Organic Geochemistry of Meteorites

Sephton, Mark A.

doi:10.1016/b978-0-08-095975-7.01002-0

Cited by 35 publications

(63 citation statements)

References 221 publications

(344 reference statements)

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“…Primitive objects in our solar system, such as asteroids, can contain substantial amounts of organic matter (Sephton, 2014). Organic matter represents an aliquot of the pre-existing and ongoing chemical evolution in the early solar system.…”

Section: Introductionmentioning

confidence: 99%

“…Finally, on asteroidal meteorite parent bodies liquid phase reactions, surface catalysis and thermal processing may modify or produce organic structures. With the number of possible environments and mechanisms available it is possible that the organic macromolecular material is not formed from a single source or by one process but has a mixed heritage (Sephton, 2014).…”

Section: Introductionmentioning

confidence: 99%

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Heat, Aromatic Units, and Iron-Rich Phyllosilicates: A Mechanism for Making Macromolecules in the Early Solar System

Watson

Sephton

2015

Astrobiology

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The major organic component in carbonaceous chondrites is a highly aromatic macromolecular material. Aromatic organic matter and phyllosilicates are colocated in these meteorites, and it is possible that the physical association represents a synthetic chemical relationship. To explore the potential reactions that could take place to produce the aromatic macromolecular material, we heated various simple aromatic units in the presence of montmorillonite with different exchanged cations. The majority of cation-exchanged montmorillonites tested, sodium-, aluminum-, iron-, nickel-, and cobalt-rich montmorillonites, do not produce polymerization products. By contrast, Fe(3+) cation-exchanged montmorillonite readily facilitates addition reactions between aromatic hydrocarbons. A feasible mechanism for the process is oxidative coupling, which involves a corresponding reduction of the Fe(3+) cation to its Fe(2+) counterpart. A similar reduction process for the other metal cations does not take place, highlighting the importance of iron. This simple process is one feasible mechanism for the construction of aromatic macromolecules such as those found in carbonaceous chondrites. The search for a relationship between Fe(3+)-rich phyllosilicates and aromatic organic structures (particularly dimers, trimers, and more polymerized forms) in carbonaceous chondrites would represent an effective test for constraining the role of clay catalysis in the early Solar System.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Heat, Aromatic Units, and Iron-Rich Phyllosilicates: A Mechanism for Making Macromolecules in the Early Solar System

Watson

Sephton

2015

Astrobiology

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“…Organic carbon‐rich meteorites from asteroids (Grady et al. ) are good examples of the widespread nature of nonbiological organic chemistry in the solar system (Sephton ) and most organic materials in Martian meteorites appear to indicate origins by nonbiological processes, including igneous, hydrothermal, and impact‐based synthesis mechanisms (Steele et al. , ).…”

Section: Objective 2: Assess and Interpret The Potential Biological Hmentioning

confidence: 99%

The potential science and engineering value of samples delivered to Earth by Mars sample return

Beaty¹,

Grady²,

McSween³

et al. 2019

Meteorit & Planetary Scien

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Executive Summary Return of samples from the surface of Mars has been a goal of the international Mars science community for many years. Affirmation by NASA and ESA of the importance of Mars exploration led the agencies to establish the international MSR Objectives and Samples Team (iMOST). The purpose of the team is to re‐evaluate and update the sample‐related science and engineering objectives of a Mars Sample Return (MSR) campaign. The iMOST team has also undertaken to define the measurements and the types of samples that can best address the objectives. Seven objectives have been defined for MSR, traceable through two decades of previously published international priorities. The first two objectives are further divided into sub‐objectives. Within the main part of the report, the importance to science and/or engineering of each objective is described, critical measurements that would address the objectives are specified, and the kinds of samples that would be most likely to carry key information are identified. These seven objectives provide a framework for demonstrating how the first set of returned Martian samples would impact future Martian science and exploration. They also have implications for how analogous investigations might be conducted for samples returned by future missions from other solar system bodies, especially those that may harbor biologically relevant or sensitive material, such as Ocean Worlds (Europa, Enceladus, Titan) and others. Summary of Objectives and Sub‐Objectives for MSR Identified by iMOST This objective is divided into five sub‐objectives that would apply at different landing sites. 1.1 Characterize the essential stratigraphic, sedimentologic, and facies variations of a sequence of Martian sedimentary rocks. 1.2 Understand an ancient Martian hydrothermal system through study of its mineralization products and morphological expression. 1.3 Understand the rocks and minerals representative of a deep subsurface groundwater environment. 1.4 Understand water/rock/atmosphere interactions at the Martian surface and how they have changed with time. 1.5 Determine the petrogenesis of Martian igneous rocks in time and space. This objective has three sub‐objectives: 2.1 Assess and characterize carbon, including possible organic and pre‐biotic chemistry. 2.2 Assay for the presence of biosignatures of past life at sites that hosted habitable environments and could have preserved any biosignatures. 2.3 Assess the possibility that any life forms detected are alive, or were recently alive. Summary of iMOST Findings Several specific findings were identified during the iMOST study. While they are not explicit recommendations, we suggest that they should serve as guidelines for future decision making regarding planning of potential future MSR missions. The samples to be collected by the Mars 2020 (M‐2020) rover will be of sufficient size and quality to address and solve a wide variety of scientific questions. Samples, by definition, are a statistical representation of a larger entity...

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“…Importantly for our project, there is one class of meteorites that contains appreciable amounts of carbon, the carbonaceous chondrite meteorites. Their carbon content is ∼ 2% by mass, their parent bodies are the C-class asteroids (Sephton et al, 2002;Sephton, 2014). The vast majority of the remaining asteroids are S types, the parent bodies of ordinary chondrite meteorites.…”

Section: Asteroidsmentioning

confidence: 99%

“…Comets are known to contain substantial amounts of organics, which was shown by measurements on Halley, 67P/Churyumov-Gerasimenko, and by Stardust on Wild 2 (Goesmann et al, 2015;Jessberger et al, 1988;Sandford et al, 2006). Among the various types of meteorites found on Earth, the carbonaceous chondrites are rich in organics (Sephton et al, 2002;Sephton, 2014); their parent bodies are the C-class asteroids. Iglesias-Groth et al (2011) have shown that organic molecules in comets and asteroids are able to survive a radiation dose equal to the expected total dose received during the age of the Solar System.…”

Section: Introductionmentioning

confidence: 99%

Delivery of organics to Mars through asteroid and comet impacts

Frantseva

Mueller

Kate

et al. 2018

Icarus

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Given rapid photodissociation and photodegradation, the recently discovered organics in the Martian subsurface and atmosphere were probably delivered in geologically recent times. Possible parent bodies are C-type asteroids, comets, and interplanetary dust particles (IDPs).The dust infall rate was estimated, using different methods, to be between 0.71 and 2.96 × 10 6 kg/yr (Nesvorný et al., 2011;Borin et al., 2017;Crismani et al., 2017); assuming a carbon content of 10% (Flynn, 1996), this implies an IDP carbon flux of 0.07 − 0.3 × 10 6 kg/yr. We calculate for the first time the carbon flux from impacts of asteroids and comets.To this end, we perform dynamical simulations of impact rates on Mars. We use the N-body integrator RMVS/Swifter to propagate the Sun and the eight planets from their current positions. We separately add comets and asteroids to the simulations as massless test particles, based on their current orbital elements, yielding Mars impact rates of 4.34 × 10 −3 comets/Myr and 3.3 asteroids/Myr.We estimate the delivered amount of carbon using published carbon content values. In asteroids, only C types contain appreciable amounts of carbon.Given the absence of direct taxonomic information on the Mars impactors, we base ourselves on the measured distribution of taxonomic types in combination with dynamic models of the origin of Mars-crossing asteroids.We estimate the global carbon flux on Mars from cometary impacts to be ∼ 0.013 × 10 6 kg/yr within an order of magnitude, while asteroids deliver ∼ 0.05 × 10 6 kg/yr. These values correspond to ∼ 4 − 19% and ∼ 17 − 71%, respectively, of the IDP-borne carbon flux estimated by Nesvorný et al., Borin et al. and Crismani et al.. Unlike the spatially homogeneous IDP infall, impact ejecta are distributed locally, concentrated around the impact site. We find organics from asteroids and comets to dominate over IDP-borne organics at distances up to 150 km from the crater center. Our results may be important for the interpretation of in situ detections of organics on Mars.

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Organic Geochemistry of Meteorites

Cited by 35 publications

References 221 publications

Heat, Aromatic Units, and Iron-Rich Phyllosilicates: A Mechanism for Making Macromolecules in the Early Solar System

Heat, Aromatic Units, and Iron-Rich Phyllosilicates: A Mechanism for Making Macromolecules in the Early Solar System

The potential science and engineering value of samples delivered to Earth by Mars sample return

Delivery of organics to Mars through asteroid and comet impacts

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