Helium-3 - all is not lost

September 3, 2005

Is there a reservoir of primordial rock deep within the Earth, left over from the birth of our planet? Geochemical data have traditionally indicated 'yes', but evidence from seismology seemed inconsistent with the survival of such a reservoir. This week in Nature, Cornelia Class and Steven Goldstein present a theory that may allow geologists to resolve this contradiction.

The question arose because the rocks of ocean islands like Hawaii contain relatively large amounts of helium-3, an isotope that must be mainly left over from the days when the Earth first formed, because it is not generated from the radiogenic decay of other elements. Researchers believed that helium-3-rich minerals should only come from untouched primordial rock that has welled up from deep within the mantle and has not previously been 'degassed' when partially melted near the Earth's surface.

But seismologists look upon this evidence with dismay. They see no evidence that large portions of the mantle have escaped the mixing and melting that drives plate tectonics and makes volcanoes.

Class and Goldstein show that the other minerals in ocean island rocks tell a different story - the most helium-3-rich rocks also contain elements that resemble the composition of rock that has melted before, such as that found at mid-ocean ridges. The best explanation for all this, they say, is simply that the mantle loses less of its helium than expected during melting. Their model, which will need physical experiments to back it up, explains how this might happen. A News and Views article by William M. White accompanies this research.

Source: Nature Publishing Group

Explore further: Researchers shed new light on the origins of Earth's water

Related Stories

Researchers shed new light on the origins of Earth's water

November 12, 2015

Water covers more than two-thirds of Earth's surface, but its exact origins are still something of a mystery. Scientists have long been uncertain whether water was present at the formation of the planet, or if it arrived ...

Saturn's moon Rhea

October 26, 2015

The Cronian system (i.e. Saturn and its system of rings and moons) is breathtaking to behold and intriguing to study. Besides its vast and beautiful ring system, it also has the second-most satellites of any planet in the ...

Venus considered for clues on early Earth geology

October 30, 2015

Imagine thousands of huge asteroids raining down on ancient Earth, smashing craters as big as metropolitan Perth and a few much larger rocks which gouged holes as big as Australia into the planet.

Saturn's moon Dione

November 2, 2015

Thanks to the Cassini mission, a great deal has been learned about Saturn's system of moons (aka. the Cronian system) in the past decade. Thanks to the presence of an orbiter in the system, astronomers and space exploration ...

Recommended for you

'Material universe' yields surprising new particle

November 25, 2015

An international team of researchers has predicted the existence of a new type of particle called the type-II Weyl fermion in metallic materials. When subjected to a magnetic field, the materials containing the particle act ...

CERN collides heavy nuclei at new record high energy

November 25, 2015

The world's most powerful accelerator, the 27 km long Large Hadron Collider (LHC) operating at CERN in Geneva established collisions between lead nuclei, this morning, at the highest energies ever. The LHC has been colliding ...


Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.