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This image depicts a laser-shock experiment on Earth that recreated conditions deep within the planet as part of the study.
Eugene Kowaluk, University of Rochester
This image depicts a laser-shock experiment on Earth that recreated conditions deep within the planet as part of the study.
By
updated 11/23/2012 1:32:34 PM ET 2012-11-23T18:32:34

Within supersized alien versions of Earth, a common transparent ceramic may become a flowing liquid metal, perhaps granting those distant worlds magnetic fields to shield life from harmful radiation, researchers say.

Among the hundreds of extrasolar planets, or exoplanets, that astronomers have discovered in recent years are so-called " super-Earths," which are rocky planets like Earth but larger, at up to 10 times its mass. Scientists have discovered super-Earths that may support oceans of water on their surfaces on their surfaces, and others that may even be planets made of diamond.

The increased mass of super-Earths would bring about internal pressures much greater than Earth's. Such high pressures would lead to large viscosities and high melting temperatures, meaning the interiors of super-Earths might not separate into rocky mantles and metallic cores like Earth's does.

Earth's magnetic field results from its flowing liquid metallic core. If super-Earths lack such dynamic cores, investigators suggested they might lack magnetic fields as well. [ The Strangest Alien Planets (Photos) ]

Now, researchers find that magnesium oxide, a common rocky mineral on Earth, can transform into liquid metal at the extreme pressures and temperatures found in super-Earths. This fluid metal could help generate magnetic dynamos in super-Earths, they say.

Magnesium oxide is a transparent ceramic found from Earth's surface to its deepest mantle. To see how this rocky material might behave in alien planets, researchers fired powerful lasers at small pieces of magnesium oxide, in just 1 billionth of a second, heating and squeezing this mineral to conditions found inside super-Earths, such as pressures up to 14 million times normal Earth atmospheric pressure and temperatures as high as 90,000 degrees Fahrenheit (50,000 Celsius). They watched this rocky substance change to a solid with a new crystal structure, and finally into a liquid metal.

"What was most surprising was how well-behaved magnesium oxide is in the laboratory," said lead study author R. Stewart McWilliams, a geophysicist at the Carnegie Institution of Washington. "The physical properties of magnesium oxide look very similar to what has been predicted for decades by theorists. As scientists, we can't ask for much better."

These findings might blur the distinction between planetary cores and mantles.

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"For many decades we have usually imagined terrestrial planets — the Earth, its neighbors such as Mars, and distant super-Earths — as all having Earth-like properties: that is, they have a outer shell or mantle composed of nonmetallic oxides, and an iron rich core which is metallic and from which planetary magnetic fields originate," McWilliams told SPACE.com.

"This rule is central to our thinking about super-Earths, yet it is clearly anthropocentric — that is, we are applying what we know from our own observations on Earth to remote planets for which we can observe very little — and, as for many anthropocentric ideas, we are finding that more imagination is needed to understand such alien worlds.

"Our results show that the usual assumption that planetary magnetic fields originate exclusively in iron cores is too limiting," McWilliams said. "Magnetic fields might also form within planetary mantles. In fact, this idea has been speculated on for decades, but now we have hard data to show that, indeed, such a 'mantle-dynamo' is plausible."

Earth's magnetic field helps protect it from hazardous electrically charged particles from space.

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"It is often said that life on planets may require the presence of a strong magnetic field to protect organisms from dangerous radiation from space such as cosmic rays — at least this may be true for certain types of life, similar to humans, that live on a planet's surface," McWilliams said. "We find that magnetic fields may occur on a wider range of planets than previously thought, possibly creating unexpected environments for life in the universe."

McWilliams noted that much remains unknown about the physics of super-Earths, and that researchers need to generate computer models to see where and how this liquid metal might exist in nature.

"Everyone, both scientists and the public, should keep in mind that super-Earths are, and probably will remain for some time, a big mystery," McWilliams said. "It is easy to speculate as to their properties — to draw a picture of one, for example — but quite difficult to make certain conclusions such as we have for our own Earth. This is both exciting and daunting — there are many possibilities to explore, but scientists have much work to do. We hope the public has a lot of patience."

The scientists detailed their findings online today (Nov. 22) in the journal Science.

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© 2013 Space.com. All rights reserved. More from Space.com.

Photos: Month in Space: January 2014

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  1. Southern stargazing

    Stars, galaxies and nebulas dot the skies over the European Southern Observatory's La Silla Paranal Observatory in Chile, in a picture released on Jan. 7. This image also shows three of the four movable units that feed light into the Very Large Telescope Interferometer, the world's most advanced optical instrument. Combining to form one larger telescope, they are greater than the sum of their parts: They reveal details that would otherwise be visible only through a telescope as large as the distance between them. (Y. Beletsky / ESO) Back to slideshow navigation
  2. A balloon's view

    Cameras captured the Grandville High School RoboDawgs' balloon floating through Earth's upper atmosphere during its ascent on Dec. 28, 2013. The Grandville RoboDawgs’ first winter balloon launch reached an estimated altitude of 130,000 feet, or about 25 miles, according to coaches Mike Evele and Doug Hepfer. It skyrocketed past the team’s previous 100,000-feet record set in June. The RoboDawgs started with just one robotics team in 1998, but they've grown to support more than 30 teams at public schools in Grandville, Mich. (Kyle Moroney / AP) Back to slideshow navigation
  3. Spacemen at work

    Russian cosmonauts Oleg Kotov, right, and Sergey Ryazanskiy perform maintenance on the International Space Station on Jan. 27. During the six-hour, eight-minute spacewalk, Kotov and Ryazanskiy completed the installation of a pair of high-fidelity cameras that experienced connectivity issues during a Dec. 27 spacewalk. The cosmonauts also retrieved scientific gear outside the station's Russian segment. (NASA) Back to slideshow navigation
  4. Special delivery

    The International Space Station's Canadian-built robotic arm moves toward Orbital Sciences Corp.'s Cygnus autonomous cargo craft as it approaches the station for a Jan. 12 delivery. The mountains below are the southwestern Alps. (NASA) Back to slideshow navigation
  5. Accidental art

    A piece of art? A time-lapse photo? A flickering light show? At first glance, this image looks nothing like the images we're used to seeing from the Hubble Space Telescope. But it's a genuine Hubble frame that was released on Jan. 27. Hubble's team suspects that the telescope's Fine Guidance System locked onto a bad guide star, potentially a double star or binary. This caused an error in the tracking system, resulting in a remarkable picture of brightly colored stellar streaks. The prominent red streaks are from stars in the globular cluster NGC 288. (NASA / ESA) Back to slideshow navigation
  6. Supersonic test flight

    A camera looking back over Virgin Galactic's SpaceShipTwo's fuselage shows the rocket burn with a Mojave Desert vista in the background during a test flight of the rocket plane on Jan. 10. Cameras were mounted on the exterior of SpaceShipTwo as well as its carrier airplane, WhiteKnightTwo, to monitor the rocket engine's performance. The test was aimed at setting the stage for honest-to-goodness flights into outer space later this year, and eventual commercial space tours.

    More about SpaceShipTwo on PhotoBlog (Virgin Galactic) Back to slideshow navigation
  7. Red lagoon

    The VLT Survey Telescope at the European Southern Observatory's Paranal Observatory in Chile captured this richly detailed new image of the Lagoon Nebula, released on Jan. 22. This giant cloud of gas and dust is creating intensely bright young stars, and is home to young stellar clusters. This image is a tiny part of just one of 11 public surveys of the sky now in progress using ESO telescopes. (ESO/VPHAS team) Back to slideshow navigation
  8. Fire on the mountain

    This image provided by NASA shows a satellite view of smoke from the Colby Fire, taken by the Multi-angle Imaging SpectroRadiometer aboard NASA's Terra spacecraft as it passed over Southern California on Jan. 16. The fire burned more than 1,863 acres and forced the evacuation of 3,700 people. (NASA via AP) Back to slideshow navigation
  9. Where stars are born

    An image captured by NASA's Spitzer Space Telescope shows the Orion Nebula, an immense stellar nursery some 1,500 light-years away. This false-color infrared view, released on Jan. 15, spans about 40 light-years across the region. The brightest portion of the nebula is centered on Orion's young, massive, hot stars, known as the Trapezium Cluster. But Spitzer also can detect stars still in the process of formation, seen here in red hues. (NASA / JPL-Caltech) Back to slideshow navigation
  10. Cygnus takes flight

    Orbital Sciences Corp.'s Antares rocket rises from NASA's Wallops Flight Facility on Wallops Island, Va, on Jan. 9. The rocket sent Orbital's Cygnus cargo capsule on its first official resupply mission to the International Space Station. (Chris Perry / NASA) Back to slideshow navigation
  11. A long, long time ago...

    This long-exposure picture from the Hubble Space Telescope, released Jan. 8, is the deepest image ever made of any cluster of galaxies. The cluster known as Abell 2744 appears in the foreground. It contains several hundred galaxies as they looked 3.5 billion years ago. Abell 2744 acts as a gravitational lens to warp space, brightening and magnifying images of nearly 3,000 distant background galaxies. The more distant galaxies appear as they did more than 12 billion years ago, not long after the Big Bang. (NASA / NASA via AFP - Getty Images) Back to slideshow navigation
  12. Frosty halo

    Sun dogs are bright spots that appear in the sky around the sun when light is refracted through ice crystals in the atmosphere. These sun dogs appeared on Jan. 5 amid brutally cold temperatures along Highway 83, north of Bismarck, N.D. The temperature was about 22 degrees below zero Fahrenheit, with a 50-below-zero wind chill.

    Slideshow: The Year in Space (Brian Peterson / The Bismarck Tribune via AP) Back to slideshow navigation
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