A primordial 15N-depleted organic component detected within the carbonaceous chondrite Maribo

Abstract

We report on the detection of primordial organic matter within the carbonaceous chondrite Maribo that is distinct from the majority of organics found in extraterrestrial samples. We have applied high-spatial resolution techniques to obtain C-N isotopic compositions, chemical, and structural information of this material. The organic matter is depleted in 15N relative to the terrestrial value at around δ15N ~ -200‰, close to compositions in the local interstellar medium. Morphological investigations by electron microscopy revealed that the material consists of µm- to sub-µm-sized diffuse particles dispersed within the meteorite matrix. Electron energy loss and synchrotron X-ray absorption near-edge structure spectroscopies show that the carbon functional chemistry is dominated by aromatic and C=O bonding environments similar to primordial organics from other carbonaceous chondrites. The nitrogen functional chemistry is characterized by C-N double and triple bonding environments distinct from what is usually found in 15N-enriched organics from aqueously altered carbonaceous chondrites. Our investigations demonstrate that Maribo represents one of the least altered CM chondrite breccias found to date and contains primordial organic matter, probably originating in the interstellar medium.

Macromolecular organic matter in samples of the asteroid (162173) Ryugu

“…15 N-depleted coldspots (δ 15 N = −100 to −380‰) were detected. 15 N coldspots have previously been reported in the matrices of carbonaceous chondrites ( 57 – 59 ) and IDPs ( 43 ) and have been interpreted as indicating organic grains that have been partially equilibrated with protosolar or interstellar N 2 gas ( 43 ).…”

Tracing the earliest stages of hydrothermal alteration on the CM chondrite parent body

“…Amorphous silicates are highly reactive and expected to be preserved only in the matrix of the least altered meteorites. LAP 04514, LAP 04796, and LAP 04565 contain Fe‐bearing amorphous silicates in their matrices (Abreu & Crispin, 2017; Abreu et al., 2017, 2020), and they have also been found in A‐12169, LEW 85311, Paris, and Maribo (Hewins et al., 2014; Kimura et al., 2020; Lee, Cohen, King & Greenwood, 2019; Leroux et al., 2015; Vollmer et al., 2020). Leroux et al.…”

“…Most CM chondrites are complex breccias consisting of multiple lithologies that preserve differing hydration conditions (Lentfort et al., 2020; Verdier‐Paoletti et al., 2019); however, only a handful of CM chondrites have been found to contain lithologies that record the earliest stages (CM ≥2.6) of aqueous alteration. Some of the least altered CM chondrites include Paris (CM2.9–2.7) (Hewins et al., 2014; Leroux et al., 2015; Marrocchi et al., 2014; Rubin, 2015), Maribo (CM2.7–2.6) (Haack et al., 2012; Lentfort et al., 2020; Vollmer et al., 2020), Elephant Moraine (EET) 96029 (CM2.7) (Lee et al., 2016), Queen Alexandra Range (QUE) 97990 (CM2.6) (Rubin et al., 2007; Takir et al., 2013), and possibly Yamato (Y)‐791198 (CM2.4) (Chizmadia & Brearley, 2008; Howard, Benedix, Bland & Cressey, 2011; Rubin et al., 2007). Lewis Cliff (LEW) 85311 is classified as a CM2.7–2.6 (CM2.3 in Friedrich et al., 2018) but has properties distinct from other CMs including a higher abundance of refractory inclusions and an unusual carbonate mineralogy (Lee, Cohen, King & Greenwood, 2019).…”

“…Typical characteristics of mildly altered CM chondrites include pristine amorphous silicates and metal in the matrix, the retention of glassy mesostasis in chondrules, melilite‐bearing CAIs, and high presolar grain abundances (Chizmadia & Brearley, 2008; Hewins et al., 2014; Kimura et al., 2020; Lee et al., 2016; Leroux et al., 2015; Marrocchi et al., 2014; Nittler et al., 2021; Palmer & Lauretta, 2011; Rubin, 2015; Rubin et al., 2007; Vollmer et al., 2020). They often have lower bulk phyllosilicate and water contents and higher δD and δ 15 N values than more altered CM chondrites (Alexander et al., 2013; Garenne et al., 2014; Howard et al., 2015; Vacher et al., 2020), and several have oxygen isotopic compositions that either fall at the 16 O‐rich end of the CM field or overlap with the CV‐CK/CO fields (Ebert et al., 2019; Haack et al., 2012; Hewins et al., 2014; Howard, Benedix, Bland, Gibson et al., 2011; Kimura et al., 2020; Lee et al., 2016; Lee, Cohen, King & Greenwood, 2019).…”

Heterogeneous nature of the carbonaceous chondrite breccia Aguas Zarcas – Cosmochemical characterization and origin of new carbonaceous chondrite lithologies

“…18b, d, f). These peaks are commonly observed in the type 1 and 2 carbonaceous chondrites (Le Guillou et al, 2014) as well as in the least-altered CMs (Vinogradoff et al, 2017;Vollmer et al, 2020). While OM1 and OM2 exhibit common peaks, their intensities vary.…”