Skip to main content

7 billion-year-old stardust is oldest material found on Earth

Dust-rich outflows of evolved stars similar to the pictured Egg Nebula are plausible sources of the large presolar grains found in meteorites like Murchison.
Dust-rich outflows of evolved stars similar to the pictured Egg Nebula are plausible sources of the large presolar grains found in meteorites like Murchison.
(Image: © NASA, W. Sparks (STScI) and R. Sahai (JPL). Inset: SiC grain with ~8 micrometers in its longest dimension. Inset image courtesy of Janaína N. Ávila)

Scientists recently identified the oldest material on Earth: stardust that's 7 billion years old, tucked away in a massive, rocky meteorite that struck our planet half a century ago. 

This ancient interstellar dust, made of presolar grains (dust grains that predate our sun), was belched into the universe by dying stars during the final stages of their lives. Some of that dust eventually hitched a ride to Earth on an asteroid that produced the Murchison meteorite, a massive, 220-lb. (100 kilograms) rock that fell on Sept. 28, 1969, near Murchison, Victoria, in Australia.  

New analysis of dozens of presolar grains from the Murchison meteorite revealed a range of ages, from about 4 million years older than our sun — which formed 4.6 billion years ago — up to 3 billion years older than our sun, researchers reported in a new study.

Related: Space-y Tales: The 5 Strangest Meteorites

Though the universe abounds with floating stardust, no presolar grains have ever been found in Earth's rocks. That's because plate tectonics, volcanism and other planetary processes heated and transformed all the presolar dust that may have collected during Earth's formation, said lead study author Philipp Heck, the Robert A. Pritzker Associate Curator of Meteoritics and Polar Studies at the Field Museum of Natural History in Chicago. 

When large, orphan space rocks form — such as the asteroid that produced Murchison — they, too, can pick up ancient, interstellar dust. But unlike dynamic planets, Murchison's parent asteroid is "an almost-inert piece of rock that formed from the solar nebula and hasn't changed since then," so the presolar grains haven't been cooked down into another type of mineral, Heck told Live Science.

Most presolar grains measure about 1 micron in length, or are even smaller. But the grains the scientists analyzed for the study were much bigger, ranging from 2 to 30 microns in length. 

"We call them 'boulders,'" Heck said. "We can see them with an optical microscope."

Stellar "baby boom"

For the study, Heck and his colleagues examined 40 of these so-called boulders from Murchison, grinding up bits of the meteorite and adding acid, which dissolved minerals and silicates and revealed the acid-resistant presolar grains. 

"I always compare it to burning down the haystack to find the needle," Heck said.

The researchers used a dating technique that measured the grains' exposure to cosmic rays during their interstellar journey over billions of years. In space, high-energy particles emanate from different sources, bombarding and penetrating solid objects that pass by. Those cosmic rays react with rock to form new elements that accumulate over time. By measuring the quantity of different elements in presolar grains, scientists can estimate how long the dust has been bathing in cosmic rays. 

Think of it this way: Imagine putting a bucket outside during a rainstorm. As long as the rain falls at a steady rate, you could calculate how long the bucket had been outside based on the amount of rain that it collects, Heck explained.

Most of the grains — about 60% — dated to around 4.6 billion to 4.9 billion years ago. One possible explanation for why there were so many grains of this age is that they were all the product of a "little baby boom" of star birth in our galaxy that took place around 7 billion years ago. 

"And then it took about two to two-and-a-half billion years for those stars to become dust producing," Heck explained. "When a star forms, it doesn't produce dust. During most of its life, the star doesn't produce dust. The stars only produce dust at the end of their lives."

This discovery supports findings by other astronomers that indicate a dramatic spike in star formation around 7 billion years ago, the researchers reported.

What's more, many of the grains weren't traveling through space alone; they journeyed as clumps, "almost like granola clusters," according to Heck. Though it's uncertain what bound these grains, other studies have shown that some presolar grains are coated with a sticky film of organic matter, which could have cemented these clusters together, Heck said.

Related: 7 Theories on the Origin of Life

Smells like science

Grinding and analyzing bits of space rock also presented the researchers with an unusual by-product — a strong and very pungent smell. The paste of ground-up meteorite released a stench "like rotten peanut butter," study co-author Jennika Greer, a graduate student at the Field Museum and the University of Chicago, said in a statement.

"I've never smelled rotten peanut butter," Heck told Live Science. "But it did smell really strong."

Another meteorite that was recently added to the Field Museum's collection, the Aguas Zarcas from Costa Rica, or "cosmic mudball meteorite," was said to smell like cooked Brussels sprouts. Volatile organic compounds in rocky meteorites that are abiotic — not formed by living organisms — produce these distinctive smells when they are heated or dissolved, Heck said. 

And Murchison was an especially smelly meteorite, Heck said. When he visited the town of Murchison in 2019 for the 50th anniversary of the meteorite's landing, he spoke with people who had witnessed the event or collected fragments of the space rock. Many of them had tales to tell about the meteorite's distinctive aroma.

"They said the whole town smelled like methylated spirits, a very strong organic smell," Heck said. "Even those who hadn't seen the meteorite themselves — they smelled it."

The findings were published online today (Jan. 13) in the journal Proceedings of the National Academy of Sciences.

Originally published on Live Science.

All About Space Holiday 2019

Need more space? Subscribe to our sister title "All About Space" Magazine for the latest amazing news from the final frontier! (Image credit: All About Space)

Join our Space Forums to keep talking space on the latest missions, night sky and more! And if you have a news tip, correction or comment, let us know at: community@space.com.

  • Torbjorn Larsson
    Stunning discovery of material of half the age of the universe!

    For another paper on star formation rate to add to the paper references, we have a recent Gaia result where it seems the pre-solar dust grains can come from that model tail of the Milky Way initial high rate: https://www.aanda.org/articles/aa/pdf/2019/04/aa35105-19.pdf .
    Reply
  • rod
    Admin said:
    Scientists recently identified the oldest material on Earth: stardust that's 7 billion years old, tucked away in a massive, rocky meteorite that struck our planet half a century ago.

    7 billion-year-old stardust is oldest material found on Earth : Read more

    "The researchers used a dating technique that measured the grains' exposure to cosmic rays during their interstellar journey over billions of years."

    The method of CRE ages goes back quite a way, I think back to Clair Patterson et al in mid-50s and others. Many meteorites with CRE ages show much younger ages too, <=1E+8 years old (NASA ADS service), also the Apollo lunar mission rocks had young CRE ages too. Mars has young CRE ages too, A Habitable Past for a Desert Planet?, Sky & Telescope 127(3):12, 2014, March 2014, ""Cumberland's 'exposure age' is comparatively young, only 50 to 100 million years..."

    This is a *stunning* report here for the CRE age determination.
    Reply
  • Truthseeker007
    I find it hard to wrap around in my head that our sun is billions of years old.
    Reply
  • rod
    I did some more digging into this report for the Murchison meteorite ages. The Murchison meteorite, like the Allende is critical in dating the age of the Sun and solar system. Apparently the presolar grains with CRE ages 5 billion years old or more are said to be derived from another generation of stars that formed in a *bumper crop* 7 billion years ago. The explanation for the various presolar grain ages, chondrules ages, and don't forget the radiometric age (melt-age) - looks like a complex history to reconcile the different ages found on the meteorite.

    ‘Meteorite contains the oldest material on Earth: 7-billion-year-old stardust’, https://phys.org/news/2020-01-meteorite-oldest-material-earth-billion-year-old.html

    Here is a 2017 report on Murchison meteorite CRE ages, 1-2 million years for some chondrules, some others 4-40 million years.

    ‘Cosmogenic He and Ne in chondrules from clastic matrix and a lithic clast of Murchison: No pre-irradiation by the early sun’, https://ui.adsabs.harvard.edu/abs/2017GeCoA.213..618R/abstract
    Reply