Source of ozone-depleting chemical baffles NASA

Satellites observed the largest ozone hole over Antarctica in 2006. Purple and blue represent areas of low ozone concentrations in the atmosphere; yellow and red are areas of higher concentrations. 

Credit: NASA, Nasa Ozonewatch

A chemical used in dry cleaning and fire extinguishers may have been phased out in recent years but NASA said Wednesday that carbon tetrachloride (CCl4) is still being spewed into the atmosphere from an unknown source.

The world agreed to stop using CCl4 as part of the Vienna Convention on Protection of the Ozone Layer and its Montreal Protocol, which attained universal ratification in 2009.

"Parties to the Montreal Protocol reported zero new CCl4 emissions between 2007-2012," the US space agency said in a statement.

"However, the new research shows worldwide emissions of CCl4 average 39 kilotons per year, approximately 30 percent of peak emissions prior to the international treaty going into effect."

CCl4 levels are not enough to reverse the decreasing trend of ozone-depletion, but experts are still mystified as to where it is coming from.

With no new reported emissions, atmospheric concentrations of the compound should have declined at an expected rate of four percent per year since 2007.

However, observations from the ground showed atmospheric concentrations were only declining one percent per year.

"We are not supposed to be seeing this at all," said Qing Liang, an atmospheric scientist at NASA's Goddard Space Flight Center in Greenbelt, Maryland.

"It is now apparent there are either unidentified industrial leakages, large emissions from contaminated sites, or unknown CCl4 sources."

Researchers used NASA's 3-D GEOS Chemistry Climate Model and data from global networks of ground-based observations to establish the first estimate of average global CC14 emissions from 2000 to 2012.

In going through the data, researchers also learned that the chemical stays in the atmosphere were 40 percent longer than previously thought.

"People believe the emissions of ozone-depleting substances have stopped because of the Montreal Protocol," said Paul Newman, chief scientist for atmospheres at NASA.

"Unfortunately, there is still a major source of CCl4 out in the world."

The study "Constraining the carbon tetrachloride (CCl4) budget using its global trend and inter-hemispheric gradient" was published in the journal Geophysical Research Letters.

Cosmic rays Hotspot: Physicists closer to finding the mysterious sources

This map of the northern sky shows cosmic ray concentrations, with a "hotspot" with a disproportionate number of cosmic rays shown as the bright red and yellow spot, upper right. 

An international team of physicists using the University of Utah-operated Telescope Array near Delta, Utah, say their discovery of the hotspot should narrow the search for the mysterious source or sources of ultrahigh-energy cosmic rays, which carry more energy than any other known particle in the universe. 

Credit: Kazumasa Kawata, University of Tokyo Institute for Cosmic Ray Research.

An observatory run by the University of Utah found a "hotspot" beneath the Big Dipper emitting a disproportionate number of the highest-energy cosmic rays.

The discovery moves physics another step toward identifying the mysterious sources of the most energetic particles in the universe.

Gordon Thomson

"This puts us closer to finding out the sources, but no cigar yet," says University of Utah physicist Gordon Thomson, spokesman and co-principal investigator for the $25 million Telescope Array cosmic ray observatory west of Delta, Utah; the Northern Hemisphere's largest cosmic ray detector.

"All we see is a blob in the sky, and inside this blob there is all sorts of stuff – various types of objects, that could be the source" of the powerful cosmic rays, he adds. "Now we know where to look."

A new study identifying a hotspot in the northern sky for ultrahigh-energy cosmic rays has been accepted for publication by Astrophysical Journal Letters.

Thomson says many astrophysicists suspect ultrahigh-energy cosmic rays are generated by active galactic nuclei (AGNs), in which material is sucked into a supermassive black hole at the center of galaxy, while other material is spewed away in a beam-like jet known as a blazar.

Another popular possibility is that the highest-energy cosmic rays come from some supernovas (exploding stars) that emit gamma rays bursts.

Lower-energy cosmic rays come from the sun, other stars and exploding stars, but the source or sources of the most energetic cosmic rays has been a decades-long mystery.

The study was conducted by 125 researchers in the Telescope Array project, including Thomson and 31 other University of Utah physicists, plus 94 other scientists from the University of Tokyo (ICRR) and 28 other research institutions in Japan, the United States, South Korea, Russia and Belgium.

Read the full article here

More Information: Indications of Intermediate-Scale Anisotropy of Cosmic Rays with Energy Greater Than 57 EeV in the Northern Sky Measured with the Surface Detector of the Telescope Array Experiment - Authors: K. Kawata, et al.

Mojave Crater on Mars is source of Mars rocks found on Earth

Mojave crater showing its well-preserved morphology and ray pattern. 

The direction of the red arrow indicates distant examples of secondary crater clusters shown in Figure 1B in the manuscript. 

Credit: Science/AAAS

A trio of researchers, two from France and one from Norway, has published a paper in the journal Science claiming to have found sufficient evidence to identify a specific crater on Mars as the origin of Mars rocks found on the Earth's surface.

In their paper Stephanie Werner (CEED Norway), Anouck Ody (France) and François Poulet describe their extensive research and how they came to their conclusions.

Scientists have known for many years that some of the meteorites that strike the Earth came from Mars. Such rocks are ejected from the surface of Mars when struck by meteorites themselves.

Mars rocks have been classified into three main categories depending on their chemical makeup: chassignites, nakhlites and shergottites.

The latter make up roughly three quarters of all such rocks found and have been studied extensively over the years.

In this new effort, the researchers contend that all shergottites come from a single source on Mars: Mojave Crater.

To establish Mojave Crater as the source, the researchers combined several types of data, each of which suggest the crater as a likely suspect, though there is one, the estimated age of the rocks, that is not quite as clear-cut as the others.

MRO-CTX image mosaic of Mojave’s crater interior. 

Credit: Science/AAAS

The researchers began by analyzing imagery of Mars surface taken by various spacecraft over the years—they were looking for reasonably recent formation, a large size and rays leading away from the crater indicating a blast capable of sending rocky debris into space.

Mojave Crater stood out as one of the best candidates for further study.

The team next examined data gathered by spacecraft that have orbited the Red Planet over the years, specifically those that had taken mineral scans (measures of wavelengths of light bounced back off of them) of the Mojave Crater and the area around it.

Analysis showed that the mineral composition of rocky material on the lip of the crater matched closely with the Mars rocks found on Earth.

The team also sought to determine the age of the crater by studying the surface area around it—the number of craters around it and their size allows for a model to be made based on techniques developed with the Apollo moon project.

Their study showed that the crater was likely formed approximately three million years ago. Finally, prior research has shown that the Martian rocks likely were in transit on average less than five million years, based on cosmic ray exposure.

THEMIS daytime image mosaic overlain by MOLA color-coded topography. 

Craters were counted for the plateau units (brown), channel units (blue-grey), and the continuous ejecta unit of Mojave Crater (red line). 

Credit: Science/AAAS

Prior research has shown that the plateau in which Mojave Crater exists is approximately 4.3 billion years, which suggests that rocks blasted from its surface should be near the same age. Unfortunately, that's where things don't match as well.

Most studies of Mars rocks have found them to be only 150 to 600 million years old.

The researchers suggest this anomaly can be explained by events (shock waves, etc.) that transpired on Mars that set their age clock back.

More information: The Source Crater of Martian Shergottite Meteorites, Science DOI: 10.1126/science.1247282

ESA NASA Hubble discovers source of Magellanic Stream

These images show wide and close-up views of a long ribbon of gas called the Magellanic Stream, which stretches nearly halfway around the Milky Way.

Credit: Credit for the radio/visible light image: David L. Nidever, et al.,

Astronomers using the NASA/ESA Hubble Space Telescope have solved the 40-year-old mystery of the origin of the Magellanic Stream, a long ribbon of gas stretching nearly halfway around the Milky Way.

New Hubble observations reveal that most of this stream was stripped from the Small Magellanic Cloud some two billion years ago, with a smaller portion originating more recently from its larger neighbour.

The Magellanic Clouds, two dwarf galaxies orbiting our galaxy, are at the head of a huge gaseous filament known as the Magellanic Stream.

Since the Stream's discovery in the early 1970s, astronomers have wondered whether this gas comes from one or both of the satellite galaxies.

Now, new Hubble observations show that most of the gas was stripped from the Small Magellanic Cloud about two billion years ago—but surprisingly, a second region of the stream was formed more recently from the Large Magellanic Cloud.

A team of astronomers determined the source of the gas filament by using Hubble's Cosmic Origins Spectrograph (COS), along with observations from ESO's Very Large Telescope, to measure the abundances of heavy elements, such as oxygen and sulphur, at six locations along the Magellanic Stream.

COS detected these elements from the way they absorb the ultraviolet light released by faraway quasars as it passes through the foreground Stream. Quasars are the brilliant cores of active galaxies.

The team found low abundances of oxygen and sulphur along most of the stream, matching the levels in the Small Magellanic Cloud about two billion years ago, when the gaseous ribbon was thought to have been formed.

In a surprising twist, the team discovered a much higher level of sulphur in a region closer to the Magellanic Clouds.

Andrew Fox

"We're finding a consistent amount of heavy elements in the stream until we get very close to the Magellanic Clouds, and then the heavy element levels go up," says Andrew Fox, a staff member supported by ESA at the Space Telescope Science Institute, USA, and lead author of one of two new papers reporting these results.

"This inner region is very similar in composition to the Large Magellanic Cloud, suggesting it was ripped out of that galaxy more recently."

This discovery was unexpected; computer models of the Stream predicted that the gas came entirely out of the Small Magellanic Cloud, which has a weaker gravitational pull than its more massive cousin.

"As Earth's atmosphere absorbs ultraviolet light, it's hard to measure the amounts of these elements accurately, as you need to look in the ultraviolet part of the spectrum to see them," says Philipp Richter of the University of Potsdam, Germany, and lead author on the second of the two papers.

"So you have to go to space. Only Hubble is capable of taking measurements like these."

All of the Milky Way's nearby satellite galaxies have lost most of their gas content—except the Magellanic Clouds. As they are more massive than these other satellites they can cling on to this gas, using it to form new stars.

However, these Clouds are approaching the Milky Way and its halo of hot gas. As they drift closer to us, the pressure of this hot halo pushes their gas out into space. This process, together with the gravitational tug-of-war between the two Magellanic Clouds, is thought to have formed the Magellanic Stream.

"Exploring the origin of such a large stream of gas so close to the Milky Way is important," adds Fox. "We now know which of our famous neighbours, the Magellanic Clouds, created this gas ribbon, which may eventually fall onto our own galaxy and spark new star formation. It's an important step forward in figuring out how galaxies obtain gas and form new stars."

Thrusters powered by Ionic Wind: An efficient alternative energy source

When a current passes between two electrodes—one thinner than the other—it creates a wind in the air between.

If enough voltage is applied, the resulting wind can produce a thrust without the help of motors or fuel.

This phenomenon, called electro-hydro-dynamic thrust—or, more colloquially, "ionic wind"—was first identified in the 1960s.

Since then, researchers have theorised that ionic thrusters, if used as jet propulsion, would be extremely inefficient, requiring massive amounts of electricity to produce enough thrust to propel a vehicle.

Now researchers at MIT have run their own experiments and found that ionic thrusters may be a far more efficient source of propulsion than conventional jet engines.

In their experiments, they found that ionic wind produces 110 newtons of thrust per kilowatt, compared with a jet engine's 2 newtons per kilowatt.

Steven Barrett

The team has published its results in the Proceedings of the Royal Society. Steven Barrett, an assistant professor of aeronautics and astronautics at MIT, envisions that ionic wind may be used as a propulsion system for small, lightweight aircraft.

In addition to their relatively high efficiency, ionic thrusters are silent, and invisible in infrared, as they give off no heat—ideal traits, he says, for a surveillance vehicle.

"You could imagine all sorts of military or security benefits to having a silent propulsion system with no infrared signature," says Barrett, who co-authored the paper with graduate student Kento Masuyama.

Shooting the gap A basic ionic thruster consists of three parts: a very thin copper electrode, called an emitter; a thicker tube of aluminum, known as a collector; and the air gap in between.

Kento Masuyama

A lightweight frame typically supports the wires, which connect to an electrical power source. As voltage is applied, the field gradient strips away electrons from nearby air molecules.

These newly ionized molecules are strongly repelled by the corona wire, and strongly attracted to the collector.

As this cloud of ions moves toward the collector, it collides with surrounding neutral air molecules, pushing them along and creating a wind, or thrust.

To measure an ion thruster's efficiency, Barrett and Masuyama built a similarly simple setup, and hung the contraption under a suspended digital scale.

They applied tens of thousands of volts, creating enough current draw to power an incandescent light bulb.

They altered the distance between the electrodes, and recorded the thrust as the device lifted off the ground. Barrett says that the device was most efficient at producing lower thrust—a desirable, albeit counter-intuitive, result.

"It's kind of surprising, but if you have a high-velocity jet, you leave in your wake a load of wasted kinetic energy," Barrett explains.

"So you want as low-velocity a jet as you can, while still producing enough thrust." He adds that an ionic wind is a good way to produce a low-velocity jet over a large area.

Alternative Sources of Energy: Acoustic Cavitation Fusion

Scientists the lure of thermonuclear fusion has been incredibly attractive. Thermonuclear fusion held the promise of cheap, clean and unlimited energy.

Research in the field has split into many disciplines, one of these is the experiments in the hot fusion field called "acoustic inertial confinement fusion."

The idea of acoustic fusion is derived from the phenomenon called cavitation. Cavitation occurs when a liquid is exposed to rapid changes in pressure which causes the formation of gas or vapor bubbles.

An acoustic field sends pressure waves through the fluid causing the bubbles to grow and collapse and produces visible flashes of light. The researchers studying the light emitting bubbles speculate that the temperature and pressure of the gas inside bubbles could trigger a fusion reaction.

The tiny bubbles could produce the same effect as that found on the surface of the Sun and could one day be a new energy source.

While the concept has been proven in desktop experiments it's in real life applications that researchers of acoustic fusion run into problems. Building a fusion reactor that generates more energy that it consumes is particularly challenging and many skeptics question whether desktop experiments could work in the real world.

Compared to other forms of fusion power being researched today like magnetic and laser inertial confinement fusion, acoustic fusion requires inexpensive equipment, facilities and materials.

Acoustic fusion is relatively simple and its commercial success could be achieved in the next few years. One company, Impulse Devices has been exploring acoustic fusion and has pioneered the use of Extreme Acoustic Cavitation.

According to Dr. Wylene Dunbar, CEO of Impulse Devices Inc., the company's unique technology generates strong acoustic cavitation but still requires only a few hundred watts of electric power. Impulse's technology has achieved "proof of concept" in several areas and the company is working with several industrial partners to integrate its technology into their processes.

If acoustic fusion works it could provide clean energy for generations to come.

The origin of malaria: The hunt continues

The greater spot-nosed monkey, Cercopithecus nictitans. (Credit: © Jean-Louis Albert, CIRMF, Gabon)

The agent of malaria has been found in the greater spot-nosed monkey, also known as putty-nosed monkey (Cercopithecus nictitans), a small African primate derived from a line different to that of humans, gorillas and chimpanzees.

This discovery challenges current thinking on the origin of the parasite and introduces a key element in the fight against malaria: knowing how it has adapted to the human species will make it possible to target its weaknesses.

This work stems from research carried out by CNRS researchers in association with other organizations and is published on the 4 July 2011 in the journal PNAS.

Malaria, also known as paludism, is one of the greatest global scourges. This pathology, which causes a million human deaths each year, is especially rampant in Africa. The question of whether the primary infection originated from rodents or birds has long remained unanswered. Also found in gorillas, it was thought that the parasite was specific to hominids.

By working on the subject, a team of CNRS researchers headed by Franck Prugnolle and François Renaud of the Laboratoire MIVEGEC(1)(CNRS/IRD/Université Montpellier, jointly with the Centre International de Recherches Médicales de Franceville in Gabon, and in collaboration with other organizations, has demonstrated the presence of Plasmodium falciparum, the agent of malaria, in the greater spot-nosed monkey (Cercopithecus nictitans), a small African monkey derived from a line different to that of humans. The origin of the parasite probably predates the origins of the African hominids line.

The presence of Plasmodium falciparum in this Old World Monkey opens the way to the analysis of the genome of the parasite found in this species. Comparing its sequence with that (already known) of falciparum in humans will enable researchers to discover the molecular signatures of the human parasite and to find out how it has adapted to humans. Knowing the weaknesses of the parasite will be a major asset in combating malaria.

Climate Control: Scientists measure methane at the source

In a lush pasture near Buenos Aires, this cow and its compatriots are digesting important information: how much methane—a greenhouse gas 20 times as potent as carbon dioxide—is released by the country’s 55 million bovines.

Researchers from Argentina’s National Institute of Agricultural Technology connected inflatable tanks to the cows’ first stomach, where methane is made, through a small hole between their ribs.

By measuring methane production directly inside each cow, biologist Silvia Valtorta hopes to more accurately determine the country’s overall agricultural contribution to global warming. According to the data, an average cow releases more than 70 gallons of the stuff every day. But a change in diet could reduce that. Cows that eat mostly grain produce 20 to 25 percent less methane than grazing cows, and adding tannin—a bitter chemical found in wine—to the feed could lower it further.