Picking Up a Second Language Is Predicted by Ability to Learn Patterns

Some people seem to pick up a second language with relative ease, while others have a much more difficult time. Now, a new study suggests that learning to understand and read a second language may be driven, at least in part, by our ability to pick up on statistical regularities.

The study is published in Psychological Science, a journal of the Association for Psychological Science.

Some research suggests that learning a second language draws on capacities that are language-specific, while other research suggests that it reflects a more general capacity for learning patterns. According to psychological scientist and lead researcher Ram Frost of Hebrew University, the data from the new study clearly point to the latter:

"These new results suggest that learning a second language is determined to a large extent by an individual ability that is not at all linguistic," says Frost.

In the study, Frost and colleagues used three different tasks to measure how well American students in an overseas program picked up on the structure of words and sounds in Hebrew. The students were tested once in the first semester and again in the second semester.

The students also completed a task that measured their ability to pick up on statistical patterns in visual stimuli. The participants watched a stream of complex shapes that were presented one at a time. Unbeknownst to the participants, the 24 shapes were organized into 8 triplets -- the order of the triplets was randomized, though the shapes within each triplet always appeared in the same sequence. After viewing the stream of shapes, the students were tested to see whether they implicitly picked up the statistical regularities of the shape sequences.

The data revealed a strong association between statistical learning and language learning: Students who were high performers on the shapes task tended to pick up the most Hebrew over the two semesters.

"It's surprising that a short 15-minute test involving the perception of visual shapes could predict to such a large extent which of the students who came to study Hebrew would finish the year with a better grasp of the language," says Frost.

According to the researchers, establishing a link between second language acquisition and a general capacity for statistical learning may have broad implications.

Read more at Science Daily

Evolution Driven by Humans' Unnatural Selections

In the film "After Earth," the main characters return to Earth after the planet has evolved natural defenses against humans.

In real life, plants and animals are evolving in response to human action as well, although with less malicious intent than on the silver screen.

Tuskless Elephants

Criminal armies equipped with high powered weapons have declared war on Earth's largest land animal. Outlaw organizations, such as Joseph Kony's Lord's Resistance Army, sell black market ivory to finance their rampages in Central Africa.

Elephants can't fight back like the creatures in "After Earth," but evolution is helping to make some of them less attractive to poachers. The frequency of female elephants (Loxodonta africana) without tusks increased from 10.5 percent to 38.2 percent in South Luangwa National Park, Zambia, according to research published in the African Journal of Ecology. The tuskless trait appeared to run in families and may have been a result of tuskless females being spared by poachers. Tuskless mothers survived in greater numbers and hence had more tuskless daughters.

Car-Dodging Birds

U.S. Department of Agriculture scientists estimated that 80 million birds die in collisions with motor vehicles in the United States every year. One bird may be evolving to dodge vehicles.

Over the last 30 years, a decreasing number of cliff swallows have been killed along roads in southwestern Nebraska, according to research published in Current Biology. At the same time, ornithologists' measurements of the birds wings have been decreasing. Birds with shorter wings are more nimble.

The study's authors suggested that automobiles may be killing higher numbers of long-winged birds, leaving more of the nimble, nubbier-winged swallows to pass on their genes.

 Not-So-Bighorned Sheep

Like the ivory poachers, bighorn sheep trophy hunters gun for animals that have the most impressive headgear.

Males in some populations of bighorn sheep (Ovis canadensis) no longer grow large horns, which the authors of a 1995 study in Conservation Biology suggested may have resulted from human hunters' unnatural selection. Having no horns could cause problems for males since they butt heads when sparring for dominance and access to females.

Read more at Discovery News

First Evidence of Leopard Eating a Chimp Found

Only rarely have people seen what happens when chimpanzees and leopards come into close quarters in the wilds of Africa. On these occasions, chimpanzees have made loud, fearful calls, or played the aggressor: In one case, chimps even surrounded a leopard den and killed a cub.

But the big-brained primates don't always win: For the first time, scientists have found evidence of a leopard eating a chimpanzee.

In Tanzania's Mahale Mountains National Park, researchers spent 41 days collecting African leopard scat from June to August 2012 (summer internship, anyone?). In one of the cat's "offerings," scientists found several chimpanzee patella and phalanges, corresponding to kneecaps and toe bones, respectively. DNA analysis showed that the bones came from an adult female chimp.

The researchers can't be entirely certain that the leopard hunted down the chimp, because the cats occasionally eat dead animals; in other words, it's possible the chimp keeled over and then became leopard chow. However, the finding has led scientists to re-examine three mysterious wounds incurred by three different chimps in Mahale over the last few years. The wounds were deeper than thought to be possible from fights with other chimps, which is what scientists previously thought had happened.

A 2009 study suggested that chimpanzees face only negligible pressure from predators. If it's indeed true that the leopard ate a live chimp, scientists may need to rethink this view and further examine how predation from leopards, or other animals, might have driven the chimpanzee's evolution, the researchers said. One study from 1993 found evidence of lions eating four chimpanzees, also in Mahale Mountains National Park. The park is one of the few places with ongoing research where the range of leopards and chimpanzees overlap, which helps explain why this was witnessed there.

The new research was published online May 21 in the Journal of Human Evolution.

From Discovery News

Child Abuse Evident in Ancient Egyptian Cemetery

A 2- to 3-year-old child from a Romano-Christian-period cemetery in Dakhleh Oasis, Egypt, shows evidence of physical child abuse, archaeologists have found. The child, who lived around 2,000 years ago, represents the earliest documented case of child abuse in the archaeological record, and the first case ever found in Egypt, researchers say.

The Dakhleh Oasis is one of seven oases in Egypt's Western Desert. The site has seen continuous human occupation since the Neolithic period, making it the focus of several archaeological investigations, said lead researcher Sandra Wheeler, a bioarchaeologist at the University of Central Florida. Moreover, the cemeteries in the oasis allow scientists to take a unique look at the beginnings of Christianity in Egypt.

In particular, the so-called Kellis 2 cemetery, which is located in the Dakhleh Oasis town of Kellis (southwest of Cairo), reflects Christian mortuary practices. For example, "instead of having children in different places, everyone is put in one place, which is an unusual practice at this time," Wheeler told LiveScience. Dating methods using radioactive carbon from skeletons suggest the cemetery was used between A.D. 50 and A.D. 450.

When the researchers came across the abused toddler — labeled "Burial 519" -- in Kellis 2, nothing seemed out of the ordinary at first. But when Wheeler's colleague Tosha Duprasbegan brushing the sand away, she noticed prominent fractures on the child's arms.

"She thought, 'Whoa, this was weird,' and then she found another fracture on the collarbone," Wheeler said. "We have some other kids that show evidence of skeletal trauma, but this is the only one that had these really extreme fracture patterns."

Signs of abuse

The researchers decided to conduct a series of tests on Burial 519, including X-ray work, histology (microscopic study of tissues) and isotopic analyses, which pinpoint metabolic changes that show when the body tried to repair itself. They found a number of bone fractures throughout the body, on places like the humerus (forearm), ribs, pelvis and back.

Whereas no particular fracture is diagnostic of child abuse, the pattern of trauma suggests it occurred. Additionally, the injuries were all in different stages of healing, which further signifies repeated nonaccidental trauma.

One of the more interesting fractures was located on the child's upper arms, in the same spot on each arm, Wheeler said. The fractures were complete, broken all the way through the bone — given that children are more flexible than adults, a complete break like that would have taken a lot of force.

After comparing the injury with the clinical literature, the researchers deduced that someone grabbed the child's arms and used them as handles to shake the child violently. Other fractures were also likely caused by shaking, but some injuries, including those on the ribs and vertebrae, probably came from direct blows.

The archaeologists aren't sure what ultimately killed the toddler. "It could be that last fracture, which is the clavicle fracture," Wheeler said, referring to the collarbone. "Maybe it wasn't a survivable event."

A unique case

Child abuse in the archaeological record is rare. One possible reason, Wheeler said, is that archaeologists didn't really pay much attention to child remains until about 20 years ago, believing that children couldn't tell them much about the past.

A few cases of possible child abuse have since come out of France, Peru and the United Kingdom, all of which date back to medieval times or later. "Certainly, our case has the best context in terms of the archaeology and skeletal analysis," Wheeler said.

Of the 158 juveniles excavated from the Kellis 2 cemetery, Burial 519 is the only one showing signs of repeated nonaccidental trauma, suggesting child abuse wasn't something that occurred throughout the community. The uniqueness of the case supports the general belief that children were a valued part of ancient Egyptian society.

By contrast, though Romans loved their kids immensely, they believed children were born soft and weak, so it was the parents' duty to mold them into adults. They often engaged in such practices as corporal punishment, immobilizing newborn infants on wooden planks to ensure proper growth and routinely bathing the young in cold water as to not soften them with the feel of warm water.

Read more at Discovery News

Researchers Identify Genetic Suspects in Sporadic Lou Gehrig's Disease

Researchers at the Stanford University School of Medicine have identified mutations in several new genes that might be associated with the development of spontaneously occurring cases of the neurodegenerative disease known as amyotrophic lateral sclerosis, or ALS. Also known as Lou Gehrig's disease, the progressive, fatal condition, in which the motor neurons that control movement and breathing gradually cease to function, has no cure.

Although researchers know of some mutations associated with inherited forms of ALS, the majority of patients have no family history of the disease, and there are few clues as to its cause. The Stanford researchers compared the DNA sequences of 47 patients who have the spontaneous form of the disease, known as sporadic ALS, with those of their unaffected parents. The goal was to identify new mutations that were present in the patient but not in either parent that may have contributed to disease development.

Several suspects are mutations in genes that encode chromatin regulators -- cellular proteins that govern how DNA is packed into the nucleus of a cell and how it is accessed when genes are expressed. Protein members of one these chromatin-regulatory complexes have recently been shown to play roles in normal development and some forms of cancer.

"The more we know about the genetic causes of the disorder, the greater insight we will have as to possible therapeutic targets," said Aaron Gitler, PhD, associate professor of genetics. "Until now, researchers have primarily relied upon large families with many cases of inherited ALS and attempted to pinpoint genetic regions that seem to occur only in patients. But more than 90 percent of ALS cases are sporadic, and many of the genes involved in these cases are unknown."

Gitler is the senior author of the study, which will be published online May 26 in Nature Neuroscience. Postdoctoral scholar Alessandra Chesi, PhD, is the lead author. Gitler and Chesi collaborated with members of the laboratory of Gerald Crabtree, MD, professor of developmental biology and of pathology. Crabtree, a Howard Hughes Medical Institute investigator, is also a co-author of the study.

Chesi and Gitler combined deductive reasoning with recent advances in sequencing technology to conduct the work, which relied on the availability of genetic samples from not only ALS patients, but also the patients' unaffected parents. Such trios can be difficult to obtain for diseases like sporadic ALS that strike well into adulthood when a patient's parents may no longer be alive. Gitler and Chesi collaborated with researchers from Emory University and Johns Hopkins University to collect these samples.

The researchers compared the sequences of a portion of the genome called the exome, which directly contributes to the amino acid sequences of all the proteins in a cell. (Many genes contain intervening, non-protein-coding regions of DNA called introns that are removed prior to protein production.) Mutations found only in the patient's exome, but not in that of his or her parents', were viewed as potential disease-associated candidates -- particularly if they affected the composition or structure of the resulting protein made from that gene.

Focusing on just the exome, which is about 1 percent of the total amount of DNA in each human cell, vastly reduced the total amount of DNA that needed to be sequenced and allowed the researchers to achieve relatively high coverage (or repeated sequencing to ensure accuracy) of each sample.

"We wanted to find novel changes in the patients," Chesi said. "These represent a class of mutations called de novo mutations that likely occurred during the production of the parents' reproductive cells." As a result, these mutations would be carried in all the cells of patients, but not in their parents or siblings.

Using the exome sequencing technique, the researchers identified 25 de novo mutations in the ALS patients. Of these, five are known to be in genes involved in the regulation of the tightly packed form of DNA called chromatin -- a proportion that is much higher than would have been expected by chance, according to Chesi.

Furthermore, one of the five chromatin regulatory proteins, SS18L1, is a member of a neuron-specific complex called nBAF, which has long been studied in Crabtree's laboratory. This complex is strongly expressed in the brain and spinal cord, and affects the ability of the neurons to form branching structures called dendrites that are essential to nerve signaling.

"We found that, in one sporadic ALS case, the last nine amino acids of this protein are missing," Gitler said. "I knew that Gerald Crabtree's lab had been investigating SS18L1, so I asked him about it. In fact, they had already identified these amino acids as being very important to the function of the protein."

When the researchers expressed the mutant SS18L1 in motor neurons isolated from mouse embryos, they found the neurons were unable to extend and grow new dendrites as robustly as normal neurons in response to stimuli. They also showed that SS18L1 appears to physically interact with another protein known to be involved in cases of familial, or inherited, ALS.

Although the results are intriguing, the researchers caution that more work is necessary to conclusively prove whether and how mutations in SS18L1 contribute to sporadic cases of ALS. But now they have an idea of where to look in other patients, without requiring the existence of patient and parent trios. They are planning to sequence SS18L1 and other candidates in an additional few thousand sporadic ALS cases.

Read more at Science Daily

New Gene Discovery for Babies Born With Hole in the Heart

New gene discovery for babies born with hole in the heart A new gene associated with a form of congenital heart disease in newborn babies -- known as "a hole in the heart" has been discovered by researchers. British Heart Foundation (BHF) Professor Bernard Keavney, from The University of Manchester and Newcastle University, led the research which saw investigators from Newcastle, Nottingham, Oxford and Leicester universities in the UK, together with colleagues in Europe, Australia and Canada pool resources.

The discovery, published in Nature Genetics today, will help lead to better understanding of why some patients are born with the disorder. Congenital heart disease (CHD) is the most common form of congenital malformation, occurring in seven in 1000 babies born and is one of the major causes of childhood death and illness. Most patients born with CHD now survive to adulthood, so identifying the responsible genes is important as experts attempt to provide individual-specific genetic counselling for these people.

In about 20% of cases, a predisposing cause can be identified, for example Down's Syndrome, but in the remainder of patients, although genes are recognised to be important, scientists do not know the identity of these genes. The study, funded by the BHF and the Wellcome Trust, looked at over 2,000 CHD patients and measured over 500,000 genetic markers which vary in the general population. The genetic markers in the patients were compared to the markers of over 5,600 people in good health who acted as a control group.

The researchers found a relationship between a particular region of the human genome and risk of atrial septal defect (ASD) -- a "hole" between the heart's blood-collecting chambers, which they went on to confirm in additional cases of atrial septal defect and healthy controls. BHF Professor Keavney, Director of the Institute of Cardiovascular Sciences at The University of Manchester, said identifying a gene associated with one type of CHD was an important step forward. "We found that a common genetic variation near a gene called Msx1 was strongly associated with the risk of a particular type of CHD called atrial septal defect or hole in the heart," he said. "ASD is one of the most common forms of congenital heart disease, and it carries a risk of heart failure and stroke. We estimated that around 10% of ASDs may be due to the gene we found. We can now work to find out how Msx1 and/or its neighbour genes affect the risk of ASD."

Researchers looked at all the major types of congenial heart disease (CHD), but they did not find a genetic marker common in all types of CHD. Professor Keavney added: "Our work also suggests that if we conduct larger studies we will be able to find genes that cause other types of CHD. Although we are not there yet, further studies may enable us to give better genetic counselling to high risk families. Also, when we identify genes important in the development of the heart because they have gone wrong, it helps us understand normal development better. Such an understanding is fundamental to any attempt to treat people with heart disease at any age -- for example those suffering from heart failure -- using regenerative medicine." Dr Shannon Amoils, Senior Research Advisor at the BHF, which part-funded the study, said: "We've made great strides in treating congenital heart disease; most babies born with a heart defect have a much brighter future now than they would have had in the 1960s when the BHF was founded. But we still need to fund much more research like this, to better understand the fundamental causes of congenital heart defects. "These important results show how large collaborative studies are incredibly useful for uncovering the influence of our genes on congenital heart disease.

Read more at Science Daily

Rats Have a Double View of the World

Scientists from the Max Planck Institute for Biological Cybernetics in Tübingen, using miniaturised high-speed cameras and high-speed behavioural tracking, discovered that rats move their eyes in opposite directions in both the horizontal and the vertical plane when running around. Each eye moves in a different direction, depending on the change in the animal's head position. An analysis of both eyes' field of view found that the eye movements exclude the possibility that rats fuse the visual information into a single image like humans do. Instead, the eyes move in such a way that enables the space above them to be permanently in view -- presumably an adaptation to help them deal with the major threat from predatory birds that rodents face in their natural environment.

Like many mammals, rats have their eyes on the sides of their heads. This gives them a very wide visual field, useful for detection of predators. However, three-dimensional vision requires overlap of the visual fields of the two eyes. Thus, the visual system of these animals needs to meet two conflicting demands at the same time; on the one hand maximum surveillance and on the other hand detailed binocular vision.

The research team from the Max Planck Institute for Biological Cybernetics have now, for the first time, observed and characterised the eye movements of freely moving rats. They fitted minuscule cameras weighing only about one gram to the animals' heads, which could record the lightning-fast eye movements with great precision. The scientists also used another new method to measure the position and direction of the head, enabling them to reconstruct the rats' exact line of view at any given time.

The Max Planck scientists' findings came as a complete surprise. Although rats process visual information from their eyes through very similar brain pathways to other mammals, their eyes evidently move in a totally different way. "Humans move their eyes in a very stereotypical way for both counteracting head movements and searching around. Both our eyes move together and always follow the same object. In rats, on the other hand, the eyes generally move in opposite directions," explains Jason Kerr from the Max Planck Institute for Biological Cybernetics.

In a series of behavioural experiments, the neurobiologists also discovered that the eye movements largely depend on the position of the animal's head. "When the head points downward, the eyes move back, away from the tip of the nose. When the rat lifts its head, the eyes look forward: cross-eyed, so to speak. If the animal puts its head on one side, the eye on the lower side moves up and the other eye moves down." says Jason Kerr.

In humans, the direction in which the eyes look must be precisely aligned, otherwise an object cannot be fixated. A deviation measuring less than a single degree of the field of view is enough to cause double vision. In rats, the opposing eye movements between left and right eye mean that the line of vision varies by as much as 40 degrees in the horizontal plane and up to 60 degrees in the vertical plane. The consequence of these unusual eye movements is that irrespective of vigorous head movements in all planes, the eyes movements always move in such a way to ensure that the area above the animal is always in view simultaneously by both eyes -something that does not occur in any other region of the rat's visual field.

Read more at Science Daily

Climate Researchers Discover New Rhythm for El Niño

El Niño wreaks havoc across the globe, shifting weather patterns that spawn droughts in some regions and floods in others. The impacts of this tropical Pacific climate phenomenon are well known and documented.

A mystery, however, has remained despite decades of research: Why does El Niño always peak around Christmas and end quickly by February to April?

Now there is an answer: An unusual wind pattern that straddles the equatorial Pacific during strong El Niño events and swings back and forth with a period of 15 months explains El Niño's close ties to the annual cycle. This finding is reported in the May 26, 2013, online issue of Nature Geoscience by scientists from the University of Hawai'i at Manoa Meteorology Department and International Pacific Research Center.

"This atmospheric pattern peaks in February and triggers some of the well-known El Niño impacts, such as droughts in the Philippines and across Micronesia and heavy rainfall over French Polynesia," says lead author Malte Stuecker.

When anomalous trade winds shift south they can terminate an El Niño by generating eastward propagating equatorial Kelvin waves that eventually resume upwelling of cold water in the eastern equatorial Pacific. This wind shift is part of the larger, unusual atmospheric pattern accompanying El Niño events, in which a high-pressure system hovers over the Philippines and the major rain band of the South Pacific rapidly shifts equatorward.

With the help of numerical atmospheric models, the scientists discovered that this unusual pattern originates from an interaction between El Niño and the seasonal evolution of temperatures in the western tropical Pacific warm pool.

"Not all El Niño events are accompanied by this unusual wind pattern" notes Malte Stuecker, "but once El Niño conditions reach a certain threshold amplitude during the right time of the year, it is like a jack-in-the-box whose lid pops open."

A study of the evolution of the anomalous wind pattern in the model reveals a rhythm of about 15 months accompanying strong El Niño events, which is considerably faster than the three- to five-year timetable for El Niño events, but slower than the annual cycle.

"This type of variability is known in physics as a combination tone," says Fei-Fei Jin, professor of Meteorology and co-author of the study. Combination tones have been known for more than three centuries. They where discovered by violin builder Tartini, who realized that our ear can create a third tone, even though only two tones are played on a violin.

"The unusual wind pattern straddling the equator during an El Niño is such a combination tone between El Niño events and the seasonal march of the sun across the equator" says co-author Axel Timmermann, climate scientist at the International Pacific Research Center and professor at the Department of Oceanography, University of Hawai'i. He adds, "It turns out that many climate models have difficulties creating the correct combination tone, which is likely to impact their ability to simulate and predict El Niño events and their global impacts."

Read more at Science Daily

Cosmic Swirly Straws: Galaxies Fed by Funnels of Fuel

Computer simulations of galaxies growing over billions of years have revealed a likely scenario for how they feed: a cosmic version of swirly straws.

The results show that cold gas -- fuel for stars -- spirals into the cores of galaxies along filaments, rapidly making its way to their "guts." Once there, the gas is converted into new stars, and the galaxies bulk up in mass.

"Galaxy formation is really chaotic," said Kyle Stewart, lead author of the new study appearing in the May 20th issue of the Astrophysical Journal. "It took us several hundred computer processors, over months of time, to simulate and learn more about how this process works." Stewart, who is now at the California Baptist University in Riverside, Calif., completed the majority of this work while at NASA's Jet Propulsion Laboratory in Pasadena, Calif.

In the early universe, galaxies formed out of clumps of matter, connected by filaments in a giant cosmic web. Within the galaxies, nuggets of gas cooled and condensed, becoming dense enough to trigger the birth of stars. Our Milky Way spiral galaxy and its billions of stars took shape in this way.

The previous, standard model of galaxy formation held that hot gas sank into the centers of burgeoning galaxies from all directions. Gas clouds were thought to collide into each other, sending out shock waves, which then heated up the gas. The process is similar to jets creating sonic booms, only in the case of galaxies, the in-falling gas travels faster than the speed of sound, piling up into waves. Eventually, the gas cools and sinks to the galactic center. This process was theorized to be slow, taking up to 8 billion years.

Recent research has contradicted this scenario in smaller galaxies, showing that the gas is not heated. An alternate "cold-mode" theory of galaxy formation was proposed instead, suggesting the cold gas might funnel along filaments into galaxy centers. Stewart and his colleagues set out to test this theory and address the mysteries about how the cold gas gets into galaxies, as well as the rate at which it spirals in.

Since it would take billions of years to watch a galaxy grow, the team simulated the process using supercomputers at JPL; NASA's Ames Research Center, Moffett Field, Calif.; and the University of California, Irvine. They ran four different simulations of the formation of a galaxy like our Milky Way, starting from just 57 million years after the big bang until present day.

The simulations began with the starting ingredients for galaxies -- hydrogen, helium and dark matter -- and then let the laws of physics take over to create their galactic masterpieces. Supercomputers are needed due to the enormous number of interactions.

"The simulations are like a gigantic game of chess," said Alyson Brooks, a co-author of the paper and expert in galaxy simulations at the University of Wisconsin, Madison. "For each point in time, we have to figure out how a given particle -- our chess piece -- should move based on the positions of all of the other particles. There are tens of millions of particles in the simulation, so figuring out how the gravitational forces affect each particle is time-consuming."

When the galaxy concoctions were ready, the researchers inspected the data, finding new clues about how cold gas sinks into the galaxy centers. The new results confirm that cold gas flows along filaments and show, for the first time, that the gas is spinning around faster than previously believed. The simulations also revealed that the gas is making its way down to the centers of galaxies more quickly than what occurs in the "hot-mode" of galaxy formation, in about 1 billion years.

"We have found that the filamentary structures that galaxies are built on are key to how they build up over time, by threading gas into them efficiently," said Leonidas Moustakas, a co-author at JPL.

The researchers looked at dark matter too -- an invisible substance making up about 85 percent of matter in the universe. Galaxies form out of lumps of regular matter, so-called baryonic matter that is composed of atoms, and dark matter. The simulations showed that dark matter is also spinning at a faster rate along the filaments, spiraling into the galaxy centers.

The results help answer a riddle in astronomy about galaxies with large extended disks of material spinning around them, far from their centers. Researchers didn't understand how the outer material could be spinning so fast. The cold-mode allows for this rapid spinning, fitting another jigsaw piece into the puzzle of how galaxies grow.

"The goal of simulating galaxies is to compare them to what telescopes observe and see if we really understand how to build a galaxy," said Stewart. "It helps us makes sense of the real universe."

Read more at Science Daily

Alien Debris Found in Lunar Craters

Strange minerals detected at the centers of impact craters on the moon may be the shattered remains of the space rocks that made the craters and not exhumed bits of the moon's interior, as had been previously thought.

The foreign matter in the craters is probably asteroid debris and some could even be from Earth, which has thrown off its share of material as it's been battered by asteroids and comets over the eons.

The discovery comes not from finding anything new in the craters themselves, but by planetary scientists who were looking at models of how meteorite impacts affect the moon. Specifically, the researchers simulated some high-angle, exceptionally slow impacts -- at least slow compared to possible impact speeds -- and they were surprised at what they found.

"Nobody has done it at such high resolution," said planetary scientist Jay Melosh of Purdue University. Melosh and his colleagues published a paper on the discovery in the May 26 online issue of the journal Nature Geoscience.

They found that when a slow enough impact happened, at speeds of less than 27,000 miles per hour (43,000 kph), the rock that struck doesn't necessarily vaporize. Instead, it gets shattered into a rain of debris that is then swept back down the crater sides and piles up in the crater's central peak.

In the case of craters like Copernicus (pictured top), the foreign material stands out because it contains minerals called spinels. These only form under great pressure -- in the Earth's mantle, for instance, and perhaps in the mantle of the moon. But spinels are also common in some asteroids, said Melosh, which are fragments of broken or failed planets from earlier days in the formation of our solar system.

The team has concluded, therefore, that the unusual minerals observed in the central peaks of many lunar impact craters are not lunar natives, but imports.

That conclusion could also explain why the same minerals, if they were instead from the interior of the moon, are not found in the largest impact basins -- as would be expected if the impact event was larger and penetrated deeper into the moon.

"An origin from within the Moon does not readily explain why the observed spinel deposits are associated with craters like Tycho and Copernicus instead of the largest impact basins," writes Arizona State University researcher Erik Asphaug in a commentary on the paper. "Excavation of deep-seated materials should favor the largest cratering events."

Read more at Discovery News