From Ed Yong:

In 1996, a loggerhead turtle called Adelita swam across 9,000 miles from Mexico to Japan, crossing the entire Pacific on her way. Wallace J. Nichols tracked this epic journey with a satellite tag. But Adelita herself had no such technology at her disposal. How did she steer a route across two oceans to find her destination?

Nathan Putman has the answer. By testing hatchling turtles in a special tank, he has found that they can use the Earth’s magnetic field as their own Global Positioning System (GPS). By sensing the field, they can work out both their latitude and longitude and head in the right direction.

By testing turtle hatchlings in a tank surrounded by magnets he could control, Putman showed turtles could sense it if he reversed the magnetic field around them and would begin heading in the opposite direction.

For more about the experiment—and how turtles can travel so far at such high stakes with just magnetism to guide them—check out the rest of Ed’s post at Not Exactly Rocket Science.

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Image: Wikimedia Commons

NASA’s next rendezvous with the Red Planet got the go-ahead this week. The space agency approved development of MAVEN, the Mars Atmosphere and Volatile Evolution mission, which is scheduled to launch in November 2013.

In the last decade, missions like the Phoenix Lander, the Spirit and Opportunity rovers, and the Mars Express have reinforced the case that our neighbor was once watery, and far more hospitable to life than the planet we see today. The ancient evidence of liquid water suggests that the planet once had a dense atmosphere, which is now long gone. MAVEN’s mission is to investigate the interaction between Mars’s now-thin atmosphere and the solar wind, and to look for clues to how and when the sun stripped away the planet’s thick atmosphere.

Many researchers think that Mars’s loss of its magnetic field billions of years ago started the process.

“Mars can’t protect itself from the solar wind because it no longer has a shield, the planet’s global magnetic field is dead,” said [lead investigator Bruce] Jakosky, describing how the magnetic field disappeared and the atmosphere then exposed to the punishing solar wind. [AFP]

For more details about MAVEN, check out our coverage from 2008, when NASA first announced the mission. The team’s critical design review will come next July, which could be the true make-or-break time for the mission.

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Image: NASA

Chalk up one more mind-blowingly beautiful Saturn image to the Cassini spacecraft. The fruitful mission beamed home this stunner as part of a video of the auroras on the sixth planet.

Auroras on Saturn form like those on Earth, when charged particles in the solar wind stream down the planet’s magnetic field towards its poles, where they excite gas in the upper atmosphere to glow. Some auroras on the ringed planet are also triggered when some of its moons, which are electrically conducting, move through the charged gas surrounding Saturn. [New Scientist]

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Had compass-toting Boy Scouts existed around fifteen million years ago, they may have had a fun time making it through the forest. New geological research questions if the Earth’s magnetic field changed, at that time, at the remarkable pace of one degree per week, leading to a particularly fast magnetic pole flip.

In a paper to appear in Geophysical Research Letters, Scott Bogue and Jonathan Glen suggest that the Earth’s magnetic field changed 53 degrees in one year’s time, based on their study of preserved lava flows in Nevada. As the solid rock formed from cooling liquid lava, it preserved a pattern corresponding to the “super-fast” geomagnetic field reversal, the researchers believe. This is the second time that Bogue has controversially argued for the existence of such speedy flips, finding hints of a faster one in 1995.

In 1995 an ancient lava flow with an unusual magnetic pattern was discovered in Oregon. It suggested that the field at the time was moving by 6 degrees a day–at least 10,000 times faster than usual. “Not many people believed it,” says Scott Bogue of Occidental College in Los Angeles. [New Scientist]

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They went to investigate solar wind-stirred storms in our planet’s magnetic field, but, after working for three years, two NASA solar-powered probes faced a dark demise, trapped in the Earth’s shadow. NASA researchers now think they can give the twin satellites another shot by altering their courses and sending them instead to study the moon.

NASA launched the probes in 2007 as a set of five identical satellites in the THEMIS Mission (Time History of Events and Macroscale Interactions during Substorms), meant to orbit Earth and send information during brief (2-3 hour) “substorms” when the magnetic field surrounding the Earth releases stored energy from solar winds. To understand the start of these “space tornadoes” responsible for the northern and southern lights, NASA placed the probes in very precise orbits, but for two craft that meant, one day, they would face prolonged battery-draining time in the Earth’s shadow.

“When we realized that the satellites would be going into very deep shadows, we started thinking of different methods for saving them–even before they were launched,” lead scientist Vassilis Angelopoulos, at the University of California, Berkeley, told Discovery News. “We realized that if we had enough fuel to change their orbits, the moon’s gravity would start pulling them up.”[Discovery News]

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Here we are drinking coffee and tweeting and otherwise going about our lives, generally not giving much thought to the protection that the Earth’s magnetic field affords us from the solar wind. But that magnetic field is crucial for our existence. Now, new findings in Science say that this protective shield originated even 200 million years earlier than scientists had previously thought, perhaps protecting the planet’s water from evaporating away and aiding the rise of life on the early Earth.

To know about the planet’s magnetic field three and a half billion years ago, you need iron, which records not only the direction but also the strength of the magnetic field when it forms. In South Africa, study leader John Tarduno and his team found quartz with iron tucked inside that had remained unchanged in all those years. Using a specially designed magnetometer and improved lab techniques, the team detected a magnetic signal in 3.45-billion-year-old rocks that was between 50 and 70 percent the strength of the present-day field, Tarduno says [Science News]. Three years ago he made a similar find in rocks 3.2 billion years old; thus, this find pushes back the Earth’s magnetic field at least another 200 million years.

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Some migratory birds that have to navigate across continents have an extremely useful tool at their disposal–an internal compass that points unerringly towards magnetic north. Researchers already knew that some birds possess these biological compasses, but their mechanism has been unclear. “This is basically the sixth sense of biology, but no one knows how it works…. The magnetic sense is by far the least understood sense in the natural world,” [Science News], says study coauthor Henrik Mouritsen.

Now, researchers have determined that light-sensing cells in the eye convey the crucial message to a special visual center of a robin’s brain, called cluster N. Special proteins called cryptochromes in the birds’ eyes may mediate this light-dependent magnetic sensing, Mouritsen says. Light hitting the proteins produces a pair of free radicals, highly reactive molecules with unpaired electrons. These electrons have a property called spin which may be sensitive to Earth’s magnetic field. Signals from the free radicals may then move to nerve cells in cluster N, ultimately telling the birds where north is [Science News].

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To zero in on air pollution, just follow the magnetic tree leaves.

That’s the conclusion of an odd new study, which determined that the microscopic metallic particles spewed out of tailpipes and smokestacks actually magnetize the nearby leaves they settle on and adhere to. The study found that the leaves from trees along heavily traveled bus routes were up to 10 times more magnetic than leaves from little traveled roads. The pollution can be detected easily and on the cheap with magnets, according to the study’s authors. Even “a strong magnet wouldn’t [attract] the leaf, but it definitely gives you a detectable signal” [National Geographic News], says researcher Bernie Housen.

The authors admit that finding more pollution along bus routes isn’t exactly shocking, but their efforts may help local communities pinpoint and clean up places that have an abundance of air pollution, especially at places where people spend time outdoors, like on bike trails and walking paths. The research team says that using magnets would be an advance in pollution detection because conventional tests for measuring the amounts of these tiny particles are often expensive and time-consuming [National Geographic News]. The study was presented at the Geological Society of America conference in Portland, Oregon.

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Image: flickr / d_vdm

Mix one part science fiction, one part misunderstood Mayan history, one part Hollywood movie hype, and quite a bit of public credulity, and what do you get? A new wave of doomsday hysteria that is causing scientists to step forward to reassure the public that the world is not, actually, going to end on December 21, 2012.

The rumors flying around the Internet offer a number of ways in which the world may end, including a planetary collision and changes to the Earth’s rotation or magnetic field, but they all agree on that date of doom. You can bet that the viral marketing campaign promoting the upcoming planetary disaster movie 2012 has a little something to do with the recent uptick in paranoia.

“Two years ago, I got a question a week about it,” said NASA scientist David Morrison, who hosts a website called Ask an Astrobiologist. “Now I’m getting a dozen a day. Two teenagers said they didn’t want to see the end of the world so they were thinking of ending their lives” [Los Angeles Times]. In response, Morrison put together a list [pdf] of 10 frequently asked questions about the potential for apocalypse, and refuted them one by one. The clamor has grown so loud that Morrison coined a new word to describe the phenomenon: “cosmophobia,” a fear of the cosmos.

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Magnets may have seemed simple when you learned about them in elementary school, but physicists are coaxing some very odd behaviors out of magnetic materials these days. In the latest new development, scientists created the magnetic equivalent of electricity and named the phenomenon “magnetricity.” In the same way that electrically charged particles flow to create an electric current, individual north and south magnetic poles have been observed flowing along to generate a magnetic current.

The basis of the experiment was a refutation of a rule of magnetism observed in our day-to-day lives: No matter how many times you divide a magnet, the resulting fragments will always have both north and south poles. But more than 70 years ago, physicist Paul Dirac theorized that elementary particles should exist that have only a north or south pole, and dubbed these theoretical particles magnetic monopoles. Last month, researchers got closer to spotting a monopole than ever before, when they created ripples that had the same magnetic properties as monopoles.

The new study, published in Nature, describes the phenomenon in a strange, crystalline material known as spin ice. These crystals are made up of pyramids of charged atoms, or ions, arranged in such a way that when cooled to exceptionally low temperatures, the materials show tiny, discrete packets of magnetic charge. Now one of those teams has gone on to show that these “quasi-particles” of magnetic charge can move together, forming a magnetic current just like the electric current formed by moving electrons [BBC News].

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In an experiment that might be classified more as a cool party trick than a scientific breakthrough, researchers levitated a mouse using a powerful superconducting magnet. Other scientists have previously levitated frogs and bugs using the same technique, but the floating mouse was the first mammal to have the honor. The trick works because the magnet generates a strong magnetic field, and because the water in the mouse’s body is weakly diamagnetic–it generates a magnetic field of its own that pushes back against the external field. Since the researchers had a strong enough magnet, the repulsive force generated by the water in each mouse cell combined to make its whole body float.

The researchers used a tiny three-week-old mouse that was only as heavy as a stack of four pennies. When the scientists levitated the youngster it appeared agitated and disoriented, seemingly trying to hold on to something. “It actually kicked around and started to spin, and without friction, it could spin faster and faster, and we think that made it even more disoriented,” said researcher Yuanming Liu…. They decided to mildly sedate the next mouse they levitated, which seemed content with floating [LiveScience]. 

The technique will be a boon for space research, the scientists say. “We’re trying to see what kind of physiological impact is due to prolonged microgravity, and also what kind of countermeasures might work against it for astronauts,” Liu said. “If we can contribute to the future human exploration of space, that would be very exciting” [LiveScience].

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Image: Da-Ming Zhu et al.

Physicists can come off like monster hunters sometimes–their theories predict that a rare beast lurks in the atomic-scale underbrush, so they forge on against all odds, determined to catch a glimpse of their quarry. The latest target is the magnetic monopole, and researchers say they’ve come closer than ever before to spotting it.

Every magnet has a north and a south pole; if you break a magnet into hundreds of pieces, each fragment will also have a north and a south pole of its own. But researchers think that magnetic monopoles exist–particles with only a north or south pole–and there are several reasons physicists would like to see them. In 1931, famed British theorist Paul Dirac argued that the existence of monopoles would explain the quantization of electric charge: the fact that every electron has exactly the same charge and exactly the opposite charge of every proton [ScienceNOW Daily News].

Scientists have scoured the world and the cosmos looking for such particles, says Jonathan Morris, coauthor of one of the two new studies published in Science. “People have been looking for monopoles in cosmic rays and particle accelerators — even Moon rocks” [Nature News], he says. And while the two research groups didn’t quite find the elusive particles, they did detect ripples in strange materials known as spin ices, and found that the ripples have the same magnetic properties as monopoles.

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When the Messenger spacecraft swooped low past the planet Mercury on October 6 2008, it gathered up a wealth of data that will have planetary scientists puzzling for years. As researchers sort through findings regarding Mercury’s volcanic past, meteor impacts, and the effect of the solar wind on the innermost planet’s magnetosphere, one broad conclusion stands out: Mercury isn’t just a boring chunk of rock. Marilyn Lindstrom, a NASA program scientist, said the Messenger findings show that Mercury is “just an amazingly dynamic planet, both in the past and in the present” [Baltimore Sun].

Superficially, Mercury looks a lot like the moon: small, grayish-brown and pockmarked with craters. Some scientists assumed that Mercury’s surface formed the same way the moon’s did, with lighter rocks rising to the surface of a magma ocean and congealing into a brittle crust early on. But the new observations reveal that 40 percent of the surface was formed by volcanoes. “Up until before Messenger’s arrival, we weren’t even sure that volcanism existed on Mercury” [Wired],  says researcher Brett Denevi. The presence of titanium oxide also suggests that the planet was hot enough in its first 100 million years to be covered in magma oceans.

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Thanks to a quintet of satellites and a backup posse of ground-based telescopes, researchers have gotten their best look ever at how auroras–also known as the southern and northern lights–begin to form in space. The dazzling light displays are provoked by “space tornadoes,” researchers say.

Whirling at more than a million miles per hour, these invisible, funnel-shaped solar windstorms carry electrical currents of more than a hundred thousand amps—roughly ten times that of an average lightning strike—scientists announced….  And they’re huge: up to 44,000 miles (70,000 kilometers) long and wide enough to envelop Earth [National Geographic News].

The observations were made as part of NASA’s THEMIS mission, which uses the satellites and telescopes to study how solar winds, the charged particles that stream from the sun, interact with the Earth’s magnetic field. On the Earth’s dark side, the solar wind stretches out the field, forming a region known as the magnetotail. The magnetotail is like a rubber band; when it is stretched too far, “eventually it snaps and releases the energy”, says team member Andreas Keiling [New Scientist]. That snap creates turbulence and forms the tornadoes, researchers announced at the European Geosciences Union meeting.

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A tiny moon rock only two inches across that was picked up by one of the last astronauts to walk on the moon has given researchers new insight into the geological history of Earth’s satellite. The rock, scooped up during the Apollo 17 mission in 1972, is about 4.2 billion years old, and shows evidence that the moon once had a molten iron core that generated a magnetic field in the satellite’s early days. The findings are forcing researchers to rethink the prevailing notion that objects smaller than Mars can’t maintain a stable magnetic field.

Many of the rocks brought back from the Moon have a faint magnetic signal, suggesting that they originally cooled from magma when the Moon had a magnetic field. That was a surprise to many scientists who thought the Moon was too small and too cold to have ever possessed a geomagnetic dynamo where electric currents from the convection of molten iron generate a field [The New York Times]. But a molten core wasn’t the only explanation for the magnetic traces; some researchers thought that an intense bombardment of meteorites and asteroids created shocks that magnetized the rocks.

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