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Accueil > In the headlines > Ultra-Carbonaceous Antarctic Micrometeorites reveal a new type of cometary material.

Ultra-Carbonaceous Antarctic Micrometeorites reveal a new type of cometary material.

All the versions of this article: English , français

A multidisciplinary team involving researchers from the IAS, CSNSM and SOLEIL SMIS/beam line, has characterized in the laboratory the organic component from exceptional organic-rich interplanetary dust particles, i.e. Ultra-Carbonaceous Antarctic MicroMeteorites (UCAMMs).

Interplanetary dust particles travel across the solar system and represent the largest mass flux of extraterrestrial material falling on Earth as micrometeorites, with sizes up to a few hundreds of micron. The UCAMMs characterized in this work were recovered from Antarctic snow at the vicinity of the Concordia Station [1]. UCAMMs represent a small fraction of the micrometeorite flux but contain large amounts of organic matter with characteristics differing from other type of extraterrestrial material.

In this work, the authors performed the first systematic survey of height UCAMMs by means of synchrotron infrared microspectroscopy (µ-FTIR), visible Raman spectroscopy and electron microprobe analyses. The results reveal an organic component with a low aliphatic CH versus aromatic C=C ratio. This UCAMMs organic component is nitrogen-rich and oxygen-poor compared to carbonaceous chondrites and IDPs. The µ-FTIR spectra are in agreement with the presence of ketone or aldehyde functional groups and some spectra show both IR and Raman nitrile signature. The spectra are compatible with the presence of C-N bondings in the carbonaceous network, and are significantly different from that reported in organic matter extracted from meteorite. Finally, the silicate-to-carbon ratio in UCAMMs is well below that reported in both IDPs and meteorites.

This comprehensive set of results indicates that the formation of this specific organic compound occurs via physicochemical mechanisms taking place in a cold, nitrogen rich environment, exposed to energetic radiations (photons, cosmic rays), like the surface of icy parent bodies in the outer solar system. Both the C/Si and N/C abundance ratios measured in this work are the highest observed in solar system solids. This peculiar composition of UCAMMs provides an additional hint of the presence of a heliocentric positive gradient in the C/Si and N/C abundance ratios in the solar system protoplanetary disc evolution.

The UCAMMs provides new insight on the composition of the surface of small icy bodies well above the Neptune orbit, and participate to a better understanding of the origin of interplanetary organic matter.

This experimental research is detailed in a recent article published in Astronomy and Astrophysics and highlighted by this journal.

Contacts:

Associated reference:
« Dome C ultracarbonaceous Antarctic micrometeorites - Infrared and Raman fingerprints » E. Dartois, C. Engrand, J. Duprat, M. Godard, E. Charon, L. Delauche, C. Sandt and F. Borondics, Astronomy & Astrophysics 609, A65 (2018), DOI: https://doi.org/10.1051/0004-6361/201731322

Notes:
This work was funded by national programmes (PNP, PCMI), the centre national d’études spatiales (CNES), the ANR, the DIM-ACAV, Paris-Saclay University and the CNRS. The micrometeorite collect at the Concordia Antarctic station was financially and logistically supported by the IPEV.

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Images en électrons rétrodiffusés mesurées à 15kV des fragments de micrométéorites (UCAMMs) analysées dans cette étude. Les barres d’échelle correspondent à 5 µm pour chaque image.
PNG - 101.1 ko
À gauche, les abondances atomiques relatives azote/carbone des UCAMMs (étoiles) sont comparées à celles de corps solides du système solaire, en fonction la distance au Soleil. À droite : même figure pour les abondances atomiques relatives carbone/silicium.

[1The Concordia Station is operated by the french and italian polar institut (IPEV and PNRA).