Friday, 25 September 2009

Johnald's Fantastical Daily Link Splurge

Johnald's Fantastical Daily Link Splurge

How to Truck 66 200,000-Pound Antennas to 16,000 Feet

Posted: 25 Sep 2009 11:31 AM PDT


After a 17-mile trek up to a plateau in the Chilean Andes, scientists installed the first of 66 giant antennae on the European Southern Observatory's Atacama Large Millimeter/submillimeter Array (ALMA) telescope this week.

The antenna, which weighs about 100 tons and measures 40 feet in diameter, was carried to its operations site at 16,400 feet by a massive, custom-built transporter. Eventually, the antenna will be linked with dozens of others to form a single, enormous telescope. Scientists hope the extremely dry air on the Chajnantor Plateau will help ALMA study some of the coldest and most distant objects in the observable universe.

But because of the harsh conditions on the plateau, each antenna must be built at a base camp at 9,500 feet and then transported up to its concrete pad at the observation site. Once there, the array must be able to survive harsh winds and freezing temperatures, while still maintaining enough precision to point out a golf ball from about 10 miles away.

The first antenna began its journey when one of the two ALMA transporters, affectionately called "Otto," hoisted the enormous white disk onto its back (below).


While the transporter can theoretically travel more than seven miles per hour with an antenna on its back, the vehicle moved extra carefully on its first trek, taking a total of seven hours to travel 17 miles across the Chilean desert.



Once the antenna reached its new home, the transporter used laser-guided steering and ultrasonic collision detectors to guide the disk into its docking station, a concrete pad equipped with power and fiber optic connections.


As more and more antennae are added to the array, the transporter's special sensors will be crucial to keep it from accidentally colliding with an antenna. Even after ALMA is fully operational, ESO scientists say they'll use the custom-built transporters to move antennae between the concrete pads, which will adjust the telescope's view of the sky.



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Sydney’s Apocalyptic Dust Storm Seen From Space

Posted: 25 Sep 2009 08:54 AM PDT


On September 23, Sydney woke up to a surreal scene that looked more like Mars than Australia. The entire city had turned red due to an enormous dust storm. Our readers in Sydney sent us their eerie photos of this event as it was happening. NASA's Terra satellite also captured the incredible event in these images with a spectroradiometer.

Above, the wall of dust blown from inland stretches along the populated coast around Sydney on the morning of September 23. The outline of the continent is faintly traced in the image for reference. Individual point sources for the dust can be discerned. And, according to NASA and the Australian Broadcasting Corporation, some of them were identified as rectangular agricultural plots that have been dried out by several years of drought in Australia. A high-resolution image is available from NASA.

Below, the Terra satellite imaged the dust beneath storm clouds the next morning, September 24, as it blew south across the Tasman Sea toward New Zealand, which is in the bottom right corner of the image. The picture covers 1,450 miles from north to south with a resolution of 155 miles per pixel. At this point, the plume had stretched 2,700 miles, roughly the width of the continental United States. A high-resolution image is available from NASA.


Images: NASA

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Photo: The Sun Gets Its Spots (Back)

Posted: 24 Sep 2009 03:27 PM PDT


Two sunspots are visible on our star's face for the first time in more than a year, possibly ending an unexpected lull in solar activity.

Solar flares rise and fall on an 11-year cycle, so scientists thought sunspot activity would pick up some time in 2008. It didn't. And this year has been quiet, too. No sunspots have been visible on the sun for 80 percent of the days this year.

Sunspot activity is correlated with the total amount of energy we receive from the sun. If the sun's activity were to change remarkably, it would have an influence on global climate. So, in the context of climate change, the fact that the current solar minimum has been the longest and deepest in more than a century has been of special interest.

In May, a big sunspot seemed to augur a return to normal, but it faded away and sunspotless days returned. The latest activity might not mark the end of the solar minimum, however. People have been counting sunspots since Galileo first observed one in the early 17th century. Through the 28 documented cycles, stretching from 1745 to today, some variation in cycle length has been observed.

That's why NASA's former chief sunspot watcher, Michael Kaiser, told us earlier this year that the minimum was "not out of the extreme ordinary."

The photo above is of one of the sunspots, AR 1026. It was sent to by solar photographer, Trevor Little. Little lives in southern England and snaps his gorgeous photos with "a Solarmax 60 telescope and a Lumenera Skynyx 2-0m CCD camera."

If you're an astronomer and you want to share images with Wired Science. Please Tweet us @wiredscience or send an email to our editor, Betsy Mason.

(For you sticklers out there, the polarity of solar storms alternates, so technically, a full solar cycle is 22 years long.)

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Craters Show 1970s Viking Lander Missed Martian Ice by Inches

Posted: 24 Sep 2009 12:38 PM PDT


Meteorites that crashed into the Martian surface last year exposed buried ice to the digital eyes of NASA spacecraft.

Scientists have used those images to deduce that there is a lot more ice on Mars — and that it's closer to the equator — than previously thought. In fact, subterranean Martian ice should extend all the way down beyond 48 degrees of latitude, according to the model, which was published in Science Thursday.

That happens to be where the Viking Lander 2 was in operation from 1976 to 1980. As part of its science program, the Lander dug a trench about 6 inches deep. The new model predicts that if it had gone an extra 3.5 inches — a bit longer than a credit card — it would have hit ice.

It's difficult to project backwards in time what that discovery would have done to the Martian science program, but its impact could have been large.

"To find ice that far from the pole where Viking 2 was, it would have changed the way everyone looked at Mars for the next 20 years," said NASA Goddard archivist, David Williams, who curates the Viking project historical site. "It would have been a whole different model for Mars… If they'd dug down just a little more, they'd have this complete opposite view of Mars."

At the time, scientists didn't really know a lot about the Red Planet. Finding ice underground might not have been that surprising, but largely because the planetologists didn't have a lot of firm theories about water on Mars. They thought there was ice at the poles, Williams said, but not much more than that.

Unlike the Phoenix Lander, the Viking 2 Lander's trenching tool wasn't designed to search for or find ice. Its job was to deliver Martian soil to a series of tests.

As such, Viking 2 wouldn't have been able to do much with any hard ice that it found, said Steven Squyres, an astronomer at Cornell and lead investigator of the Mars Rover missions. Its arm just wasn't powerful enough. Squyers also noted that the Viking missions were a tremendous success, without a water ice find.

But the Viking 2 Lander's work did give the impression that water ice did not exist near the Martian surface in the mid-latitudes. We'll never know how NASA's "Follow the Water" missions to Mars might have changed if, for some reason, the Lander had been commanded to dig just a bit deeper and hit a hard, icy surface.

It goes to show that sometimes scientific discoveries can come down to a few inches and some luck, even on the surface of a planet hundreds of millions miles away.


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Butterflies Use Antenna GPS to Guide Migration

Posted: 24 Sep 2009 11:19 AM PDT


Scientists have finally located the 24-hour clock that guides the migration of monarch butterflies. Instead of being in the brain where most people expected, it turns out the circadian clock is located in the butterflies' antennae.

Every fall, monarchs make an impressive 2,000-mile trek south, using the sun to guide them to the exact same wintering spot in central Mexico. But because the sun is a moving target, changing position throughout the day, biologists have long speculated that in addition to having a "sun compass" in their brains, butterflies must use some kind of 24-hour clock to guide their migration. Now, researchers have located this special GPS system, but it's not what everyone expected.

"The assumption was that we knew where in the brain the molecular clock for this process was," said biologist Steven Reppert of the University of Massachusetts, who co-authored the paper published Thursday in Science. "Almost everyone you would ask prior to this work would say, 'Well, of course the clock has to be in the brain. Where else would it be?'"

Reppert and his team had been studying the ability of butterfly antenna to sense odors when they uncovered something surprising: When they clipped off the insects' antennae and tethered them in a flight simulator, the butterflies no longer flew in a uniform direction.

"It was remarkable, the difference," Reppert said. "The ones without antennae still flew straight, but as a population they were flying in all different directions, compared to the population of migrants with intact antennae that was all going in a southwesterly direction." Without their feelers, the butterflies lost the ability to navigate using the sun, as if they could no longer adjust their direction based on the time of day.

But when the researchers looked for molecular changes in the brains of the antennae-less butterflies, they found that circadian rhythms in the brain were unaffected by clipping the antennae. "This raised the heretical prospect that the timing mechanism may actually be in the antennae," Reppert said.

The researchers tested their hypothesis by painting the antennae of half their butterflies with black enamel, which blocked all input from the sun, and the other half with clear paint that allowed the sun's rays through. While the monarchs covered with clear paint kept flying south, the butterflies with blacked-out antennae started to drift consistently north, suggesting that their molecular clock was running about an hour off schedule.

butterflygps2"The antennal clock is therefore rather like a standalone global positioning system that one might use while driving, which now eclipses the paper map (brain clock)," biologist Charalambos Kyriacou of the University of Leicester wrote in a commentary about the research, also published Thursday in Science. "This result is surprising, given that several studies have set the stage for a brain clock to mediate navigation."

Reppert says the new finding not only changes how scientists think about butterfly antennae, but may also suggest a similar role for an antennal clock in other types of insects, such as bees and ants, that also operate elaborate navigation systems. Like butterflies, honeybees use a sun compass to find flowers and communicate their specific position to the rest of the hive, and they could be using a circadian clock in their antenna to adjust the sun's position to the time of day.

"I think it's a really interesting and elegant paper," said butterfly researcher Karen Oberhauser of the University of Minnesota, who was not involved in the research. But given the incredible sensory powers of insect antennae, she said she's not too surprised that the feelers can also keep time.

"Our sensory systems are really localized to our heads, but insects can taste with their feet and smell with their antennae, and probably their abdomens have pretty complex sensory systems, too," Oberhauser said. "Because insect sensory systems are so different than our sensory systems, it's sometimes difficult for us to even ask the right questions. That's what's so interesting about the work that's being done in the Reppert lab— they're really delving into these detailed questions."

Image 1: Monarch Watch/Chip Taylor. Image 2: M. Twombly, copyright AAAS/Science.

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Brain Scans Reveal What You’ve Seen

Posted: 24 Sep 2009 08:54 AM PDT


Scientists are one step closer to knowing what you've seen by reading your mind.

Having modeled how images are represented in the brain, the researchers translated recorded patterns of neural activity into pictures of what test subjects had seen.

Though practical applications are decades away, the research could someday lead to dream-readers and thought-controlled computers.

"It's what you would actually use if you were going to build a functional brain-reading device," said Jack Gallant, a University of California, Berkeley neuroscientist.

The research, led by Gallant and Berkeley postdoctoral researcher Thomas Naselaris, builds on earlier work in which they used neural patterns to identify pictures from within a limited set of options.

The current approach, described Wednesday in Neuron, uses a more complete view of the brain's visual centers. Its results are closer to reconstruction than identification, which Gallant likened to "the magician's card trick where you pick a card from a deck, and he guesses which card you picked. The magician knows all the cards you could have seen."

In the latest study, "the card could be a photograph of anything in the universe. The magician has to figure it out without ever seeing it," said Gallant.

To construct their model, the researchers used an fMRI machine, which measures blood flow through the brain, to track neural activity in three people as they looked at pictures of everyday settings and objects.

As in the earlier study, they looked at parts of the brain linked to the shape of objects. Unlike before, they looked at regions whose activity correlates with general classifications, such as "buildings" or "small groups of people."

Once the model was calibrated, the test subjects looked at another set of pictures. After interpreting the resulting neural patterns, the researchers' program plucked corresponding pictures from a database of 6 million images.

Frank Tong, a Vanderbilt University neuroscientist who studies how thoughts are manifested in the brain, said the Neuron study wasn't quite A pure, draw-from-scratch reconstruction. But it was impressive nonetheless, especially for the detail it gathered from measurements that are still extremely coarse.

The researchers' fMRI readings bundled the output of millions of neurons into single output blocks. "At the finer level, there is a ton of information. We just don't have a way to tap into that without opening the skull and accessing it directly," said Tong.

Gallant hopes to develop methods of interpreting other types of brain activity measurement, such as optical laser scans or EEG readings.

He mentioned medical communication devices as a possible application, and computer programs for which visual thinking makes sense — CAD-CAM or Photoshop, straight from the brain.

Such applications are decades away, but "you could use algorithms like this to decode other things than vision," said Gallant. "In theory, you could analyze internal speech. You could have someone talk to themselves, and have it come out in a machine."

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Citation: "Bayesian Reconstruction of Natural Images from Human Brain Activity." By Thomas Naselaris, Ryan J. Prenger, Kendrick N. Kay, Michael Oliver, and Jack L. Gallant. Neuron, Vol. 63 Issue 6, September 24, 2009.

Image: From Neuron. Images seen by test subjects are in the left column. In the middle the image reconstructions returned by the researchers' older, structure-focused analysis. At right are the image reconstructions produced by the newer, category-including model.

Brandon Keim's Twitter stream and reportorial outtakes; Wired Science on Twitter. Brandon is currently working on a book about ecosystem and planetary tipping points.

Water Found on the Moon

Posted: 23 Sep 2009 05:47 PM PDT


Scientists' understanding of the moon could be all wet. Its surface is surprisingly dewy and its interior contains more water than previous analyses of moon rocks have indicated, according to new studies.

sciencenewsObservations from three spacecraft suggest that water is widely distributed over a thin layer of the lunar surface rather than locked up in icy enclaves predicted to lie at the moon's poles. The results, detailed in a trio of papers posted online September 24 in Science, suggest that liquid water may be more available to future moon explorers than had been thought. Concentrations in sunlit soil might average about 1,000 parts per million, the equivalent of roughly a quart of water per ton of material. That water doesn't remain on the moon, but comes and goes each lunar day.

In contrast, water molecules bound to phosphate minerals within volcanic rocks — material that formed well beneath the lunar surface — date back several billion years, says Francis McCubbin of the Carnegie Institution for Science in Washington D.C. A fourth, unpublished study led by McCubbin finds a surprisingly high abundance of this interior water, which may shed new light on how the moon formed.

The researchers who made the surface observations caution that their observations, which are based on low-resolution spectroscopy of minerals on the lunar surface, cannot clearly distinguish between water and the hydroxyl ion, which can serve as a marker for water.

Nonetheless, Roger N. Clark of the U.S. Geological Survey in Flagstaff, Ariz., asserts that "this is the first detection of water on the moon and we see it all over, not just in the polar regions." Clark, a coauthor of two of the Science papers, led a team that found evidence of water in spectra taken by the Cassini spacecraft as it flew past the moon in 1999. Clark says he knew his team had a real signal a while ago, but he says he waited to publish because "the detection was so fantastic, I felt we needed confirmation."

Confirmation has now come in the form of spectra taken by instruments aboard NASA's Deep Impact spacecraft and Chandrayaan-I, India's first mission to the moon. Each of the papers in Science reports data from one of the spacecraft.

Last week, other researchers reported that the Lunar Reconnaissance Orbiter spacecraft had found hydrogen on the moon's surface, a possible marker of water (SN Online: 9/18/09).

The three Science papers "present a strong case for surficial water on the moon, and this could certainly be the result of delivery by icy impactors or solar wind interactions long after the moon formed," comments Robin Canup of the Southwest Research Institute in Boulder, Colorado, who is not a member of any of the teams.

Data collected by Deep Impact one-quarter of a lunar day apart reveal that layers of water only a few molecules thick form, evaporate into space and then reform each lunar day, notes Jessica Sunshine of the University of Maryland in College Park, lead author of the Deep Impact study.

An obvious driver of such a cycle would be hydrogen ions delivered by the solar wind. The ions could interact with oxygen-rich minerals on the lunar surface to produce water, Sunshine suggests. Heat from the sun could then vaporize the water each lunar noon. Although the long-term effects of this interaction on the moon are unknown, "this same process should be occurring on airless, silicate-rich bodies throughout the inner solar system," she says.

In McCubbin's study of the lunar interior, he and his colleagues calculate that phosphate minerals contain a concentration of water as high as several thousand parts per million. This result, combined with lower abundances of water in other volcanic material reported in 2008 by Alberto Saal of Brown University in Providence, Rhode Island points to an average overall abundance of water in the lunar mantle significantly higher than the previous estimate of 1 part per billion.

It's been a long-standing assumption, notes Canup, that if the moon formed when a giant, Mars-sized impactor smacked into the young Earth, any water would have been vaporized by the high temperatures generated during such a cataclysm and that vapor would have escaped into space. However, that assumption "has yet to be evaluated with direct models," she adds.

McCubbin agrees that there may have been some way for water to be retained in this accepted model of the moon's formation. Any alternative explanation of moon formation will have to account for all the water now known to reside inside the moon.

On October 9, a NASA spacecraft called LCROSS will deliberately crash into a cratered area of the moon's south pole, where frozen water likely resides. The resulting plume of kicked-up soil should reveal the abundance of water there.

Says Canup: "Our picture of a bone-dry moon is clearly in need of updating."

Image: Schematic showing the stream of charged hydrogen ions carried from the sun by the solar wind. / University of Maryland, F. Merlin, McREL
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1 Million Spiders Make Golden Silk for Rare Cloth

Posted: 23 Sep 2009 12:39 PM PDT


A rare textile made from the silk of more than a million wild spiders goes on display today at the American Museum of Natural History in New York City.

To produce this unique golden cloth, 70 people spent four years collecting golden orb spiders from telephone poles in Madagascar, while another dozen workers carefully extracted about 80 feet of silk filament from each of the arachnids. The resulting 11-foot by 4-foot textile is the only large piece of cloth made from natural spider silk existing in the world today.

1-spiders"Spider silk is very elastic, and it has a tensile strength that is incredibly strong compared to steel or Kevlar," said textile expert Simon Peers, who co-led the project. "There's scientific research going on all over the world right now trying to replicate the tensile properties of spider silk and apply it to all sorts of areas in medicine and industry, but no one up until now has succeeded in replicating 100 percent of the properties of natural spider silk."

Peers came up with the idea of weaving spider silk after learning about the French missionary Jacob Paul Camboué, who worked with spiders in Madagascar during the 1880s and 1890s. Camboué built a small, hand-driven machine to extract silk from up to 24 spiders at once, without harming them.

"Simon managed to build a replica of this 24-spider-silking machine that was used at the turn of the century," said Nicholas Godley, who co-led the project with Peers. As an experiment, the pair collected an initial batch of about 20 spiders. "When we stuck them in the machine and started turning it, lo and behold, this beautiful gold-colored silk started coming out," Godley said.

Father Comboué, who one historical text erroneously calls Father Comboné, had a partner in designing his machine, M. Nogué. Together, they got quite a spider silk fabric industry going in Madagascar and even exhibited "a complete set of bed hangings" at the Paris Exposition of 1898. That fabric has since been lost, but the exhibition brought them some attention, excerpted below.

"It should be said that the female halabe allows herself to be relieved of her silken store with exemplary docility and this in spite of the fact that she is distinguished for her ferocity; her usual treatment of the males who pay her court is to eat them and she feasts without compunction on members of her own sex weaker than herself. M Nogue's apparatus consists of a sort of stocks arranged to pin down on their backs a dozen spiders. The spiders accept this imprisonment with resignation and lie perfectly quiet while the silken thread issuing from their bodies is rapidly wound on to a reel by means of a cleverly devised machine worked by hand." — Great Britain Board of Trade Journal

"The first experiments of Father Comboné were made in the simplest manner. The spiders were imprisoned in match boxes and by slightly compressing the abdomen he managed to extract and wind upon a little reel turned by hand it thread that sometimes attained a length of 500 yards… it is to the ingenuity of M. Nogue, one of the sub directors, that we owe the apparatus which permits the thread to be wound mechanically and to be twisted and doubled in the quickest and most practical manner. This is done by means of a curious little machine, not easy to describe, in which the spiders are imprisoned by the throat while undergoing the operation. Young Malagasy girls go daily to a park near the school to gather three or four hundred spiders which they carry in osier baskets with wooden covers to be divested of their webs… Generally after having submitted to the reeling operation the spiders are put back in the park for a couple of weeks… [The silk's] color when first spun is a beautiful gold and it requires no carding or preparation of any sort before being woven. Will this be the silk of the future?" — The Literary Digest

But to make a textile of any significant size, the silk experts had to drastically scale up their project. "Fourteen thousand spiders yields about an ounce of silk," Godley said, "and the textile weighs about 2.6 pounds. The numbers are crazy."

Researchers have long been intrigued by the unique properties of spider silk, which is stronger than steel or Kevlar but far more flexible, stretching up to 40 percent of its normal length without breaking. Unfortunately, spider silk is extremely hard to mass produce: Unlike silk worms, which are easy to raise in captivity, spiders have a habit of chomping off each other's heads when housed together.

3-weavingTo get as much silk as they needed, Godley and Peers began hiring dozens of spider handlers to collect wild arachnids and carefully harness them to the silk-extraction machine. "We had to find people who were willing to work with spiders," Godley said, "because they bite."

By the end of the project, Godley and Peers extracted silk from more than 1 million female golden orb spiders, which are abundant throughout Madagascar and known for the rich golden color of their silk. Because the spiders only produce silk during the rainy season, workers collected all the spiders between October and June.

Then an additional 12 people used hand-powered machines to extract the silk and weave it into 96-filament thread. Once the spiders had been milked, they were released into back into the wild, where Godley said it takes them about a week to regenerate their silk. "We can go back and re-silk the same spiders," he said. "It's like the gift that never stops giving."

Of course, spending four years to produce a single textile of spider silk isn't very practical for scientists trying to study the properties of spider silk or companies that want to manufacture the fabric for use as a biomedical scaffold or an alternative to Kevlar armor. Several groups have tried inserting spider genes into bacteria (or even cows and goats) to produce silk, but so far, the attempts have been only moderately successful.

Part of the reason it's so hard to generate spider silk in the lab is that it starts out as a liquid protein that's produced by a special gland in the spider's abdomen. Using their spinnerets, spiders apply a physical force to rearrange the protein's molecular structure and turn it into solid silk.

"When we talk about a spider spinning silk, we're talking about how the spider applies forces to produce a physical transformation from liquid to solid," said spider silk expert Todd Blackledge of the University of Akron, who was not involved in creating the textile. "Scientists simply can't replicate that as well as a spider does it. Every year we're getting closer and closer to being able to mass-produce it, but we're not there yet."

For now, it seems we'll have to be content with one incredibly beautiful cloth, graciously provided by more than a million spiders.

Images: 1) AMNH/R. Mickens 2) Nicholas Godley and Simon Peers

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9 Environmental Boundaries We Don’t Want to Cross

Posted: 23 Sep 2009 11:39 AM PDT


Climate change threatens to turn the planet into a stormy, overheated mess: That much we know. But according to 28 leading scientists, greenhouse gas pollution is but one of nine environmental factors critical to humanity's future. If their boundaries are stretched too far, Earth's environment could be catastrophically altered — and three have already been broken, with several others soon to follow.

This grim diagnosis, published Wednesday in Nature, is the most ambitious assessment of planetary health to date. It's a first-draft users' manual for an era that scientists dub the "anthropocene," in which nearly seven billion resource-hungry humans have come to dominate ecological change on Earth. The scientists' quantifications are open to argument, but not the necessity of their perspective.

"It's a crude attempt to map the environmental space in which we can operate," said Jon Foley, director of the University of Minnesota's Institute on the Environment and one of the paper's lead authors. "We need to keep our activities in a certain range, or the planet could tip into a state we haven't seen in the history of our civilization."

Thresholds for atmospheric carbon dioxide and ozone have already been described, and are widely known to the public. But the scientists say five other factors are just as important: ocean acidification, nitrogen and phosphorus pollution, land use, freshwater use and biodiversity. They say chemical pollution and atmospheric aerosols may also be essential, but can't yet be quantified.

Values for the proposed boundaries are still just estimates, and don't account for how pushing one could affect another — how, for example, acidification that kills plankton could make it harder for the ocean to absorb CO2 and rebound from nitrogen pollution. Ecological models still can't capture the entirety of Earth's biological, geological and chemical processes, and it's impossible to run whole-Earth experiments — except, arguably, for the experiment that's going on now.

Despite those uncertainties, one aspect of Earth's behavior is becoming clear. Records of global transitions between geological ages, and of regional changes between environmental stages, suggest that planet-wide change could happen relatively quickly. It might not take thousands or millions of years for Earth's environment to be altered. It could happen in centuries, perhaps even decades.

Exactly what Earth would look like is difficult to predict in detail, but it could be radically different from the mild environment that has prevailed for the last 10,000 years. It was temperate stability that nurtured the rise of civilization, and it should continue for thousands of years to come, unless humanity keeps pushing the limits.

"The Earth of the last 10,000 years has been more recognizable than the Earth we may have 100 years from now. It won't be Mars, but it won't be the Earth that you and I know," said Foley. "This is the single most defining problem of our time. Will we have the wisdom to be stewards of a world we've come to dominate?"


Foley's team put the atmospheric carbon dioxide threshold at 350 parts per million, a level the Intergovernmental Panel for Climate Change says should keep Earth's average temperature from rising by more than four degrees Fahrenheit. Current atmospheric CO2 levels are already approaching 400 parts per million.

Also exceeded are limits for species loss, which the scientists set at 10 per year per million species, and nitrogen use, pegged at 35 million tons per year. The current extinction rate is ten times higher than advised, ostensibly compromising the ability of ecosystems to process nutrients. The use of nitrogen — which is needed for fertilizer, but causes oxygen-choking algae blooms — is nearly four times higher than recommended.

On the positive side, atmospheric levels of ultraviolet radiation-blocking ozone are safe, thanks to a 1987 ban on ozone-destroying chemicals. Total rates of ocean acidification, freshwater consumption and land use are also acceptable, but those thresholds are expected to be exceeded in coming decades.

The seven boundary points are certain to be controversial, and Nature commissioned seven separate critiques by leading experts in each field.

William Schlesinger, president of the Cary Institute of Ecosystem Studies, said the recommended nitrogen limit "seems arbitrary." Echoing his words was Steve Bass of the International Institute for Environment and Development, who said the 15 percent cap on land devoted to agriculture could as easily be 10 or 20 percent.

International Water Management Institute researcher David Molden said the 4,000 cubic kilometer ceiling on freshwater use — roughly one-third of all freshwater — "may be too high." Myles Allen, an Oxford University climatologist, argued that CO2 emissions should be counted in a different way. Cristian Samper, director of the U.S. Natural History Museum, said that taxonomic family loss is a more relevant measure than species loss.

According to Foley, who called his team's threshold values a "cave painting" version of the true limits, the paper is less important for its details than its approach. And though the critics argued over the numbers, all agreed that exceeding them will be disastrous.

"Planetary boundaries are a welcome new approach," wrote Molden. "It is imperative that we act now on several fronts to avert a calamity far greater than what we envision from climate change."

Peter Brewer, an ocean chemist at the Monterey Bay Aquarium Research Institute, criticized the paper's lack of proposed solutions. Given the ongoing failure of governments and citizens to follow their scientists' advice on climate change, more than dire warnings is clearly needed.

"Is it truly useful to create a list of environmental limits without serious plans for how they may be achieved?" Brewer wrote. "Without recognition of what would be needed economically and politically to enforce such limits, they may become just another stick to beat citizens with."

"It's unsatisfactory, I agree. We don't answer the question of how to keep humanity from crossing the boundaries," said Johan Rockstrom, director of the Stockholm Environment Institute and a lead author of the Nature paper. "That's the next challenge. To stay within planetary boundaries, we need tremendous social transformation."

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Note: The Nature paper is an edited version of the full article, which is available from the Stockholm Resilience Institute.

Citations: "A safe operating space for humanity." By Johan Rockström, Will Steffen, Kevin Noone, Åsa Persson, F. Stuart Chapin, III, Eric F. Lambin, Timothy M. Lenton, Marten Scheffer, Carl Folke, Hans Joachim Schellnhuber, Björn Nykvist, Cynthia A. de Wit, Terry Hughes, Sander van der Leeuw, Henning Rodhe, Sverker Sörlin, Peter K. Snyder, Robert Costanza, Uno Svedin, Malin Falkenmark, Louise Karlberg, Robert W. Corell, Victoria J. Fabry, James Hansen, Brian Walker, Diana Liverman, Katherine Richardson, Paul Crutzen, Jonathan A. Foley. Nature, Vol. 461 No. 7263, September 24, 2009.

"Thresholds risk prolonged degradation." By William Schlesinger. Nature, Vol. 461 No. 7263, September 24, 2009.

"Keep off the grass." By Steve Bass. Nature, Vol. 461 No. 7263, September 24, 2009.

"Tangible targets are critical." By Myles Allen. Nature, Vol. 461 No. 7263, September 24, 2009.

"Identifying abrupt change." By Mario J. Molina. Nature, Vol. 461 No. 7263, September 24, 2009.

"The devil is in the detail." By David Molden. Nature, Vol. 461 No. 7263, September 24, 2009.

"Consider all consequences." By Peter Brewer. Nature, Vol. 461 No. 7263, September 24, 2009.

"Rethinking biodiversity." By Cristian Samper. Nature, Vol. 461 No. 7263, September 24, 2009.

Images: 1. NASA 2. Encyclopedia of Earth

Brandon Keim's Twitter stream and reportorial outtakes, Wired Science on Twitter. Brandon is currently working on a book about ecosystem and planetary tipping points.

The Pinwheel Galaxy Captured in Dazzling Color

Posted: 23 Sep 2009 11:04 AM PDT


The Pinwheel Galaxy is one of the most fantastic spiral galaxies to view from Earth because it is facing us, displaying the full glory of its awesome shape. This new three-color composite image was captured by the Isaac Newton Telescope in La Palma, Spain.

Known more officially as Messier 101 or NGC 5457, this classic spiral galaxy is 27 million light years from Earth in the Ursa Major constellation, also known as the Big Dipper. Its slight asymmetry is thought to be the result of an encounter with another galaxy in the recent (astronomically speaking) past. This event also left many huge clouds of glowing gas and plasma known as H II regions.

Though the galaxy, which measures 170,000 light-years across, is visible with the naked eye as a fuzzy spot, large telescopes are needed to see any detail.

Image: Isaac Newton Group of Telescopes / Instituto de Astrofisica de Canarias

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