Evidence for Magnesium Isotope Heterogeneity in the Solar Protoplanetary Disk

Larsen, Kirsten; Trinquier, Anne; Paton, Chad; Schiller, Martin; Wielandt, D.; Ivanova, М. А.; Connelly, James N.; Nordlund, Åke; Krot, Alexander N.; Bizzarro, Martin

doi:10.1088/2041-8205/735/2/l37

Cited by 282 publications

(490 citation statements)

References 43 publications

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“…Thus, CI chondrites provide a lower limit for the average μ 54 Cr value of thermally unprocessed molecular cloud material. Primordial molecular cloud material unpolluted by 26 Al is expected to have a μ 26 Mg* value consistent with the Solar System initial composition, which is inferred to be −20.4 ± 2.9 ppm relative to CI chondrites (13). Therefore, unlike inner Solar System objects, the isotopic signature of the thermally unprocessed and 26 Al-poor primordial molecular cloud matter is expected to show a decoupling between their μ 26 Mg* and μ 54 Cr values (Fig.…”

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confidence: 93%

“…Therefore, these objects may provide a direct window into the formation history of the outer Solar System. presolar carriers, producing residual isotopic heterogeneity (12)(13)(14)(15). In this model, the correlated μ 26 Mg*−μ 54 Cr array represents the unmixing of distinct dust populations with contrasting thermal properties, namely unmixing of old, galactically inherited homogeneous dust from a young supernovae-derived dust component formed shortly before or during the evolution of the giant molecular cloud structure parental to the protosolar molecular cloud core.…”

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confidence: 99%

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Isotopic evidence for primordial molecular cloud material in metal-rich carbonaceous chondrites

Kooten

Wielandt

Schiller

et al. 2016

Proc. Natl. Acad. Sci. U.S.A.

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The short-lived 26 Al radionuclide is thought to have been admixed into the initially 26 Al-poor protosolar molecular cloud before or contemporaneously with its collapse. Bulk inner Solar System reservoirs record positively correlated variability in mass-independent 54 Cr and 26 Mg*, the decay product of 26 Al. This correlation is interpreted as reflecting progressive thermal processing of infalling 26 Al-rich molecular cloud material in the inner Solar System. The thermally unprocessed molecular cloud matter reflecting the nucleosynthetic makeup of the molecular cloud before the last addition of stellar-derived 26 Al has not been identified yet but may be preserved in planetesimals that accreted in the outer Solar System. We show that metal-rich carbonaceous chondrites and their components have a unique isotopic signature extending from an inner Solar System composition toward a 26 Mg*-depleted and 54 Cr-enriched component. This composition is consistent with that expected for thermally unprocessed primordial molecular cloud material before its pollution by stellar-derived 26 Al. The 26 Mg* and 54 Cr compositions of bulk metal-rich chondrites require significant amounts (25-50%) of primordial molecular cloud matter in their precursor material. Given that such high fractions of primordial molecular cloud material are expected to survive only in the outer Solar System, we infer that, similarly to cometary bodies, metal-rich carbonaceous chondrites are samples of planetesimals that accreted beyond the orbits of the gas giants. The lack of evidence for this material in other chondrite groups requires isolation from the outer Solar System, possibly by the opening of disk gaps from the early formation of gas giants. molecular cloud | outer Solar System | metal-rich chondrites | isotopes | chondrite accretion regions L ow-mass stars like our Sun form by the gravitational collapse of the densest parts of molecular clouds comprising stellarderived dust and gas. Collapsing clouds swiftly evolve into deeply embedded protostars that rapidly accrete material from their surrounding envelopes via a protoplanetary disk (1), in which planetesimals and planetary embryos form over timescales of several million years (2). Chondritic meteorites (chondrites) are fragments of early-formed planetesimals that avoided melting and differentiation and, therefore, provide a record of the earliest evolutionary stages of the Sun and its protoplanetary disk. Most chondrites contain calcium−aluminum-rich inclusions (CAIs) and chondrules, which formed by high-temperature processes that included evaporation, condensation, and melting during short-lived heating events (3). CAIs represent the oldest dated solids and, thus, define the age of the Solar System at 4,567.3 ± 0.16 Ma (4). It is inferred that CAIs formed near the proto-Sun during a brief time interval (<0

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confidence: 93%

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confidence: 99%

Isotopic evidence for primordial molecular cloud material in metal-rich carbonaceous chondrites

Kooten

Wielandt

Schiller

et al. 2016

Proc. Natl. Acad. Sci. U.S.A.

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140

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“…Recent high-precision 26 Al- 26 Mg systematics of bulk CV CAIs define the so-called canonical 26 Al/ 27 Al ratio of (5.252 ± 0.019) × 10 -5 (7). The uncertainty of the canonical 26 Al/ 27 Al ratio corresponds to ∼4,000 y, implying a brief episode of condensation and melt evaporation that resulted in Al/Mg fractionation event(s).…”

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confidence: 99%

¹⁸² Hf– ¹⁸² W age dating of a ²⁶ Al-poor inclusion and implications for the origin of short-lived radioisotopes in the early Solar System

Holst

Olsen

Paton

et al. 2013

Proc. Natl. Acad. Sci. U.S.A.

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Refractory inclusions [calcium–aluminum-rich inclusions, (CAIs)] represent the oldest Solar System solids and provide information regarding the formation of the Sun and its protoplanetary disk. CAIs contain evidence of now extinct short-lived radioisotopes (e.g., 26 Al, 41 Ca, and 182 Hf) synthesized in one or multiple stars and added to the protosolar molecular cloud before or during its collapse. Understanding how and when short-lived radioisotopes were added to the Solar System is necessary to assess their validity as chronometers and constrain the birthplace of the Sun. Whereas most CAIs formed with the canonical abundance of 26 Al corresponding to 26 Al/ 27 Al of ∼5 × 10 −5 , rare CAIs with fractionation and unidentified nuclear isotope effects (FUN CAIs) record nucleosynthetic isotopic heterogeneity and 26 Al/ 27 Al of <5 × 10 −6 , possibly reflecting their formation before canonical CAIs. Thus, FUN CAIs may provide a unique window into the earliest Solar System, including the origin of short-lived radioisotopes. However, their chronology is unknown. Using the 182 Hf– 182 W chronometer, we show that a FUN CAI recording a condensation origin from a solar gas formed coevally with canonical CAIs, but with 26 Al/ 27 Al of ∼3 × 10 −6 . The decoupling between 182 Hf and 26 Al requires distinct stellar origins: steady-state galactic stellar nucleosynthesis for 182 Hf and late-stage contamination of the protosolar molecular cloud by a massive star(s) for 26 Al. Admixing of stellar-derived 26 Al to the protoplanetary disk occurred during the epoch of CAI formation and, therefore, the 26 Al– 26 Mg systematics of CAIs cannot be used to define their formation interval. In contrast, our results support 182 Hf homogeneity and chronological significance of the 182 Hf– 182 W clock.

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“…After being incorporated in solids, these short-lived radioactive isotopes function as potentially very accurate clocks, in that both parent and daughter nuclei are locked in minerals and differences in their ratios can be recovered today, using high precision mass spectrometers (e.g. Trinquier et al 2008;Larsen et al 2010). In addition 26 Al was present in sufficient quantities to melt the interior of even rather small asteroids (Baker et al 2005), and more long lived radioactive isotopes are still important contributors to the internal heat balance of planets.…”

Section: Evidence From Cosmo-chemistrymentioning

confidence: 99%

“…Recent improvements in the precision of 26 Al → 26 Mg analysis indicate, additionally, that the thermal processing caused significant heterogeneity of the 26 Al distribution (Larsen et al 2010). This introduces significant uncertainties in previous age determinations based on the assumption that 26 Al was still homogeneously distributed at the time when the first solids formed in the solar system.…”

Section: Evidence From Cosmo-chemistrymentioning

confidence: 99%

Formation of brown dwarfs and planets

Nordlund

2010

Proc. IAU

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Abstract. Brown dwarfs and massive planets have similar structures, and there is probably an overlap in mass between the most massive planets and the lowest mass brown dwarfs. This raises questions as to what extent the structures of the most massive planets and lowest mass brown dwarfs differ, and what similarities (or not) there might be between their formation mechanisms. Here I discuss these issues on the background of recent numerical simulations of star formation, new evidence from cosmochemistry about the conditions in the early solar system, and recently discovered mechanisms that can expedite planetesimal and possibly planet formation greatly.

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Evidence for Magnesium Isotope Heterogeneity in the Solar Protoplanetary Disk

Cited by 282 publications

References 43 publications

Isotopic evidence for primordial molecular cloud material in metal-rich carbonaceous chondrites

Isotopic evidence for primordial molecular cloud material in metal-rich carbonaceous chondrites

¹⁸² Hf– ¹⁸² W age dating of a ²⁶ Al-poor inclusion and implications for the origin of short-lived radioisotopes in the early Solar System

Formation of brown dwarfs and planets

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Evidence for Magnesium Isotope Heterogeneity in the Solar Protoplanetary Disk

Cited by 282 publications

References 43 publications

Isotopic evidence for primordial molecular cloud material in metal-rich carbonaceous chondrites

Isotopic evidence for primordial molecular cloud material in metal-rich carbonaceous chondrites

182 Hf– 182 W age dating of a 26 Al-poor inclusion and implications for the origin of short-lived radioisotopes in the early Solar System

Formation of brown dwarfs and planets

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¹⁸² Hf– ¹⁸² W age dating of a ²⁶ Al-poor inclusion and implications for the origin of short-lived radioisotopes in the early Solar System