Planetary and pre-solar noble gases in meteorites

The Paris carbonaceous chondrite represents the most pristine carbonaceous chondrite, providing a unique opportunity to investigate the composition of early solar system materials prior to the onset of significant aqueous alteration. A dual origin (namely from the inner and outer solar system) has been demonstrated for water in the Paris meteorite parent body (Piani et al. 2018 ). Here, we aim to evaluate the contribution of outer solar system (cometary‐like) water ice to the inner solar system water ice using Xe isotopes. We report Ar, Kr, and high‐precision Xe isotopic measurements within bulk CM 2.9 and CM 2.7 fragments, as well as Ne, Ar, Kr, and Xe isotope compositions of the insoluble organic matter ( IOM ). Noble gas signatures are similar to chondritic phase Q with no evidence for a cometary‐like Xe component. Small excesses in the heavy Xe isotopes relative to phase Q within bulk samples are attributed to contributions from presolar materials. CM 2.7 fragments have lower Ar/Xe relative to more pristine CM 2.9 fragments, with no systematic difference in Xe contents. We conclude that Kr and Xe were little affected by aqueous alteration, in agreement with (1) minor degrees of alteration and (2) no significant differences in the chemical signature of organic matter in CM 2.7 and CM 2.9 areas (Vinogradoff et al. 2017 ). Xenon contents in the IOM are larger than previously published data of Xe in chondritic IOM , in line with the Xe component in Paris being pristine and preserved from Xe loss during aqueous alteration/thermal metamorphism.

Section: Discussionsupporting

confidence: 91%

Section: Discussionmentioning

confidence: 99%

Primordial heavy noble gases in the pristine Paris carbonaceous chondrite

Bekaert

Marrocchi

Meshik

et al. 2018

“…Ne three‐isotope plot (main) and 21 Ne cos versus 20 Ne (inset). Noble gas components from Ott (). Crosses show the end member compositions of solar wind ( SW ), implantation mass‐fractionated solar wind ( fSW ), primoridal Q gases component found in “phase Q” (Q), Earth's atmosphere (Air), primordial HL gases component enriched in both heavy and light elements found in presolar diamonds ( HL ), and galactic cosmogenic radionuclides ( GCR ).…”

Section: Resultsmentioning

confidence: 99%

The CM carbonaceous chondrite regolith Diepenveen

Langbroek

Jenniskens

Kriegsman

et al. 2019

A carbonaceous chondrite was recovered immediately after the fall near the village of Diepenveen in the Netherlands on October 27, 1873, but came to light only in 2012. Analysis of sodium and poly‐aromatic hydrocarbon content suggests little contamination from handling. Diepenveen is a regolith breccia with an overall petrology consistent with a CM classification. Unlike most other CM chondrites, the bulk oxygen isotopes are extremely 16O rich, apparently dominated by the signature of anhydrous minerals, distributed on a steep slope pointing to the domain of intrinsic CM water. A small subset plots closer to the normal CM regime, on a parallel line 2 ‰ lower in δ17O. Different lithologies in Diepenveen experienced varying levels of aqueous alteration processing, being less aqueously altered at places rather than more heated. The presence of an agglutinate grain and the properties of methanol‐soluble organic compounds point to active impact processing of some of the clasts. Diepenveen belongs to a CM clan with ~5 Ma CRE age, longer than most other CM chondrites, and has a relatively young K‐Ar resetting age of ~1.5 Ga. As a CM chondrite, Diepenveen may be representative of samples soon to be returned from the surface of asteroid (162173) Ryugu by the Hayabusa2 spacecraft.

“…; Huss et al. ; Ott ). Almost all of the Q gases can be lost by HNO 3 treatment, but the corresponding weight loss of IOM is small (less than 1%; Lewis et al.…”

Section: Introductionmentioning

confidence: 99%

“…All attempts to separate Q from IOM in pure form have failed (Matsuda et al. ; Ott ; Marrocchi et al. ) because of the very similar chemical properties of the two phases.…”

Section: Introductionmentioning

confidence: 99%

Reaction of Q to thermal metamorphism in parent bodies: Experimental simulation

Verchovsky

Hunt

Montgomery

et al. 2018

Planetary noble gases in chondrites are concentrated in an unidentified carrier phase, called “Q.” Phase Q oxidized at relatively low temperature in pure oxygen is a very minor part of insoluble organic matter (IOM), but has not been separated in a pure form. High‐pressure (HP) experiments have been used to test the effects of thermal metamorphism on IOM from the Orgueil (CI1) meteorite, at conditions up to 10 GPa and 700 °C. The effect of the treatment on carbon structural order was characterized by Raman spectroscopy of the carbon D and G bands. The Raman results show that the IOM becomes progressively more graphite‐like with increasing intensity and duration of the HP treatment. The carbon structural transformations are accompanied by an increase in the release temperatures for IOM carbon and 36Ar during stepped combustion (the former to a greater extent than the latter for the most HP treated sample) when compared with the original untreated Orgueil (CI1) sample. The 36Ar/C ratio also appears to vary in response to HP treatment. Since 36Ar is a part of Q, its release temperature corresponds to that for Q oxidation. Thus, the structural transformations of Q and IOM upon HP treatment are not equal. These results correspond to observations of thermal metamorphism in the meteorite parent bodies, in particular those of type 4 enstatite chondrites, e.g., Indarch (EH4), where graphitized IOM oxidized at significantly higher temperatures than Q (Verchovsky et al. ). Our findings imply that Q is less graphitized than most of the macromolecular carbonaceous material present during parent body metamorphism and is thus a carbonaceous phase distinct from other meteoritic IOM.