Tiny Fish Skull May Be Ancestor of Jawed Vertebrates

The remains of a 415-million-year-old fish skull from Siberia — though miniscule in size — offer hints about the origins of all jawed vertebrates, ranging from reptiles to humans, a new study finds.

Researchers originally uncovered the roughly 0.8-inch-long (2 centimeters) skull in the 1970s, and classified the specimen as a bony fish. There are two main types of living jawed vertebrates: those made of bone and those made of cartilage. Now, a new, more in-depth examination of the ancient fish's brain case shows that the fossil has characteristics of both bony fish, such as salmon and trout, and fish made of cartilage, including sharks and manta rays.

The Siberian fossil also suggests that sharks — which are made of cartilage and long thought to be more primitive than bony-jawed vertebrates — are more evolved than had been previously thought, the researchers said.

"It's a very interesting fossil, and it's very small," said Sam Giles, the study's lead researcher and a paleobiology doctoral candidate at Oxford University in the United Kingdom. "It's surprising that something so tiny could have so much information in it."

The researchers named the new genus Janusiscus schultzei, for "Janus," the Roman god of doorways and transitions, who is often depicted with two faces, and the Latin "piscis" for fish. The species is also named for Hans-Peter Schultze, of the University of Kansas, who first described the fossil in 1977.

Giles and her colleagues used a specialized computed tomography (CT) scanner to look at the skull, which was still embedded in rock. They imaged the fossil hundreds of times from different angles, allowing them to create a 3D model.

The incredibly detailed scans show that the fish has sensory line canals on its skull. Bony fish use these canals, located on the outside of the body, to sense changes in pressure around them and avoid predators.

But the skull also has features characteristics of fish made of cartilage. The scans showed that there are blood vessels at the bottom of the ancient fish's brain case, located inside the skull, above and between the jaws,that supply the brain with oxygen. The blood vessels are something that "is a lot more like you would see in a cartilaginous fish," Giles told Live Science.

Although bony and cartilaginous fish had a common ancestor, they split apart around 420 million years ago, Giles said. The Siberian fossil is likely one of the common ancestors of the two groups, and may provide clues as to what the animals' earliest common ancestor looked like.

"There are over 60,000 species of living jawed vertebrates, and they encompass pretty much everything you can think of [with a backbone] that lives on land or in the sea," Giles said. "But we don't really know what they looked like when they split."

Moreover, researchers have long believed that the common ancestor of bony and cartilaginous fish had more cartilage than bone, Giles said. This would mean that vertebrates made of cartilage, such as sharks, would have evolved less over the ages than did bony creatures.

"But what this animal tells us that actually the last common ancestor of the two groups had lots of bone," Giles said. "So rather than sharks being primitive, sharks are actually very highly evolved in their own way, and just as highly evolved as we are."

The new findings are "truly remarkable," said John Long, a professor of paleontology at Flinders University in Adelaide, Australia, who was not involved with the study.

"I think it is a highly significant discovery, as the origin and diversification of modern bony-jawed fishes is still shrouded in mystery," Long told Live Science in an email. "But Janiusiscus takes us a big step closer to really understanding this major evolutionary transition, from primitive jawed fishes to the beginning of the modern jawed fish fauna."

Read more at Discovery News

First Conversations 2 Mln Yrs Ago Likely About Tools

The first verbal conversations likely occurred between 2.5 and 1.8 million years ago and were about tool-making, a new study suggests.

The study, published in the journal Nature Communications, presents compelling evidence that stone tool-making helped to drive the evolution of language and teaching among prehistoric human ancestors in the African savanna. A possible first sentence might have been, "Tool bad."

"We suggest that the use of tools drove the evolution of language, and it seems likely that 'words' for things other than current emotional states would have been very useful for learning to knap," lead author Thomas Morgan told Discovery News.

"The use of sounds or gestures for non-emotional concepts such as 'yes,' 'no,' 'here,' 'there,' 'good' and 'bad' would likely have been really useful," added Morgan, who is a postdoctoral researcher in psychology at the University of California at Berkeley.

Morgan, University of Liverpool archaeologist Natalie Uomini and their team conducted a series of experiments in teaching contemporary humans the art of "Oldowan stone knapping." Oldowan refers to the oldest known stone cutting tools, which were likely made by Homo habilis (aka "The Handy Man") and possibly also Homo rudolfensis, Australopithecus garhi and Paranthropus boisei.

The earliest known Oldowan tools date to 2.5 million years ago. They consist of butchering "flakes" created by hammering a hard rock against certain volcanic or glassy rocks, like basalt or flint. The tools remained largely unchanged until 1.8 million years ago, when more sophisticated Acheulean hand-axes and cleavers marked the next generation of stone tool tech.

In testing five different ways to convey Oldowan stone-knapping skills to more than 180 college students, the researchers found that the demonstration using spoken communication, versus imitation, non-verbal presentation or gestures, yielded the highest volume and quality of flakes in the shortest amount of time and with the least waste.

He suspects that other tasks, such as hunting and gathering, also could have been involved in the development of language and teaching skills, but probably not to the same degree as tool making.

Since language has likely been around for at least 2 million years, there is little doubt that other human-like species, such as Neanderthals, did a lot of talking.

"Language was certainly already present before the Neanderthals and our ancestors split," Uomini said. "The Neanderthals had some of the most complex stone tools ever made, which are also the most difficult for modern day knappers to replicate. That's why we think that their communication and teaching system must have been sophisticated enough to transmit the subtle and long 'recipes' for making their tools."

Erella Hovers of the Hebrew University of Jerusalem's Institute of Archaeology said that the new study offers "some intriguing ideas," but she is not sure that the lack of stone tool tech advancement just after 2.5 million years ago "can be attributed exclusively to low-fidelity teaching modes."

Dietrich Stout, an assistant professor of anthropology at Emory University, has conducted studies on the cognitive mechanisms underlying tool making. He recently trained subjects to make stone tools over a 2-year period and measured changes in their brain structure associated with learning. The results showed that brain systems associated with language were affected, supporting the proposed link between tool manufacture and language.

Read more at Discovery News

Animal DNA on the Go Seen for First Time

A type of DNA for the first time has been observed moving from one cell to another in animals.

Genetic material called mitochondria convert energy from food into a form that can be used by cells. In the experiment, a tumor cell without mitochondrial DNA formed tumors after pulling in DNA from normal cells.

“Our findings overturn the dogma that genes of higher organisms are usually constrained within cells except during reproduction," Mike Berridge, a professor from the Malaghan Institute of Medical Research in New Zealand, said in a statement. "It may be that mitochondrial gene transfer between different cells is actually quite a common biological occurrence.”

Berridge along with Jiri Neuzil from Griffith University in Queensland, Australia, led a team that examined breast cancer tumors in mice. Mitochondrial DNA was removed from cells, which then pulled replacement DNA from surrounding, normal mouse tissue.

The effect has been observed in the lab before, the researchers said, but not in an animal tumor.

The researchers initially thought the cells had adapted to grow without the mitochondrial DNA that had been removed. But after testing, the scientists discovered the cells did have mitochondrial DNA pulled from non-tumor cells.

The researches say the findings may help in understanding more about 200 diseases besides cancer that involve defective mitochondrial DNA. "It could also usher in a new field where synthetic mitochondrial DNA is custom-designed to replace defective genes," the researchers wrote.

If mitochondrial DNA sounds familiar, that may be because it's used in studying human ancestry. The genetic material is passed down only by one's mother, and has been instrumental in tracing a common human ancestor back to Africa 60-70,000 years ago.

The results were published in the journal Cell Metabolism.

From Discovery News

Monster Black Hole Belches Record Flare

The giant black hole at the center of the Milky Way galaxy recently spit out the largest X-ray flare ever seen in that region, astronomers say.

The enormous eruption from the Milky Way's core was detected on Sept. 14, 2013, very close to the supermassive black hole known as Sagittarius A*. Pronounced "Sagittarius A star" and abbreviated as Sgr A*, the Milky Way's monster black hole has a mass that is about 4.5 million times that of the sun. Scientists unveiled the discovery of the record-breaking flare this month at the 225th meeting of the American Astronomical Society.

The so-called "megaflare" was spotted by NASA's Chandra X-ray Observatory, which can peer through dust and starlight to the center of the Milky Way. The event was 400 times brighter than the normal level of radiation from this region and nearly three times brighter than the previous record-holding flare, recorded in 2012. A second X-ray flare, with a flash 200 times brighter than normal levels, was then seen on Oct. 22, 2014.

Daryl Haggard, of Amherst College in Massachusetts, presented the findings at a news conference here at the AAS meeting on Jan. 5. Haggard and her colleagues have two possible explanations for what might have caused the flare. First, the black hole may be behaving like our own sun, which also emits bright X-ray flares. In the sun, these flares occur when magnetic-field lines become very tightly packed together or twisted, and the researchers said it's possible something similar took place near the black hole.

It's also plausible that the flare was the product of Sgr A* having a snack. An asteroid or other object may have come too close to the black hole, ripping it apart. The debris would have accelerated rapidly and potentially radiated a bright burst of X-rays.

"If an asteroid was torn apart, it would go around the black hole for a couple of hours — like water circling an open drain — before falling in," Fred Baganoff, of the Massachusetts Institute of Technology and a member of the research team, said in a statement. "That's just how long we saw the brightest X-ray flare last, so that is an intriguing clue for us to consider."

Researchers saw the flare by chance while watching Sgr A* in anticipation of a different event: A gas cloud called G2 was set to make a close pass by Sgr A*, and some scientists hypothesized that material from G2 would fall into the black hole, generating a bright display of X-rays, NASA officials said in a statement. But no X-ray signal was detected as G2 made its closest approach to Sgr A*. The new flares do not appear to be part of the missing light show, according to Haggard.

"We do not think flares are connected to the G2 object," Haggard said. "And the reason for that is that the time scales don't quite match. The time scale for these flares is fairly rapid — thousands of seconds," or an hour or two, she said.

Read more at Discovery News

They see flow signals: Researchers identify nature of 'sixth sense' in fish

A team of scientists has identified how a "sixth sense" in fish allows them to detect flows of water, which helps resolve a long-standing mystery about how these aquatic creatures respond to their environment. Their findings, which appear in the journal Physical Review Letters, illustrate how sensory systems evolve in accordance with physical principles while also offering a framework for understanding how sensory networks are structured.

"We identified a unique layout of flow sensors on the surface of fish that is nearly universal across species, and our research asks why this is so," explains Leif Ristroph, an assistant professor at New York University's Courant Institute of Mathematical Sciences and one of the study's authors. "The network of these sensors is like a 'hydrodynamic antenna' that allows them to retrieve signals about the flow of water and use this information in different behaviors."

The study's other authors were James Liao, an assistant professor at the University of Florida's Whitney Laboratory for Marine Bioscience, and Jun Zhang, a professor of physics and mathematics at NYU and NYU Shanghai.

It is well known that fish respond to changes in their fluid environment. These include avoiding obstacles, reducing swimming effort by slaloming between vortices, or whirlpools, and tracking changes in water flow left by prey -- even without the aid of vision.

To explore how fish exploit flow information, the research team focused on a fish's "lateral line" -- a system of sensory organs known to detect both movement and vibration in the water that surrounds them -- with particular consideration to the line's sensory-laden canals that open to the environment through a series of pores. They specifically focused on the placement of these canals along the body, noting that their location can help explain how a fish's sixth sense functions. For instance, the concentration of these canals at the heads of blind cave fish seems well-suited for detecting obstacles.

To test their theory, the researchers created a plastic model of a rainbow trout that replicated the location of the fish's canals and included illuminated markers used to detect the speed of surrounding water.

In their experiments, the model fish was put through a series of tests the replicated real- life aquatic conditions -- changes in water flow that altered water pressure or mimicked the presence of "prey" -- and examined where the canals were located in relation to strongest changes in water pressure.

Their results showed that, as predicted, the canal system is concentrated at locations on the body wherever strong variations in pressure occur. Just as the shape of a TV or radio antenna is designed to detect electromagnetic signals, the fish's canal system is like an antenna laid out on the body surface and configured to be sensitive to pressure changes. The team's use of finely detailed models -- developed with the help of a taxidermist who made custom molds from real trout -- made it possible to record this data for the first time.

Read more at Science Daily

Two-faced fish clue that our ancestors 'weren't shark-like'

An investigation of a 415 million year-old fish skull strongly suggests that the last common ancestor of all jawed vertebrates, including humans, was not very shark-like. It adds further weight to the growing idea that sharks are not 'primitive'.

The fossil skull's external features meant it had always been thought to belong to the bony fishes (osteichthyans), a group which includes familiar fishes such as cod and tuna as well as all land-dwelling creatures with backbones. But when scientists from Oxford University and Imperial College London used X-ray CT scanning to look inside the skull they found the structure surrounding the brain was reminiscent of cartilaginous fishes (chondrichthyans) such as sharks and rays. The fish fossil's 'two faces' led to it being named Janusiscus after the double-faced Roman god Janus.

A report of the research is published in the journal Nature.

'This 415 million year-old fossil gives us an intriguing glimpse of the 'Age of Fishes', when modern groups of vertebrates were really beginning to take off in an evolutionary sense,' said Dr Matt Friedman of Oxford University's Department of Earth Sciences, an author of the report. 'It tells us that the ancestral jawed vertebrate probably doesn't fit into our existing categories.'

Chondrichthyans have often been viewed as primitive, and treated as proxies for what the 'ancestral' jawed vertebrate would have looked like. A key component of this view is the lack of a bony skeleton in cartilaginous fishes.

'The results from our analysis help to turn this view on its head: the earliest jawed vertebrates would have looked somewhat more like bony fishes, at least externally, with large dermal plates covering their skulls,' said Sam Giles of Oxford University's Department of Earth Sciences, first author of the report. 'In fact, they would have had a mix of what are now viewed as cartilaginous- and bony fish-like features, supporting the idea that both groups became independently specialised later in their separate evolutionary histories.'

Dr Friedman said: 'This mix of features, some reminiscent of bony fishes and others cartilaginous fishes, suggests that humans may have just as many features that you might call 'primitive' as sharks.'

The fossil skull was originally found near the Sida River in Siberia in 1972 and is currently held in the Institute of Geology at the Tallinn University of Technology, Estonia. Study author Martin Brazeau of Imperial College London spotted the specimen in an online catalogue and the team decided it would be worth studying in greater detail using modern investigative techniques.

The team then used X-ray CT (computed tomography) to 'virtually' cut through the fossil. Different materials attenuate X-rays to different amounts -- just as in a hospital X-ray, bones show up brighter than muscles and skin. This same principle can be applied to fossils, as fossilised bone and rock attenuate X-rays to different degrees. This technique was used to build a 3D virtual model of the fossil, enabling its internal and external features to be examined in great detail. Traces left by networks of blood vessels and nerves, often less than 1/100th of a centimetre in diameter, could then be compared to structure in a variety of jawed vertebrate groups, including sharks and bony fishes.

Read more at Science Daily

Motorboat-Sized Predator Swam in Jurassic Scotland

A motorboat-sized beast that was at the top of its food chain 170 million years ago is Scotland's first known native marine reptile.

The formidable ocean predator, described in the latest issue of the Scottish Journal of Geology, might have munched on dinosaurs and sharks, since both also lived at or around what is now the Isle of Skye. The predator was an ichthyosaur, meaning an extinct marine reptile that had a pointy head, four flippers and a vertical tail. Together, these features made such animals look like sinister dolphins.

A group of paleontologists working in Scotland studied the remains of the newly discovered ichthyosaur, named Dearcmhara shawcrossi. Dearcmhara --[/i ]pronounced jark vara -- is Scottish Gaelic for "marine lizard." The species is one of just a handful ever to have been given a Gaelic name.

"Believe it or not, this is the first distinctly Scottish marine reptile species that has ever been described, and our paper is the first paper on ichthyosaurs from Scotland," project leader Steve Brusatte of the University of Edinburgh's School of GeoSciences told Discovery News.

Remains of the animal were found at the Isle of Skye's Bearreraig Bay, where amateur collector Brian Shawcross found them. Instead of keeping or selling them, which often happens, Shawcross donated the specimens to the Hunterian Museum in Glasgow. This allowed researchers to study them, determine their significance and piece together what this animal looked like in the flesh.

"It would have been roughly 14 feet long or so, and probably would have fed on fish and marine invertebrates," Brusatte said.

Much of Skye was under water 170 million years ago. Skye was joined to the rest of the U.K. then, and was part of a large island positioned between land masses that gradually drifted apart and became Europe and North America.

Sharks in the region during the marine reptile's lifetime were generally smaller and more primitive than today's sharks, so it's possible that Dearcmhara ate them.

As for dinos, Brusatte said, "Dinosaurs did live in other parts of Scotland at the same general time as this ichthyosaur was living in the water. We know this from other rare fossils from Skye -- bones, teeth and footprints of very different type of dinosaurs, including big long-necked sauropods and carnivorous theropods."

If any waded or fell into the shallow, warm seas where Dearcmhara lived, they likely would have been dinner for the stealthy ichthyosaur.

Nick Fraser of National Museums Scotland is excited by the discovery, and what it means for his country.

"Scotland is well noted for its geology and geologists, including perhaps the most famous of all, James Hutton (often dubbed the Father of Modern Geology, although he lived from 1726 to 1797)," Fraser told Discovery News. "However, it is not widely noted in the public realm for its fossils, which is unfortunate, as it boasts some incredibly important localities and specimens."

He explained that remains for prehistoric fishes and very early reptiles from the Triassic have been found in Scotland.

"Admittedly, there are not the huge rock exposures in Scotland that permit the excavation of spectacular death-beds of dinosaurs as you might find in the American West," Fraser said. "Yet, even some of the fragmentary remains that we do find are often of great scientific importance, and that is certainly the case with the Skye Jurassic fossils."

Fraser said that the remains represent a time period, the Middle Jurassic, which is rather poorly known worldwide in the fossil record. Evidence, however, from surrounding periods suggests that animal life then, in the seas and on land, was incredibly rich and diverse.

Read more at Discovery News

Did Meteorite Carve Icy Antarctic Crater?

Researchers in remote East Antarctica think a massive area of fractured ice discovered last month could be a newfound meteorite impact crater.

The mile-wide crater (about 2 kilometers across) is a circular scar marked by fractured, rumpled ice — a striking blot in this otherwise smooth section of Antarctica's King Baudouin Ice Shelf. It was spotted by German scientist Christian Müller during an aerial survey by plane on Dec. 20, 2014.

"I looked out of the window, and I saw an unusual structure on the surface of the ice," Müller said in a video describing the discovery. "There was some broken ice looking like icebergs, which is very unusual on a normally flat ice shelf, surrounded by a large, wing-shaped, circular structure," said Müller, a geoscientist with Fielax, a private company assisting Antarctic research.

The possible impact crater is about twice the size of Arizona's Barringer Meteor Crater. Satellite images suggest the broken-up ice could be at least 25 years old.

Lucky find

The crater was a serendipitous find, sighted by chance north of Belgium's Princess Elisabeth Research Station. German researchers at the station intended to remotely survey the surrounding bedrock, in order to gather new details on the Gondwana supercontinent's formation and breakup between 550 million and 180 million years ago. Flying over busted-up ice shelves — the floating extensions of the Antarctic Ice Sheet — was not part of the research plan.

"We were only flying that far in the north because the radar equipment had broken, and we didn't want to waste a good flying day," said Graeme Eagles, a scientist at Germany's Alfred Wegener Institute who is currently leading the geophysical research survey. "It's been a tremendously exciting couple of weeks," he added. "It really is a very raw form of science, with a lot of people speculating on what might or might not be the cause."

At first, Müller connected the crater to a 2004 meteor blast detected above this part of East Antarctica. Recently, however, the German research team discovered the crater in satellite images dating back to 1996, Eagles said. "The to the 2004 event really piqued our interest in the first place, but I don't think what we've seen in the satellite images rules out the possibility of an impact origin," Eagles told Live Science. "It just fuzzies the story a little bit."

Extraordinary claims

If a space rock did crash-land on the ice shelf, the meteorite was likely relatively large. Indeed, the crater's sheer size warrants skepticism, experts said.

As a rule of thumb, an object that formed a crater is usually about 10 to 20 times smaller than the crater itself, said Peter Brown, director of the Center for Planetary Science and Exploration at the University of Western Ontario in Canada. That means a 1.2-mile (2 km) crater would result from an object that measures roughly 325 feet (100 meters) across, Brown said.

"A very large explosion would have caused a 2-kilometer-wide crater — much larger than anything detected impacting Earth in recent history," Brown said. "So the feature seen is almost certainly not due to any meteorite impact."

Meteorite hunter Peter Jenniskens also found the crater idea implausible. "I don't think this is an impact crater," said Jenniskens, who holds dual affiliations at the SETI Institute and at NASA's Ames Research Center, both in California.

However, Eagles hinted that the German researchers have not shown all their cards. The scientists collected photos, video and data on a Dec. 26 trip to the crater site. The team mapped the ice surface in great detail with a laser-scanning instrument that records precise changes in topography. They also surveyed the area with a radar instrument that penetrates the upper surface of the ice and snow.

A number of smaller circular and subcircular structures were spotted nearby on this trip. The researchers haven't yet analyzed the data, but they hope to publish their results in a scientific journal if the structure is indeed an impact crater, Eagles said.

"This thing is very unusual indeed," Eagles said. "Extraordinary claims require extraordinary evidence, and in this case, as far as we can tell, is does look like it is extraordinary evidence."

Rock hunters

The researchers now must complete their Gondwana study before squeezing in any more trips to the crater, Eagles said. For instance, the team would like to eventually hunt for meteorites around the site.

Read more at Discovery News

Crowds, Leaders Gather for Historic Paris March of Defiance

Hundreds of thousands of people joined by world leaders flooded Paris on Sunday in a historic show of defiance and solidarity against terrorism following this week's Islamist attacks in the French capital.

As France mourned 17 victims of three days of bloodshed that included Jews and a Muslim police officer, the leaders of Israel and the Palestinian Authority were among those attending the mass rally.

Under blue skies, emotions were running high in the shell-shocked City of Light, with many of those gathering from all walks of life already in tears as they came together under the banner of freedom of speech and liberty.

Lassina Traore, a 34-year-old French-born Muslim from the Ivory Coast, gently placed 17 candles at the foot of the monument at the Place de la Republique, heaped with tributes to the dead.

The march is "a real sign of how strong France is. It shows that France is strong when she is united against these people," said the consultant.

"I want to show that we're not scared of the extremists. I want to defend freedom of expression," said 70-year-old Jacqueline Saad-Rouana.

The families of those who died in the shootings that shook France to its core will be at the very front of the march, leading royalty and heads of state.

Security was beefed up, with police snipers stationed on rooftops and plain-clothes officers among the crowd in a city still reeling from the Islamist attacks which left 12 staff and policemen dead at the Charlie Hebdo satirical magazine and claimed four lives at a Jewish supermarket. A policewoman was also killed.

"Today, Paris is the capital of the world," French President Francois Hollande said. "The entire country will rise up," he told ministers.

French Prime Minister Manuel Valls told a poignant rally on Saturday near where a gunman killed four hostages at the kosher store: "I have no doubt that millions of citizens will come to express their love of liberty, their love of fraternity."

In a foretaste of the demonstration, more than 700,000 people poured onto the streets of cities across France on Saturday, many carrying banners reading "Je suis Charlie" (I am Charlie), the tribute to Charlie Hebdo that has been the global rallying point in the wake of the slaughter.

Many brandished pens to symbolize freedom of expression after the magazine was targeted by brothers Said and Cherif Kouachi for publishing cartoons lampooning the Prophet Mohammed.

Along with Israel's Prime Minister Benjamin Netanyahu and Palestinian President Mahmud Abbas, the king and queen of Jordan were present alongside a host of top European leaders, including German Chancellor Angela Merkel and British Prime Minister David Cameron.

US President Barack Obama was represented by Attorney General Eric Holder, who took part in an emergency meeting of interior ministers to discuss the threats from Islamic extremism.

The ministers urged a strengthening of the EU external borders to limit the movement of extremists returning to Europe from the Middle East and said there was an "urgent need" to share European air passenger information.

Speaking on a visit to India, US Secretary of State John Kerry said: "We stand together this morning with the people of France. We stand together not just in anger and outrage but in solidarity and commitment in confronting extremists."

President Hollande, ahead of the march met representatives from the Jewish community who said authorities had agreed to even deploy soldiers to protect Jewish schools and synagogues "if necessary."

The rampage by three gunmen who claimed to be members of the Al-Qaeda and Islamic State extremist groups was followed by a chilling new threat from the Yemen-based Al-Qaeda in the Arabian Peninsula.

AQAP top sharia official Harith al-Nadhari warned France to "stop your aggression against the Muslims" or face further attacks, in comments released by the SITE monitoring group.

German newspaper Bild said the bloodshed in France could signal the start of a wave of attacks in Europe, citing communications by Islamic State leaders intercepted by US intelligence.

France's three days of terror started Wednesday when the Kouachi brothers burst into the Charlie Hebdo offices in central Paris and sprayed bullets into the editorial meeting, killing some of France's best-known cartoonists.

They then slaughtered a Muslim policeman as he lay helpless on the ground before fleeing, sparking a manhunt that lasted more than 48 hours.

A day later, a third gunman, Amedy Coulibaly, shot dead a policewoman in a southern Paris suburb.

In a video posted online Sunday, a man resembling Coulibaly said the gunmen coordinated their efforts and claimed he was a member of Islamic State who was avenging attacks by the international community on the extremist group.

Read more at Discovery News

Mars Microbe Traces Spotted by Rover? Probably Not

Intriguing features photographed by NASA's Mars rover Curiosity probably don't have a biological origin, mission team members say.

An outside researcher recently analyzed photos Curiosity took of an ancient sedimentary outcrop called Gillespie Lake, and noted some similarities to "microbially induced sedimentary structures" (MISS) here on Earth. Study author Nora Noffke, a geobiologist who is not a member of the Curiosity team, said the Gillespie Lake features could be consistent with a biological origin, but stressed repeatedly that this was just a hypothesis, and that she didn't regard the structures as proof of past Mars life.

Curiosity team members also noticed the Gillespie Lake structures (which include domes, cracks and pockets, among other shapes), said mission project scientist Ashwin Vasavada, of NASA's Jet Propulsion Laboratory in Pasadena, California. But the rover team arrived at a different interpretation.

"We really didn't see anything that can't be explained by natural processes of transporting that sand in water, and the nature of the rocks suggested that it was just a fluvial sandstone," Vasavada told Space.com.

"We do have several members of our team who are always keen to look out for things that might be caused by biological processes, but there was no reason, we felt, to explore that at that site," he added. "It came down to nothing exceptional, from our point of view, that wasn't just a consequence of erosion of this sandstone."

Vasavada also stressed that he and the rest of the Curiosity rover team welcome analyses by outside researchers such as Noffke.

If mission scientists had decided to study Gillespie Lake more closely, they could have taken up-close photos using Curiosity's Mars Hand Lens Imager, Vasavada said, or drilled the rock to deliver powder to the Sample Analysis at Mars (SAM) instrument, which is capable of detecting carbon-containing organic molecules.

The Curiosity team did decide to drill into a layer of fine-grained mudstone dubbed Sheepbed, which lies directly beneath Gillespie Lake within a broader region near the rover's landing site called Yellowknife Bay.

SAM's analysis of the Sheepbed mudstone, along with other Curiosity observations, allowed the rover team to determine that Yellowknife Bay could have supported microbial life in the ancient past. About 3.5 billion years ago, the area was part of a lake-stream system that may have been habitable for millions of years, mission scientists said.

SAM also detected organics in the Sheepbed sample, marking the first definitive detection of life's building blocks on Mars.

"We feel that choice paid off," Vasavada said of the focus on Sheepbed.

Read more at Discovery News