Meteorite is 4.6 billion years old and still rocking the solar system dating scene

Presence of aluminum isotope might help age other objects from space

At 4.6 billion years old, meteorite Erg Chech 002 is among the oldest found on Earth. A new analysis of its composition promises to help understanding of the early solar system and date other space rocks.

A research team led by Evgenii Krestianinov, a PhD candidate at the Australian National University, has found that the space rock – found in 2020 in the Erg Chech region of the Sahara Desert in Algeria – contains Aluminum -26 (26Al) within a magnesium alloy.

The radioactive isotope is known to have been a major heat source for early planetary melting. Its discovery in Erg Chech 002 can help to understand its initial distribution within the early solar system, the researchers argue.

Erg Chech 002 is an andesitic achondrite, a type of stony meteorite among the oldest on earth. The question the researchers puzzled over is whether 26Al was distributed evenly throughout the early solar system as this could become important for determining the ages of other meteorites.

To figure that out, they also had to look at lead isotopes within the rock which revealed an age of about 4.566 billion years. Comparing the data with analysis of other "very old" meteorites they concluded that the isotope had an uneven distribution within the early solar nebula, likely associated with the late infall of stellar materials with freshly synthesized radioactive elements.

"Our analysis, in conjunction with [earlier] published data, reveals that the initial 26Al/27Al in the source material of this achondrite was notably higher than in various other well-preserved and precisely dated achondrite," the researchers said in a paper published in Nature Communications this week.

The results suggest that other relative ages based on aluminum-magnesium alloy (Al-Mg) alone should be reevaluated.

"Developing a generalized approach for isotopic dating with Al-Mg and other extinct isotope chronometers that accounts for heterogeneous distribution of the parent [radioactive elements] would allow to produce more accurate and reliable age data for meteorites and asteroidal and planetary materials to advance a better understanding for the formation of our solar system," the researchers said. ®

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