Geologists unlock mysteries of our Earth's inner core

A research team from the University of Illinois and colleagues in China found earth's inner core has an inner core of its own, with crystals aligned in a different direction. 

Image courtesy Lachina Publishing Services.

Seismic waves are helping scientists to plumb the world's deepest mystery: the planet's inner core.

Thanks to a novel application of earthquake-reading technology, a research team at the University of Illinois and colleagues at Nanjing University in China have found that the Earth's inner core has an inner core of its own, which has surprising properties that could reveal information about our planet.

Xiaodong Song

Led by Xiaodong Song, a professor of geology at the U. of I., and visiting postdoctoral researcher Tao Wang, the team published its work in the journal Nature Geoscience on Feb. 9.

"Even though the inner core is small - smaller than the moon - it has some really interesting features," said Song.

"It may tell us about how our planet formed, its history, and other dynamic processes of the Earth. It shapes our understanding of what's going on deep inside the Earth."

Researchers use seismic waves from earthquakes to scan below the planet's surface, much like doctors use ultrasound to see inside patients.

The team used a technology that gathers data not from the initial shock of an earthquake, but from the waves that resonate in the earthquake's aftermath.

The earthquake is like a hammer striking a bell; much like a listener hears the clear tone that resonates after the bell strike, seismic sensors collect a coherent signal in the earthquake's coda.

(NB: CODA, on a recorded earthquake seismogram refers to the total length of the seismic wavetrain)

"It turns out the coherent signal enhanced by the technology is clearer than the ring itself," said Song.

"The basic idea of the method has been around for a while, and people have used it for other kinds of studies near the surface, but we are looking all the way through the center of the Earth."

Looking through the core revealed a surprise at the center of the planet, though not of the type envisioned by novelist Jules Verne.

The inner core, once thought to be a solid ball of iron, has some complex structural properties. 

The team found a distinct inner-inner core, about half the diameter of the whole inner core. 

The iron crystals in the outer layer of the inner core are aligned directionally, north-south. However, in the inner-inner core, the iron crystals point roughly east-west.

Not only are the iron crystals in the inner-inner core aligned differently, they behave differently from their counterparts in the outer-inner core.

This means that the inner-inner core could be made of a different type of crystal, or a different phase.

"The fact that we have two regions that are distinctly different may tell us something about how the inner core has been evolving," Song said.

"For example, over the history of the Earth, the inner core might have had a very dramatic change in its deformation regime. It might hold the key to how the planet has evolved. We are right in the center, literally, the center of the Earth."

NASA Mars Curiosity spots a heavy metal meteorite - Lebanon

2-meter wide iron meteorite dubbed “Lebanon,” as imaged by Curiosity’s ChemCam and Mastcam on May 25, 2014. 

Credit: NASA /JPL-Caltech /LANL /CNES /IRAP /LPGNantes /CNRS /IAS /MSSS

Talk about heavy metal! This shiny, lumpy rock spotted by NASA's Curiosity rover is likely made mostly of iron, and came from outer space!

It's an iron meteorite, similar to ones found in years past by Curiosity's forerunners Spirit and Opportunity, but is considerably larger than any of the ones the MER rovers came across… in fact, at 2 meters (6.5 feet) wide this may very well be the biggest meteorite ever discovered on Mars!

The picture above was made by combining high-resolution circular images (outlined in white) acquired with the Remote Micro-Imager (RMI) of Curiosity's ChemCam instrument with colour and context from the rover's Mastcam.

The images were taken on mission Sol 640 (May 25, 2014) and have been adjusted to simulate more Earth-like illumination.

Dubbed "Lebanon," the large meteorite has a smaller fragment lying alongside it, named "Lebanon B."

While iron meteorites are fairly common on Earth, on Mars they are by far the most common types of meteorites that have been discovered, if just for the sheer fact that they are highly resistant to erosion.

Original raw Mastcam (right) image of Lebanon and Lebanon B from Sol 640. 

Credit: NASA /JPL-Caltech /MSSS

Few asteroids are worth mining, suggests Harvard study

A new study might contain some bad news for companies hoping to mine asteroids for their valuable ores.

In the last couple of years, start-ups - including one backed by Sir Richard Branson - have announced plans to extract resources from space rocks.

But calculations by Dr Martin Elvis suggest our cosmic neighbourhood might not be such a treasure trove after all.

The Harvard astrophysicist argues just 10 near-Earth asteroids might be suitable for commercial-scale mining.

But Eric Anderson, co-founder of asteroid mining company Planetary Resources, told reporters that the values quoted in the study were off - conservatively - by a factor of 100.

Dr Martin Elvis

Dr Elvis, from the Harvard-Smithsonian Center for Astrophysics in Cambridge, US, has developed an equation to estimate the number of asteroids in the Solar System that could be exploited in a cost-effective way.

His research paper is in press at the journal Planetary and Space Science, and has been posted on the pre-print server Arxiv.org.

In 2012, Planetary Resources, backed by billionaire investors including Hollywood director James Cameron as well as Google executives Larry Page and Eric Schmidt, unveiled their vision of using robotic spacecraft to squeeze the chemical components of fuel as well as minerals out of asteroid rocks.

Several months later, the company was joined by a competitor - Deep Space Industries - which plans to use low-cost spacecraft called Fireflies and Dragonflies to reconnoitre and return samples from near-Earth asteroids.

Advocates of asteroid mining say it could turn into a trillion-dollar business, but some experts have been sceptical of the idea.

Concentrating efforts
In the latest study, Dr Elvis worked out the factors that would make an asteroid commercially viable to mine and what fraction of known space rocks met these requirements.

He emphasised there were large uncertainties in the values and called for more thorough surveys of what's out there.

He assumed that mining operations would want to focus on iron-nickel asteroids (known as M-type), considered the most promising targets for finding so-called platinum-group metals.

These include platinum, along with iridium, palladium and others.

These are rare in the Earth's crust because they dissolve in molten iron, instead being mainly concentrated in the planet's core.

Platinum and palladium are the most economically important, having a wide range of uses in industry. But according to the analysis, just 1% of near-Earth asteroids are rich in these elements.

Suitable asteroids also need to be relatively easy to reach, further narrowing the pool by ruling out all but the nearest objects to Earth.

The operative parameter here is delta-v - the change in velocity needed to send mining equipment to the target and return with a larger mass of ore.

The size of the target is also a factor; the paper suggests it wouldn't be worth mining asteroids smaller than about 100m because the total value of the ore they would produce wouldn't be enough to cover the costs of a space mission.

However, Dr Elvis points out that the ore values in his analysis range from a low of $800m to a high of $8.8bn.

"Such a large range of values could greatly change the profitability of a venture, making more accurate assays necessary," he explained.

More Information: How Many Ore-Bearing Asteroids? Arxiv.org

Scientists Discover Planet with Diamond Mantle - Twice The Size Of Our Sun

Scientists have announced the discovery of a planet made almost entirely of diamonds.

The planet, called 55 Cancri e, is located in a solar system inside the constellation of Cancer, reports NBC News.

It was discovered in 2004, and scientists have been working since then to determine its mass and radius, as well as study its host star’s composition.

The planet is called a “super-Earth,” and scientists believe that the rocky world is composed mostly of carbon (in the form of either graphite or diamond). It also includes iron, silicon carbide, and possibly silicates.

Scientists also believe, based on their research, that at least one-third of the planet’s mass is pure diamond. Lead researcher Nikku Madhusudhan of Yale University stated:

“This is our first glimpse of a rocky world with a fundamentally different chemistry from Earth. The surface of this planet is likely covered in graphite and diamond rather than water and granite.”

While worlds like the “diamond planet” of 55 Cancri e have been theorized before, and at least one has been discovered before now, it is the first of its kind to be identified orbiting around a sun-like star.

Madhusudhan’s study on the planet was published in the journal Astrophysical Journal Letters.

Princeton University astronomer David Spergel stated that it is relatively easy to find out a star’s basic structure and history once its age and mass have been discovered. He added:

“Planets are much more complex. This ‘diamond-rich super-Earth’ is likely just one example of the rich sets of discoveries that await us as we begin to explore planets around nearby stars.”