Tuesday, 30 November 2010

Johnald's Fantastical Daily Link Splurge

Johnald's Fantastical Daily Link Splurge


Dark Jupiter May Haunt Edge of Solar System

Posted: 29 Nov 2010 02:24 PM PST

A century of comet data suggests a dark, Jupiter-sized object is lurking at the solar system's outer edge and hurling chunks of ice and dust toward Earth.

"We've accumulated 10 years' more data, double the comets we viewed to test this hypothesis," said planetary scientist John Matese of the University of Louisiana. "Only now should we be able to falsify or verify that you could have a Jupiter-mass object out there."

In 1999, Matese and colleague Daniel Whitmire suggested the sun has a hidden companion that boots icy bodies from the Oort Cloud, a spherical haze of comets at the solar system's fringes, into the inner solar system where we can see them.

In a new analysis of observations dating back to 1898, Matese and Whitmire confirm their original idea: About 20 percent of the comets visible from Earth were sent by a dark, distant planet.

 

This idea was a reaction to an earlier notion that a dim brown-dwarf or red-dwarf star, ominously dubbed Nemesis, has pummeled the Earth with deadly comet showers every 30 million years or so. Later research suggested that mass extinctions on Earth don't line up with the Nemesis predictions, so many astronomers now think that object doesn't exist.

"But we began to ask, what kind of an object could you hope to infer from the present data that we are seeing?" Matese said. "What could possibly tickle [comets'] orbits and make them come very close to the sun so we could see them?"

Rather than a malevolent death star, a smaller and more benign companion called Tyche (Nemesis' good sister in Greek mythology) could send comets streaming from the Oort Cloud toward Earth.

The cosmic snowballs that form the hearts of comets generally hang out in the Oort Cloud until their orbits are nudged by some outside force. This push could come from one of three things, Matese said. The constant gravitational pull of the Milky Way's disk can drag comets out of their icy homes and into the inner solar system. A passing star can shake comets loose from the Oort Cloud as it zips by. Or a large companion like Nemesis or Tyche can pull comets out of their comfort zones.

Computational models show that comets in each of these scenarios, when their apparent origins are mapped in space, make a characteristic pattern in the sky.

"We looked at the patterns and asked, 'Is there additional evidence of a pattern that might be associated with a passing star or with a bound object?'" Matese said.

After examining the orbits of more than 100 comets in the Minor Planet Center database, the researchers concluded that 80 percent of comets born in the Oort Cloud were pushed out by the galaxy's gravity. The remaining 20 percent, however, needed a nudge from a distant object about 1.4 times the mass of Jupiter.

"Something smaller than Jovian mass wouldn't be strong enough to do the deed," Matese said. "Something more massive, like a brown dwarf, would give a much stronger signal than the 20 percent we assert."

There's one problem, however. The pattern only works for comets that come from the spherical outer Oort Cloud, which extends from about 0.3 to 0.8 light-years from the sun. Comets from the flatter, more doughnut-shaped inner Oort Cloud don't create the same distinctive pattern.

"That's troubling," Matese said. "It requires an entirely new dynamical explanation for how inner Oort Cloud comets are made observable."

That the same weird pattern from 1999 is still there today "definitely makes it a stronger case than past papers," said planetary scientist Nathan Kaib of the Canadian Institute for Theoretical Astrophysics, who was not involved in the new work. But he would still like to see more data.

"I think this whole issue will be resolved in the next five to 10 years, because there's surveys coming on line … that will dwarf the comet sample we have today," he said. "Whether these types of asymmetries in the directions that comets are coming from actually do exist or not will definitely be hammered out by those surveys."

We may not have to wait that long, Matese said. An object like Tyche could be seen directly by WISE, NASA's infrared space telescope.

"We anticipate that this WISE is going to falsify or verify our conjecture," he said. "We just have to be patient."

Images: 1) Comet Sliding Spring, a visitor from the Oort Cloud, was captured by WISE in January 2010. Credit: NASA/JPL-Caltech/UCLA
2) The layout of the solar system, including the Oort Cloud, on a logarithmic scale. Credit: NASA

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Radiation Rings Hint Universe Was Recycled Over and Over

Posted: 29 Nov 2010 12:20 PM PST

Most cosmologists trace the birth of the universe to the Big Bang 13.7 billion years ago. But a new analysis of the relic radiation generated by that explosive event suggests the universe got its start eons earlier and has cycled through myriad episodes of birth and death, with the Big Bang merely the most recent in a series of starting guns.

That startling notion, proposed by theoretical physicist Roger Penrose of the University of Oxford in England and Vahe Gurzadyan of the Yerevan Physics Institute and Yerevan State University in Armenia, goes against the standard theory of cosmology known as inflation.

The researchers base their findings on circular patterns they discovered in the cosmic microwave background, the ubiquitous microwave glow left over from the Big Bang. The circular features indicate that the cosmos itself circles through epochs of endings and beginnings, Penrose and Gurzadyan assert. The researchers describe their controversial findings in an article posted at arXiv.org on November 17.

The circular features are regions where tiny temperature variations in the otherwise uniform microwave background are smaller than average. Those features, Penrose said, cannot be explained by the highly successful inflation theory, which posits that the infant cosmos underwent an enormous growth spurt, ballooning from something on the scale of an atom to the size of a grapefruit during the universe's first tiny fraction of a second. Inflation would either erase such patterns or could not easily generate them.

"The existence of large-scale coherent features in the microwave background of this form would appear to contradict the inflationary model and would be a very distinctive signature of Penrose's model" of a cyclic universe, comments cosmologist David Spergel of Princeton University. But, he adds, "The paper does not provide enough detail about the analysis to assess the reality of these circles."

 

Penrose interprets the circles as providing a look back, past the glass wall of the most recent Big Bang, into the universe's previous episode, or "aeon," as he calls it. The circles, he suggests, were generated by collisions between supermassive black holes that occurred during this earlier aeon. The colliding black holes would have created a cacophony of gravitational waves — ripples in spacetime due to the acceleration of the giant masses. Those waves would have been spherical and uniformly distributed.

According to the detailed mathematics worked out by Penrose, when the uniform distribution of gravitational waves from the previous aeon entered the current aeon, they were converted into a pulse of energy. The pulse provided a uniform kick to the allotment of dark matter, the invisible material that accounts for more than 80 percent of the mass of the cosmos.

"The dark matter material along the burst therefore has this uniform character," says Penrose. "This is what is seen as a circle in our cosmic microwave background sky, and it should look like a fairly uniform circle."

Each circle has a lower-than-average variation in temperature, which is just what he and Gurzadyan found when they analyzed data from NASA's orbiting Wilkinson Microwave Anisotropy Probe, or WMAP, which scanned the entire sky for nine years, and the balloon-borne BOOMERANG experiment, which studied microwave background over a smaller fraction of the heavens.

Because the team found similar circular features with two different detectors, Penrose says it's unlikely he and his colleagues are being fooled by instrumental noise or other artifacts.

But Spergel says he is concerned that the team has not accounted for variations in the noise level of WMAP data acquired over different parts of the sky. WMAP examined different sky regions for different amounts of time. Maps of the microwave background generated from those regions studied the longest would have lower noise and smaller recorded variations in the temperature of the microwave glow. Those lower-noise maps could artificially produce the circles that Penrose and Gurzadyan ascribe to their model of a cyclic universe, Spergel says.

A new, more detailed map of the cosmic microwave background, now being conducted by the European Space Agency's Planck mission, could provide a more definitive test of the theory, Penrose says.

Image: Dark circles indicate regions in space where the cosmic microwave background has temperature variations that are lower than average. The features hint that the universe was born long before the Big Bang 13.7 billion years ago and had undergone myriad cycles of birth and death before that time. arXiv/V.G. Gurzadyan and R. Penrose

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Monday, 29 November 2010

Johnald's Fantastical Daily Link Splurge

Johnald's Fantastical Daily Link Splurge


Telomere Tweaks Reverse Aging in Mice

Posted: 29 Nov 2010 10:39 AM PST

By tweaking enzymes that prevent chromosome tips from unraveling, researchers have shown age-related tissue degeneration can be reversed in some mice.

Medical breakthroughs involving mice must be taken with rock-sized grains of salt because, despite their genetic similarity, the rodents aren't humans. The latest findings, published online by the journal Nature on November 28, are no exception. Nevertheless, they provide the first compelling evidence of aging's reversal — not just delay — in a high-level organism.

The work represents an "unprecedented reversal of age-related decline in the central nervous system and other organs vital to adult mammalian health," wrote the team led by Ronald DePinho, a cancer geneticist at Harvard Medical School.

The researchers genetically engineered mice to lack telomerase, the key enzyme ingredient in structures called telomeres that cap the tips of chromosomes and prevent them from fraying. In healthy mammals, telomeres shorten slightly with each round of cell division and such shortening is linked to a variety of age-related disorders, suggesting a role in aging.

DePinho's telomerase-less mice tended to be prematurely aged and infertile with small brains, damaged intestines and poor senses of smell. Four weeks after the researchers gave them a drug designed to stimulate telomerase production, however, these visible signs of aging had reversed.

In a press release, DePinho described the transformation as "akin to a Ponce de LeĆ³n effect," referring to the 16th century conquistador's search for a fountain of youth.

It may be a premature choice of phrase. Before speculation on human applications can even begin, the researchers need to determine whether telomerase activation works for "normal" mice, and not just a single strain genetically engineered to age prematurely.

Such strain-dependent effects have confounded the promise of drugs designed to mimic the apparent longevity-extending effects of low-calorie diets. But even if the findings are never translated directly to humans, they may still provide insight into the physiological basis of aging itself — something that, despite centuries of study, has yet to be pinned down.

 

Image: Fluorescent markers signify enzyme activation in the tips of telomeres./Nature.

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Citation: "Telomerase reactivation reverses tissue degeneration in aged telomerase-deficient mice." By Mariela Jaskelioff, Florian L. Muller, Ji-Hye Paik, Emily Thomas, Shan Jiang, Andrew C. Adams, Ergun Sahin, Maria Kost-Alimova, Alexei Protopopov, Juan Cadinanos, James W. Horner, Eleftheria Maratos-Flier & Ronald A. DePinho. Advance online publication, November 28, 2010.

Brandon's Twitter stream, reportorial outtakes and citizen-funded White Nose Syndrome story; Wired Science on Twitter.

Digital Creatures Evolve Firefly Flashing

Posted: 29 Nov 2010 09:29 AM PST

One hundred and fifty-one years after the publication of On the Origin of Species, digital creatures have evolved to communicate like fireflies in a computer program that blurs the boundaries of life.

Recorded in line-by-line detail, their development in a software platform called Avida may provide insight into biological behavior and inspiration for the design of distributed computer networks.

"Evolutionary programs have been around for a while, but we haven't seen them applied to distributed computing," said computer scientist Philip McKinley of Michigan State University. Synchronized communication can be "seen in the natural world. But in Avida, we can go back to how and why it evolved. We can see the key points that allowed this relatively complex behavior to emerge."

The new synchronization findings, made by McKinley and fellow MSU computer scientist David Knoester, were published November 18 in Artificial Life.

Inside the program, developed in the early 1990s at the California Institute of Technology and refined at MSU's Digital Evolution Laboratory, digital organisms called Avidians take the form of self-replicating code. Their genomes are written in assembly language and stored in separate regions of memory, executed again and again at electronic speeds. Programmers set the parameters of mutation and natural selection, and evolutionary principles manifest themselves in silico.

"We like to say 'it's not a simulation of evolution, it's evolution.' The difference is that these are computer programs," McKinley said.

 

In a previous and well-known study, researchers supported a key tenet of evolutionary theory by demonstrating how easily complexity could emerge in Avidians through incremental changes in simple, existing functions.

McKinley and Knoester specialize in organismal interactions: How complexity emerges not only in individuals, but also in groups.

Their earlier work examined the evolution of collective perception, cooperation and decision making. In the new study, however, they emphasized communication and selected for groups of Avidians that best synchronized their flashing with others.

Fireflies, which coordinate their blinking across distances spanning miles, are the best-known synchronized communicators of the biological world. How they do it isn't fully understood, but Knoester said "it was literally a three- or four-line change" in Avida.

Crucial to Avidian synchronization was the handling of the computational version of "junk DNA," or genetic code that seems to have no apparent purpose. In biology, junk DNA is now appreciated as having crucial regulatory functions. In the Avidians, individuals evolved to change their flash timing by adjusting the speed at which "junk" instructions were executed.

McKinley and Knoester don't think that fireflies necessary synchronize the same way, as Avida provided a computational and likely different route to the same outcome. More importantly, it gave the researchers algorithms they would not have otherwise imagined.

The algorithms could inspire functional code beyond Avida's confines.

"Avidians build network topologies. What sort of topologies do they come up with that are robust to damage, if the routing nodes fail?" Knoester said. "We're also collaborating with a professor in the electrical engineering department who works on robotic fish. We're not really interested in schooling; we want robots to track oil slicks, to monitor water quality. To do those things, you need to stay connected."

As for the upper limit on Avidian complexity, "I'm not sure we know yet," Knoester said.

Video: Organisms in Avida, a software platform for artificial life, running their genomic instructions. Eventually they evolve to flash in synchrony, like fireflies./Philip McKinley and David Knoester.

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Citation: "Evolution of Synchronization and Desynchronization in Digital Organisms." By David B. Knoester and Philip K. McKinley. Online publication, November 18, 2010.

Brandon's Twitter stream, reportorial outtakes and citizen-funded White Nose Syndrome story; Wired Science on Twitter.

Friday, 26 November 2010

Johnald's Fantastical Daily Link Splurge

Johnald's Fantastical Daily Link Splurge


Extragalactic Exoplanet Found Hiding Out in Milky Way

Posted: 18 Nov 2010 03:20 PM PST

Some extrasolar planets are truly out of this world.

Astronomers have for the first time discovered a planet in the Milky Way that came from another galaxy. The planet, which has a mass of at least 1.25 Jupiters, orbits an elderly star that was ripped from a small satellite galaxy some 6 to 9 billion years ago.

Johny Setiawan and Rainer Klement of the Max Planck Institute for Astronomy in Heidelberg, Germany, describe the finding online November 18 in Science.

"The coolness factor is definitely that the planet and star came from another galaxy," says Sara Seager of MIT, who was not part of the study. "The planet almost certainly formed during the time the star was in the other galaxy."

 

In hunting for extrasolar planets, Setiawan and his colleagues homed in on HIP 13044, about 2,000 light-years from Earth, because it's part of a stream of stars called Helmi, believed to have originated in another galaxy. The star's motion could also be monitored for many months each year with a spectrograph at the European Southern Observatory's La Silla site in Chile, looking for telltale wobbles that would indicate the tiny tug of an unseen, orbiting planet.

HIP 13044 and the other stars in the Helmi stream stand out in the solar neighborhood because they have elongated orbits that take them about 42,000 light-years above and below the plane of the Milky Way's disk. Such orbits strongly suggest the stars were part of a group torn from a satellite galaxy and stretched out by gravitational tidal forces into a filament or stream.

The discovery, notes planet hunter Scott Gaudi of Ohio State University in Columbus, "is doubly weird: It is a weird planet around a weird star." The star is unusual because it has the lowest abundance of metals — about 1 percent of the sun's — of any star known to have a planet. (In astronomical parlance, a metal refers to any element heavier than helium.) The vast majority of the roughly 500 extrasolar planets known are found around stars with a much higher metal abundance, and the leading theory of planet formation suggests that stars with high metal contents are those that form giant, Jupiter-like planets.

Also unusual is that HIP 13044 is old enough to have exhausted its supply of hydrogen fuel and passed through the red giant phase of evolution, in which it mushroomed in size. Since then the star contracted to a diameter about seven times that of the sun and is now burning helium at its core. A star in this phase of evolution, known as the red horizontal branch, has never before been found to have a planet.

In part, that's because the enhanced activity of old, evolved stars, including the presence of magnetically driven disturbances known as starspots, makes it more difficult to discern a stellar wobble, says Setiawan. In addition, "there is a high risk that you will not find any planets because they have been engulfed by the star during the [red giant] evolutionary phase," he adds.

In order to survive, HIP 13044's planet, which now resides much closer to the star than Mercury does to the sun, must have originally orbited at a much greater distance, the researchers say. That's the only way it could have escaped being swallowed during the time the star was a red giant. (In several billion years, the sun will also become a puffed-up red giant and is likely to engulf Earth and the other inner planets.)

Other planets that resided closer to HIP 13044 would not have been so lucky. One explanation for the star's relatively rapid rate of rotation is that it has been spun up by the angular momentum of planets it swallowed. Other rapidly rotating, elderly stars that have evolved to the red horizontal branch may have had similar dining habits, researchers have previously noted.

Even though the newfound planet has dodged one bullet, it will soon face another. In a few million years, when the star exhausts all the helium forged at its core, it will undergo a more rapid and larger expansion in which the planet is likely to be destroyed.

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Thursday, 25 November 2010

Johnald's Fantastical Daily Link Splurge

Johnald's Fantastical Daily Link Splurge


How to Make an All-Instant Thanksgiving Dinner

Posted: 24 Nov 2010 10:22 AM PST

It's the day before Thanksgiving, and you forgot to reserve a turkey. Or maybe you are short on time, or just really lazy and don't want to actually cook the meal. Either way, modern food science has the entire turkey day menu covered: Just add water.

We put together an all-instant menu, made up of only room-temperature foodstuffs requiring, at most, boiling water or a microwave to prepare. No baking, barbecuing, broiling, frying, grilling, roasting, sauteing or stewing necessary.

When it comes to instant gratification, freeze-drying is king, we're told by Washington State University food engineer Juming Tang. And it preserves flavor while making food inhospitable to bacteria.

"It was developed in the 1950s, and gives you the highest quality product over canning, pickling and other food-preservation techniques," Tang said. "But it's also the most expensive, about three to 10 times as much."

So if you are ready to boil and microwave your way out of any kind of really labor-intensive Thanksgiving preparations, here's what you need.

Turkey

You must abandon the idea of a glistening, crispy skinned bird sitting on the dinner table. No room-temperature substitute comes close. But if there must be turkey, your options abound.

Ideally, you've already saved some cooked turkey for a rainy day by freeze-drying it. A more readily available choice is canned turkey, but it's not a good sign when turkey products for your cat or dog (usually made from industrial food factory offal) overwhelm the human selection.

Beyond that, your best bet is an MRE, or "Meal, Ready to Eat," developed by food scientists to feed troops hot dishes on the front line. Simply pour a little water in a magnesium-filled pouch for an exothermic reaction, and let 'er cook.

As a last resort, take a hike to your local gas station for some turkey jerky.

 

Gravy

Kitchen wars have been fought over what gravy is, exactly, but we think it should be brownish, salty, gooey and bad for you.

Gravy cubes, gravy powder and cans of gravy make it one of the easiest Thanksgiving sides to instantly produce, but we vote for the canned species. That's because they're less likely to contain strange ingredients such as hydrogenated oils, monosodium glutamate, sulfiting agents, anti-caking agents, artificial colors and the ever-mysterious "artificial flavoring." But if you like that sort of thing, go for the powder.

Stuffing

Homemade stuffing calls for a lot of toasting and mixing and baking, but we don't have time for that. Grab any preservative-rich box of the instant variety, plus some butter (see below), and add boiling water.

Butter

Whoever said turkey is the essential element to any Thanksgiving dinner never looked at the ingredients list. Butter sneaks it way onto just about every fixin', especially dessert.

The average stick of butter lasts only a few months in a refrigerator, but powdered butter lasts for about 5 years. That's because it's a dry powder, and bacteria need water to thrive. Go ahead and grab the big can — you'll need it.

Cranberry Sauce

Don't over-think this one. Secure a can of gelatin-infused cranberry sauce and be merry.

Mashed Potatoes

You will have no problem securing some instant mashed potatoes, thanks again to the wonders of freeze-drying.

Green Bean Casserole

Merge one can of French-style green beans with one can of cream of mushroom soup, then top with FUNYUNS® or some other mysterious fried onion substitute. Not your grandmother's recipe, but it's functional.

Candied Yams

Replicating the crusty-gooey mouth feel of yams, brown sugar and marshmallows without an oven isn't impossible.

If you're boiling water on the stove top for another dish, roast the marshmallows on a stick over the flames, then drop them onto the yam and brown sugar mixture. Better yet, cram your dish into the microwave and watch the marshmallows turn into goo.

Bread

Who needs the yeasty aroma of fresh-baked bread when you've got bread-in-a-can?

Pie

Making a pie using by only adding water may sound ludicrous, but it's as easy as… not baking a pie.

For the crust, mash up vanilla wafers or graham crackers, drip in a few tablespoons of butter and shape the mix into a proper pie-filling receptacle.

Opinions on essential Thanksgiving pie fillings vary, but whatever you're making, gelatin — collagen extracted from ground-up animal bones, hides and skin — is your friend. Mix spices, primary filling (e.g. canned pumpkin), condensed milk, reconstituted eggs (see below) and any other ingredients into some water and gelatin, heat it in the microwave for a bit, then dump it into your crust.

Cooling helps gelatin molecules solidify into a wiggly matrix, so take advantage of chilly weather by setting the pie outside.

Eggs

A few dinner menu staples call for eggs as a binding agent, especially the pies. Thanks again to freeze-drying methods, there's a powder for that.

Whipped Cream

We don't know what's in it, but whipped cream powder is out there.

To play it on the safer side, get some freeze-dried heavy cream powder, add water and whip it up with an electric beater.

If we missed anything, let us know in the comments. And if anyone actually makes the Wired.com instant Thanksgiving dinner, send a photo to @wiredscience on Twitter.

Images: 1) Flickr/Mr. T 2) Flickr/Paul Pellerito 3) PackItGourmet.com 4) Flickr/pinprick 5) Flickr/sandwichgirl

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How to Catch Microbes Hitchhiking to Mars

Posted: 24 Nov 2010 09:31 AM PST

Microbial stowaways on Mars rovers could raise false alarms for astrobiologists hoping to find evidence of life — or worse, could wipe out native Martians waiting in the soil. A new study suggests that current techniques for cleaning Mars rovers could let some of the hardiest life forms, single-celled salt-lovers and tiny animals called tardigrades, slip through.

"We might actually select for these organisms," said Adam Johnson, a graduate student at Indiana University and lead author of a paper to be published in the journal Icarus. "They would be the most likely thing to be able to survive."

Johnson and colleagues subjected some of Earth's toughest life forms from the most extreme environments they could find to 40 days in a mockup Mars environment.

The subjects included bacteria from Siberian permafrost; single-celled microorganisms called haloarchaea from briny saltwater in Mexico; yeastlike organisms from cold saline springs in the Canadian arctic; and tardigrades (also known as water bears), the world's toughest multicellular animal, which have been known to survive trips into space.

"We threw a lot of organisms at the experiment," Johnson said. "A lot of studies just focus on one, but we really just threw the kitchen sink at it."

 

The researchers cooked up a batch of simulated Martian soil, called regolith, from volcanic basalt rocks taken from two different outcrops in Oregon. They baked the mixture for 12 hours at 750 degrees Fahrenheit to make sure it was free of organic materials.

Then they mixed carefully measured samples of the organisms into the soil, and let the concoction sit in a glass chamber meant to simulate the Martian atmosphere for a week. After that first week, Johnson set the chamber to mimic the daily temperature variations, solar cycle and ultraviolet radiation at the Martian surface for 40 days.

Earlier studies had found that the single biggest threat to Earthly microbes was ultraviolet radiation, but being buried in just a millimeter of soil could protect organisms enough to keep them alive.

Johnson and colleagues expected organisms that like extreme cold, called psychrophiles, to fare best in the negative-40-degree Martian nights.

Surprisingly, cold-loving critters dropped off quickly in their first week in the chamber, when temperatures were held at a balmy 50 degrees Fahrenheit.

"Really temperature and atmosphere doesn't matter," Johnson said. "It seemed to be the actual conditions of the regolith and [the organisms] themselves that determined the chance of survival."

Most of the creatures died from drying out, or from the harsh chemical conditions in the fake Martian soil.

"They become almost mummified," Johnson said. "It looks like organisms go almost into a freeze-dried type state."

The only organisms that made it were the salt-loving haloarchaea from Mexico, and the hardy tardigrades. Tardigrades can slow down their metabolisms by a factor of 10,000 under harsh conditions, allowing them to dry up without dying. Based on their success in the simulated Mars chamber, Johnson thinks they could last more than 300 days on Mars.

"This is the first study where we've actually shown that an organism could potentially last for several hundred days on the surface of Mars," he said.

Current techniques for sterilizing spacecraft use dry-heat treatments and chemicals similar to those that could be produced in the Martian soil. Whatever organisms survive those treatments are also the most likely things to survive and thrive once they reach Mars, Johnson said.

"Everybody knows that this is not the greatest way to go about it, but that's the way they do it," said astrobiologist Rocco Mancinelli of the SETI Institute, a coauthor of the paper. "I personally think it has to be revamped."

"This paper points out the need for ongoing re-examination and updating of sterilization and detection methods used for planetary protection purposes during cleaning and preparation of spacecraft," said Margaret Race of the SETI Institute, who studies how best to avoid contaminating Mars with earthly life, and vice versa, but was not involved in the new study. "We are continuing to find microorganisms that surprise us in their hardiness."

Image: Brett's Blog

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Aerial Art Sends Climate Message

Posted: 24 Nov 2010 09:18 AM PST

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With a series of large-scale artworks visible from above, activists at 350.org hope to harness the power of aerial imagery to raise environmental consciousness beyond the local, drawing attention to climate policy in ways that statistics do not.

The organization's name comes from what climate scientists say is the upper limit on atmospheric carbon dioxide levels. Beyond 350 parts per million, climate change will likely outpace the ability of natural and human systems to adapt. As of now, atmospheric CO2 is about 390 ppm.

The artworks precede next week's United Nations climate-policy meeting in Cancun, where negotiators will try to strike a global deal on fossil fuel emissions. Their last attempt, in Copenhagen one year ago, ended in failure.

Since then, the global weather has become even weirder, with extreme events — heat waves in Russia, floods in South Asia, megastorms on the U.S. East Coast — fitting predicted climate-change patterns. In the United States, still the world's major producer of greenhouse gases, a bipartisan climate-change bill failed.

It's easy to become cynical about the situation. But the people filling a dry riverbed in these images and forming other symbolic messages in the other images in this gallery still have hope.

Top: Girl Scouts, church groups and other local citizens in Santa Fe, New Mexico, stand with blue tents and posters in the Santa Fe riverbed./DigitalGlobe and 350.org. Bottom: Don Usner/350.org

<< Previous | Next >>

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Brandon's Twitter stream, reportorial outtakes and citizen-funded White Nose Syndrome story; Wired Science on Twitter.

Pulsing Stars Could Fill in for GPS Satellites

Posted: 24 Nov 2010 08:57 AM PST

To find your favorite coffee shop in an unknown city, getting directions via satellite works like a charm. But that technology won't get you from Earth to Jupiter.

So theorists have proposed a new type of positioning system based on blinking stars instead of satellites. By receiving radio blips from pulsars, stars that emit radiation like clockwork, a spacecraft above the atmosphere could figure out its place in space.

Unlike the Global Positioning System of satellites used in cars and smart phones, the pulsar positioning system wouldn't need humans to make daily corrections.

"You could be on a spacecraft and you could be able to navigate without having any help from Earth," says Angelo Tartaglia, a physicist at the Polytechnic University of Turin in Italy.

 

Though the navigation system proposed by Tartaglia and colleagues is just a proof of concept, a GPS-like system under construction in Europe called Galileo could implement the ideas within a decade, he says.

The principle behind the pulsar positioning is not too different from ordinary GPS. The GPS receiver in a car or phone receives radio signals from satellites orbiting the Earth. The satellites are synchronized with atomic clocks to emit signals simultaneously. Because the satellites are all different distances from the receiver, each message reaches the device at a different time. From those time differences, a GPS device infers the distance to each satellite, and hence can calculate its own position. The best consumer devices can pinpoint your location to within a meter under ideal conditions, but tall buildings or other interference can throw them off by 10 to 20 meters or more.

Because the satellites move so fast (they orbit the Earth twice every day), Einstein's special theory of relativity must be considered. Relativity requires that clocks on board tick slower than those on Earth. After two minutes, the satellite's clocks are already out of sync with Earth clocks. Transmitting the correct time to each satellite is a constant chore for the Department of Defense, which determines the real time from an ensemble of clocks on Earth.

A pulsar's regular blips can be used to tell time just like the signals received from GPS satellites. But the math in the new pulsar-based system already accounts for relativity, so those corrections aren't necessary. Pulsars, the dense leftovers of supernovae that sweep beams of radiation from their poles, serve as really good clocks, in some cases comparable to atomic clocks. Plus, a pulsar doesn't move much relative to the Earth in the time between its pulses, and the distance it does move over several months is predictable.

Instead of tracking real pulsars, the Italian team simulated its proposed navigation system on computers by using software that mimics pulsar signals as if they were received at an observatory in Australia. The researchers recorded these fake pulses every 10 seconds for three days. Inferring the distance between the pulsars and the observatory, the team tracked the trajectory of the observatory on the Earth's spinning surface to an accuracy of several nanoseconds, or the equivalent of several hundred meters, the team reported in a paper posted at arXiv.org on October 30.

Pulsars are extremely weak sources, however, and detecting them normally requires a large radio telescope—a heavy payload for spacecraft. So the researchers propose to create their own sources of pulsing radiation by planting bright radio wave emitters on celestial bodies like Mars, the moon or even asteroids. At least four sources have to be visible at a time to determine a position in the three dimensions of space and one dimension of time. Including just one particularly bright radio pulsar outside the plane of the solar system would be ideal because it would be the tip of a tetrahedron, a configuration that would make calculations more accurate, Tartaglia says.

Or, you could look for pulsars that emit X-rays, a much brighter signal. X-ray antennas are also smaller and lighter, says physicist Richard Matzner at the University of Texas at Austin. Their drawback is oversensitivity to electrons surrounding the Earth. But an X-ray–based positioning system could pinpoint an object to within 10 meters, an improvement on the 100-meter or so accuracy of the radio pulsar system.

Either system would be accurate enough to track a spacecraft speeding at 19,000 meters per second, the maximum speed the exploratory spacecraft Cassini reached zipping past the Earth in 1999 on its way to Saturn. It's easy to calculate a satellite's position along the line of sight by measuring Doppler shift —the change of frequency with an object's speed — but more difficult to create a three-dimensional picture of a spacecraft trajectory, says Scott Ransom, an astronomer at the National Radio Astronomy Observatory in Charlottesville, Va. A pulsar system could track those three dimensions and detect if the spacecraft was straying from its course.

Pulsar-based systems may not be as precise as GPS, but they could be a backup system for GPS if the ground control for the satellites fails.

"It would be better than nothing," says Matzner. "It's an insurance policy."

Image: A Chandra X-ray observatory image of the Crab Nebula's pulsar. NASA/CXC/SAO/F. D. Seward, W. H. Tucker, R. A. Fesen

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