Dark Matter May Have Powered Universe's First Stars

Dark matter may have fueled the formation of the universe's first stars—vast, invisible giants totally unlike the blazing suns of today—scientists say.

According to a new theory, disintegrating fragments of the mysterious substance could have created "dark stars" hundreds of thousands of times wider than the sun around 13 billion years ago, just after the big bang.

Because these stars weren't fueled by fusing hydrogen and helium like known present-day stars, they would have been completely invisible—but scorching hot.

The findings "drastically alter the current theoretical framework for the formation of the first stars," said study co-author Paolo Gondolo, an astrophysicist at the University of Utah.

Scientists still don't know what dark matter is exactly, so the research could shed light on it and other astronomical mysteries, he added.

"We are always searching for ways to determine the nature of dark matter," Gondolo said.

The paper will appear in next month's issue of the journal Physical Review Letters.

Annihilation Engine

According to some theories of the universe, dark matter likely consists of hypothetical particles called neutralinos.

The new paper suggests that neutralinos annihilated each other in the early universe, producing subatomic particles called quarks and their antimatter counterparts, antiquarks.

The heat from this process was enough to prevent embryonic hydrogen and helium from cooling and shrinking. Such contraction ignites the self-sustaining fusion process that powers conventional stars.

"The heating can counteract the cooling, and so the star stops contracting for a while, forming a dark star" some 80 million to 100 million years after the big bang, Gondolo said.

Dark stars, made up mostly hydrogen and helium, would be vastly larger than the sun and other stars—up to 15,000 times the size of our solar system. And instead of shining, they would glow in the infrared.

"With your bare eyes, you can't see a dark star," Gondolo said. "But the radiation would fry you."

Wide-Ranging Implications

The theory may have wide-ranging implications about the importance of dark matter in the earliest stages of the universe.

For example, dark matter is widely believed to have helped with early galaxy formation, said Rennan Barkana, an astrophysicist at Tel Aviv University in Israel who was not involved with the new paper.

But until now it was thought that "the dark matter does not play any significant role in the formation of the star itself," he said.

That's important, because the substance is believed to make up most of the universe's matter, partly because galaxies rotate faster than can be explained by the visible matter within them.

In total, about 23 percent of the universe is thought to be dark matter, as opposed to 4 percent for the ordinary matter that makes up stars, planets, and moons.

The remaining 73 percent is thought to be dark energy, an even more mysterious force helping the universe to expand at increasing rates.

Search Is On

Emanuele Ripamonti, an astronomer at Universita' dell'Insubria in Como, Italy, said that in order for the new research to be plausible, the formation of stars from dark matter must rely on a cascade of events that are not yet well studied.

"Every time they make a choice, the authors pick the 'most likely' option, but in some cases there is no real consensus" about what would happen, he said.

Barkana called the theory intriguing and novel but agreed that more research is necessary.

"It is unclear whether in the end an observational prediction will come out that will allow the dark star possibility to be clearly distinguished from other scenarios," he said.

If dark stars exist, however, they would likely give themselves away by spewing gamma rays, neutrinos, and antimatter, study author Gondolo said. The stars would also be associated with clouds of cold, molecular hydrogen gas that wouldn't normally harbor such energetic particles.

If found, dark stars wouldn't only provide insights into dark matter, he added. They could also help unravel phenomena like the formation of heavy elements—thought to come from exploding conventional stars—and the rapid formation of black holes, which defies theoretical predictions.

"Without detailed simulations, we cannot pinpoint the further evolution of dark stars," he said. "We have to search for them."

"Zombie" Roaches Lose Free Will Due to Wasp Venom

The parasitic jewel wasp uses a venom injected directly into a cockroach's brain to inhibit its victim's free will, scientists have discovered.

The venom blocks a chemical substance called octopamine in the cockroach's brain that controls its motivation to walk, the study found.

Unable to fight back, the "zombie" cockroach can be pulled into the wasp's underground lair, where an egg is laid in its abdomen. The larva later hatches and eats the still living but incapacitated cockroach from the inside out.

"The whole thing takes about seven to eight days, during which the meat has to be fresh," said study co-author and neurobiologist Frederic Libersat of Ben-Gurion University of the Negev in Be'ér Sheva, Israel.

"If you kill a cockroach, it rots within a day."

The mature wasp emerges from the bug victim's body after about a month.

The study recently appeared in the Journal of Experimental Biology.

Zombie Science

The team of researchers at Ben-Gurion University believe that the octopamine discovery is an important piece of the puzzle of how the tropical wasp's venom turns its victims into the living dead.

Octopamine is a brain substance that places insects in an alert state, inspires them to move, and allows them to perform demanding physical tasks.

"It serves the same functions as noradrenaline, which is involved in the fight-or-flight reaction ... in the vertebrate brain," Libersat said.

The team determined that the wasp injects its venom into a specific area of the cockroach's brain, the protocerebrum.

This region, which contains octopamine-secreting nerve cells, controls the ability to start walking. The venom interferes with the release of octopamine, they found.

The researchers then reversed the process: they injected an octopamine-like substance directly into the protocerebrum of cockroaches that had already been turned into zombies by wasp stings.

The result was significant recovery and restoration of the cockroach's free will.

"This helps us understand how movement is initiated in animals," Libersat said. "We know how movement itself is generated, but to understand what makes an animal decide to move or not to move is a different issue."

Parasite Strategies

The jewel wasp is the only parasite known to inject its venom directly into its host's brain.

But other parasites also control the behavior of their hosts, said David Richman, curator of the Arthropod Museum at New Mexico State University in Las Cruces, who was not involved in the new study.

"This is not uncommon. There are a tremendous number of parasites, and they all have different strategies for survival and for propagation of their species," Richman said.

The behaviors of land snails, grasshoppers, and types of ants, for example, can all be affected by parasites.

"Not only that," Richman added, "[some parasites] can take over certain aspects of the host's biology, particularly as you get into microorganisms."

Shuttle Atlantis Launch Delayed

NASA called off Thursday's launch of space shuttle Atlantis after detecting problems with a pair of fuel gauges in the shuttle's external tank.

Shuttle managers said they would try again Friday—if the problem can be solved before then.

Engineers were testing the four engine-cutoff sensors in Atlantis's liquid hydrogen tank, and two of them failed.

Even though they were commanded to indicate the tank was empty, the two kept showing the tank was full, said NASA spokesman Paul Foerman.

At least three of the sensors must work properly to proceed with a launch.

Officials said the problem might be related to wiring and connectors, rather than the sensors themselves. It was not immediately clear how any repairs might be made.

The sensors are critical to ensure that the shuttle's three main engines don't shut down too soon or too late during liftoff. Problems with the sensors have delayed shuttle launches before, most recently in September 2006. The trouble began cropping up following the 2003 Columbia disaster.

NASA had been hoping for an on-time takeoff. Each of the year's three previous shuttle countdowns had ended with an on-the-dot departure.

Atlantis is loaded with Europe's long-awaited space station lab, named Columbus.

The seven astronauts had yet to board their spaceship when the delay was announced.

About 750 Europeans connected to the scientific laboratory—a 2 billion U.S. dollar project begun nearly a quarter-century ago—were in town for the launch and had begun gathering at the space center.

It was yet another disappointing flight delay for the European Space Agency, which has been working on Columbus for more than 22 years.

Columbus is "our cornerstone, our baby, our module, our laboratory," Alan Thirkettle, the European Space Agency's station program manager, said Wednesday.

Columbus will be the second laboratory added to the international space station. NASA's Destiny lab made its debut in 2001, and Japan's huge lab Kibo—which means "hope"—will go up in three sections beginning on the next shuttle mission in February.

Once Columbus arrives at the space station, scientific work can start almost immediately inside the lab, which is essentially packaged and ready to go.

Aside from the interruption caused by the 2003 Columbia tragedy, the actual building of the space station in orbit has gone well, NASA Administrator Michael Griffin said.

That's in stark contrast to the space station's planning and development, which dragged on for years and contributed to Columbus' prolonged grounding.

"We the United States, as the senior partner in the space station coalition, did not plan it well," NASA Administrator Michael Griffin said Thursday, on the eve of Columbus' originally scheduled launch. "It has taken far too long, and I'll just leave it at that."

Copyright 2007 Associated Press. All rights reserved. This material may not be published, broadcast, rewritten, or redistributed.

Shark Ate Amphibian Ate Fish: First "Food-Chain Fossil"

About 290 million years ago, Earth's lakes were a shark-eat-amphibian-eat-fish world, new fossil evidence reveals.

A new fossil discovery looks like a set of Russian dolls: It's the preserved remains of a fish, which was eaten by an amphibian, which was then eaten by a shark.

The fossil provides the first ever snapshot of an ancient, three-level, vertebrate food chain.

An animal's last meal is very rarely preserved, because corrosive acids quickly erupt from the decaying stomach, dissolving any food remnants before fossilization can take place.

But in this case, "the shark didn't just die and sink down and decompose," said Jürgen Kriwet, a paleontologist from Berlin's Museum of Natural History and co-author of a new study on the find.

"It was probably still alive when it got trapped under a rapid influx of sediment from surrounding hills," he said.

A Single Food Chain

The fossilized trio lived 290 million years ago in the shallow coastal waters of a freshwater lake in the Saar-Nahe Basin of southwestern Germany. The lake had previously been linked to the sea but was landlocked for millions of years before the three animals lived and died.

Several pieces of evidence suggest the animals must have formed part of a single food chain.

For one thing, "the orientation of the fossils fits perfectly," Kriwet said.

Permian-period sharks—like the one in the fossil—were only 19 inches (50 centimeters) long and ambushed their prey, swimming up from behind and swallowing it whole.

The fossilized amphibian is also in exactly the right position to suggest it had been eaten—it was lying tail-first along the shark's digestive tract, according to Kriwet.

"Also, the fish remains are fully enclosed within the amphibian's outer covering of scales," he added. That confirms that it was indeed eaten by the amphibian and not the shark.

Before the shark ate it, the amphibian had caught a young fish known as an acanthodian, which was covered in bony spines.

"The fish was swallowed side on, otherwise the spines could have got stuck in the amphibian's mouth or throat," Kriwet said.

"The fish is situated in quite the correct area of digestive tract of the amphibian," said said study co-author Ulriche Heidtke, a paleontologist from the National History Museum of the Palatinate in Bad Dürkheim, Germany.

"It clearly shows the hallmarks of digestion, [such as] disintegration," he added.

If the shark had eaten the fish first and then the amphibian, they would be placed one after the other in the shark's stomach, he explained.

John Maisey, a curator of paleontology at the American Museum of Natural History in New York, was not involved in this study.

"Well-documented examples of predator-prey relationships such as this are very rare," he said.

Such fossils allow scientists to reconstruct parts of extinct food chains, Maisey added.

"Three tiers are exceptional—if [only] we could find a four-tier example."

Unusual Sharks

Unlike their ancient ancestors, no modern-day sharks are fully adapted to living in fresh water.

"Today we find some rays and skates—close relatives of sharks—living in fresh water, but sharks invade lakes and rivers only for a short time," said study co-author Kriwet.

"We don't understand why this is," he said.

Another odd difference is that none of the sharks that swim through the oceans today are known to eat amphibians.

"There are no reports of sharks eating amphibians, even in the tropics, where there are large amphibians living close to the lakes and rivers that sharks temporarily enter," Kriwet said.

These ancient amphibians—known as temnospondyls—were reminiscent of modern-day crocodiles but lived in a world that was still crocodile free. (Related news: "Ancient Amphibians Bit Instead of Sucking, Skull Study Says" [April 16, 2007].)

"The amphibians had a short legs, long snouts, big teeth, and a long tail that they used as a rudder, much like crocodiles today," Kriwet said.

"Before the Permian extinction event, amphibians and sharks were the main top predators," he said.

The Permian extinction, Earth's most extreme die-off, occurred 251 million years ago.

"But by the end of the Triassic [199.6 million years ago]," Kriwet said, "there was a shift to crocodiles and bony fish being the top predators."

Leaves' Fall Colors Have "Dirty" Secret, Study Finds

New Englanders are blaming this year's lackluster fall-color season on drought, but if you don't like the colors in your own backyard, you might blame the dirt, a new study says.

In an undergraduate research project, Emily Habinck, who has since graduated from the University of North Carolina at Charlotte, found that autumn leaf color is related to the richness of the soil.

She determined that on a North Carolina floodplain that was rich in nitrate—a nitrogen-containing nutrient—yellow-leafed trees dominated. But in the poorer soils of the hillside behind it, there were more reds.

Even among the trees that typically bear red leaves no matter the conditions, poorer soils made for redder hues.

Habinck based her study on her faculty advisor's observation that floodplain trees tended to be yellow and that soil nutrients might have something to do with it.

While Habinck was at work on the project, William Hoch, a plant physiologist at Montana State University, wrote a paper suggesting an additional link between the red-leaf pigment anthocyanin and autumn sunlight.

"It wasn't until I read his paper that it became a full story," Habinck said.

Leaf Protection

Leaves turn color in the fall as trees start shutting down their energy production and withdrawing nutrients into their roots.

"[The tree] pulls as many of these in as it can, then tries to drop just a skeleton of a leaf when it's done," Hoch said in a telephone interview.

But nutrient withdrawal takes time, and the process leaves the leaves vulnerable to damage from sunlight.

Anthocyanins protect leaves by "shading" them from excessive sunlight during the plant's relatively vulnerable autumn season, Hoch explained.

In a study of plants that had been genetically modified not to be produce anthocyanins, Hoch found that the modified plants were unable to send as many nutrients to their roots for winter storage.

"So the bottom line is that the plants that were able to produce red pigments were able to squeeze more of the nutrients out of their leaves than the ones that couldn't," he said.

Thus, Hoch says, plants living in nutrient-poor soils benefit more from anthocyanin than those living on better soils.

Scientists only recently made these connections, Habnick said, because when most other leaf-peepers are taking their fall-color tours, biologists are busy with academics.

"Most people's field season is in the summer," she said.

"Brainbows" Illuminate the Mind's Wiring

Genetically engineered mice furnished with fluorescent proteins are providing the most detailed pictures yet of the brain's intricate circuitry.
The innovation offers an intimate peek into the development and inner workings of the nervous system at the level of individual neurons, researchers say.

"Imagine the brain as a radio for which we never had a good wiring diagram," said Jeff Lichtman, a neurobiologist at Harvard University and a co-author of the study.

"The aim of this work is to tag the individual wires with their own color" to get a better idea of their connections, he added.

If every cell in the brain were imaged using a single color, Lichtman explained, numerous wires bunched together would be indistinguishable.

But the various fluorescent proteins used in the new research make the multitudes of strands that comprise the complex tissue of the nervous system stand out from each other.

In their effort to tease out the details of connections in the nervous system, Lichtman and his colleagues developed about 30 lines of mice.

The team incorporated a chain of three different fluorescent protein genes—which they call a brainbow—into these mice.

The researchers then crossed the genetically engineered mice with mice that expressed an Cre, an enzyme in their brains.

In the offspring of this cross, Cre randomly snipped off or rearranged the brainbow sequence. This process caused just one of the brainbow colors to turn on at any given point.

Since each cell contains multiple copies of the brainbow, the end result is a unique mixture of red, green, and blue colors in each cell—and a random riot of color in the brain overall.

"It is like a television monitor where three basic colors—red, blue, and green—mix together and form various other colors," said Lichtman, whose findings will appear tomorrow in the journal Nature.

Shape Matters

Ed Lein is director of neuroscience at the Allen Institute for Brain Science in Seattle, Washington.

The Harvard researchers, he said, have essentially developed a novel technique that allows one to look at the shape of many different neurons simultaneously.

"The shape of the neuron is a pretty powerful piece of information. It allows you to infer, and in some cases demonstrate, who that cell is connected to," Lein said. " It lets you look at detailed microcircuitry in the brain."

The technique, he explained, will help researchers look at the shape of cells during embryo development and postnatal development in real time—and perhaps understand the progression of disease.

"It is too difficult to trace the 'wires' of the brain, because they are so thin and it is easy to make mistakes," said Sebastian Seung, a computational neuroscientist at MIT.

"The brainbow technique makes it easier to trace them."

Moonlet Study Sheds Light on Origins of Saturn's Rings

A new study of Saturn's striking rings has found clusters of "moonlets," lending support to the theory that large icy moons were slowly pulverized to form the ring system.

The boulder-size chunks, spotted in a narrow belt, could only have been formed when something collided into an object at least as large as Pan, Saturn's innermost moon, which is about 15 miles (25 kilometers) wide, scientists say.

The origin of Saturn's ring system remains a mystery. Some experts say the rings are remnants of the same gas and dust that formed Saturn.

Others support the idea that the ring's icy chunks formed from moons that were battered by asteroid impacts or blasted apart by collisions with meteors.

Unraveling the mystery of the rings' formation will help scientists better understand how our solar system—and alien ones—form.

"The origin and evolution of planetary rings is one of the prominent unsolved problems of planetary sciences," write the study authors in this week's issue of the journal Nature.

Encircled in Mystery

At ten times Earth's diameter, Saturn is the second-largest planet in the solar system.

Its rings are among the most beautiful features in the solar system: wide, flat discs of ice crystals that seem to float serenely in space.

The ice pieces range from the size of dust to more than ten feet (three meters) across.

For years researchers have noticed strange, paired bright streaks within Saturn's outermost ring, which is dubbed the A ring. The narrow band lies about 80,000 miles (130,000 kilometers) from the planet's surface.

Scientists call the streaks "propeller features," because they resemble the propellers of airplanes. Scientists now know that the features form when a larger object pushes debris into a wake, as if the moonlets were boats in water.

"These moons are not massive enough to make too much havoc in the rings, but they are still big enough to create some disturbance," said study co-author Miodrag Sremčević, a postdoctoral researcher at the University of Colorado in Boulder. "It's like a mini-moon inside of the ring."

One prevailing theory has been that larger pieces formed when some of the smallest ice fragments came together over time. But the new study calls that into question.

Tumultuous Realm

Sremčević and his colleagues studied images captured by NASA's Cassini spacecraft in August 2005, when Saturn's rings were backlit by the sun.

The team found that eight of the moonlets in Saturn's A ring were concentrated in a narrow belt, not scattered throughout the ring like a peaceful origin would suggest.

All eight of the moonlets are between 160 and 500 feet (60 and 140 meters) across.

"I really did not expect that," Sremčević said. "I was thinking these moonlets are everywhere, and with more patience and observation we would find them throughout the rings."

The images instead suggest the rings are a tumultuous realm where massive collisions break apart football-field-sized ice chunks, and time grinds the pieces into ever smaller bits, kind of like how sand forms on Earth.

"Some bigger moon was orbiting within the ring and was struck by a larger meteorite or comet," Sremčević said. "What we see today are remnants of that larger moon."

Solar Clock

The boulders may be useful as a sort of clock to chronicle the rings' history, Sremčević said.

Particles larger than about 30 feet (10 meters) tend to get ground down over time by meteorite impacts and interactions with other particles in rings, he pointed out.

So it's possible that the larger the particle, the more recently it was formed, he added, though this idea needs to be tested a lot more.

Sremčević said a rough estimate for the timing of the collision that formed the eight moonlets is about a hundred million years ago.

Scientists have evidence that in 1984 a similarly catastrophic impact occurred when a three-foot (one meter) object slammed into an icy boulder of similar size in Saturn's inner D ring.

"We actually came up with one hypothesis that could match up everything," Sremčević said. "That was: the rings were created a long time ago. That's an old idea. These moonlets are younger than the rest of the rings."

Dozens of Propellers

Matthew S. Tiscareno, a researcher at Cornell University, originally revealed the A ring's propeller features in a 2006 Nature study but didn't have a wide enough view to say how widespread they were.

He said the discovery of discrete belts is indeed surprising—and it may soon become even more complicated.

Tiscareno recently submitted a paper to the Astronomical Journal in which he catalogues 158 propeller features.

"My paper clearly resolves the 'belt of moonlets' into three sub-belts, perhaps indicating that the population of moonlets was sculpted by other ring processes after the break-ups that originally formed them," he told National Geographic News by email.

Moonlight Triggers Mass Coral "Romance"

Australian and Israeli scientists have discovered the trigger for the planet's biggest group sex spectacle: the mass spawning of hard corals along Australia's Great Barrier Reef.

One week each year in spring, after a full moon, millions of corals release eggs and sperm in what Bill Leggat, a co-author of the new study, called "a slow symphony."

But until now how the primitive animals—which lack brains or eyes—synchronized the mass spawning was a mystery.

In today's issue of the journal Science, researchers reveal that they have isolated an ancient gene in the corals' DNA that can detect moonlight.

By exposing corals to different colors and intensities of light, the team found that the gene—known as Cry2—was most active in Acropora corals during a full moon.

Leggat, a lecturer at James Cook University in Cairns, Australia, said Cry2 encodes a type of protein known as a cryptochrome, which appears to trigger the corals' reproductive cycle.

"This particular gene allows the coral to sense blue light and to actually work out what phase the moon is in," he added.

The research also suggests that the basic ability to sense changes in light and adapt a 24-hour cycle appeared early in the evolution of animals.

Sophisticated Spawning

Cry2 prompts a series of biochemical reactions that is surprisingly sophisticated, Leggat said.

Some 400 or 500 species of corals all spawn simultaneously during the week, creating vast slicks across the ocean, he pointed out.

"It's just magical," Leggat said. "To just sit in front of an individual coral and watch the pink sperm bundles get slowly pushed out of the corals' mouth and float away—it's incredible to watch."

"It's one of the greatest sights in nature, but the amazing thing is that, after going on for millions of years, it wasn't witnessed until the 1980s," he added.

How the right sperm ends up with the right egg is a complicated process that may rely on refined chemical pathways, he said. But scientists are still working on unraveling the exact details.

"To me, the really exciting thing is this huge, well-orchestrated symphony [is] going on, yet we still don't know how it works," Leggat said.

"We're only really just starting to understand corals and reefs in general, and something that's both exciting and worrying is that these reefs are threatened, that they may not be around in 50 years."

Night and Day

The new research also offers insights into the development of vision and the evolution of daily rhythms in animals.

Ove Hoegh-Guldberg, director of marine science at the University of Queensland, said cryptochromes are closely linked to primitive proteins known as photolyases—which harness blue light to repair DNA damaged by ultraviolet radiation.

"[In the Precambrian era] there were very high doses of ultraviolet reaching the planet surface, so organisms probably had to retreat out of range of the UV" in addition, said Hoegh-Guldberg, who was also a co-author on the new research.

"One way to do that would be to go into the deeper layers of the ocean during the day and to rise during the night as levels dropped" by adapting the light-sensing properties of the photolyases, he added.

From there, it was "a very simple step to evolve cryptochromes to set your clock to do the right things at the right time," he said.

"The first creatures wouldn't have had eyes," Hoegh-Guldberg continued. "They would have been depending on cellular biochemistry to detect changes in light. So cryptochromes are, in a sense, the functional forerunners of eyes."

Cryptochromes are still present in humans and other mammals, as well as insects, he said. They play an important role in regulating the circadian system, a "body clock" attuned to Earth's 24-hour rhythms that regulates things like cycles of metabolism and alertness.

"[These proteins] are the Swiss timing mechanism of biology," Hoegh-Guldberg said.

Surprising Complexity

In addition, the work shows the surprising level of sophistication of even the earliest animals.

"We think of corals as being very simple, but they're not," Leggat, of James Cook University, said. "They're actually incredibly complex—they have almost the same number of genes and proteins as humans.

"Many of these genes developed in deep time, in the earliest phases of organized life on the planet," he added. "They were preserved for hundreds of millions of years before being inherited by corals when they developed about 240 million years ago, and are still found today in modern animals and humans."

They are an indicator that corals and humans are in fact distant relatives, sharing a common ancestor way back."

Hoegh-Guldberg said the team would head back to the reef this spring to delve deeper into the secrets of cryptochromes.

"We've got all the smoking guns of this mechanism," he said. "The next step is to track down the way they drive things like reproduction. We fully expect to uncover other behavior that they are controlling."

"Vibrating Mice" Develop Less Fat, Study Shows

A new study in mice could shake up the fight against fat.

Laboratory mice that spent 15 minutes a day on a vibrating platform developed 28 percent less fat than control mice during a recent experiment.

But forget the ads for waistband-jiggling vibration belts guaranteed to "burn away fat." These mice experienced very subtle, almost undetectable, tremors.

Scientists theorize that as the mice developed, the vibrations mimicked muscle activity and induced their stem cells to develop into bone or muscle cells rather than fat cells.

"We're not burning fat or taking fat mice and making them skinny," said lead author Clinton Rubin, a biomedical engineer at the State University of New York, Stony Brook.

"We're taking mice who are growing and ... influencing the decision of stem cells [so that they don't] become fat cells."

The finding came in part from research in human spaceflight. Rubin and colleagues are trying to induce stem cells to become bone cells in order to offset the bone loss that results in zero-gravity space environments.

Rubin has also co-founded a for-profit company, Juvent Medical, that is using a similar concept to treat osteoporosis.

The study will appear this week in the journal Proceedings of the National Academy of Science.

Fighting Fat Before it Appears

The human body needs fat cells, which store food energy for future use.

Most doctors believe that obesity is the result of consuming more calories than a body burns. Recent research suggests that genetics and other factors may also play a role.

Rubin cautions that the study is preliminary and raises as many questions as it answers.

But the possibilities for human weight control are intriguing, and they may include developmental as well as metabolic factors.

"Just imagine a way to keep people from getting fat that is not [only] about how many Oreos they eat or how much they exercise—but about keeping them from forming fat cells in the first place," he said.

No Guilt-Free Solutions

But if the prospect of consequence-free overeating and sloth sounds too good to be true, it probably is, experts say.

"The reason we have those cells is to take [in] excess fat," said Roger Unger, an obesity researcher at the University of Texas Southwestern Medical Center.

"If you inhibit [fat cells] and overeat, you haven't done that person a favor," said Unger, who was not involved in the new research.

"The surplus lipids would end up in organs where you don't want to have surplus lipids—like the heart and the liver."

"People that don't have [as many] fat cells, if they overeat, get very sick—[they get] sicker at a much earlier age than people who first get fat and then develop complications."

Rexford Ahima is a University of Pennsylvania endocrinologist.

"The idea that 'non-strenuous work' can reduce body fat is intriguing; however, the findings have to be interpreted with caution," he said.

Ahima noted that key information regarding the mice's energy expenditure, hormones, and metabolism remains unknown and may have impacted the results.

Mars Volcanoes May Re-Erupt, Hawaii Comparison Shows

A trio of volcanoes on Mars may have been created by a similar geologic process to the one that formed the Hawaiian Islands, a new study says.

The observations also suggest that the three Martian volcanoes might not be extinct.

If sufficiently large eruptions do eventually occur, they could spew enough heat-trapping carbon dioxide and water into the atmosphere to warm the red planet up from its current cold, dry state—at least for a little while.

Those are the findings of a research team led by Jacob Bleacher of Arizona State University and NASA's Goddard Space Flight Center in Greenbelt, Maryland.

The researchers traced the flow of molten rock under three large Martian volcanoes in the Tharsis Montes mountain range, partly by comparing their surface features to those found on Hawaiian volcanoes.

They discovered that the same basic process formed the mountains but that it worked in very different ways because of each planet's unique geology.

"On Earth the Hawaiian Islands were built from volcanoes that erupted as the Earth's crust slid over a hot spot—a plume of rising magma," Bleacher said in a press release.

"Our research raises the possibility that the opposite happens on Mars—a plume might move beneath stationary crust."

The results appeared in the September 19 issue of the Journal of Geophysical Research, Planets.

Mysterious Mountains

Tharsis Montes contains three large shield volcanoes—Arsia Mons, Pavonis Mons, and Ascraeus Mons—in a northeast-trending chain across the Tharsis rise on Mars.

The rise spans about 2,800 miles (4,500 kilometers) of Mars' western hemisphere and includes seven partly buried shield volcanoes, lava plains with clusters fissure vents, and other features that intrigue geologists.

The same region contains the giant Olympus Mons volcano, the largest volcano in the solar system. At about 373 miles (600 kilometers) in diameter—about the size of the state of Arizona—Olympus Mons is twice the size of each of the Tharsis Montes volcanoes.

So far no volcanic activity has been observed at Tharsis Montes.

But the Mars Express, Mars Global Surveyer, and Mars Odyssey spacecraft have recently sent back high-resolution images of the region, providing insights into each volcano's explosive past.

Hawaii and Mars

Bleacher and his team compared the new images with information on Hawaii's volcanoes.

On the Big Island, the youngest volcanoes are on the southeastern end, directly over a magma hot spot.

As the Pacific crustal plate slowly moves to the northwest, the volcanoes are carried away from the hot spot. Over time the movement has created Hawaii's chain of volcanic islands.

Volcanoes over the hot spot have the hottest lava. As the mountains move away, though, only isolated pockets of rising magma remain.

The researchers found the Martian volcanoes had similar surface features and seemed to evolve in a similar way as the Hawaiian volcanoes.

But there is no evidence for such plate movement on Mars. So the researchers suggest that the mountain-creating plume instead moved beneath the stationary Martian crust.

Sleeping Giants?

The findings have some bizarre implications for the evolution of the red planet.

On Earth, cooling magma releases trapped gas, which creates short, explosive eruptions of cinders. Earlier flows become covered with piles of cinders, called cinder cones, which form around these eruptions.

The Tharsis Montes chain show no evidence of cinder cone eruptions—the final stage of hot spot volcanoes—suggesting the mountains might only be dormant, not extinct.

The mountains also erupted relatively recently in Martian history, judging from the lack of large impact craters near the chain.

Volcanic eruptions release large amounts of greenhouse gases, such as carbon dioxide, into the atmosphere.

If eruptions begin again on Mars—and the future eruptions are large enough—they could contribute significant amounts of water and carbon dioxide to the atmosphere.

That's unlikely to make the planet hospitable, though, scientists warn.

"The Martian environment becoming habitable in the future due to a volcanic eruption is extremely improbable," Bleacher told National Geographic News.

Mars once had a magnetic field, but currently lacks one strong enough to protect the atmosphere from solar wind, he pointed out.

"The current Martian surface environment is very hostile towards life as we know it to exist," he added.

"From a planet-wide perspective, a single volcanic eruption—if one was to occur on Mars—would not create an environment suitable for life to survive. Any erupted gases would quickly be stripped away by the solar wind."

Randy Kirk, a geophysicist at the U.S. Geological Survey in Flagstaff, Arizona, said the paper represents an interesting hypothesis that could explain why the three Tharsis volcanoes are equally spaced in a straight line, "which is something people have wondered about for a long time.

"At some level this explanation seems like it just resolves a matter of minor curiosity, why these three volcanoes happen to be in the places they are," he said.

But the work could have farther-reaching implications toward our understanding of magma circulation inside planets, he added—for "Mars definitely, and maybe this will also say something about Earth, eventually."

Most Massive Stellar Black Hole Found in Binary System

A strange black hole locked in a tight orbit with a huge star in a nearby galaxy could be the most massive stellar black hole known, astronomers say.

Stellar black holes form when a weighty, dying star's core collapses, creating a region with such a strong gravitational pull that even light can't escape.

Astronomers also believe that supermassive black holes with masses equal to millions of suns exist at the centers of many galaxies, including our own Milky Way.

The newly described stellar black hole has a mass almost 16 times that of our sun, said lead study author Jerome A. Orosz, a professor of astronomy at San Diego State University.

"Before this, the most massive known stellar black hole was GRS 1915+105, with a black-hole mass estimated to be 14 plus or minus 4 solar masses," Orosz said. But the mass of GRS 1915+105 has recently come into question, he added.

Orosz's team also found that the black hole's companion star has a mass about 70 times that of the sun—making it the most massive star in a binary system containing a black hole.

"The present-day companion is no more than about three million years old," Orosz said. "The model suggests that it will die in another two to three million years, forming another black hole."

Orosz and colleagues report their puzzling new observations in this week's issue of the journal Nature.

X-Ray Vision

Since black holes can't be seen directly, astronomers look for the intense radiation released as hot matter spirals into a singularity.

Researchers can then detect the existence of a black hole in a binary system by observing a visible star in orbit around its invisible companion.

The mass of the black hole in such a system can then be deduced by measuring its gravitational tug on the star.

NASA's Einstein X-Ray Observatory Satellite first spotted the black hole and its companion described in the new study in 1981.

The binary system—dubbed M33 X-7—lies in Meisser 33, a spiral galaxy about three million light-years away.

Astronomers soon realized that the companion star passes directly in front of the black hole on its three-day orbit, eclipsing the black hole's x-ray emissions.

This arrangement allowed the team to combine data from NASAs orbiting Chandra X-Ray Observatory and the Gemini North Telescope on Mauna Kea, Hawaii, to calculate the two object's masses more accurately than usual.

Tight Orbit

Orosz and his team don't fully understand how a massive black hole formed in close orbit around a massive companion star.

But experts think the formation of close binaries that contain the remains of dead stars—such as white dwarfs, neutron stars, and black holes—might involve a process called the common-envelope phase.

During this phase, a dying star in a binary system expells its outer layers while sucking the other star closer.

This leads to either a merger of the two objects or the formation of a tight binary system.

"During the common-envelope phase, the progenitor of the M33 X-7 black hole must have lost a large amount of mass for the two objects to be so close," Tomasz Bulik, of the University of Warsaw in Poland, writes in a commentary article also appearing in Nature.

"In this system we know that quite a lot of mass was expelled, and on the other hand that the remaining mass formed the black hole," Bulik told National Geographic News.

"Thus we have an upper and lower bound on the amount of mass expelled."

According to lead study author Orosz, "the reason M33 X-7 is so hard to understand is that both the black hole and the companion star have a very high mass.

"The predicted mass loss [of the star as it died before becoming a black hole] is so great that M33 X-7 should not have been able to enter a common-envelope phase."

Researchers hope that by understanding systems like M33 X-7, they can gain better insight into the formation of tight binary systems.

"The common-envelope stage is poorly known," Bulik said, "and this system will help us understand it."

Also this week, an independent team led by Andrea H. Prestwich of the Harvard-Smithsonian Center for Astrophysics described what it says could be an even more massive stellar black hole weighing 24 to 33 times as much as the sun.

The object is also part of a binary system that includes a massive star, and it lies 2.2 million light-years away in the starburst galaxy IC 10.

The researchers, who published their findings online this week in the Astrophysical Journal Letters, say more data are needed to confirm that the object is actually a black hole.

Brightest Known Supernova Detected

Scientists have spotted the brightest supernova yet—a star explosion that at its peak was a hundred billion times brighter than the sun.

Robert Quimby, an astronomer at the California Institute of Technology, discovered the spectacle in 2005 using a small robotic telescope at McDonald Observatory in West Texas.

But only recently did he calculate the true power of the supernova, known as 2005ap.

The explosion is 300 times brighter than average and is the most luminous supernova ever identified, Quimby said.

"It's amazing to me that after decades of in-depth studies, the brightest and seemingly most obvious supernovae are still being found," he added.

2005ap lies about 4.7 billion light-years away in a dwarf galaxy in the constellation Coma Berenices, behind the famous Coma cluster of galaxies.

The new find is a Type II supernova. These explosions are thought to occur when the cores of massive stars—more than seven times as heavy as the sun—collapse under their own weight and trigger an explosion.

A study on the supernova will appear in the October 20 edition of Astrophysical Journal Letters.

Two in a Row

For Quimby, the discovery is almost a hat trick.

The new supernova is roughly twice as bright as the previous record holder, SN 2006gy—which he also found.

Quimby discovered that explosion last year while working on the Texas Supernova Search project, part of his doctoral degree program at the University of Texas.

He actually observed supernova 2005ap there before 2006gy. But only recent follow-up studies that pinpointed distance revealed 2005ap's true power.

"There's no question that [his results] have gotten everybody's attention," J. Craig Wheeler, Quimby's colleague and a supernova expert at the University of Texas at Austin, said in a press release.

On the Hunt

Supernovae are rare events, occurring roughly twice a century in a galaxy like the Milky Way.

Researchers study them for insights into the fates of stars bigger than our sun. The explosions also serve as evidence that the expansion of the universe is accelerating, because the most distant ones appear dimmer than expected.

Supernovae are also the only way elements heavier than iron are seeded throughout the universe and play a vital role in the evolution of galaxies, Quimby said.

"Plus, they're huge explosions, and that's just cool," he said.

Despite their massive size and power, however, finding supernovae amidst the glare of other cosmic objects isn't easy.

Galaxies get much brighter toward their cores, which can wash out the contrast of a new supernova, Quimby said.

The University of California's Lick Observatory Supernova Search actually studied the area containing 2006gy before him, Quimby said, but missed it because they couldn't distinguish the explosion from its galaxy's brilliant core.

Quimby said part of his supernova-hunting success is his technique. He checks dwarf galaxies as well as galaxies with active black holes at their centers, which other studies avoid, raising the possibility of discovering new types of supernovae previously overlooked.

2006gy, for example, was found in the core of a galaxy with a weak central black hole.

"I've worked too damn hard for this to be luck," he said.

Rare T. Rex Footprint Found?

Odds are 50/50 that the dinosaur that left this mark in Montana was a Tyrannosaurus rex, says the scientist who announced the find yesterday.

Whatever it was, it was big.

"We have two large theropods to choose from [in this region], Nanotyrannus and T. rex," Phil Manning (pictured) told National Geographic News via email. "So either [dinosaur] (or an unknown) could have generated the track."

Referring to some breathless headlines of the past 24 hours, he added, "You can imagine which one the media wants!

"Unless you find an animal dead in its tracks, it is nigh impossible to identify the track maker," added the University of Manchester paleontologist, whose work is partially funded by the Expeditions Council of the National Geographic Society (which also owns National Geographic News).

If confirmed, it would be only the second known T. rex print. The first was found in 1983 in New Mexico.

Manning originally saw the three-foot-wide (meter-wide), 65-odd-million-year-old track in 2006 in the dinosaur-rich Hell Creek formation, and he is preparing a report for full scientific review.

In the meantime, he wrote, "we intend to keep the site secret until suitable measures can be taken to preserve the track."

Titan Forecast: Cold, Drizzly Mornings

Methane drizzles down every morning on Titan, according to a new study of Saturn's largest moon.

The rain is probably widespread across Titan and may even close the loop in a methane cycle that closely resembles the water cycle on Earth, the researchers suggest..

Scientists involved with the Huygens probe, which landed on Titan's surface in late 2004, have long suspected such an atmospheric cycle.

"The most important part of these results is that there is a way to monitor methane condensation from ground-based telescopes," said Mate Adamkovics of the University of California at Berkeley, who led the new research.

"Monitoring how often and to what extent the drizzle occurs might be an indication of seasonal changes on Titan that is more sensitive than watching other types of clouds come and go."

The results will be published in this week's issue of the journal Science.

Exotic Moon

Titan is a mysterious and alluring ball of rock and ice surrounded by a thick, orange, methane-heavy atmosphere.

Some scientists believe that the moon is a likely place to harbor alien life. One reason is that several studies have suggested that Titan has long-lasting lakes most likely made of methane.

On Earth, methane is produced in gas form through biological reactions such as digestion. It can exist as a liquid only under very high pressures.

But at about minus 290 degrees Fahrenheit (about minus 180 degrees Celsius), the surface of Titan is so frigid that methane doesn't need pressure to remain in liquid form.

Using ground-based telescopes and computer models, Adamkovics and his colleagues found a solid methane cloud 15 to 21 miles (25 to 35 kilometers) from Titan's surface.

A constant methane rain pelts Xanadu, the moon's brightest continent, each morning, the researchers discovered.

It's the first time researchers have seen differences between day and nighttime weather on Titan, Adamkovics pointed out.

"They were unexpected, because day-to-night temperature changes are expected to be small," he said.

Still Mysterious

Martin Tomasko, an astronomer at the University of Arizona in Tucson who designed Huygens' camera system, has long suspected methane smog and condensation occurred on Titan.

He has proposed that methane rains from Titan's sky as a thick, tarry gunk. The chemical then travels through channels until it reaches reservoirs visible as dark patches on the moon's surface.

The exact nature of the dark patches remains in dispute, however.

If methane rain is indeed widespread, it could be the main method that atmospheric methane returns to the surface, the study authors write.

But Adamkovics said there's still a long way to go to understand the process.

"Many predictions are being made, but we are far from conclusions," he said, "and I would wager that more surprises are going to be discovered before we have a textbook description of Titan's atmospheric cycling."

Rare Gorillas at Risk as Rebels Seize Congo Park

Heavy fighting continues to rage in the Democratic Republic of the Congo's (DRC) troubled Virunga National Park, one of the last remaining homes for rare mountain gorillas.

On Sunday rebels loyal to renegade general Laurent Nkunda—who have been clashing with DRC military forces in the area since September 3—took control of the park's gorilla sector.

The fighting has sparked further fears for the safety of the critically endangered mountain gorillas, which have been left largely unprotected for more than a month, ever since the clashes forced rangers to evacuate the park.

Today the fighting between rebels and the Congolese army heated up near Bukima, the park's main gorilla monitoring station.

Rangers could also hear the exchange of heavy gunfire near park headquarters at Rumangabo, according to Norbert Mushenzi, director of Virunga's gorilla sector for the Congolese Institute for the Conservation of Nature (ICCN).

"Rangers and local inhabitants are fleeing from all around the park, and the mountain gorillas are totally unprotected," Mushenzi said.

"This whole situation is precarious and frustrating."

Rebels vs. Rangers

About 700 wild mountain gorillas remain in the world, roughly 380 of which live in the Virunga Volcanoes Conservation Area shared by the DRC, Rwanda, and Uganda.

Of these, about 120 are found in the DRC.

But rangers there have been able to track only one family of gorillas since the fighting started five weeks ago, and they have yet to account for 54 of the region's 72 habituated gorillas.

Until last week the situation had appeared to be calming, and rangers were hoping to re-enter the sector to track the gorillas.

But last Friday rangers who had been monitoring gorillas from a post inside the park had to flee when the rebels reportedly tried to force them to become combatants.

Rebel leader Nkunda, who is an ethnic Tutsi, maintains that the government is collaborating with ethnic Hutu rebels hiding in the DRC who are accused of involvement in the 1994 genocide against Tutsis in neighboring Rwanda.

On September 3 the rebels surrounded two ranger stations inside Virunga. The men seized rifles and communications equipment and forced park workers and their families to evacuate.

Since then the rebels have consolidated their grip on the park, conservationists say.

"The army seems to be weakening vis-à-vis the rebels—and this does not bode well for the gorilla sector at all," said Samantha Newport, a spokesperson for WildlifeDirect, an environmental group that supports the DRC rangers.

Fighting for Control

Conservationists said control of the park is important for the rebels.

"The gorilla sector is a key strategic point in this conflict. The rebels want to control it and have access to neighboring countries to replenish their materials and equipment," said Emmanuel de Merode, head of WildlifeDirect.

"The mountain gorillas are stuck right in the middle."

At least ten gorillas have been killed in Virunga this year, and some of the deaths have been blamed on the rebels.

The worst attack occurred on July 22 when five gorillas, including a silverback, were shot dead execution-style.

That attack was linked to the burgeoning charcoal trade in the park. (Read "Congo Gorilla Killings Fueled by Illegal Charcoal Trade" [August 16, 2007].)

In September a dead infant female was found in the hands of alleged traffickers who are now facing judicial procedures in the city of Goma, just south of Virunga.

Newport said there is a strong possibility that the rebels may soon cut off the road between Goma and park headquarters at Rumangabo, thereby totally isolating the 34 rangers there.

The rangers have removed all valuable tracking equipment from Rumangabo in case the clashes reach the area.

One ranger also died this week in a car accident.

The man was coming back with his colleagues from an anti-charcoal burning patrol when he fell out of the pick-up truck they were riding in. He was taken to a hospital, but later died from brain damage.

Early Venus Had Oceans, May Have Been Habitable

Venus, not Mars, may have been the most likely planet in the solar system to have also developed life, scientists say.

The cloud-shrouded planet most likely started with oceans much like Earth's, which evaporated as Venus heated up, according to new research.

The oceans didn't disappear overnight, said David Grinspoon of the Denver Museum of Nature and Science.

Speaking yesterday at a meeting of planetary scientists in Orlando, Florida, Grinspoon said that preliminary results of new computer models indicate Venus may have retained its oceans for a billion years after it formed, possibly longer.

Prior models had indicated that rising Venusian temperatures had turned the oceans to steam within the planet's first 600 million years.

The extra 400 million years are even more significant than they sound, Grinspoon added, because early Venus was constantly bombarded by asteroids, reducing the likelihood of life.

The new finding suggests that the oceans existed for much longer after the asteroid bombardment tapered off.

"There may have been a sizeable interval when [Venus] was habitable," he said.

Today, however, Venus is about 100,000 times drier than Earth and is 860º F (460º C) at its surface, Grinspoon said.

New Discovery From Venus

Future studies might further refine our understanding how long the planet was habitable.

If samples can be collected from the surface, for example, scientists might find rocks that formed when the planet was wet, Grinspoon said.

Determining how much water remains locked in these rocks may allow scientists to figure out how long ago the planet dried out.

Similarly, studies of Venusian gases could help scientists better estimate the rate at which water was lost into space.

Already such research is playing a role in our understanding of Venusian heating.

At the Orlando meeting, French researcher Jean-Loup Bertaux reported that the Venus Express spacecraft, now orbiting the planet, has discovered a rare form of carbon dioxide never before detected on Venus.

Instead of containing the most common form of oxygen, which has eight protons and eight neutrons, this one has one atom of oxygen with eight protons and ten neutrons.

That causes it to absorb more infrared light than normal carbon dioxide, increasing its strength as a greenhouse gas.

(See a photo of "airglow" created by oxygen in the Venusian atmosphere.)

The upsurge of interest in Venus comes hard on the heels of a recent finding that early Mars might have been colder and drier—and therefore less habitable—than previously believed.

Thunderstorm Gamma Rays Linked to Lightning

The formation of gamma rays—the most energetic form of light—in thunderclouds may be linked to lightning production, a new study shows.

Gamma rays are typically produced by cosmic cataclysms like supernovae, but terrestrial thunderstorms can also energize particles enough to create the powerful rays.

Scientists first spotted gamma rays in thunderstorms in the early 1990s. The Compton Gamma Ray Observatory unexpectedly detected radiation originating from the ground while peering at distant supernovae.

"The fact that they are [even] created in something as garden variety as thunderstorms is a surprise," said Steven Cummer, an electrical engineer and lightning researcher at Duke University in Durham, North Carolina.

Lightning Mystery

How thunderclouds produce the rays has not been explained. Neither has the nature of their apparent link to lightning formation, about which many long-standing mysteries remain.

But a new study led by Teruaki Enoto of the University of Tokyo and Harufumi Tsuchiya of RIKEN, Japan's Institute of Physical and Chemical Research, has provided the best look yet at the phenomena.

The team trained an array of gamma ray detectors on two powerful low-pressure air masses that collided over the Sea of Japan on January 6, 2007.

The researchers found that gamma rays were produced some 70 seconds before a lightning strike. They also determined that gamma bursts, which had been previously measured to last less than a second, could occur for almost a minute.

The findings suggest that whatever triggers gamma rays might also be involved in creating lighting—and that their origin might be tied to powerful particles known as cosmic rays that continually rain down from space.

The work will appear in an upcoming issue of the journal Physical Review Letters.

Cosmic Ray Trigger

In the new study, the researchers provide additional evidence that cosmic rays trigger gamma ray generation by releasing a "seed electron" from an atom of air.

This begins "runaway breakdown"—a theoretical process in which the liberated electron ionizes nearby air molecules. These molecules become accelerated in the very high electric fields inside a thundercloud, which can reach up to ten million volts in strength.

A group of fast electrons is then formed, which can emit gamma rays as they are gradually slowed down by contact with surrounding air molecules.

"Everybody agrees that in some way this basic process of runaway breakdown is involved, but whether it has to be triggered by a cosmic ray [is uncertain]," said Cummer, who did not participate in the new Japanese research.

"It's appealing on some levels, but others have suggested ways that don't necessarily [require] a cosmic ray coming through."

Cosmic rays are constantly raining down onto Earth, so it is difficult to isolate their impact on any single event, he pointed out.

Lightning Link

Still, studying thundercloud gamma rays could eventually unlock some secrets of Earth's weather, the Japanese researchers say.

"One significance of our result is the prospect that we can use these gamma rays as a good probe to understand how the strong electric field develops in thunderclouds and how lightning discharges occur," study lead author Enoto said.

The electric fields in thunderstorms appear to be too weak to form lightning, so scientists have been puzzled by how the bolts form. Cosmic rays have also been suggested as a trigger for the flashes.

The researchers are now looking into the exact connection—if any—between runaway breakdown and lightning, especially if such a link applies only to certain kinds of lightning or in certain areas of storms.

Thundercloud gamma rays could also shed light on more exotic cosmic processes like solar flares, pulsars, and jets from black holes, Enoto added.

"Our result shows that thunderclouds may be a natural particle accelerator," he said. "Thunderclouds could provide a nearby hidden prototype for other energetic cosmic accelerators."

No Radiation Danger

Powerful gamma rays can be dangerous in some cases, since the radiation can reach energies a hundred to a thousand times higher than x-rays used in medical devices, Enoto said.

But storm clouds are unlikely to produce enough radiation to cause any worry.

"The total number of detected gamma rays is so small that the overall radiation dose is meager—perhaps seven orders of magnitude less than that of a single medical radiography shot," he explained.

"So this event, we presume, has little impact on Earth or human bodies."

Steamier Earth Likely, Due to Global Warming

Human activity has long made the bedroom a hot and steamy place. Now, less sexy activities like burning coal and oil—major contributors to global warming—are making the whole planet steamier, a new study says.

Scientists expect the rising humidity to cause heavier rains, stronger hurricanes, and increased human heat stress.

Climate scientists have long predicted that a warmer world will allow more water to evaporate, thus making the planet more humid.

Indeed, several studies have shown trends of increasing surface humidity around the planet, but until now scientists were uncertain what was driving the trend.

The new study combined a fresh data set of surface humidity with climate models, "and actually attribute[s] those trends to human influence," said study co-author Nathan Gillett, a climate scientist at the University of East Anglia in Norwich, England.

He and his colleagues report the findings in tomorrow's issue of the journal Nature.

Stormy, Steamy Future

Climate models predict that increased water vapor in the atmosphere will lead to heavier rains and raise the maximum potential intensity for hurricanes, Gillett noted.

"In heat waves, if the humidity is higher, then that results in larger heat stress on humans," he said.

And increased water vapor will accelerate the warming, said Benjamin Santer, a climate modeler at the Department of Energy's Lawrence Livermore National Laboratory in California who was not involved in the study.

"Our best understanding is as we increase greenhouse gases and warm the atmosphere, we increase the atmosphere's capacity to hold moisture. And water vapor is in itself a potent greenhouse gas.

"Therefore you accelerate the warming," he said.

Steve Sherwood is a climate scientist at Yale University in New Haven, Connecticut, who was not involved in the study. He said the findings are uncontroversial, but the new data set is a boon.

"People haven't really been talking enough about what higher humidity is going to mean in the future," he said, "and part of the reason they haven't been talking about it is that we haven't had very good data."

"They've put out a data set that people can actually use to look at long-term changes," he added.

Global Warming Evidence

Santer of the U.S. Department of Energy led research published recently in the journal Proceedings of the National Academy of Sciences that linked human activity to an increase in atmospheric water vapor. (Gillett was a co-author of that paper.)

Gillett, co-author on the new Nature study, also contributed to a July paper in the journal Nature that linked human activity to changes in rainfall patterns over the past century.

This body of work should silence criticism that the only evidence of global warming comes from surface and ocean temperature records, Santer said. Human influence is prevalent throughout the climate system, he added.

The combined studies should also help scientists more accurately predict Earth's response to increasing levels of greenhouse gases, Gillett said.

For example, he said the models used for the July Nature study underestimated the change in rainfall due to global warming, but that the models do a "reasonably good" job of capturing the humidity changes.

"These results will help to pin down which parts of the hydrological cycle the models can simulate well and which not so well ... and help improve the models," he said.

Nanotech Find Earns Two Europeans Nobel in Physics

Frenchmen Albert Fert and German Peter Grünberg have won the 2007 Nobel Prize in Physics for their discovery of the phenomenon that makes modern-day hard-drive technology possible.

The Royal Swedish Academy of Sciences today announced that the two scientists will equally split the prize "for the discovery of giant magnetoresistance [GMR]," which amplifies small magnetic changes into large electrical signals.

The discovery has made possible the massive hard drives used in modern computers, cell phones, and music players, which store data magnetically.

"The practical benefits of this physics could not be greater," said Phillip Schewe, a spokesperson for the American Institute of Physics. "GMR is at the heart of the multi-billion-dollar hard-drive industry."

"This discovery played a key role in the phenomenal increase in storage capacity and reduction in size of magnetic recording systems that are the essential components of modern consumer products such as iPods and computers," added S.A. Solin, a professor of physics at Washington University in St. Louis, Missouri.

In the prize announcement, the Royal Swedish Academy also said that "GMR can also be considered one of the first real applications of the promising field of nanotechnology."

"Weird" Physics

Hard drives store data by magnetizing extremely small sections of material, similar to how VCRs and tape recorders work. But as more data is stored in the same amount of space, the magnetic signals get weaker.

This fact limited hard drive capacities until Fert, of the Université Paris-Sud in Orsay, France, and Grünberg, of Forschungszentrum Jülich in Germany, independently came across giant magnetoresistance in 1988.

The effect is a far better method for reading stored data, and the first GMR-based hard disks were created less than a decade later.

The scientists uncovered the phenomenon while studying the exact properties of extremely thin stacks of metal.

At just a few atoms thick, the layers were expected to experience unusual quantum effects. Fert and Grünberg found this included magnifying very weak magnetic changes into major differences in electrical conductivity.

"It's just an esoteric, weird type of physics, but a force that can be exploited to make valuable products," Schewe said.

"This is a wonderful example of how an accidental scientific discovery can have an extraordinary impact in technology—a marked increase in magnetic storage for information processing," added David Awschalom, a professor of physics and electrical engineering at the University of California, Santa Barbara.

Future storage devices might also be inspired by giant magnetoresistance, which relies on a property of electrons called spin.

Scientists are now exploring how to use spin to create new kinds of circuits and electronics, a field known as "spintronics."

"The increasing interest in semiconductor spintronics—our field—has partly also been inspired by the success of the GMR and its consequences," said physicist Manfred Ramsteiner of Paul Drude Institute in Berlin, Germany.

Fert and Grünberg will equally split the prize of 10 million Swedish kronor (about 1.5 million U.S. dollars).

Nobel Pursuits

Last year U.S. scientists John C. Mather and George F. Smoot won the Nobel Prize in Physics for research that helped solidify the big bang theory of the origin of the universe.

And yesterday three scientists— Mario R. Capecchi and Oliver Smithies of the United States and Sir Martin J. Evans of Britain—won the 2007 Nobel Prize in Physiology or Medicine for work on manipulating mouse genes to improve studies of genetic diseases.

The Nobel prizes have been awarded since 1901 based on the will of chemist and engineer Alfred Nobel, who invented dynamite.

The 2007 prizes in chemistry, literature, peace, and economics will be announced over the next two weeks.

The awards will be officially presented on December 10, the anniversary of Nobel's death.

"Missing" Moons, "Dirty" Ice Among Jupiter Flyby Finds

"Missing" moonlets, a huge volcanic eruption, and new maps of possible ocean ice are among the results of a recent flyby of Jupiter's moons.

The observations were made as NASA's New Horizons spacecraft whipped around the gas giant this past spring on its way to rendezvous with the dwarf planet Pluto in 2015.

Using Jupiter's gravity like a slingshot allowed New Horizons to shave years off its travel time to distant, icy Pluto.

The approach was also the first time a probe had been that close to Jupiter since the Galileo mission ended in September 2003.

Several teams of scientists used the opportunity to capture detailed images that allowed them to study different aspects of Jupiter.

Their findings appear in this week's issue of the journal Science.

No Tiny Moons

Perhaps the most surprising find for astronomers was an absence of tiny moonlets within the planet's rings.

Prior missions had revealed four small moons orbiting inside the orbit of the large moon Io.

The smallest of these are Adrastea, at 12 miles (20 kilometers) in diameter, and Metis, at 25 miles (40 kilometers) in diameter.

Earlier instruments weren't sensitive enough to spot moons much smaller than these. But scientists presumed that moonlets existed, because where there are big objects, there are usually lots of smaller ones.

"That's sort of how these things work," said Mark Showalter, a planetary scientist at the SETI Institute and lead author of a study on the "missing" moonlets.

Looking for moonlets is important, Showalter said, because they are thought to be the source of the dust that forms Jupiter's faint rings.

Such dust can be created when meteorites hit small moons within the rings, forming puffs of smokelike particles.

But despite the probe's ability to spot objects as small as 0.6 mile (a kilometer) in diameter, New Horizons found no new moons.

"It was really a surprise," Showalter said.

The most likely explanation, he continued, is that meteorite bombardment has battered such small bodies to the point that they are too small for New Horizons to detect.

But the new pictures did produce an unexpected find: clumps of debris within the planet's main ring.

While clumps of material aren't unusual, Jupiter's clumps were found in clusters that should have been rapidly dispersed by orbital forces.

"We haven't seen anything like this in any other planetary rings," Showalter said.

Lava and Frost

Other scientists examined three of Jupiter's larger moons—Io, Europa, and Ganymede.

Io is the most volcanically active body in the solar system.

During the flyby, a team led by John Spencer of the Southwest Research Institute in Boulder, Colorado, took a close look at the moon's giant Tvashtar volcano.

The massive mound happened to be undergoing a major eruption at the time of the flyby—as seen in an image released by NASA in May.

The volcanic plume was more than 215 miles (350 kilometers) high and 680 miles (1,100 kilometers) wide.

In their new study of the volcano images, Spencer and colleagues suggest that the plume's visible particles were not spewed from inside the moon but are instead gases that condensed in the frigid vacuum of space.

The team also notes that the magma inside Tvashtar and other Ionian volcanoes appear to be hot enough to be made of an Earthlike basaltic rock.

Another team, led by Kurt Retherford of the Southwest Research Institute, tried to determine what fraction of Io's atmosphere comes from volcanic emissions.

Io, Retherford said, has a very tenuous atmosphere made up of sulfur dioxide.

The scientists predicted that some of this gas comes from volcanism but that the rest comes from the evaporation of sulfur dioxide frost beneath the daytime sun.

The New Horizons flyby allowed the team to test this theory by studying Io's atmosphere when the moon passed out of the sun into Jupiter's shadow.

When there was no longer any solar heating, they found, 97 percent of the atmosphere quickly turned back into frost.

Ice Maps

When examining Europa and Ganymede, New Horizons scientists were primarily interested in mapping the distribution of "dirty" versus "clean" ice on the moons' surfaces.

The ultimate goal is to resolve a longstanding debate over the source of the material that contaminates the ice, particularly on Europa.

Europa is widely believed to have an ocean beneath its permanently frozen surface.

Scientists hope that the "dirty" ice is salt water that once welled up from below, which would provide proof of the undersurface ocean. But it could also be ice contaminated with sulfur compounds from nearby Io.

Studying the ice might offer clues to whether the underlying ocean is suitable for life, said William Grundy, a planetary scientist at the Lowell Observatory in Flagstaff, Arizona, who led the study.

The New Horizons instruments are sophisticated enough to tell what materials might be in the dirty ice, Grundy added, but at the time of the flyby the instruments hadn't been calibrated.

Once calibration is complete, he hopes to reanalyze the data to get a better answer.

Sex-Changing Chemicals Found in Potomac River

Ever since the discovery of gender-bending fish in the Potomac River, scientists have wondered what could be changing the sex of large numbers of fish in the waterway outside Washington, D.C.

They may not have to wonder much longer.

A recent U.S. government study has found large quantities of chemicals in the river and its tributaries—pollutants that are known to cause sex change in animals.

These chemicals, from both residential and industrial sources, may be linked to the unnatural fish, says the U.S. Geological Survey (USGS) report, which was released late last month.

Males With Eggs

The discovery of the abnormal fish "was largely accidental," said Douglas Chambers, a USGS scientist who led the study.

"In 2002 we were looking at stream-water chemistry to understand the large fish die-offs at these sites. It was then that we found smallmouth bass with intersex, a condition where male fish develop premature egg cells."

During a 2003 survey of the Potomac River and the Cacapon River of West Virginia, Chambers and his colleagues found large numbers of intersex fish.

The researchers also found chemicals from pesticides and flame retardants as well as fragrances commonly found in products such as soaps, antiperspirants, and deodorants.

"We analyzed blood plasma of 30 smallmouth bass from six sites," Chambers said. "All the fish contained at least one of the polluting chemicals, including fish that were not intersex."

However, Chambers said, the study has so far not turned up a single case of "imposex"—the condition in which female fish have malformed ovaries or produce sperm.

Once absorbed by the body, these chemicals—known as endocrine disruptors—interfere with normal bodily functions either by mimicking or blocking the production of hormones.

Experts say endocrine disruptors are found in pesticides, pharmaceuticals, fumigants, and fungicides. Municipal and domestic sewage and wastewater from farms and industries might be routing these chemicals into the water supply.

The presence of such chemicals is not unique to the Potomac. The pollutants have previously been documented in bodies of water in other parts of the United States as well as in Europe.

Scientists have also found reproductive problems in fish and birds in habitats along the U.S. Great Lakes. Similarly, declining alligator populations in Florida's Lake Apopka have been linked to synthetic chemicals that hinder reproduction.

Pollution Cocktail

Chambers says the USGS is analyzing data from last year and is planning to release a more detailed report later this year. The next report will try to make a definitive link between these chemicals and their effects on the environment.

"Currently many of these compounds have not been well researched for their environmental characteristics, how they are taken up by living organisms, and how they can be removed from streams," he added.

Dana Kolpin is a USGS research hydrologist and director of the agency's Emerging Contaminants Project. He reviewed Chambers' study but is not connected with it.

"This is the first step to understanding a very complex issue," Kolpin said.

"We need to understand the cocktail of compounds that are in the environment and whether there are certain bad actors that are causing feminization of males—and what it means for humans [who use this water]."

"It is critical to know where the sources are, how the compounds are being transported, and which ones are being degraded. What happens to them [after they enter the river] is the million-dollar question."

Coal Mining Causing Earthquakes, Study Says

The most damaging earthquake in Australia's history was caused by humans, new research says.

The magnitude-5.6 quake that struck Newcastle in New South Wales on December 28, 1989, killed 13 people, injured 160, and caused 3.5 billion U.S. dollars worth of damage.

That quake was triggered by changes in tectonic forces caused by 200 years of underground coal mining, according to a study by Christian D. Klose of Columbia University's Lamont-Doherty Earth Observatory in Palisades, New York.

The quake wasn't enormous, but Australia isn't generally considered to be seismically active and the city's buildings weren't designed to withstand a temblor of that magnitude, Klose said.

All told, he added, the monetary damage done by the earthquake exceeded the total value of the coal extracted in the area.

Klose presented his findings at a meeting of the American Geophysical Union in San Francisco, California, last month.

Heavy Burden

The removal of millions of tons of coal from the area caused much of the stress that triggered the Newcastle quake, Klose said.

But even more significant was groundwater pumping needed to keep the mines from flooding.

"For each ton of coal produced, 4.3 times more water was extracted," Klose said.

Other mining operations, he added, sometimes require as much as 150 tons of water to be removed for each ton of coal produced.

"So this is on the low end," he said.

Human-Caused Quakes

Coal mining isn't the only human activity that can trigger earthquakes.

Klose has identified more than 200 human-caused temblors, mostly in the past 60 years. "They were rare before World War II," he said.

Most were caused by mining, he said, but nearly a third came from reservoir construction.

Oil and gas production can also trigger earthquakes, he added.

Three of the biggest human-caused earthquakes of all time, he pointed out, occurred in Uzbekistan's Gazli natural gas field between 1976 and 1984

Each of the three had a magnitude greater than 6.8, and the largest had a magnitude of 7.3.

Human-triggered earthquakes are particularly dangerous, Klose said, if they occur in seismically inactive areas.

That's partly because people aren't prepared for them. But also, he said, "regions that are naturally inactive are very trigger-sensitive, because stress has built up over long periods of time."

Expensive Implications

Klose's presentation drew considerable attention from the assembled geophysicists, who wondered if there were ways to reduce the risk by altering mining practices.

"One way would be to find a way that doesn't reduce the water in the mine," Klose said.

But as far as he knows, mining engineers aren't examining this, because they are currently unaware of the earthquake risk.

The danger is also relevant to proposals to sequester carbon dioxide by injecting it into geologic formations deep underground where the gas cannot escape and contribute to global warming.

"That alters stress in the crust [too]," Klose said, adding that the risk of earthquakes should be taken into account in planning the locations of such facilities.

Basically, he said, "don't put the injection fields close to large cities."

The research could also have an impact on earthquake-insurance premiums, André Unger of the University of Waterloo, in Ontario, told National Geographic News by email.

The precise method by which premiums are calculated is a deeply guarded trade secret, but they appear to be based on a region's historical earthquake risk—"a purely statistical methodology," he said.

The new finding indicates that other factors are now at work, he said.

Furthermore, Unger noted that underground carbon sequestration might be a mixed blessing from insurance companies' points of view.

A carbon-sequestration plan could reduce the risk of some types of damage (such as from hurricanes, which some scientists say are being strengthened by global warming), while increasing the risk of others, like earthquakes.

Corals May Have Defense Against Global Warming

Ancient corals may have been more adaptable to changing ocean chemistry than previously thought, a new study shows.

The findings may offer hope that if the diversity of modern corals is preserved, they may be able to adapt as global warming causes seas to become more acidic.

These fossil corals in diverse reef communities adjusted to an acidic environment by altering the way they built their chalky skeletons.

Modern hard corals—known as scleractinians—form reefs of thousands of tiny skeletons made from a calcium carbonate called aragonite.

Aragonite is susceptible to the corrosive effects of acidic oceans, which today has become a byproduct of a build-up of carbon dioxide in the atmosphere.

"We now have many different arguments to prove that these corals were actually made originally out of calcite—and not just aragonite that was transformed after the coral died and become fossilized," said study co-author Jaroslaw Stolarski, a paleontologist from the Institute of Paleobiology at the Polish Academy of Sciences.

Curious Coral

The calcite skeletons were identified using several tests. Scientists inspected the microscopic structure of the skeleton and detected a high ratio of magnesium to calcium—a telltale fingerprint of calcite, not aragonite.

The fossil corals look like two-inch-long (five-centimeter-long) sea anemones nestled in porcelain egg cups. They belonged to the genus Coelosmilia, which existed during the Cretaceous period about 70 million years ago.

The Cretaceous oceans had a chemistry different than today, with much less of the metal ion magnesium and higher acidity.

"In the same environment there were coral neighbors, some with aragonitic skeletons, some with calcitic skeletons," Stolarski said.

"There was great biological variability among the corals, and some of them adjusted perfectly to the prevailing geochemical situation," he said.

Rachel Wood, a geologist from the University of Edinburgh, who was not involved in the study, said, "It begs the question: If having a calcite skeleton was so much better for life in such a corrosive sea, why aren't there more of them?"

The research will appear tomorrow in the journal Science.

Diversity Benefits

"This study has opened the door to the possibility that coral skeletons can potentially change back and forth from aragonite to calcite," said Stephen Cairns, research zoologist at the Smithsonian Institution's National Museum of Natural History in Washington, D.C.

"It suggests that animals and plants in general are quite adaptable creatures, and even though Earth changes—sometimes dramatically, like [in the case of] a comet hitting and wiping out 90 percent of animal life—it is so resilient that a vestige still gets through."

Co-author Stolarski said that diversity may be the key to adaptability, even in today's corals, which are under threat from warming seas.

"We should be extremely careful about coral reefs today, because they can only adapt to these changing environments if they maintain their diversity."

"If we completely eliminate some families or groups of corals, we may lose the very corals that would be able to adjust to changing environments in the future."

Cycad Plants "Woo" Insects With Heat, Odor

A primitive type of cycad plant from Australia relies on a surprisingly sophisticated system of meting out food to ensure successful pollination.

These plants take an active role in their reproduction by selectively attracting and repelling small insects known as thrips, a new study shows.

Scientists had long thought that cycads were passively wind-pollinated.

But in a push-pull system, male cones of this "living fossil" species heat up and emit strong odors to send pollen-bearing insects fleeing.

Female cones then emit a more attractive perfume to lure the bugs back in.

Pollination accomplished.

"I think the work demonstrates that plants aren't just sitting there looking pretty or just smelling good to attract their pollinators and that there's a lot more dynamics involved," said study co-author Irene Terry, a biologist at the University of Utah.

The mechanics of such primeval systems could provide insight into how pollination occurs in natural environments such as forests, something that Terry says there is still much to learn about.

The study appears this week in the journal Science and was funded in part by the National Geographic Society, which owns National Geographic News.

Nagging Mystery

Cycads are one ancient lineage of seed-producing plants called gymnosperms, which also include firs, spruce, pines, sequoias, and redwoods.

Found in tropical and subtropical areas, all species of cycads have separate male and female parts, often producing cones that look similar to a pinecone.

Tiny cracks between the tightly woven scales of the cones allow thrips to gain access to pollen in male cones and to structures containing eggs in female cones.

Both larval and adult thrips prefer the male cones, because the insects feed only on pollen.

But using some chemical tricks, the plants looked at in the new study ensure that thrips carry the male reproductive cells into the female cones.

"Twenty-five years ago when I began studying cycad pollination, it was still widely believed that cycads, like other gymnosperms, were wind-pollinated," said William Tang, an entomologist with the U.S. Department of Agriculture.

"Although I was involved in some of the early studies on cycad insect behavior, cone physiology, and odor analyses that supported the notion of insect pollination in this group, the precise details of this mutualism remained a nagging mystery," added Tang, who was not involved with the new study.

"This paper presents an elegant use of biochemistry, physiology, and field ecology to reveal the fine details of how this plant and its insect pollinator interact," he said.

"Through the use of heat and volatile chemicals, the plant choreographs a dance with its pollinators."

Stinky Males

Cycads have variable pollination periods, with reproduction occurring once a year to once every several years and lasting up to four weeks.

During that time, male cones use stockpiles of sugars and fats to heat themselves up, sometimes reaching 100 degrees Fahrenheit (38 degrees Celsius).

The cones also spew out huge doses of an odorous chemical called beta-myrcene.

"The odors get so strong that I don't want to be around them," study co-author Terry said.

"Some plants produce a stinky odor like a dead animal or poop, but this odor is just very harsh, hard to describe in terms of something similar."

Beta-myrcene attracts thrips at low concentrations, but in the amounts emitted by male cones, it becomes highly repellant, explained Robert A. Raguso, a chemical ecologist from Cornell University who was not involved in the study.

"This is a rather emphatic invitation for the thrips [to] leave home, and they do so bearing pollen," he said.

The plants do this "without dramatically changing their structural or visual characteristics, or even the chemistry of their scent," he added.

Tricky Females

Female cones emit much less beta-myrcene, so fleeing thrips searching for more pollen are drawn there.

When the thrips get inside the female cone, the ovule—containing the female reproductive cells—releases a little droplet, similar to a nectar droplet.

This draws the insects farther in. If they are carrying pollen, pollination is inevitable.

"The [study] highlights an elegant physiological mechanism by which cycads manipulate the behavior of thrips, transforming them from neutral or perhaps detrimental pollen predators to helpful pollinators," Raguso said.