First measurements of Earth's core radioactivity

New Scientist ^ | 7/27/05 | Celeste Biever

[LibWhacker]

EARTH'S natural radioactivity has been measured for the first time. The measurement will help geologists find out to what extent nuclear decay is responsible for the immense quantity of heat generated by Earth.

Our planet's heat output drives the convection currents that churn liquid iron in the outer core, giving rise to Earth's magnetic field. Just where this heat comes from is a big question. Measurements of the temperature gradients across rocks in mines and boreholes have led geologists to estimate that the planet is internally generating between 30 and 44 terawatts of heat.

Some of this heat comes from the decay of radioactive elements. Based on studies of primitive meteorites known as carbonaceous chondrites, geologists have estimated Earth's uranium and thorium content and calculated that about 19 terawatts can be attributed to radioactivity. But until now there has been nothing definitive about exactly how much uranium there is in the planet, says geologist Bill McDonough of the University of Maryland in College Park. "There are fundamental uncertainties."

There is one way to lessen this uncertainty, and that is to look for antineutrinos. These particles are the antimatter equivalent of the uncharged, almost massless particles called neutrinos and are released when uranium and thorium decay to form lead. If antineutrinos are being created deep within the planet they should be detectable, because they can pass through almost all matter.

Now, the KamLAND antineutrino detector in Kamioka, Japan, has counted such antineutrinos. An international team of scientists analysed the data and found about 16.2 million antineutrinos per square centimetre per second streaming out from Earth's core. They calculate that the nuclear reactions creating these particles could be generating as much as 60 terawatts, but are most likely putting out about 24 terawatts (Nature, vol 436, p 499). "We have made the first measurements of the radioactivity of the whole of Earth," says John Learned, who heads the KamLAND group at the University of Hawaii in Manoa. The KamLAND group's finding is like unwrapping a birthday present, says McDonough.

With time, as more antineutrinos are detected, KamLAND may be able to determine once and for all whether radioactivity is entirely responsible for heating Earth or whether other sources, such as the crystallisation of liquid iron and nickel in the outer core, also play a significant role. "[Detecting anti-neutrinos] is the way of the future in terms of hard numbers about the system," says McDonough.

Antineutrinos could also reveal the radioactive composition of the crust and mantle, which will give geologists clues as to when and how they formed. But to do that, they will have to be able to pin down exactly where the antineutrinos are coming from, and this will require a whole network of detectors. "We are heading towards doing neutrino tomography of the whole Earth," says Learned. "This is just the first step."

[Physicist]

I'd like to see the Sudbury Neutrino Observatory repeat this observation, if it can. There are systematic biases in the KamLAND design that aren't present in the SNO design, although I don't know to what extent they'd affect this particular measurement.

[Willie Green]

Free Beer!

[absolootezer0]

hasn't anyone read verne? everyone knows that in the middle of the earth there's a huge ocean and in the middle there's an island and that's where the dinosaurs still live.
in related news, the reason that atlantis sunk was because they were experimenting with drilling to the earth's core.

[GSlob]

What silver? The planet core contains something like 100+ metric tons of platinum for every contemporary planet inhabitant. At present-day prices it would make EVERYONE into a billionaire. (What a horror! Imagine the squalor and corruption it would cause in the third world!)

[RightWhale]

Forget bimetallism. We're going for trimetallism. Think the Fed would ever put their stamp on platinum?

[Sense]

For more on how deep we've dug, Google "Mohole Project"

The rest is addressed pretty well elsewhere here, although the development of the necessary technologies isn't. There are active efforts to solve parts of the technical challenges, but there are limits in the utility of sharing information about them... and as many elements of the technical drivers have "other" applications, you're unlikely to find out much that is useful (or meaningful) without getting a PhD in Physics and an appointment to a government lab.

Still, I expect that "most" of the solution to the technical problems will be made available somewhere around the year 2008 to 2012... in a form that enables functional products to be produced and marketed.

[GSlob]

Why not? There already are platinum Maple Leaves from Canada and also Australian coins - Koalas or Kangaroos, I forgot which.

[thoughtomator]

Such a energy facility would probably come in the form of a borehole. Here's an example of a borehole:

[ApplegateRanch]

The planet core contains something like 100+ metric tons of platinum for every contemporary planet inhabitant.

Geeze-Louise! That would mean I could finally have a set of platinum cookware!

No more worry about polluting my precious bodily fluids due to aluminium or iron compounds being leached from cooking acidic foods; nor would I need 'dangerous' Teflon coatings!

An added plus: I KNOW my stove doesn't get hot enough to melt or burn the bottom out of an unattended platinum pan.

[GSlob]

Yep, but such cookware will be VERY heavy. Good for family fights, though. Imagine hitting somebody with 10+ pounds platinum frying pan.

[ApplegateRanch]

Well, many recipes do call for "a heavy pan".

Also, just think how much harder it would be for 'The Little Woman' to hurl a 3 qt sauce pot across the room.LOL

And another advantage is that it would make assaying and certain other 'kitchen chemistry' experiments less messy.

[RightWingAtheist]

Fermilab director Robert R Wilson suggested something like this years ago. He suggested that we could use an artifical source of neutrinos to detect oil and coal deposits within the earth.

Although it might be cost-prohibitive, I wonder if we could also use this technique as a means of exploring the interiors of other planets and moons in the solar system.

[SunkenCiv]

Scientific maverick's theory on Earth's core up for a test
SF Chronicle | Monday, November 29, 2004 | Keay Davidson
Posted on 12/05/2004 11:17:28 AM PST by SunkenCiv
http://www.freerepublic.com/focus/f-chat/1294934/posts

[Ernest_at_the_Beach]

Place marker here....

[Fred Nerks]

Sounds promising:

"...Deep geothermal, or “hot rocks”, exploits granite deep in the earth's crust that is heated naturally over millions of years by radiogenic decay from the elements within it. Geodynamics has proven that it can pump water down a 4km well to 300C rocks that heat it and then recover the resultant steam from a second well nearby. By the end of the year, it plans to have a pilot electricity plant in place. It will then look to provide base-load power to the grid by 2012, with a 50 megawatt plant. Its output should eventually reach 10,000 megawatts - the equivalent of 10 to 15 coal-fired power stations..."

Australia looks for power from hot rocks

[SunkenCiv]

Thanks Ernest!

J. Marvin Herndon site:freerepublic.com

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