When we talk about extremely “old” things on Earth, that usually means a few billion years old. After all, Earth itself is only about four and a half billion years old. Scientists now say they’ve found something much much older on Earth. However, it didn’t come from Earth. Studying the remains of a meteorite have yielded the oldest known material ever studied up close.
A team of researchers from the US and Switzerland collaborated to analyze the Murchison meteorite (see above), which fell to Earth in the 1960s. This is a carbonaceous chondrite, a very common but ancient type of asteroid. These objects are of interest because they contain the primordial material that coalesced to form the planets in our solar system. Like some sort of cosmic cereal box, this one had prizes inside.
The researchers took samples from a fragment of the Murchison meteorite, crushed them, and dissolved the remains in acid. They were able to harvest tiny grains of material a few micrometers across. They have various compositions and ages, so categorizing them was a challenge.
To figure out how old these hearty little flecks were, scientists had to turn to the cosmos itself. Space rocks drifting through the void are constantly bombarded by cosmic rays. These collisions leave subtle isotopic signatures, which can point to the age of the object. This process is known as surface exposure dating. In this analysis, the team found the long-lived Neon-21 isotope particularly useful in determining the age of the grains.
One of the pre-solar grains, about 8 micrometers across.
While most of the material harvested from the Murchison meteorite was no more than a few hundred million years old, some of it was much, much older. Roughly 8 percent of the sample was around 7.5 billion years old, which is 3 billion years older than the solar system itself.
Scientists are interested in carbonaceous chondrites because they are pristine samples of the material that formed the planets billions of years ago. By studying them, we can learn a great deal about how solar systems come together. There may be even more to learn from these space rocks, though. The realization that there are even older materials in them could help unravel mysteries on a galactic scale. For example, the team believes the composition of the pre-solar samples in the Murchison meteorite supports the idea that the galaxy went through a period of increased star formation seven billion years ago.
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