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Caltech: Rare type of stellar grain discovered, scientists further explain the origin of water on Earth

Scientists recently discovered a rare type of stardust whose structure specifies that it formed during a rare form of nucleosynthesis, a process by which new atomic nuclei are developed, and could provide a new light on the history of water on Earth.

A team led by cosmochemists from Caltech and Victoria University of Wellington in New Zealand, according to a report by Caltech, examined aggregates of ancient material within the Allende meteorite that in 1969 fell on this planet , and found that many of them had an extraordinarily high amount of strontium-84, a relatively rare light isotope of the element strontium which is so named for the “84 neutrons in its nucleus”.

François LH Tissot, assistant professor of geochemistry at Caltech, said that strontium-84 is part of a family of isotopes produced by a nucleosynthetic process, called the p process, which remains a mystery.

Their findings, he added, indicate the survival of trains potentially containing pure strontium-84. This, he continued, is exciting, as the physical identification of these grains would provide an extraordinary chance to learn more about the p process.

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(Photo: Wikimedia Commons)
Pure strontium in a protective atmosphere of argon gas.

Strontium has been shown to be useful

Tissot and his collaborator Bruce LA Charlier of Victoria University of Wellington are co-lead authors on the research, “Ssurvival of presolar carriers of p-nuclides in the nebula revealed by the gradual leaching of refractory inclusions of Allende “, Posted in Scientists progress.

It’s quite interesting, explained Charlier, adding that they want to know what the nature of this material is and how it fits into a mixture of ingredients that have formed the recipe for the planet.

Strontium, a chemically reactive metal, WebMD explained, includes four stable isotopes: strontium-84, including its heavier cousins ​​with 86, 87, or 88 neurons in their nucleus.

Scientists have found that strontium is useful for dating objects in the early solar system because strontium-87, one of its heavy isotopes, is generated by the decay of the radioactive isotope rubidium-87.


Rubidium-87 has a very long half-life, 49 billion years, more than three times the age of the universe.

Half-life is the time it takes for the isotope’s radioactivity to drop to half of its original value, allowing isotopes to serve as stopwatches for dating samples at different time scales.

The most widely used radioactive isotope for dating is carbon-14, the radioactive isotope of carbon; with its half-life of approximately 5,700 years, carbon-14 can be used to identify the ages of organics over time scales up to approximately 60,000 years.

On the contrary, Rubidium-87 can be used to date the oldest objects in the universe and, closer to us, objects in the solar system.

Rubidium-Strontium pair

As noted in the study, what is particularly interesting about the use of the rubidium-strontium couple for dating is that the former is a volatile element.

This means that it tends to evaporate to form a gas phase even at relatively low temperatures. Strontium, on the other hand, is not volatile.

As such, rubidium exists in a higher proportion in an object in the solar system that is richer in other volatile compounds like water because they formed at lower temperatures.

Counterintuitively, the Earth has an RB / SR ratio, which is 10 times lower than that of water-rich meteorites, suggesting that this planet either accreted from water-poor materials or from materials rich in water although it has lost most of its water over time, as well as its rubidium. Understanding which of these circumstances occurred is essential to deciphering the origin of water on Earth.

Theoretically, the Rb-Sr chronometer, as explained in the SOA / NASA astrophysics data system, should be able to stand out with said two scenarios because the amount of strontium-87 that radioactive decay produces in a given period of time not be the same if this planet started with a lot of rubidium versus less material.

Related information on rubidium can be found on the Nanotechnology World Association YouTube video below:

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Find more chemistry news and information at Science Times.

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