New Finding Changes Understanding of Solar System Formation

 

         

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 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 geological events in the mantles of Earth and other terrestrial planets in the early solar system.

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 terrestrial planets — 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 Solar System 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 co wrote 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.

The Daily Planet via the University of Notre Dame

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Comments

[Narendra Nath]

Such a large change in half life measurement beyond the errors means that we follow a procedure that has lacuna in the estimations. There is a need to sit together and remove such possibilities in future. Otherwise scientists will become jokers to fool the public for whom they work and are paid for.Let sensible Geophysicists do this job and standardize procedures and methodology for reliability of results in future.

[Bob Greenwade]

Two points:

First, the article tells us that the new number for the Samarium-146 half-life gives us new dates for the formation of the solar system and other major geological events. I assume that means the formation happened more recently than was previously thought, but by how much? Is the age of the Earth now shortened from 5 billion years to 3.4 billion, or what?

Second, as Nerendra points out, this is a pretty big error. Five percent would be understandable, and even ten percent would be tolerable, but this is a thirty-four percent error, and that's pretty huge. In my view, it casts some similar, serious doubt on every other radioactivity-based measurement we use to tell how old our planet is.

[Andrew]

This is a pretty big change, but I'd like to point out that neither the old nor the new errors on the half-life estimates were quoted here. Has anybody commenting checked them? It may be that the old errors were large so the new estimate could be within the errors of the old one. (I just did a quick Google search and didn't find the error estimates for either the old or the new values.) Anyway, I hope the Young Earth creationists don't read too much into this.

[Louis-Alexandre]

Appart from the fact that a 34% discrepency is
huge, what really scares me is the doubt (in the eyes of the general population at least)
it will cast on other forms of radiological dating. This could very well become the mistake creationists, and literal interpreters of the bible have been waiting for to try and get their lies across more easily

[JohnR]

OK, so the "error" is large - and that's gonna boggle the minds of the general public. However, we probably need to keep in mind that such a stable, superheavy element was undiscovered not many years ago and given the multimillion year half lives involved (either number), the precious little of the stuff to sample, and the short time we've had to study it, any such "half life" number will be an estimate at best - one or two atoms decaying when the accepted value says it shouldn't will vary the statistics wildly. Standard small sample size problem in polls or any other statistical analysis.

[Captain]

What you say!!

[California Z]

It's absurd to use numbers with 3 significant digits if the error is anywhere near 30%. WTF was going on here?