The analysis of CAIs (calcium-aluminum-rich inclusions), IDPs (interplanetary dust particles), and GEMS (glass with embedded metal and sulfides) provides a unique opportunity to sample from hundreds of asteroids and comets and interstellar space, dramatically differing from the traditional strategy of single-destination missions.
CAIs (Calcium-Aluminum-Rich Inclusions)
Calcium-aluminum-rich inclusions (CAIs), found in chondritic meteorites, are the oldest-known objects formed in the infant solar nebula. They preserve clues to the chemical processes and environments that existed during their formation in the nebula phase of the Solar System, which was extremely hot and reducing leading to a volatility-controlled elemental composition. The isotopic compositions of CAIs retain some presolar components which can indicate their nucleosynthetic origin. The CHILI Lab has collaborated with researchers at the Smithsonian to analyze the isotopic compositions of CAIs in order to better understand the major processes that accompanied the formation of the Sun and the solar nebula.
(Source: MacPherson et al.)
FeO temperature map of the 27cE, a CAI from the Efremovka meteorite.
(Image credit: Andrew Davis, taken with our SEM)
An amorphous silicate region in a fine-grained rim, containing a nanophase sulfide and metal grain. A) Scanning transmission electron microscopy image. B-E) Various elemental maps of the same area. F) Metal grain nanodiffraction pattern.
(Image credit: Villalon et al.)
IDPs (Interplanetary Dust Particles)
Remnants from the formation of the Solar System exist in the form of interstellar dust, sitting in our galactic neighborhood. Similarly, interplanetary dust (IDPs), shed by passing comets, can provide information on the processes that occurred during Solar System formation. Sampling from these reservoirs uncovers the identities of the typical feedstock of the planets, revealing our cosmic roots. Characterizing interstellar dust enables the determination of the raw materials that were present during the formation of the solar system and resolves conflicting information about its makeup and size distribution from optical starlight observations, Ulysses and Cassini in situ measurements, and laboratory analysis of Stardust samples. Interplanetary dust samples can be used to determine the degree to which the material in comets was processed by heat and water in the early solar system and to characterize organics delivered by comets to the planets.
(Source: Horányi et al.)
GEMS (Glass with Embedded Metal and Sulfides)
The CHILI Lab has been involved in analyzing GEMS and comparing the isotopic composition with amorphous silicates found in meteorites. GEMS are unique grains found in large quantities within IDPs. These grains are typically under 0.5 micrometers in diameter and are composed of subgrains made from FeNi metal and sulfides within an amorphous Mg-Fe-Al silicate matrix. Their importance comes from their abundance in IDPs, suggesting they are a significant building block in the early Solar System. However, the origin of GEMS is unknown, with two major hypotheses that are fueled by the grain-size limitations in isotopic measurements:
Bright-field images comparing GEMS-like material in A) the Paris meteorite and B) an IDP.
(Image credit: Villalon et al.)
They are presolar in origin and started as free-floating crystal grains in the interstellar medium (ISM) which were exposed to ionizing radiation. They were then sputtered, redeposited, and homogenized in the formation of the Solar System.
They originated in the solar nebula as a late-stage, non-equilibrium condensate and did not undergo homogenization. The isotopic heterogeneity in GEMS stems from non-equilibrium condensation points, with GEMS potentially coming from the same reservoir as IDPs.
(Source: PSRD Discoveries)
Relevant Papers Recently Published by CHILI Lab:
Korsmeyer J. M., Stephan T., Davis A. M., Bloom H. E., MacPherson G. J., and Ivanova M. A. (2022) Molybdenum and ruthenium isotopic composition of a metal grain in a calcium–aluminum-rich inclusion from the Efremovka CV3 chondrite (abstract). Lunar Planet. Sci. 53, #2795. [pdf]
Villalon K. L., Ohtaki K. K., Bradley J. P., Ishii H. A., Davis A. M., and Stephan T. (2021) Search for meteoritic GEMS II: Comparison of inclusions in amorphous silicates from the Paris chondrite and from anhydrous chondritic interplanetary dust particles. Geochim. Cosmochim. Acta 310, 346–362. [html]
Ohtaki K. K., Ishii H. A., Bradley J. P., Villalon K. L., Davis A. M., Stephan T., Bustillo K. C., and Ciston J. (2021) Search for meteoritic GEMS I: Comparison of amorphous silicates in Paris and Acfer 094 chondrite matrices and in anhydrous chondritic interplanetary dust particles. Geochim. Cosmochim. Acta 310, 320–345. [html]
Horányi M., Turner N. J., Alexander C., Balint T., Castillo-Rogez J., Draine B., Engrand C., Hillier J., Ishii H., Kempf S., Lugaro M., Merouane S., Munsat T., Nesvorný D., Nittler L., Pokorný P., Postberg F., Srama R., Stephan T., Sterken V., Sternovsky Z., Stroud R., Szalay J., Westphal A., Wooden D., Grün E., Poppe A., Hu Z., Fries M., and Graps A. (2021) Interplanetary and interstellar dust as windows into solar system origins and evolution. Bulletin of the AAS 53. [html]
Villalon K. L., Ohtaki K. K., Bradley J. P., Ishii H. A., Heck P. R., Keating K., Davis A. M., and Stephan T. (2020) Nanoscale properties of GEMS-like material in primitive carbonaceous chondrites (abstract). Goldschmidt Abstracts 2020, 2685. [pdf]