Researchers investigated the composition of a pristine meteorite and discovered material similar to the outermost protoplanetary disk. This material likely originated in the comet-forming region.
New Finding
Contrary to previous beliefs, the isotope signature of the comet-forming region appears to be common among outer Solar System bodies. This finding sheds light on the formation and early evolution of our Solar System. Most carbonaceous asteroids in the Solar System contain material from the comet-forming region, a signature absent in the terrestrial planet region.
Winchcombe Meteorite
Meteorites are invaluable cosmic time capsules that preserve the primordial building blocks of our solar system and offer insights into the origins of life on Earth. The Winchcombe meteorite, which fell in England in 2021, is a pristine carbonaceous chondrite that has remained uncontaminated by Earth’s environment. This allowed researchers to precisely identify vital nitrogen compounds like amino acids and heterocyclic hydrocarbons within the meteorite without chemical treatments, a groundbreaking achievement.
Ryugu Asteroid
The Ryugu asteroid particles, brought back by the Hayabusa spacecraft, are also pristine extraterrestrial materials that closely match the composition of CI (Ivuna-type) chondrites, which are proxies for the bulk solar system composition. These particles display an intricate relationship between organic matter and phyllosilicates, indicating maximum temperatures of ~30°C during aqueous alteration, and their isotopic compositions suggest an outer solar system origin.
Pristine Metorite Research
Pristine meteorites are crucial for studying the early solar system and the origins of life, as they have not been altered by terrestrial processes. Researchers took extensive measures to prevent contamination during the handling and analysis of the Winchcombe and Ryugu samples, such as using airtight containers, glove boxes with inert atmospheres, and specialized sample holders.
The advanced analytical techniques employed, like high-resolution electron microscopy and synchrotron-based X-ray techniques, allowed for the characterization of these delicate organic compounds without chemical extraction, preserving their integrity. These pristine meteorites provide the most authentic glimpse into the primordial materials that seeded life on Earth and offer new insights into our cosmic origins.
Pristine Meteorites Composition
Common minerals and materials found in pristine meteorites, along with the temperatures at which they form:
1. Olivine (Mg,Fe)_2SiO_4:
• Forms at high temperatures, around 1,500°C to 1,800°C.
2. Pyroxene (Mg,Fe)SiO_3:
• Forms at temperatures between 1,000°C and 1,500°C.
3. Plagioclase Feldspar (NaAlSi_3O_8 – CaAl_2Si_2O_8):
• Forms between 1,000°C and 1,400°C.
4. Metallic Iron-Nickel (Fe-Ni alloys):
• Forms at temperatures above 1,000°C, with significant metal solidification occurring around 1,200°C to 1,600°C.
5. Troilite (FeS):
• Forms at temperatures around 900°C to 1,100°C.
6. Chromite (FeCr_2O_4):
• Forms at temperatures between 1,000°C and 1,300°C.
7. Calcium-Aluminum-rich Inclusions (CAIs):
• Form at very high temperatures, around 1,300°C to 1,700°C. These are among the first solids to condense from the solar nebula.
8. Chondrules (spherical silicate inclusions):
• Form at high temperatures, approximately 1,600°C to 1,700°C, during rapid cooling from molten droplets.
9. Phyllosilicates (clay minerals):
• Form at relatively low temperatures, below 500°C, typically through aqueous alteration processes.
These components and their formation temperatures illustrate the diverse thermal history and conditions within the parent bodies of meteorites.
Outer Solar System Temperatures:
In the Kuiper Belt, which extends from about 30 to 55 astronomical units (AU) from the Sun, the temperatures can range from about 30 to 50 Kelvin (-243 to -223 degrees Celsius or -405 to -369 degrees Fahrenheit).
Beyond the Kuiper Belt, in the more distant Oort Cloud, temperatures can drop even further. The Oort Cloud is located approximately 2,000 to 100,000 AU from the Sun. Here, the temperatures are estimated to be around 4 to 20 Kelvin (-269 to -253 degrees Celsius or -452 to -423 degrees Fahrenheit).
The cosmic microwave background temperature, which is about 2.7 Kelvin.
References:
The Winchcombe meteorite, a unique and pristine witness from the outer solar system
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Extraterrestrial building blocks of life discovered in UK meteorite
https://www.earth.com/news/extraterrestrial-building-blocks-of-life-discovered-in-uk-meteorite/
A pristine record of outer Solar System materials from asteroid Ryugu’s returned sample
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The Winchcombe meteorite, a unique and pristine witness from the outer solar system
King, A. & Daly, Luke & Rowe, James & Joy, Katherine & Greenwood, R. & Devillepoix, Hadrien & Suttle, Martin & Chan, Queenie H. S. & Russell, Sara & Bates, Helena & Bryson, James & Clay, Patricia & Vida, Denis & Lee, M. & O’Brien, Aine & Hallis, L. & Stephen, Natasha & Tartese, Romain & Sansom, Eleanor & Wilcock, Rob.
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The nucleosynthetic fingerprint of the outermost protoplanetary disk and early Solar System dynamics
ELISHEVAH VAN KOOTEN HTTPS://ORCID.ORG/0000-0003-3333-4421 , XUCHAO ZHAO HTTPS://ORCID.ORG/0000-0003-0268-8139, IAN FRANCHI HTTPS://ORCID.ORG/0000-0003-4151-0480, PO-YEN TUNG HTTPS://ORCID.ORG/0000-0002-2338-1219, SIMON FAIRCLOUGH HTTPS://ORCID.ORG/0000-0003-3781-8212, JOHN WALMSLEY HTTPS://ORCID.ORG/0000-0002-9320-500X, ISAAC ONYETT, MARTIN SCHILLER HTTPS://ORCID.ORG/0000-0003-4149-0627, AND MARTIN BIZZARRO HTTPS://ORCID.ORG/0000-0001-9966-2124
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Circular Astronomy 