A search for C60 in carbonaceous chondrites

Area of Science:

• Astrochemistry
• Cosmochemistry
• Planetary Science

Background:

• Carbon compounds, including fullerenes (C60) and polycyclic aromatic hydrocarbons (PAHs), are key components of interstellar and meteoritic material.
• The Murchison meteorite, known for its rich organic content and likely interstellar components (indicated by deuterium enrichment), is a prime target for studying extraterrestrial carbon chemistry.

Purpose of the Study:

• To quantify the C60 content in interior samples of the Murchison meteorite.
• To investigate the formation pathways of carbon compounds in space and their relationship to interstellar observations.
• To explore the presence and significance of high molecular weight PAHs in meteorites.

Main Methods:

• Analysis of interior meteorite samples using two distinct analytical routes.
• Gas chromatography-mass spectrometry (GC-MS) for identifying and quantifying organic molecules.
• Spectroscopic analysis to compare meteorite-derived compounds with interstellar emission features.

Main Results:

• An upper limit of 2 parts per billion (ppb) for C60 content was determined in the Murchison meteorite.
• High molecular weight PAHs, including coronene and its derivatives, were identified in both Murchison and Allende meteorites.
• Experimental results suggest PAHs can replace fullerenes as stable end products during carbon condensation in the presence of hydrogen.

Conclusions:

• The low C60 abundance in Murchison argues against its ubiquitous presence in the interstellar medium.
• PAHs, particularly high molecular weight ones like coronene, may be more significant interstellar carbon compounds than previously thought.
• The spectral features of coronene derivatives align with unidentified interstellar infrared emission bands, suggesting a potential link.