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Courtesy of Argonne National Laboratory.

Argonne physicist Richard Pardo stands next to CARIBU, part of the ATLAS accelerator. Using the accelerator, Pardo is one of many scientists involved in recalculating the time it took to form the early earth.


Clocks measuring Earth's formation off by millions of years

by Eric Eckstrom
April 10, 2012


Timing is everything and astrophysicists at Argonne National Laboratory may reset the “clocks” that time the formation of our planet.

The problem is that the Earth formed far more rapidly than previously thought, according to new research pursued at Argonne and several other labs.  If accurate, researchers say there are significant implications for not only the planetary history of Earth, but for the moon, Mars, and the early history of the solar system.

“It helps better congeal our ideas and models about how the early sun evolved and on what time scale,” said Richard Pardo, operations manager of the physics division of Argonne.

The idea was born during a conversation between Michael Paul, one of the Argonne physicists involved in the research, and a colleague working in Japan. The timeline of Earth’s early formation had been calculated several times in the past, but the clock used still had to be verified.

“Previous methods to calibrate the clock were old, and methods were different,” Paul said.

Thus began a 4-year journey to recalculate the planetary history of Earth.

By manufacturing and studying a previously "extinct" isotope called Samarium-146 – one of the elements present during the formation of the solar system – their suspicions were eventually confirmed. 

Samarium-146’s half-life, or time it takes the isotope to decrease by half, was 30 percent shorter than previously determined.  

This was significant because Samarium-146 was the “clock” physicists and geochemists used to gauge the speed at which the Earth formed during its early history, and the speed of that clock had been wrong by a weighty margin.  

“It shrinks the chronology of early events in the solar system, like the formation of planets into a shorter time span,” Paul said in a statement.  “It also means some of the oldest rocks on Earth would have formed earlier – as early as 120 million years after the solar system was formed” rather than approximately 200 million years after.  

To put it another way, the age of the solar system itself remains at 4.5 billion years old, but the time between its formation and when the Earth evolved into a layered solid of a planet occurred much more rapidly.    

The Samarium-146 was studied using Argonne’s superconducting linear accelerator known as ATLAS, a machine that shoots beams of subatomic particles in materials to unravel near invisible mysteries.

“We use it to find a needle in a haystack,” said Ernst Rehm, another Argonne Physicist involved in the study.

To better understand the function of ATLAS, Rehm used an analogy involving Lake Garda, the largest lake in Italy, and wine.  Imagine someone poured a single glass of wine at a far end of the lake.  ATLAS, according to Rehm, would allow someone 30 miles away, at the other end, to notice the wine has been added.

This technology permitted scientists to isolate the Samarium-146 and measure its precise half-life.
Researchers said the impact of this study is not limited to Earth, but suggests the moon and mars formed at a much faster rate as well.  

“In 20 or 30 years, this technology will move forward and can be used as a precise dating tool when studying Mars,” Rehm said.

For now, the researchers said they are enjoying the satisfaction of finally being able to convince others of something they suspected for years.

“It’s hard to say everyone else was wrong and you are right. The satisfaction was being able to convince others,” Paul said.

Paul said the study is symbolic of the importance of "interbreeding" across all areas of science. According to Paul, “Measurements must always be measured and verified, also this one.”