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An artist's impression of a disk of gas and dust formed during the birth of the Sun.
Image Credit: NASA/FUSE/Lynette Cook
Scientific Frontline: Extended "At a Glance" Summary: Iron Meteorite Composition and Solar System Formation
The Core Concept: Recent laboratory experiments and chemical modeling of iron meteorite crystallization reveal that the earliest planetary bodies (planetesimals) possessed distinct nitrogen and phosphorus ratios, reshaping our understanding of how life-essential elements were distributed in the young solar system.
Key Distinction/Mechanism: The study identifies a critical shift in elemental distribution over time. Early iron meteorite parent bodies in the inner solar system had lower phosphorus-to-nitrogen ratios than those in the outer system. However, later-forming chondrites show the opposite trend, a mechanism attributed to the rapid growth of Jupiter, which eventually blocked the inward transport of these elements.
Major Frameworks/Components:
- High-pressure, high-temperature laboratory recreation of iron meteorite core crystallization.
- Chemical analysis of early planetesimal compositions to determine the spatial distribution of nitrogen and phosphorus.
- Comparative modeling between early iron meteorite asteroidal bodies and subsequent chondrite formations (occurring 2-3 million years later).
- Analysis of planetary dynamics, specifically how Jupiter's formation and the cooling of the gas-dust medium influenced elemental transport.
Branch of Science: Planetary Science, Cosmochemistry, Astrophysics, and Earth Systems Science.
Future Application: These findings refine theoretical models used to map the distribution of volatile, life-essential elements in exoplanetary systems, which will directly assist astrobiologists and astronomers in identifying habitable environments beyond our solar system.
Why It Matters: The research challenges previous assumptions that Earth's life-essential elements migrated inwards from the outer solar system. Instead, it suggests that these vital ingredients were likely sourced directly from the first generation of planetesimals formed within the inner solar system.
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| Rajdeep Dasgupta (left) and Debjeet Pathak (right). Photo Credit: Rice University/Jared Jones |
Habitable planets require life-essential elements, such as nitrogen and phosphorus. Understanding how those elements ended up in a planetary body can give insight into the formation of the solar system and Earth. Rice University researchers recently published a paper in Science Advances showing that the nitrogen and phosphorus composition of iron meteorites is different from the composition found in later asteroids known as chondrites.
“We recreated the crystallization of iron meteorites in the lab and used the known chemical composition of iron meteorites available to us,” said Debjeet Pathak, a graduate student and the corresponding author on the paper. “That allowed us to determine the chemical composition of the small planetary bodies, called planetesimals, from which the iron meteorites came.”
Over 4.5 billion years ago, nitrogen and phosphorus, which traveled through space in gas and dust, were incorporated into these small planetary bodies. As the planetesimals formed, they developed crystallized metallic cores; when they were degraded or destroyed, iron meteorite fragments from their cores were released into space. Most iron meteorites are now found in the asteroid belt between Mars and Jupiter, which separates the inner solar system, stretching from Mercury to Mars, from the outer solar system, stretching from Jupiter to Neptune.
The researchers, led by Rice professor Rajdeep Dasgupta, recreated the formation of planetesimal bodies from both the inner and outer solar system. To do so, they took the chemicals that made up these iron meteorites and cooked them in a high-pressure, high-temperature facility. This provided insight into how much phosphorus and nitrogen were in these early planetary bodies and, consequently, where these life-essential elements were located at the beginning of the solar system: in the inner or outer solar system.
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| Iron meteorites (top) have a lower phosphorus-to-nitrogen ratio in the inner solar system compared to the outer solar system. Chondrites (bottom) have higher ratios in the inner solar system compared to the outer solar system. Image Credit: Rice University/Rajdeep Dasgupta |
The team’s analysis showed that the ratio of phosphorus to nitrogen was lower in iron meteorites’ asteroidal bodies from the inner solar system than in those from the outer solar system.
This ratio of elements, however, was different from the ratios observed in later planetesimals from which chondrites originated. Chondrites from the inner solar system have a higher phosphorus-to-nitrogen ratio, which gradually decreases from the inner to the outer solar system.
“As Jupiter grew in size,” Pathak said, “it slowly began to block the transport of phosphorus and nitrogen, resulting in a gradual decrease in the observed ratios found in chondrites, which formed as much as 2–3 million years after the iron meteorite bodies.”
While the changes in the ratios were different between the two generations of planetesimals, one thing was the same: The phosphorus-to-nitrogen ratio in the inner solar system was closest to the life-supporting ratio found on Earth. This study, along with other work in the field, suggests that these life-essential elements did not come from the outer solar system and then move inward, as previously thought. Instead, they may have been sourced from the first-formed planetesimals in the inner solar system.
“We think this finding tells us how the dust and, consequently, the planetesimal compositions in the inner versus outer solar system evolved within the first few million years, affected by Jupiter’s growth and the gradual cooling of the gas-dust medium,” said Dasgupta, the W. Maurice Ewing Professor of Earth Systems Science and director of the Rice Space Institute Center for Planetary Origins to Habitability.
Funding: This research was funded by NASA (80NSSC18K0828 and 80NSSC22K0635).
Published in journal: Science Advances
Authors: Debjeet Pathak, Rajdeep Dasgupta, and Naidhruv Iyer
Source/Credit: Rice University | Rachel Leeson
Edited by: Scientific Frontline
Reference Number: ps060426_01
