New finding affects understanding of formation of the solar system

April 2, 2012 By Melissa Gebhard

( -- A global collaboration including five University of Notre Dame researchers has revised the half-life of samarium-146 (146Sm), reducing it to 68 million years from 103 million years. The finding is published in the journal Science.

The revised half-life, which is 34 percent shorter than the previously adopted value, affects the understanding of processes leading to the formation of the solar system, and the dating of some major in the mantles of and other terrestrial planets in the .

Samarium-146 is one of the main tools for establishing the evolution of the solar system over its first few hundred million years. It is a radioactive atom that is used as a clock for dating the separation of mantles of the — e.g., Earth, the moon, Mars and meteorite parent bodies — to regions with different chemical compositions, including the formation of crust from the mantle, in the early solar system.

Samarium-146, which is produced only in stars, does not occur naturally on Earth. It decays to neodymium-142 (142Nd), so the presence of excess 142Nd in the geological record indicates the previous presence of 146Sm. The researchers produced 146Sm samples in a reactor and used Accelerator Mass Spectrometry (AMS) to separate the isotope from other material with mass 146 (called isobars). Measurements were taken using the high-energy ATLAS accelerator facility at Argonne National Laboratory utilizing the gas-filled magnet technique. This technique was developed by a collaboration between Argonne physicists; Philippe Collon, professor of physics at the University of Notre Dame; and Michael Paul from the Hebrew University in Jerusalem.

“Samarium-146 has a whole number of different applications that are specific to geological dating of these events. It goes back to the formation of the Solar System and the formation of Earth. That clearly changes some of the models and is an important piece of information. It is going to have implications on some of the models we have and our understanding of the formation of the and any extraterrestrial planetary system we are looking at,” Collon said.

Collon along with Xiaodong Tang, a professor of physics; Yoav Kashiv, a visiting scholar who cowrote the paper; and graduate students Dan Robertson and Chris Schmitt were part of the research collaboration that involved groups from Israel, Japan and Argonne National Laboratory.

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4.1 / 5 (14) Apr 02, 2012
No, this doesn't mean it's 6,000 years old...
5 / 5 (4) Apr 02, 2012
Would you go 7,000?:)Do I hear 8? Who'll give me 8, 8 ,8, going, going, 8,000 it is...

Does that mean the solar system is 34% younger? 2.97 bil?
4.4 / 5 (7) Apr 02, 2012
No, because the rate is measuring the gap between Solar system start up and the Earth forming. So it's just saying the earth as well as other objects must have formed sooner after the solar system started.

So say Planet X began 10 years after the solar system started, based on a half life, but then you cut that half life in half due to the refined measurements then Planet X now began about 5 years after. (Just picking arbitrary numbers to make it simple).

4.6 / 5 (5) Apr 02, 2012
No, this doesn't mean it's 6,000 years old...

He must have wept openly when he couldn't post first....
1 / 5 (1) Apr 02, 2012
So what does it mean?
5 / 5 (4) Apr 02, 2012
The former statements made with authority are now to be revised and the new statements are made with authority. Any realization that at its core science is uncertain should be ignored.

But seriously, when politics is left out, how great is it that something this fundamental is re-checked and found to be in need of major correction.
1 / 5 (1) Apr 03, 2012
An arch requires all of its elements to hold it together, raising the question of how an arch is constructed. One answer is to build a frame (historically, of wood) which exactly follows the form of the underside of the arch. This is known as a centre or centring. The voussoirs are laid on it until the arch is complete and self-supporting.


Never replace the framing with the fundamentals - if you dare to remove even one element from your fundament/foundation.

Be prepare to dodge all the(falling)elements when removing one.
Framing is great. Fundamentals are written in/with stone and/or religions.

5 / 5 (2) Apr 03, 2012
What does it mean, re Stargazer? I had to check with a modern review, "Chronometry of Meteorites and the Formation of the Earth and Moon", Kleine & Rudge, 2011.

Apparently it doesn't do much to the time constraints of terrestrial planet (Earth) formation, which are mainly set by other chronometers (Hf-W & U-Pb chronometers).

But unless I am mistaken it strengthens the hypothesis of collisional erosion of terrestrial planet (Earth) crust. That hypothesis predicts the slight 142Nd (to 182W) excess of the mantle compared to chondrites. This would have taken place before (mostly) and after the Earth-Moon impactor, which is now later and in some hypotheses much later than the bulk of the 146Sm converts.

Presumably the excess is much harder to predict by processes in the mantle if the 142Nd was early present instead of a Sm/Nd mix. So it should strengthen the erosion case.
3.3 / 5 (3) Apr 03, 2012
[cont] If crust erosion happened, it prolongs the timescale of core formation from ~ 30 million years to ~ 40 million year. (Compare with the ~ 3-4 million years for Mars core to form!) It also means chemical to biological evolution may have happened late, closer to the traditional ~ 3.8 - 3.5 billion years ago than the ~ 4.5 - 4 billion years that some molecular clocks and some geophysical possibilities points to.

But ha, creationist crackpots presuming to discuss science claim it isn't science producing facts, so presumably no threat to religion! Then what is the point of trolling? LOL!
not rated yet Apr 04, 2012
samarium and neodymium are very similar geochemically so there is unlikely to be a good separation of them on earth to take advantage of isotope variations in dating. However if the isotopes can be detected in the spectra of stars (perhaps in future) it could give a good clue as to their age.
not rated yet Apr 04, 2012
Graeme, thanks for that! Yes, it would be minute to non-existent difference and so separation cause at a guess. It could then be more mass based than chemically (if at all), since it looks like an alpha conversion. (146 - 142 ~ 4 H ~ 2 H2 of mass.)

Since I commented I read claims that this _tightens_ instead of loosen the time to the Earth-Moon impactor, but I can't see how that works on the background of my linked review.

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