Comets Impact Life

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Did lack of comet impacts help life evolve?

IT SEEMS we got off lightly in the cosmic lottery. Deadly comet impacts may be much rarer in our solar system than in others nearby.

We can’t directly measure the rate of comet collisions in other solar systems but we can detect signs of the dust that such smashes kick up because the dust gets warmed by the star and so gives off infrared radiation. That radiation shows up as extra infrared in the spectrum of light coming from the star. Because such dust should dissipate quickly, it is thought to provide a good snapshot of the recent collision rate.

Jane Greaves of the University of St Andrews, UK, analysed observations by the Spitzer Space Telescope and found that the vast majority of sun-like stars near us have more dust than our solar system does and therefore have had more collisions in their vicinity. Our solar system may be one of the few that have been safe for life. Greaves presented her results at the Cosmic Cataclysms and Life symposium in Frascati, Italy, this month.

The vast majority of sun-like stars near us have had more collisions in their vicinity than our solar system has.

About 25 per cent of the stars have a very strong dust signature. The rest of them have too little dust for it to be readily apparent when each spectrum is studied in isolation. Adding the measurements from these stars together, however, is like looking through a stack of slightly dusty windowpanes, making the total amount of dust easier to see. Greaves’s analysis revealed that 90 per cent of solar systems are dustier and so more collision-ridden than our own.

Mark Wyatt of the University of Cambridge agrees that the rate of comet impacts is probably lower in our neck of the woods. But as the temperature of the dust found by Greaves indicates it tends to sit far from the parent stars, the impacts might not have affected life on habitable planets, which would sit closer to their star, he says.

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Using Invisibility to Increase Visibility

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The Institute of Physics posted some interesting new research into light.

Using invisibility to increase visibility

Research into the development of invisibility devices has spurred two physicists’ thought on the behaviour of light to overcome the seemingly intractable problem of optical singularities which could soon lead to the manufacturing of a perfect cat’s eye.

A research paper published in a New Journal of Physics’ focus issue ‘Cloaking and Transformation Optics’ called ‘The Transmutation of Singularities in Optical Instruments’, written by Thomas Tyc, Masaryk University, and Ulf Leonhardt, the University of St. Andrews and Singapore National University, shows that it is possible to reflect light from all directions.

Cat’s eyes and glow-in-the-dark clothing are effective because they send light back from where they came to either provide direction to a driver on the road or alert drivers of, say, a cyclist’s presence but although this works well for light from some angles, it does not work well for all.

When light is shone through a glass of water with a straw in it and it appears as though the straw is bent, it is because the speed of light has been affected by the glass and the water that the light has been obstructed by. Physicists measure the effect that materials have on light using the refractive index, with 1 as the speed of light unobstructed in air, and, approximately, 1.5 as the point on the index when light meets glass and water.

What happens however when the material forces light down to zero or shoots it up to infinity on the refractive index? These are called optical singularities and have long been thought impossible to produce but it is what physicists need to understand to create a material that can reflect light from all directions and thereby create the perfect cat’s eye.

Tyc and Leonhardt use ideas from one of the latest trends of optics called transformation optics to transmute the infinity mark on the refractive index into something more practical. Put simply, the scientists have developed a recipe of materials to create optical illusions – some can be used for invisibility devices, others to make things perfectly visible.

As Tyc and Leonhardt write, “Our method works for optical singularities which are the curse of physics, often seeming intractable, but we have found a way of transmuting optical singularities with just harmless crystal defects as a side-effect.”

Applications will probably first appear in wireless technology and radar, for electromagnetic microwaves instead of light, because the required materials for electromagnetic microwaves are easier to manufacture.

Leonhardt and Tyc’s findings appear alongside other scientists’ work in the focus issue where scientists have developed recipes for other optical illusions where physical space appears to be transformed, for example for making invisibility devices.

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Azure Crown

Found on Flickr and just splasherific.

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Batman RIP

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Comic Batman reaches end of road

Warning: If you do not want to know about the plot of Batman RIP, stop reading now.

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Batman’s alter ego Bruce Wayne has apparently been killed off in the latest issue of the superhero comic.

Scottish writer Grant Morrison revealed earlier this year that Wayne would either retire or be killed in a clash with crime syndicate Black Glove.

The story – Batman RIP – sees Batman shot by villain Simon Hurt, who claims to be Wayne’s father Dr Thomas Wayne.

Morrison told BBC News there would be “a lot more twists and turns to come” before the story was finally resolved.

‘Definitive story’

“It’s great that it stirs up such passion,” he said.

“Nobody loves Bruce Wayne more than me, and I hope everybody understands that this is part of the great ongoing adventure of Batman.”

The caped crusader first appeared in comics in 1939, and has spawned a 1960s TV series and a host of films.

The “death” of Wayne’s father – shot alongside his mother by a robber when he was a boy – was the catalyst for the young industrialist to become the vigilante crime fighter Batman.

In the final scene, Hurt tries to escape in a helicopter after shooting Batman.

But the wounded superhero throws himself at the helicopter, causing it to crash. The comic story ends without a frame showing Wayne’s body, however.

Morrison, from Glasgow, told BBC News on Friday that the next two issues of the Batman comic would see a “summing up” of the superhero’s career before “the absolute, final fate” of Bruce Wayne was revealed in a sister publication, Final Crisis, in January.

“It’s the end of a story that goes back to 2005, a story to tell the definitive story of Batman,” he explained.

“We wanted to see what would happen if the most evil, richest people in the world decided they didn’t like Batman, and decided to take him apart piece by piece and destroy him.

“And then have Batman come back, and we could see why he’s so great,” added Morrison.

The storyline included clues which dated back to Batman comics from 40 years ago, he added.
Wayne may be dead, but publisher DC Comics shows no sign of bringing to an end the Batman franchise.

Frontrunners to take over as Batman include Tim Drake, who has been Robin since 1991, and Dick Grayson – the original Boy Wonder – who now protects Gotham City as Nightwing.

It is not the first time a superhero has met an unfortunate end in the comic world.

Last year, Captain America was killed after being shot by a sniper in New York.

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I personally think this is a very bad trend.

This is like a ratings hunt in Dallas and it annoys me when they do overly dramatic things just for sales. Because it always has to end with The Man From Atlantis in the shower and the rest of us dreaming he’s dead. Not a good scene.

I guess we can blame Superman for getting killed and selling millions a few years ago, or for Captain Mar-vell dying of cancer decades before — but for whatever reason, this is a horrible tend. Superheroes are larger than life and our modern myths. They need to remain above and beyond the common fray. Don’t kill for ratings. If you decide to cancel the comic forever, then fine, have an epic finale. Otherwise, just stop.

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Martian Atmosphere Is Being Ripped Away

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Solar Wind Rips Up Martian Atmosphere

Researchers have found new evidence that the atmosphere of Mars is being stripped away by solar wind. It’s not a gently continuous erosion, but rather a ripping process in which chunks of Martian air detach themselves from the planet and tumble into deep space. This surprising mechanism could help solve a longstanding mystery about the Red Planet.

“It helps explain why Mars has so little air,” says David Brain of UC Berkeley, who presented the findings at the 2008 Huntsville Plasma Workshop on October 27th.

Billions of years ago, Mars had a lot more air than it does today. (Note: Martian “air” is primarily carbon dioxide, not the nitrogen-oxygen mix we breathe on Earth.) Ancient martian lake-beds and river channels tell the tale of a planet covered by abundant water and wrapped in an atmosphere thick enough to prevent that water from evaporating into space.

Some researchers believe the atmosphere of Mars was once as thick as Earth’s. Today, however, all those lakes and rivers are dry and the atmospheric pressure on Mars is only 1% that of Earth at sea-level. A cup of water placed almost anywhere on the Martian surface would quickly and violently boil away—a result of the super-low air pressure.

So where did the air go? Researchers entertain several possibilities: An asteroid hitting Mars long ago might have blown away a portion of the planet’s atmosphere in a single violent upheaval. Or the loss might have been slow and gradual, the result of billions of years of relentless “sand-blasting” by solar wind particles. Or both mechanisms could be at work.

Brain has uncovered a new possibility–a daily ripping process intermediate between the great cataclysm and slow erosion models. The evidence comes from NASA’s now-retired Mars Global Surveyor (MGS) spacecraft.

In 1998, MGS discovered that Mars has a very strange magnetic field. Instead of a global bubble, like Earth’s, the Martian field is in the form of magnetic umbrellas that sprout out of the ground and reach beyond the top of Mars’ atmosphere. These umbrellas number in the dozens and they cover about 40% of the planet’s surface, mainly in the southern hemisphere.

For years, researchers thought the umbrellas protected the Martian atmosphere, shielding pockets of air beneath them from erosion by the solar wind. Surprisingly, Brain finds that the opposite can be true as well: “The umbrellas are where coherent chunks of air are torn away.”

Addressing his colleagues at the Workshop, he described how he made the discovery just a few months ago:

Brain was scrolling through archival data from Global Surveyor’s particles and fields sensors. “We have measurements from 25,000 orbits,” he says. During one of those orbits, MGS passed through the top of a magnetic umbrella. Brain noticed that the umbrella’s magnetic field had linked up with the magnetic field in the solar wind. Physicists call this “magnetic reconnection.”

What happened next is not 100% certain, but Global Surveyor’s readings are consistent with the following scenario: “The joined fields wrapped themselves around a packet of gas at the top of the Martian atmosphere, forming a magnetic capsule a thousand kilometers wide with ionized air trapped inside,” says Brain. “Solar wind pressure caused the capsule to ‘pinch off’ and it blew away, taking its cargo of air with it.” Brain has since found a dozen more examples. The magnetic capsules or “plasmoids” tend to blow over the south pole of Mars, mainly because most of the umbrellas are located in Mars’ southern hemisphere.

Brain isn’t ready to declare the mystery solved. “We’re still not sure how often the plasmoids form or how much gas each one contains.” The problem is, Mars Global Surveyor wasn’t designed to study the phenomenon. The spacecraft was only equipped to sense electrons, not the heavier ions which would make up the bulk of any trapped gas. “Ions and electrons don’t always behave the same way,” he cautions. Also, MGS sampled the umbrellas at fixed altitudes and at the same local time each day. “We need to sample many altitudes and times of day to truly understand these dynamic events.”

In short, he told the audience, “we need more data.”

Brain is pinning his hopes on a new NASA mission named MAVEN. Short for “Mars Atmosphere and Volatile Evolution,” MAVEN is an upper atmosphere orbiter currently approved for launch to Mars in 2013. The probe is specifically designed to study atmospheric erosion. MAVEN will be able to detect electrons, ions and neutral atoms; it will be able to measure both magnetic and electric fields; it will travel around Mars in an elliptical orbit, piercing magnetic umbrellas at different altitudes, angles, and times of day; and it will explore regions both near and far from the umbrellas, giving researchers the complete picture they need.

If magnetized chunks of air are truly being torn free, MAVEN will see it happening and measure the atmospheric loss rate. “Personally, I think this mechanism is important,” says Brain, “but MAVEN may yet prove me wrong.”

Meanwhile, the Mystery of the Missing Martian Air is shaping up to be a ripping good yarn.

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Two Degrees From Meltdown

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Two degree rise could spark Greenland ice sheet meltdown

A less than two degree Celsius rise in global temperatures might be sufficient to spark a meltdown of the Greenland Ice Sheet and Arctic sea ice, the WWF warned in a new study released Thursday.

“Scientists now suggest that even warming of less than 2 degree Celsius might be enough to trigger the loss of Arctic sea ice and the meltdown of the Greeland Ice Sheet,” the WWF said in a statement to accompany the findings.

“As a result, global sea levels would rise by several metres, threatening tens of millions of people worldwide.”

The melting of Arctic sea ice could affect ecosystems, while a meltdown of the Greenland Ice Sheet could lead to a sea level rise of up to seven metres, with a devastating impact for the rest of the world.

The WWF urged governments meeting for UN climate talks in Poland starting Monday to “develop a strong negotiation text for a new climate treaty” due at the end of next year.

Kim Carstensen, WWF Global Climate Initiative leader said: “The early meltdown of ice in the Arctic and Greenland may soon prompt further dangerous climate feedbacks accelerating warming faster and stronger than forecast.

“Responsible politicians cannot dare to waste another second on delaying tactics in the face of these urgent warnings from nature.”

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No Moving Parts Zeolite Gas Pump

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Gas pump made of minerals has no moving parts

Scientists have discovered that a type of hard mineral called zeolite can provide a high rate of gas flow in a micro-scale gas pump. Because the pump is based simply on temperature differences and has no moving parts, it could provide reliable and precise control of gas flow for a variety of applications, such as gas-sensing breath analyzers and warfare agent detectors.

Mechanical engineers Naveen Gupta and Yogesh Gianchandani from the University of Michigan have published their study on the zeolite gas pump in a recent issue of Applied Physics Letters. The researchers used a type of zeolite called clinoptilolite that, like all zeolites, contains billions of nanopores which a gas can flow through. The nanopores in clinoptilolite are packed much more densely than could be achieved through lithographic techniques, and so the mineral can enable a higher rate of gas flow.

“Unlike zeolite gas pumps, most of the traditional micropumping mechanisms have moving parts,” Gupta told PhysOrg.com. “As we go smaller in size, the ratio of the surface area to volume of the parts increases, which results in increased frictional losses of power. Larger frictional forces result in increased wear and tear in the devices, which affects the reliability of the system adversely.”

Using clinoptilolite, the engineers built a gas pump that operates on the principle of thermal transpiration, the phenomenon that gas molecules drift from the cold end to the hot end of a narrow channel. Their handheld-size gas pump, called a Knudsen pump, consisted of a thin, flexible heater in the center, sandwiched between two thin pieces of the porous mineral. The researchers added pieces of perforated aluminum between the layers to maintain a uniform temperature. Finally, the entire assembly was sandwiched between two pieces of insulating polyvinyl chloride (PVC).

The pump operated on 296 mW/cm2 of power, and contained two inlet ports for the gas to enter at opposite ends of the device. When the heater started operating, cold gas molecules from the inlet ports began drifting through nanopores in the zeolite mineral toward the heater in the center. The gas quickly flowed out through a central outlet port, and could be used for a specific application.

As the researchers explained, the thinner the nanopores (or nanochannels) through which the gas flowed, the higher the pressure at which the pump could operate. Using the zeolite’s large number of thin nanochannels, the device could pump gas at a high flow level. These nanochannels were so thin (in this case, about half a nanometer), that they were thinner than the mean free path of the molecules at atmospheric pressure, resulting in “free molecular gas flow.”

“The free molecular regime is a name given to the gas flow conditions in which the mean free path of the gas molecules is much larger than the characteristic length of the channel,” Gupta explained. “Unlike the case for the continuum gas flow regime, in the free molecular regime the gas molecules bounce against the channel walls much more frequently than they bounce against each other. Under these conditions, the wall interaction dominates and tends to cause the molecules to drift from the cold end to the warm end of the channel.”

Clinoptilolite, which has a greenish-white color, is one of the most abundant zeolites, and is also inexpensive, easily accessible, and mechanically strong. Along with having no moving parts, these advantages may make the pump useful for various purposes.

“These miniature pumps may someday be useful for a variety of applications ranging from ventilation to vacuum pumping,” Gupta said. “They may also assist as gas reservoirs and gas separation elements in miniature or handheld system diagnostic. However, the Knudsen pumping technology is still evolving and will need quite a bit of effort before it gets there.”

More information: Gupta, Naveen K. and Yogesh B. Gianchandani. “Thermal transpiration in zeolites: A mechanism for motionless gas pumps.” Applied Physics Letters 93, 193511 (2008).

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