between a matt and a glossy painted surface shows that there's more to the appearance of real-world objects than colour alone. But reproducing that variation in printed images has been beyond the capabilities of even the best colour printers. Now an international team of computer scientists says that could soon change thanks to a printer that can reproduce sheen as well as colour.
Spot the difference

Some modern printers can use matt, glossy or metallic inks to change the reflectivity of an image, but the inks are always used on their own, as so-called spot colours. But by carefully mixing a range of such metallic inks, Fabio Pellacini at Adobe Systems and Dartmouth College in Hanover, New Hampshire, says it's possible to reproduce subtle differences in reflectivity in the same way that mixing cyan, magenta and yellow can reproduce a range of colours.

Pellacini worked with colleagues including Wojciech Matusik and Szymon Rusinkiewicz at Adobe Systems. The team used a colour thermal printer, which is versatile enough to print many metallic inks and foils as well as standard inks.