When a meteor flashes through the sky, it’s more than a striking sight—it’s nature delivering a time capsule to Earth. Inside are clues to the solar system’s earliest days and the processes that shaped planets, including our own.
In a recent Space Science Reviews paper—soon to be included as a chapter in an upcoming textbook—Lawrence Livermore National Laboratory (LLNL) scientist Thomas Kruijer and his colleagues explain how meteorites reveal the history of the early solar system.
“The ultimate goal is to understand how habitable planets like Earth form,” Kruijer said. “How do you create the planet we live on every day, and how does it become capable of supporting life? These questions are still actively debated.”
How Planetesimals and Meteorites Take Shape
Researchers do have some well-supported ideas. As the solar system took shape, gas and dust from a giant molecular cloud collapsed into a flattened disk around the young sun. This protoplanetary disk was initially extremely hot but gradually cooled, allowing material to clump together. Gravity pulled dust into increasingly larger aggregates, eventually forming small bodies—about 1 to 100 miles across—known as planetesimals.
“These planetesimals are considered the building blocks of planets, so they’re crucial to understand,” Kruijer explained. “To learn how Earth formed, we first need to understand how planetesimals formed. In a sense, we’re like detectives or historians, trying to piece together the sequence of events.”
Meteorites provide the key evidence for this detective work. Many originate in the asteroid belt, a kind of graveyard for some of the earliest bodies in the solar system. By studying these rocks in the lab—a discipline known as cosmochemistry—scientists can determine the ages and compositions of samples more than 4.5 billion years old.
“It might be a piece no bigger than your fingernail, yet that rock is the oldest thing on Earth,” Kruijer said. “It has remained unchanged for billions of years, preserving information from the time it formed.”
Meteorite Varieties and their Importance
The authors explain the different types of meteorites and the insights they offer. Undifferentiated meteorites come from planetesimals that formed without melting, containing calcium-aluminum-rich inclusions—possibly the first solids to condense from the protoplanetary disk—and chondrules, small spheres that can be precisely dated to reveal when the body formed.
Differentiated meteorites, on the other hand, experienced heating and melting. Heavy materials like iron sank to form a core, while lighter materials rose to create a mantle.
“That’s especially valuable because Earth also has an iron core, but it’s buried so deep that we can never access it directly,” Kruijer said. “By studying iron meteorites, we can examine the cores of planetary bodies.”
LLNL houses numerous advanced tools for analyzing meteorite samples, specializing in precise measurements of isotopes, ages, and chemical compositions from tiny samples. For instance, when NASA’s OSIRIS-REx mission returned the first U.S. asteroid sample to Earth, LLNL scientists conducted some of the analyses.
Advancing Lunar Sample Analysis at LLNL
The team plans to apply the same techniques to samples from future Artemis lunar missions. In the meantime, they are studying historical lunar samples brought back by the Apollo missions to prepare.
“We are currently expanding our scientific capabilities in preparation for Artemis,” said Kruijer. “Cosmochemistry is a major focus at LLNL, and we aim to maintain and enhance our ability to study lunar samples.”
These analytical methods are essential for the Laboratory. Advanced cosmochemistry tools also support nuclear forensics, helping researchers trace the origin and history of nuclear materials.
Ultimately, Kruijer hopes that meteorite sample analyses will inform large-scale astrophysical models of the protoplanetary disk. He also envisions the paper’s overview of meteorite research becoming a valuable reference for early-career scientists and experts in related fields.
“You can use AI to get a summary of the latest developments, which gives a general overview,” he said. “But scientific papers involve a lot of nuance and precise terminology. A carefully curated review written by experts who understand these subtleties remains extremely valuable.”
Read the original article on: Phys.Org
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