Galactic Danger Zone

 Not every place within a galaxy experiences the same conditions for habitability - some parts are lethal thanks to supernovae, whilst others do not possess enough heavy elements to allow rocky planets and life to develop. Credit: The Hubble Heritage Team, AURA/STScI/NASA

We know for certain that life exists in the Milky Way galaxy: that life is us. Scientists are continually looking to understand more about how life on our planet came to be and the conditions that must be met for its survival, and whether those conditions can be replicated elsewhere in the Universe. It turns out that looking at our entire Galaxy, rather than focusing just on life-giving properties of our planet or indeed the habitability of regions of our own Solar System, is a good place to start.  

How far our planet orbits from the Sun, along with other factors such as atmospheric composition, a carbon cycle and the existence of water, has told astronomers much about the conditions that are required for life to not only originate, but to survive on rocky worlds. 

This distance from a star is referred to, quite simply, as the ‘Habitable Zone’ or sometimes the ‘Goldilocks Zone’ because conditions here are neither too hot or too cold for water to be liquid on the planet’s surface -- conditions just right for life as we know it to thrive. 

Copernican theory tells us that our world is a typical rocky planet in a typical planetary system. This concept has spurred some astronomers to start thinking bigger, way beyond the simplicity of any one planetary system and instead towards much grander scales. Astronomers are exploring whether there is a Galactic Habitable Zone (GHZ) in our Galaxy – a region of the Milky Way that is conducive to forming planetary systems with habitable worlds. The Galactic Habitable Zone implies that if there are conditions just right for a planet around a star, then the same must go for a galaxy.  

This concept was first introduced by geologist and paleontologist Peter Ward and Donald Brownlee, an astronomer and astrobiologist, in their book, ‘Rare Earth’. The idea of a GHZ served as an antagonistic view point to the Copernican principle. 

Despite scientists such as Carl Sagan and Frank Drake favoring the theory of mediocrity based on the Copernican model, which supports the probability of the Universe hosting other forms of complex life, Ward and Brownlee were certain our Earth and the conditions within our Galaxy that allowed such life to evolve are both extremely rare. 

Their answer to the famous Fermi paradox – if extraterrestrial aliens are common, why is their existence not obvious? – is that alien life more complex than microbes is not very common at all, requiring a number of factors, each of low possibility, to come into play. In short, Ward and Brownlee were suggesting that much of the Galaxy was inhospitable to complex life. In their view, only a narrow belt around the Galaxy was fertile: the Galactic Habitable Zone.

Since then, many astronomers have looked at the idea of the GHZ. Not all believe that it necessarily supports Ward and Brownlee’s Rare Earth hypothesis.

One recent assessment of the GHZ, by Michael Gowanlock of NASA’s Astrobiology Institute, and his Trent University colleagues David Patton and Sabine McConnell, has suggested that while the inner sector of the MIlky Way Galaxy may be the most dangerous, it is also most likely to support habitable worlds. 

Their paper, accepted for publication in the journal Astrobiology, modeled habitability in the Milky Way based on three factors: supernova rates, metallicity (the abundance of heavy elements, used as a proxy for planet formation) and the time taken for complex life to evolve. They found that although the greater density of stars in the inner galaxy (out to a distance of 8,100 light years from the galactic center) meant that more supernovae exploded, with more planets becoming sterilized by the radiation from these exploding stars, the chances of finding a habitable planet there was ten times more likely than in the outer Galaxy. 

This contradicts previous studies that, for example, suggested the GHZ to be a belt around the Galaxy between distances of 22,800 light years (7 kiloparsecs) and 29,300 light years (9 kiloparsecs) from the galactic center. What’s noticeable is that our Sun orbits the Galaxy at a distance of about 26,000 light years (8 kiloparsecs) – far outside GHZ proposed by Gowanlock’s team. Why is their proposed galactic habitable zone so different? 

“We assume that metallicity scales with planet formation,” says Gowanlock. Heavy elements are produced by dying stars, and the more generations of stars there have been, the greater the production of these elements (or ‘metals’ as they are termed by astronomers). Historically, the greatest amount of star formation has occurred in the inner region of the Milky Way. “The inner Galaxy is the most metal-rich, and the outer Galaxy is the most metal-poor. Therefore the number of planets is highest in the inner Galaxy, as the metallicity and stellar density is the highest in this region.”  

    A supernova sterilizes an alien world in this artist's impression. Credit: David A Aguilar (CfA)

However, amongst so much star formation lurks a danger: supernovae. Gowanlock’s team modeled the effects of the two most common forms of supernovae – the accreting white dwarfs that produce type Ia supernovae, and the collapsing massive stars of type II supernovae. 

Measurements of the galactic abundance of the isotope aluminum-26, which is a common by-product of type II supernovae, have allowed astronomers to ascertain that a supernova explodes on average once every 50 years. Meanwhile, previous studies have indicated that a supernova can have a deleterious effect on any habitable planet within 30 light years. 

“In our model, we assume that the build-up of oxygen and the ozone layer is required for the emergence of complex life,” says Gowanlock. “Supernovae can deplete the ozone in an atmosphere. Therefore, the survival of land-based complex life is at risk when a nearby supernova sufficiently depletes a great fraction of the ozone in a planet's atmosphere.” 

The team discovered that at some time in their lives, the majority of stars in our Galaxy will be bathed in the radiation from a nearby supernova, whereas around 30% of stars remain untouched or unsterilized. “Sterilization occurs on a planet that is roughly [at a distance] between 6.5 to 98 light years, depending on the supernovae,” says Gowanlock. “In our model, the sterilization distances are not equal, as some supernovae are more lethal than others.” 

Although the outer regions of the Galaxy, with their lower density of stars and fewer supernovae, are generally safer, the higher metallicity in the inner Galaxy means that the chances of finding an unsterilized, habitable world are ten times greater, according to Gowanlock’s model. However, their model does not stipulate any region of the Galaxy to be uninhabitable, only that it’s less likely to find habitable planets elsewhere.

This explains why our Solar System can reside far outside of the inner region, and it also gives hope to SETI – Gowanlock’s model proposes that there are regions of the Galaxy even more likely to have life, and many SETI searches are already targeted towards the galactic center. 

However, not all are in favor of the new model. Ward and Brownlee noted that the Sun’s position in the Galaxy is far more favorable because planets that dance around stars that are too close to the galactic center are more likely to suffer from a perturbed orbit by the gravity of another star that has wandered too close. Others question some of the assumptions made in the research, such as the accuracy of the percentage of planets that are habitable in the galaxy (1.2 percent), or that tidally-locked worlds can be habitable.

 An artist's impression of a potentially habitable planet around a Sun-like star. The habitability of such worlds not only depends on conditions on the planet and its distance from the star, but may also depend on where in the Galaxy it is located. Credit: ESO/M Kornmesser

“The authors may be making some assumptions that aren’t too well justified,” says Professor Jim Kasting of Penn State University and author of How to Find a Habitable Planet. “They seem well ahead of the rest of us who are still pondering these questions.” 

However, others believe that the research is promising. “This is one of the most complete studies of the Galactic Habitable Zone to date,” says Lewis Dartnell, an astrobiologist at University College London. “The results are intriguing, finding that white dwarf supernovae are over five times more lethal to complex life on habitable worlds than core collapse supernovae.” 

The GHZ isn’t static; the research paper written by Gowanlock’s team points out that over time the metallicity of the Galaxy will begin to increase the farther out one travels from the galactic center.

“This is why stars that form at a later date have a greater chance of having terrestrial planets,” says Gowanlock. As a result, perhaps the heyday for life in our Galaxy is yet to come.

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Deadline 2014 To Stop Global Warming

Coal-Fired Power Plants Coal-fired power plants, such as this one in the Conesville, Ohio, are by far the 'dirtiest' means of producing electricity in terms of amount of carbon released into the atmosphere. This has made coal a primary target in the effort to keep total emissions of carbon dioxide below the threshold that will yield two degrees celcius of warming. Scientists have settled identified this threshold as the marker for avoiding "catastrophic" consequences from climate change. 

It’s no secret that the world is warming, but a new report published by the World Wildlife Fund suggests we may not have as much time to mull solutions as we think. If the world doesn’t commit to green technologies by 2014, the report says, runaway global warming and economic meltdown are all but unstoppable.

Written by a group at the experts at Australian insurance consultancy Climate Risk, the transformation to a low-carbon world requires an effort “greater than any other industrial transformation witnessed in our history.” At minimum, the world needs to embrace – and by embrace, they mean to the absolute maximum – low-carbon technologies by 2014.

A minimum growth in all green industries of 22% a year is necessary to achieve that goal, according to their research, and that’s just to cut emissions to 63% of 1990 levels by 2020.

But the WWF has more ambitious plans: a reduction to 80% of 1990 levels by 2050, an industrial revolution that would require growths between 24% and 29% every year. This is the best way to stave off the doomsday scenario of 2 degree Celsius (about 3.6 degrees Fahrenheit) warming across the board, according to the report. Unfortunately, we have a long way to go.

The research relied on complex Monte Carlo models of industrial growth, resource allocation, and technological advance, but the basic reasoning is thus: total greenhouse gasses in the atmosphere are estimated 463 parts per million. Scientific research shows that a good comfortable spot for our atmosphere is about 400 ppm. But at around 475 ppm, a threshold that we are dangerously close to crossing, runaway climate change becomes increasingly more likely, at which point it will be difficult if not impossible to put the brakes on global warming.

Now, having said all that, it’s important to note that this isn’t the first doomsday climate change scenario to emerge, especially recently. Just today, two British Cabinet ministers showed off their own doomsday map, detailing rising sea levels and submerged cities that would result from a 4 degree Celsius (7.2 degree Fahrenheit) rise in global temps.

President Obama has pledged a greenhouse gas reduction of 80 percent by 2050 (an easy promise to make with a two term limit), while the EU has stated that it will match those efforts if a deal is sealed at December’s UN climate change conference in Copenhagen.

But the WWF report, if taken seriously, places a new urgency on the issue. For one, most climate strategies rely upon an incremental ratcheting down of emissions while slowly transitioning to low-carbon sources of energy all the way up to 2050.

According to WWF, this schedule simply won’t hack it. Further, WWF points out that only three of the 20 green technologies they’ve reviewed are moving forward fast enough to hit the 2014 deadline: wind, solar, and biodiesel. Other technological initiatives like low-carbon agriculture, sustainable forestry, and other forms of green energy generation are sorely lacking. The outlook, it seems, is dim.

What happens if we miss the deadline? According to the WWF report, from there things become increasingly difficult. Post-2014, low-carbon industries will need to grow at a minimum of 29% per year, and that’s just to have a better than 50% chance of staving off that nearly 4-degree Fahrenheit spike in global temperatures.

But the news isn’t all bad: while the transition will be tough, long term investment in green energies should pay off, with renewable energy savings alone in the period between 2013 and 2050 expected to hit $47 trillion if we cut by 80 percent, a positive number among many grim figures.

Naturally, models are models and scenarios are but scenarios. The most important takeaway is this: no matter whether you believe in runaway warming or not, technology is the way forward in our warming world, and right now we are woefully under-prepared for the transition to a low-carbon future.

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Fake Plastic Trees and Algae Tanks on Every Roof

                                   Fake Plastic Trees It looks like the real thing ... well, not really.

Geoengineering is a popular idea, for Bill Gates and just about everyone else these days. Now the Institute of Mechanical Engineers proposes that the UK adopt technologies such as carbon-capturing artificial trees, biofuel algae tanks on rooftops, and coating surfaces in reflective materials to cut down on heating from the sun's rays.

Those technologies may sound familiar, because PopSci has examined similar concepts in the past. Reflective rooftops represent perhaps one of the less expensive geoengineering proposals for controlling climate change, but researchers have also pressed forward with prototypes for artificial trees that capture carbon dioxide through plastic leaves and store it for carbon sequestration.

Researchers similarly continue to puzzle out how to grow more algae as a possible biofuel solution for today's energy-hungry world. One company has even resorted to feeding algae to fish, and then squeezing our unfortunate finned friends for the oil. Maybe building owners would feel compelled to adopt rooftop algae tanks en masse and spare fish such a fate ... or maybe not.

The Register casts a critical eye over the recent IMechE report, and offers a tongue-in-cheek comment on why there's no comparison between putting solar panels on the roof versus reflective materials or the algae tanks. It also points out that an artificial tree resembling a giant fly swatter and based on today's technology would capture just over one ton of carbon dioxide per day -- one million such trees would be required to offset the UK's current emissions, at a cost of $20 billion.

Plenty of experts also still want to tread lightly when it comes to geoengineering, for fear of unintended consequences on a global scale. The White House science advisor and the U.S. National Academy of Sciences gingerly examined the topic this summer and concluded that caution is warranted.

Perhaps some of these quick fixes could stand a bit more scrutiny and development, at least before laying out the grand deployment plans.

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Your Car With 0 Emissions WIth Hydrogen-Nanobead-Based Synthetic Gas

Cella Energy's Synthetic Gasoline Cella's CEO Stephen Voller shows off the goods; hydrogen microbeads go under the microscope.

We’re going to go ahead and write this one because it’s all kinds of interesting, but know that we are doing so with all kinds of skepticism, fair readers. Because anytime anyone claims to have created inexpensive synthetic fuel that will burn in conventional automobile engines with no carbon emissions, you simply have to be on your guard. Nonetheless, UK-based Cella Energy claims to have done exactly that by devising a hydrogen-based synthetic fuel that could replace gasoline in cars.

The technology—reportedly incubated at the Rutherford Appleton Laboratory near Oxford in a top secret four-year program—is based on complex hydrides that are highly unstable, usually degrading rapidly in air. Put simply, the company claims it has found a nanotech-driven method that encapsulates hydrogen at usable concentrations in micro-capsules, allowing it to be handled and burned in conventional engines without the need to store it in dangerous high-pressure tanks or super-cooled environments. From Cella’s website:

Cella Energy have developed a method using a low-cost process called coaxial electrospinning or electrospraying that can trap a complex chemical hydride inside a nano-porous polymer that speeds up the kinetics of hydrogen desorption, reduces the temperature at which the desorption occurs and filters out many if not all of the damaging chemicals. It also protects the hydrides from oxygen and water, making it possible to handle it in air.

This means that basically the micro-capsules are stabilized hydrogen that moves like a fluid, meaning you could pump it into your automobile as-is, with no engine or fuel injection conversion—though Cella readily admits that preliminary deployment of their product would likely be as a fuel-additive that helps to cut down on carbon emissions.

Moreover, Gizmag writes that the fuel could be produced at a fixed price of about $1.50 per gallon, a price that would be stable and immune to the whims of OPEC or anyone else (except Cella, it seems). We’re not exactly sure where to attribute that dollar value, though Gizmag did interview the company’s CEO.

So: $1.50 per gallon carbon-free nano-liquid hydrogen fuel that burns in existing engines. Sound too good to be true? In theory the science makes sense assuming the “electrospinning” process works as well as Cella claims it does. But until those hydrogen micro-beads are powering our flying cars, we remain optimistically skeptical.

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Let's Lock That CO2 In A Rock

HELLISHEIDI, Iceland (AP) — Sometime next month, on the steaming fringes of an Icelandic volcano, an international team of scientists will begin pumping "seltzer water" into a deep hole, producing a brew that will lock away carbon dioxide forever.

Chemically disposing of CO2, the chief greenhouse gas blamed for global warming, is a kind of 21st-century alchemy that researchers and governments have hoped for to slow or halt climate change.

The American and Icelandic designers of the "CarbFix" experiment will be capitalizing on a feature of the basalt rock underpinning 90 percent of Iceland: It is a highly reactive material that will combine its calcium with a carbon dioxide solution to form limestone — permanent, harmless limestone.

The researchers caution that their upcoming 6-to-12-month test could fall short of expectations, and warn against looking for a climate "fix" from CarbFix any year soon.

In fact, one of the objectives of the project, whose main sponsors are Reykjavik's city-owned utility and U.S. and Icelandic universities, is to train young scientists for years of work to come.

A scientific overseer of CarbFix — the man, as it happens, who also is credited with coining the term "global warming" four decades ago — says the world's failure to heed those early warnings, to rein in greenhouse-gas emissions from coal, gasoline and other fossil fuels, is driving scientists to drastic approaches.

"Whether we do it in the next 50 years, or the 50 years after that, we're going to have to store carbon dioxide," Columbia University's Wallace S. Broecker said in an interview in New York.

The world is already storing some carbon dioxide. As a byproduct of Norway's natural gas production, for example, it is being pumped into a sandstone reservoir beneath the North Sea.

But people worry that such stowed-away gas could someday escape, while carbon dioxide transformed into stone would not.

The experimental transformation will take place below the dramatic landscape of this place 29 kilometers (18 miles) southeast of Reykjavik, Iceland's capital. On an undulating, mossy moor and surrounding volcanic hills, where the last eruption occurred 2,000 years ago, Reykjavik Energy operates a huge, 5-year-old geothermal power plant, drawing on 30 wells tapping into the superheated steam below, steam laden with carbon dioxide and hydrogen sulfide.

CarbFix will first separate out those two gases, and the CO2 will be piped 3 kilometers (2 miles) to the injection well, to combine with water pumped from elsewhere.

That carbonated water — seltzer — will be injected down the well, where the pressure of the pumped water, by a depth of 500 meters (1,600 feet), will completely dissolve the CO2 bubbles, forming carbonic acid.

"The acid's very corrosive, so it starts to attack the rocks," explained University of Iceland geologist Sigurdur Reynir Gislason, CarbFix's chief scientist.

The basalt rock — ancient lava flows — is porous, up to 30 percent open space filled with water. The carbonic acid will be pushed out into those pores, and over time will react with the basalt's calcium to form calcium carbonate, or limestone.

CarbFix's designers, in effect, are radically speeding up the natural process called weathering, in which weak carbonic acid in rainwater transforms rock minerals over geologic time scales.

The CarbFix team, beginning work in 2007, had to overcome engineering challenges, particularly in the inventive design and operation of the gas separation plant. They have applied for U.S. and Icelandic patents for that and for the injection well technique.

They plan to inject up to 2,000 tons of carbon dioxide over 6 to 12 months and then follow how far the solution is spreading via tracer elements and monitoring wells. Eventually they plan to drill into the rock to take a core sampling.

"It will take months and years to test how well it has spread," Reykjavik Energy's Bergur Sigfusson, project technical manager, said as he guided two AP journalists through the step-by-step process over the rolling green terrain of the Hengill volcano.

The team's greatest concern is that carbon "mineralization" may happen too quickly.

"If it reacts too fast, then that will clog up the system," Sigfusson explained. Quick formation of calcium carbonate would block too many paths through the basalt for the solution to spread.

If it works on a large scale, scientists say, carbon mineralization has a limitless potential, since huge basalt deposits are common — in Siberia, India, Brazil and elsewhere. One formation lies beneath the U.S. northwest, where the U.S. Pacific Northwest National Laboratory plans an experiment similar to CarbFix.

The long-term challenge then becomes capturing the carbon dioxide, and building the infrastructure to deliver it to the right places.

At a basic level, the CarbFix process might at least allow geothermal plants worldwide to neutralize their carbon emissions. At another level, "you'd line up the coal-fired power plants where the basalt is," said Gislason. Their CO2 then could be locked away permanently as rock, rather than stored in underground cavities as now generally conceived.

But ultimately "my vision for carbon capture and storage is offshore, below the sea. The whole ocean floor is basalt below the sediments," said Swiss geochemist and CarbFix manager Juerg Matter, who works with Broecker at Columbia's Lamont-Doherty Earth Observatory.

That futuristic vision would likely require technology to take carbon dioxide from the atmosphere itself — perhaps via millions of chemically treated vanes standing in the wind, a technique being investigated. Such units could be located offshore, with the captured CO2 piped to basalt below, Matter said.

In Gislason's Reykjavik university laboratories, young scientists are already conducting experiments with seawater and basalt, "and they're very promising," the chief scientist said.

"In 10, 20, 30 years' time, if climate change gets very drastic, then we are going to need solutions like this," he said of CarbFix. "We are going to need solutions 'yesterday.'"

Reykjavik Energy has supplied almost half the $10 million spent thus far on CarbFix. Other funding comes from the two universities, France's National Center of Scientific Research, the U.S. Energy Department, the European Union and Scandinavian sources.

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Rocket Nozzle Could Be Repurposed To Efficiently Capture CO2

From Rockets, Carbon-cleaning Tech By pressurizing coal plant emissions and running them through high-speed rocket nozzles, engineers think power plants could cheaply scrub carbon dioxide from exhaust. NASA

 

It's not exactly rocket science, but the same company that builds the rocket boosters that launch the Space Shuttles into orbit has a novel idea for bringing down the cost of carbon capture. Aerospace and defense company ATK wants to pressurize the exhaust emissions from such high-carbon polluters as coal-powered electrical generators and run it through rocket nozzles that will freeze the CO₂ into dry ice, causing it to fall out of exhaust gasses.

 

Such a process could replace the chemical processes used to scrub CO₂ from gas emissions. Those chemicals make up a large part of the expense of scrubbing carbon dioxide form emissions -- a full 80 percent of the cost per kilowatt hour of electricity produced at a coal plant, ATK's vice president tells Discovery News. A rocket nozzle approach could reduce that to more like 30 percent.

 

The science is pretty simple: when you pressurize something like coal plant emissions and then run them through a high-speed aerodynamic accelerator nozzle, the gasses will compress and then expand rapidly on the other side of the nozzle. That rapid expansion can cause some molecules to freeze. In the case of water vapor, the gas would turn to regular water ice. In the case of CO₂-laden coal emissions, the carbon dioxide should freeze into dry ice -- at least in theory -- allowing it to be culled from the other gases for sequestration or other uses. 

 

Considering that coal plants make up for more than a third of U.S. carbon dioxide emissions, the ability to effectively pull CO₂ out of coal emissions could restore coal's place as a viable alternative to foreign oil and as a cleaner bridge to a renewable energy future. Of course, the technology has to work first. ATK wants to get it working smoothly in the lab within 14 months and have a pilot program for the technology installed on a working power plant shortly thereafter.
 

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