¹Hassan Sabbah,¹Mickaël Carlos,²Peter Jenniskens,³Muawia H. Shaddad,⁴Jean Duprat,⁵Cyrena A. Goodrich,¹Christine Joblin
The Astrophysical Journal 931, 91 Open Access Link to Article [DOI 10.3847/1538-4357/ac69dd]
¹IRAP, Université Toulouse III—Paul Sabatier, CNRS, CNES, F-31028 Toulouse Cedex 4, France
²SETI Institute, Mountain View, CA 94043, USA
³University of Khartoum, Khartoum 11115, Sudan
⁴IMPMC, CNRS-MNHN-Sorbonne Université, 57 rue Cuvier, F-75005 Paris, France
⁵Lunar and Planetary Institute, USRA, Houston, TX 77058, USA

Buckminsterfullerene, C60, is the largest molecule observed to date in interstellar and circumstellar environments. The mechanism of formation of this molecule is actively debated. Despite targeted searches in primitive carbonaceous chondrites, no unambiguous detection of C60 in a meteorite has been reported to date. Here we report the first firm detection of fullerenes, from C30 to at least C100, in the Almahata Sitta (AhS) polymict ureilite meteorite. This detection was achieved using highly sensitive laser desorption laser ionization mass spectrometry. Fullerenes have been unambiguously detected in seven clasts of AhS ureilites. Molecular family analysis shows that fullerenes are from a different reservoir compared to the polycyclic aromatic hydrocarbons detected in the same samples. The fullerene family correlates best with carbon clusters, some of which may have been formed by the destruction of solid carbon phases by the impacting laser. We show that the detected fullerenes are not formed in this way. We suggest that fullerenes are an intrinsic component of a specific carbon phase that has yet to be identified. The nondetection of fullerenes in the Murchison and Allende bulk samples, while using the same experimental conditions, suggests that this phase is absent or less abundant in these primitive chondrites. The former case would support the formation of fullerenes by shock-wave processing of carbonaceous phases in the ureilite parent body. However, there are no experimental data to support this scenario. This leaves open the possibility that fullerenes are an interstellar heritage and a messenger of interstellar processes.

^1,2,3Debanjan Sengupta,¹Paul R. Estrada,¹Jeffrey N. Cuzzi,⁴Munir Humayun
The Astrophysical Journal 932, 82 Open Access Link to Article [DOI 10.3847/1538-4357/ac6dcc]
¹NASA Ames Research Center; Mail Stop 245-3, Moffett Field, CA 94035, USA
²Universities Space Research Association; 7178 Columbia Gateway Drive, Columbia, MD 21046, USA
³NASA Postdoctoral Program (NPP) Fellow
⁴National High Magnetic Field Laboratory and Department of Earth, Ocean and Atmospheric Science, Florida State University, 1800 E. Paul Dirac Drive, Tallahassee, FL, 32310, USA

Rocky bodies of the inner solar system display a systematic depletion of “moderately volatile elements” (MVEs) that correlates with the expected condensation temperature of their likely host materials under protoplanetary nebula conditions. In this paper, we present and test a new hypothesis in which open-system loss processes irreversibly remove vaporized MVEs from high nebula altitudes, leaving behind the more refractory solids residing much closer to the midplane. The MVEs irreversibly lost from the nebula through these open-system loss processes are then simply unavailable for condensation onto planetesimals forming even much later, after the nebula has cooled, overcoming a critical difficulty encountered by previous models of this type. We model open-system loss processes operating at high nebula altitudes, such as resulting from disk winds flowing out of the system entirely, or layered accretion directly onto the young Sun. We find that mass-loss rates higher than those found in typical T-Tauri disk winds, lasting short periods of time, are most satisfactory, pointing to multiple intense early outburst stages. Using our global nebula model, incorporating realistic particle growth and inward drift for solids, we constrain how much the MVE-depletion signature in the inner region is diluted by the drift of undepleted material from the outer nebula. We also find that a significant irreversible loss of the common rock-forming elements (Fe, Mg, Si) can occur, leading to a new explanation of another long-standing puzzle of the apparent “enhancement” in the relative abundance of highly refractory elements in chondrites.