Asteroids Scarred by Solar System's Violent Youth

Telltale evidence of the solar system’s traumatic childhood can be found in the main asteroid belt, which contains a far more integrated assortment of bodies than previously believed, a new study shows.

Previous observations of the 2,000 or so biggest asteroids in the belt -- those with diameters of roughly 100 kilometers (62 miles) or larger -- showed a neat structure, with asteroids closer to the sun having surface temperatures warmer than those located farther away.

The observations neatly match theories about the formation of the solar system, which posits that bodies formed in warm environments would be found closer to the sun and those formed in cold environments are farther away.

"We said, 'Oh look, this has been preserving the conditions from the original formation. Case closed. It all makes sense,'" astronomer Francesca DeMeo, with the Harvard-Smithsonian Center for Astrophysics, told Discovery News.

But a new analysis, this time based on 100,000 asteroids of varying sizes, tells a far different story.

"Everything is mixed. Pieces are everywhere, like they’ve been just kind of thrown all over the asteroid belt," said DeMeo, lead author of a study that appears in this week’s journal Nature.

"It’s certainly overturned a lot of traditional thinking," added University of Arizona planetary scientist Dante Lauretta, lead researcher for an upcoming NASA asteroid sample return mission.

"There is still an underlying structure and composition, but there is evidence of mixing and that just makes so much sense to me," he said.

Scientists don’t yet know why smaller asteroids buck the trend of their larger siblings, but that it is related to the gravitational elbowing by jostling planets early in the solar system’s history.

"What we’re leaning toward now is that asteroids, rather than forming in the asteroid belt, formed throughout the entire solar system ... as close (to the sun) as Mercury and as far away as Neptune, and then, through the planetary migration, you scatter them all over the place. What’s left is what you see in the asteroid belt today," DeMeo said.

Read more at Discovery News

Quasar Makes Ghostly Intergalactic Filament Glow

The grand “cosmic web” is a picture that has fascinated us since the beautiful Millennium Simulation was run in 2005, showing us a Universe full of matter often clumped together but intricately bound by thin filaments. For the first time, these thin filaments of gas have been directly seen using one of the largest telescopes on Earth.

Clouds of gas, by their nature, are diffuse and difficult to detect. Often, we can see gas that lies along a line of sight to distant bright object, such as a quasar. However, that only gives insight into one small piece of that cloud.

A quasar is the bright central region of a galaxy that is being powered by a supermassive black hole that is gobbling up surrounding material. A team of astronomers, with lead author Sebastiano Cantalupo, looked towards such a quasar 10 billion light years away and found it illuminating a gas cloud far too large to be part of a galaxy cluster.

This gas resides in the intergalactic medium, the spaces between galaxies. It is two million light years across, a distance equal to roughly the distance between the Milky Way Galaxy and the Andromeda Galaxy. It was detected in the faint glow given off by hydrogen atoms that were excited by the radiation of the nearby quasar using the 10-meter Keck I telescope in Hawaii.

This cosmic web is not only poetic but important to the formation of galaxies and galaxy clusters. According to the Millennium Simulation, these filaments help to funnel gas into the “nodes” of the web, the sites of large galaxies and galaxy clusters. Our Milky Way Galaxy is thought to have formed in a small such node in this web.

Much of the material, over 80 percent, is dark matter, or matter that does not directly interact with electromagnetic radiation. Although we’ve detected its presence indirectly for decades due to its gravitational effects, we are no at the point where dark matter in the cosmos has been thoroughly mapped out. This gas, the “normal” matter that makes up people, stars, and planets, however, can be seen.

Since it is so diffuse, this gas proved to be a challenging target. It was found near a quasar in part because the quasar made it glow. It is also an ideal place for searching for such gas because quasars tend to inhabit the more densely populated nodes of the web, thus are likely to be surrounded by more of these filaments.

Read more at Discovery News

Coral reef discovered off Greenland

By sheer coincidence, Canadian researchers have discovered a reef of living cold-water corals in southern Greenland. PhD student Helle Jørgensbye from DTU in Denmark has been investigating the reef further.

The first ever Greenlandic reef is located in southwest Greenland and was formed by cold-water corals with hard limestone skeletons. There are several species of coral in Greenland, but this is the first time that an actual reef has been found.

In the tropics, reefs are popular tourist destination for divers, but there is little prospect of Greenland becoming a similar diving hotspot. The newly discovered living reef is located off Cape Desolation south of Ivittuut, and lies at a depth of 900 metres in a spot with very strong currents, making it difficult to reach. This also means that so far little is known about the reef itself and what lives on it

The reef was discovered by accident when a Canadian research vessel needed to take some water samples. When the ship sent the measuring instruments down to a depth of 900 metres, they came back up completely smashed. Fortunately there were several pieces of broken coral branches on the instrument that showed what was responsible.

"At first the researchers were swearing and cursing at the smashed equipment and were just about to throw the pieces of coral back into the sea, when luckily they realized what they were holding," says PhD student Helle Jørgensbye, DTU Aqua, who does research into life at the bottom of the west Greenland waters.

The first photos

Another Canadian research vessel returned to the site last fall to try and lower a camera down onto the reef to explore it close up. The coral reef is on the continental shelf itself where it is very steep and where there are strong currents.

"We got some photos eventually, although we almost lost them at the bottom of the ocean as the camera got stuck fast somewhere down in the depths. Luckily we managed to get it loose again and back up to the surface," says Helle Jørgensbye.

"It's been known for many years that coral reefs have existed in Norway and Iceland and there is a lot of research on the Norwegian reefs, but not a great deal is known about Greenland. In Norway, the reefs grow up to 30 metres high and several kilometres long. The great Norwegian reefs are over 8,000 years old, which means that they probably started to grow after the ice disappeared after the last ice age. The Greenlandic reef is probably smaller, and we still don't know how old it is," says Helle Jørgensbye, expressing the hope that at some point this will be investigated more closely.

According to Helle Jørgensbye, finding a coral reef in southern Greenland was not entirely unexpected:

"There are coral reefs in the countries around Greenland and the effect of the Gulf Stream, which reaches the west coast, means that the sea temperature get up to about 4 degrees, which is warm enough for corals to thrive. In addition to the, for Greenland, comparatively warm temperature, a coral reef also needs strong currents. Both these conditions can be found in southern Greenland," she says.

Coral reefs are important areas for fish because it provides masses of food and lots of hiding places for fish fry. The Greenlandic reef is formed from Lophelia stoney corals. Other species of coral are also found in many parts of the west coast. However, they are all 'stand-alone' corals and do not form reefs. The identification of the Lophelia specimen was carried out by Professor Ole Tendal from Denmark's Natural History Museum.

Read more at Science Daily

Real-Life Hit Men Nothing Like the Movies

In the second season of the BBC's hit show "Sherlock," shadowy snipers threaten the eponymous detective's friends by skulking around stairwells with high-powered rifles or infiltrating their homes and workplaces.

In real life, targets of assassination in Britain are more likely to be killed while walking their dogs or going shopping, new research finds.

The study of contract killings spanning from 1974 to 2013, published in The Howard Journal of Criminal Justice, finds that assassinations are often rather mundane.

"Hit men are familiar figures in films and video games, carrying out 'hits' in underworld bars or from the rooftops with expensive sniper rifles," David Wilson, a criminologist Birmingham City University's Center for Applied Criminology, said in a statement. "The reality could not be more different."

The four types of hit men

Wilson and his colleagues were interested in studying contract killing, in which someone pays another person to carry out a murder. These types of killings are rarely studied, the researchers said.

They combed through newspaper archives for examples of hits in Britain and found evidence of 27 murders carried out by 35 hit men — and one hit woman. They also used court transcripts and interviews with offenders to find out details such as how much killers had been paid.

The results revealed a wide variety of ages and expertise in killing. Hit men were as young as 15 and as old as 63, with an average age of 38. There were four types of hit men: Novices, who were caught after their first murder; dilettantes, who are the least likely to have a criminal background and may lack enthusiasm for killing; journeymen, who are career criminals but not particularly stealthy; and masters.

Masters are the least likely to be caught, Wilson and his colleagues found. They often have a military or paramilitary background, and are successful because they have few local ties. Journeymen, in contrast, may be good at killing, but their criminal connections often give them away to police.

Motives for murder

The cost of a hit varies widely as well, the researchers found. The cheapest kill, in 2010, cost 200 British pounds ($331.72 in today's U.S. dollars), paid to Santre Sanchez Gayle, a 15-year-old, for killing 26-year-old Gulistan Subasi. Gayle was a "novice" hit man who was caught because he bragged about the killing later.

The highest fee for a contract killing was 100,000 pounds ($165,860 in today's U.S. dollars). The only female contract killer in the study, a New Zealander named Te Rangimaria Ngarimu, charged 7,000 pounds ($11,610 in today's dollars) to kill the business partner of two men who hired her from prison in 1992. According to news reports about her trial, she only received about one-seventh that amount.

One "dilettante" hit man, Orville Wright, became known as the hit man who lost his nerve. Wright was sentenced to two years in prison in 1998 after he threatened to kill a London woman at the behest of her ex-boyfriend. After breaking into the woman's flat and talking to her, Wright was unable to go through with the murder.

The tales hint at how pedestrian most contract killings are. While television hits usually involve shady conspiracies or megalomaniac masterminds, real contract kills are far less melodramatic.

Read more at Discovery News

300,000-Year-Old Caveman 'Campfire' Found in Israel

A newly discovered hearth full of ash and charred bone in a cave in modern-day Israel hints that early humans sat around fires as early as 300,000 years ago — before Homo sapiens arose in Africa.

In and around the hearth, archaeologists say they also found bits of stone tools that were likely used for butchering and cutting animals.

The finds could shed light on a turning point in the development of culture "in which humans first began to regularly use fire both for cooking meat and as a focal point -- a sort of campfire -- for social gatherings," said archaeologist Ruth Shahack-Gross of the Weizmann Institute of Science in Israel.

"They also tell us something about the impressive levels of social and cognitive development of humans living some 300,000 years ago," Shahack-Gross added in a statement.

The centrally located fire pit is about 6.5 feet (2 meters) in diameter at its widest point, and its ash layers suggest the hearth was used repeatedly over time, according to the study, which was detailed in the Journal of Archaeological Science on Jan. 25.

Shahack-Gross and colleagues think these features indicate the hearth may have been used by large groups of cave dwellers. What's more, its position implies some planning went into deciding where to put the fire pit, suggesting whoever built it must have had a certain level of intelligence.

Controversial cave

Qesem Cave was discovered more than a decade ago during the construction of a road some 7 miles (11 kilometers) east of Tel Aviv. At the site, excavators had previously uncovered other traces of fire (scattered deposits of ash and clumps of soil that had been heated to high temperatures) as well as the butchered bones of big game like deer, aurochs and horse left their by the prehistoric cave dwellers, possibly up to 400,000 years ago.

Anthropologists have debated what constitutes the earliest evidence of controlled fire use -- and which hominin species was responsible for it. Ash and burnt bone in Wonderwerk Cave in South Africa suggests human ancestors used fire at least 1 million years ago.

Some researchers, meanwhile, have speculated that the teeth of Homo erectus suggest this early human was adapted to eat food cooked over a fire by 1.9 million years ago. A study out last year in the Cambridge Archaeological Journal argued that fire-builders would have needed some sophisticated abilities to keep their hearths burning, such as long-term planning (gathering firewood) and group cooperation.

It's not entirely clear who was cooking at Qesem Cave. A study published about three years ago in the American Journal of Physical Anthropology described teeth found in the cave dating to between 400,000 and 200,000 years ago. The authors speculated the teeth might have belonged to modern humans (Homo sapiens), Neanderthals or perhaps a different species, though they noted they couldn't draw a solid conclusion from their evidence.

Nonetheless, study researcher Avi Gopher, an archaeologist from Tel Aviv University, said in an interview with Nature at the time, "The best match for these teeth are those from the Skhul and Qafzeh caves in northern Israel, which date later [to between 80,000 and 120,000 years ago] and which are generally thought to be modern humans of sorts."

Read more at Discovery News

Preventing and Treating a Cold: What Works?

Washing hands and taking zinc may be the best ways to avoid getting the common cold, and over-the-counter pain relievers are the recommended treatments to alleviate the symptoms, according to a new review.

The common cold strikes adults two to three times a year on average, while children under age 2 develop colds about six times a year, according to the study. There's no vaccine or cure for the cold, which usually takes only a few days to resolve on its own but can be bothersome and debilitating.

To identify the best ways to prevent getting a cold, or help alleviate its symptoms once it has struck, researchers reviewed more than 150 studies of both traditional and nontraditional approaches, ranging from gargling water to eating garlic. They detailed their findings today (Jan. 27) in the Canadian Medical Association Journal.

Prevention

The best way to avoid a cold is to keep your hands germ-free, according to the study. The researchers reviewed 67 randomized, controlled trials looking at cold prevention, and concluded that regularly washing the hands, as well as using alcohol-based disinfectants and gloves, are likely effective in preventing the cold.

Taking zinc works, too. This element is found in meat, beans and nuts, and appears to be effective in reducing the number of colds per year, at least in children, the researchers said. In studies, children who took 10 to 15 milligrams of zinc sulfate daily had fewer colds than children taking a placebo. Although these studies involved only children, there is no biological reason why zinc would not work similarly in adults, the researchers said.

There is some evidence that probiotics may help prevent colds, although the types and combinations of organisms varied in the studies, as did the formulations (for example, pills or liquids), making comparison difficult, the researchers said.

Studies of other measures — including gargling water, eating garlic, exercising and homeopathic remedies — didn't provide clear or sufficient evidence that these methods are beneficial, the researchers said.

Treatment

The pain relievers ibuprofen and acetaminophen are effective in relieving pain and fever, but not in relieving other symptoms, the researchers found. Ibuprofen appears to work better than acetaminophen in treating fever in children.

Taking antihistamines combined with decongestants or pain medications appears to be somewhat effective in treating the symptoms of colds in people older than age 5, according to the study.

Read more at Discovery News

Ancient Roman Infanticide Didn't Spare Either Sex

A new look at a cache of baby bones discovered in Britain is altering assumptions about why ancient Romans committed infanticide.

Infant girls were apparently not killed more often than baby boys, researchers report in an upcoming issue of the Journal of Archaeological Science.

"Very often, societies have preferred male offspring, so when they practice infanticide, it tends to be the male babies that are kept, and the female babies that are killed," said study researcher Simon Mays, a skeletal biologist for English Heritage, a non-governmental organization that protects historic sites.

Though ancient Romans indeed preferred boys, there is no evidence they went as far as infanticide to skew the sex ratio, Mays told LiveScience.

Tiny skeletons

Mays and his colleagues used a technique called ancient DNA analysis to study infant bones found at a site called Yewden Villa, near Hambleden, in England. Although the site was first excavated in 1912, and found to hold the remains of infants dating back about 1,800 years, the infant bones were since thought to have been lost, Mays said.

But recently, nearly a century after the initial excavation, archaeologist Jill Eyers, director of Chiltern Archaeology in England, found the bones tucked away in tiny boxes in the site archive.

In 2011, Mays and Eyers published a study of the bones suggesting the babies were victims of infanticide, based on the fact that measurements of the long bones of the arms and legs suggested that all of the babies died at the same age, right at the time of birth.

If the deaths had been natural, Mays said, you'd expect to see some premature babies, some who died around the time of birth, and others who died in the weeks after birth.

Because of the high number of skeletons, the researchers speculated the site contained a brothel, and the babies were those of prostitutes. But that idea was always "a long shot," Mays said.

In the new study, the researchers delved into why these babies were killed. Ancient Roman texts refer to infanticide as an accepted practice, and the only way people could control the size of their families in a time before reliable contraception. (In fact, Rome's foundation myth involves twin boys, Romulus and Remus, who are left to die by their mother, but are saved by wild animals.)

The texts refer to infanticide in Rome itself, however, which had a different culture than its far-flung territories, such as those in Britain, Mays said.

And although the Roman preference for boys would suggest that Romans practiced sex-selective infanticide, Mays said, there is only one document to back up that assumption — a letter from one Roman soldier stationed in England to his pregnant wife, telling her not to bother keeping the baby if it's a girl when it's born.

DNA testing

It's impossible to tell the sex of a baby by looking at the shape of the bones. Sex differences only emerge after puberty, Mays said. So the researchers turned to a newer tool: ancient DNA analysis. They tested 33 of the 35 most complete remains, but because DNA does not preserve well in old bones, the researchers were able to tease out sequences for only 12 of the 33.

Of those, seven were female and five were male, a relatively even sex ratio, Mays said.

What's more, none of the babies shared a mother, a strike against the brothel hypothesis. If the babies were the offspring of prostitutes, Mays said, the women would likely have been pregnant again and again.

The 12 babies studied in the new paper bring the total number of ancient Roman babies thought to be victims of infanticide who have undergone DNA testing to 25. Overall, there is no evidence that baby girls were killed more often.

"It seems as though they weren't using infanticide to manipulate the sex ratio," Mays said.

Read more at Discovery News

Dead Plants Hold Earthquake Secrets

With a few tricks borrowed from the oil industry, scientists are hoping to one day better understand why earthquakes start and stop.

Geologists would love to know what controls earthquakes. But one of the best ways to answer that question — drilling into faults — is expensive and difficult. An easier alternative is to study faults exposed on Earth's surface, and look at "fossilized" earthquakes preserved along the faults.

But faults can be several feet wide and filled with crushed-up rock, or they can be inch-thick cracks. How does someone walk up to a crack, point a finger at it and determine an earthquake occurred there?

Sometimes, the tremendous heat created during an earthquake melts rock inside a fault. "That was the gold standard," said Heather Savage, a geophysicist at Lamont-Doherty Earth Observatory in New York. "When you get the melt, it means the fault slipped fast."

(Faults get hot because of friction. Just as rubbing your hands warms them on a winter's day, earthquakes heat the Earth when two sides of a fault slide past each other during a quake.)

But there are plenty of old faults exposed on Earth's surface and very little of this melted rock, called pseudotachylyte, Savage said.

So, over the past few years, Savage and her colleagues have devised a new way to find old earthquakes. It turns out that earthquakes can "cook" dead plants and algae trapped in a fault, similar to how organic material transforms over eons into oil.

And because heat from an earthquake is linked to fault strength, Savage is also testing whether this cooked organic matter reveals clues about fault strength during past earthquakes.

"Temperature rise during an earthquake says something about the strength of the fault when it was slipping, and that is a big unknown in earthquake science," Savage told LiveScience's OurAmazingPlanet. "These kinds of questions are really fundamental if we're ever going to get better at making accurate earthquake predictions."

Earthquake thermometers

The technique could prove especially handy at subduction zones — the source of the world's biggest earthquakes — which are often rich in organic material scraped off the ocean floor.

In Alaska, a 60-million-year old subduction zone between the Pacific and North American plates now sits exposed above shoreline at Pasagshak Point on Kodiak Island. This is one of the only places in the world where pseudotachylyte is found on a subduction zone. Savage and her colleagues tested their earthquake "biomarker" method here, comparing the temperature recorded by organic matter to that from the pseudotachylyte at one section of the fault.

The organic chemistry was borrowed from the oil industry, which has invested millions in measuring how rocks are heated based simply on the properties of organic matter in those rocks — though the cooking usually takes millions of years, not seconds and minutes, like earthquakes.

In Alaska, the biomarkers were diamondoids, carbon and hydrogen heated until they take on the same basic structure as diamonds. By modeling the heat needed to create diamondoids, Savage and her colleagues estimate the earthquake they found was about a magnitude 7 or magnitude 8, with a temperature rise of between 1,540 and 2,140 degrees Fahrenheit (840 to 1,170 degrees Celsius) and between 3 to 30 feet (1 to 9 meters) of movement. The findings were published Jan. 6 in the journal Geology.

"We're very excited; it's one of the first times we've been able to do this with a new method," Savage said.

Savage noted that this earthquake thermometer only works on faults in sedimentary rocks that carry organic material, and that not all earthquakes will generate a lot of heat. In California, along an ancient strand of the San Andreas Fault called the Punchbowl Fault, the team found a temperature rise of only 1,150 F (625 C), despite geologic evidence of past earthquakes.

The group has several new projects in the works. They're investigating rocks from Japan's JFAST drilling site, at the source of the 2011 Tohoku earthquake, and working on the San Andreas Fault deep drilling project, to see if the slow-moving part of the San Andreas Fault ever had large earthquakes. They are also running laboratory tests to customize those petroleum-industry chemical equations and to better understand the link between temperature on faults and organic matter. And someday, Savage would like to create a "heat map" of a fault.

Read more at Discovery News

Early Spanish Hunter-Gatherer Was Dark and Blue-Eyed

The first whole human genome from the bones of a southern European who lived before farming shows he was blue-eyed, dark skinned, lactose-intolerant, and well equipped to fight diseases.

The discoveries about the 7,000-year-old Mesolithic ancestral European suggest the young man represents a transition that was still underway to create the lighter-skinned, milk-drinking people of more recent millenniums.

The genome of what's called the La Braña individual appears to have already acquired immunities to diseases that were thought to have been introduced to humans later, at the time when Europeans domesticated animals, which are thought to have transmitted the diseases to humans. The results were a surprise to the researchers who fully expected the man would have lighter skin and a more ancient set of immunity alleles, or groups of genes.

"What we found was just the reverse," said Carles Lalueza-Fox, one of 24 authors on a Jan. 26 paper reporting the discovery in the journal Nature. "So we're not sure what that means."

Other researchers agree that the precocious immunity of the La Braña individual is especially intriguing.

"The most surprising and interesting part is that the authors detected derived alleles in pathogen resistance genes," commented Albert Zink, director of the Institute for Mummies and the Iceman in Bolzano, Italy. "This can shed new light on the evolution and interaction of diseases in human populations. This is of particular interest as we know from other studies that some infectious diseases, such as tuberculosis, most probably have been present long before the Neolithic and doesn't necessarily have a (animal) origin."

The blue eye color was just as unexpected, but less problematic, said Carles Lalueza-Fox.

"We tend to think both things (skin and eye color) are related, but they are different genes," Carles Lalueza-Fox explained.

It's also not clear if there's any evolutionary advantage to blue eyes. It could just be from random genetic drift and not have any purpose. Skin color, on the other hand, is thought to be an adaptation to different amounts and intensity of sunlight.

Just how dark the La Braña man was is impossible to say, Lalueza-Fox told Discovery News, but it's clear he was much darker than modern Spaniards and that his genome is quite unlike that of the modern population level Spanish genome.

The man's lactose intolerance is the one thing that was not surprising, since a hunter-gatherer would not drink milk beyond infancy -- just like other mammals and all modern humans with the exception of those who come from milk-drinking cultures, Carles Lalueza-Fox explained.

Read more at Discovery News

Dark Matter Mystery Could Be Solved in 10 Years

Dark matter — the mysterious stuff that is thought to make up most of the matter in the known universe — may reveal itself during the next decade, one prominent scientist predicts.

When the moment comes, it will result in "a pivotal paradigm shift in physics," Gianfranco Bertone, a physicist with the University of Amsterdam in the Netherlands, said in a talk on dark matter research at a Royal Society Frontiers of Astronomy conference in London in November.

The elusive substance may show itself as researchers set out to test "the existence of some of the most promising dark matter candidates, with a wide array of experiments, including the Large Hadron Collider (LHC) at CERN and a new generation of astroparticle experiments underground and in space," Bertone said.

The universe contains much more matter than scientists can currently detect. Models suggest that this unseen matter makes up about 85 per cent of the universe, but nobody is sure what this missing matter is made of. Telescopes can't observe it, because it gives off absolutely no light.

So far, the only evidence of dark matter's existence comes from the gravitational effects it exerts on visible matter. "We see the effects on all scales with astrophysical and cosmological observations," Bertone said.

But despite promising hints from numerous recent experiments, the hunt for dark matter's true identity goes on.

The key candidates for the stuff so far remain restricted to the realm of theory — weakly interacting massive particles (WIMPs), believed to constitute the bulk of dark matter, and axions, assumed to be much lighter and colder particles. It is thought that there are a lot of axions around, and that they constantly rain down on Earth from space.

A failure to find dark matter in the near future would imply that researchers might be on the wrong track and need to rethink their approach to the problem, Bertone said.

Scientists are more hopeful than ever of success despite the failure of one of the most promising detectors, the Large Underground Xenon experiment (LUX), to spot dark matter particles during its first 90-day run in 2013.

LUX is a liquid xenon experiment set up to detect the extremely rare collisions between WIMPs and regular matter on Earth. It is buried about 1 mile (1.6 kilometers) deep in a mine in the Sanford Underground Research Facility in South Dakota.

In 2014, LUX will probe for dark matter longer than ever before, during an upcoming 300-day run.

Besides hiding detectors underground, there are other ways to search for the mysterious dark matter. For example, there are direct detectors located in space, such as the Alpha Magnetic Spectrometer, which was installed on the International Space Station in 2011. AMS looks for the shower of radiation that dark matter particles are assumed to produce as they collide and annihilate. It is thought that this radiation also includes gamma rays.

Another space-based detector is NASA's Fermi telescope, which launched in 2008. This instrument is scanning the center of the Milky Way galaxy, where dark matter is believed to be concentrated, looking for excess gamma rays.

Many scientists are placing their bets on the Large Hadron Collider. Once it is up and running again in 2015, it will resume smashing particles together, in the hope of creating dark matter in the lab.

The LHC aims to create a type of matter called supersymmetric dark matter. If the LHC finds any particles that could be dark matter, its results would be compared to the data from astroparticle experiments.

"It is quite clear that unless the theoretical description of dark matter is very simple, it will be hard to identify it with a single type of experiment, whereas a combination of them should provide sufficient information," Bertone said.

Although the current experiments are looking for specific particles that scientists believe dark matter may consist of, many researchers remain open to the possibility that dark matter could be made of something completely different.

It's also possible that a whole zoo of particles makes up the invisible matter, Bertone said. "Many studies today address the possibility that dark matter is made not of one but many particle species."

So even if scientists do not find the particles they are currently looking for, it will not automatically mean that dark matter does not exist.

"The only way to prove that dark matter does not exist is to show that all these data have been misinterpreted, for instance because the law of gravity we adopted — Albert Einstein's Theory of General Relativity — is wrong," Bertone said. "Despite much effort, no satisfactory theory of gravity exists today that can be reconciled with all observational data without assuming the existence of some forms of dark matter."

Einstein's general theory of relativity describes how objects warp space and time to create gravity.

But many scientists think that dark matter will end up showing its face, and soon.

"In my view, the single most promising class of dark matter experiments over the next decade are the underground detectors — LUX, XENON-1ton, LX, and others," said Dan Hooper, a physicist at Fermilab in Batavia, Ill.

The detectors "just keep getting more and more sensitive, and already rule out many otherwise attractive dark matter candidates. The LHC and gamma-ray telescopes are also very important players in the hunt for dark matter," he added.

Read more at Discovery News