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.
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

"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.

"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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Photos: Month in Space: January 2014

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    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
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  6. Supersonic test flight

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    More about SpaceShipTwo on PhotoBlog (Virgin Galactic) Back to slideshow navigation
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    Slideshow: The Year in Space (Brian Peterson / The Bismarck Tribune via AP) Back to slideshow navigation
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