The source and nature of carbon found in Martian meteorites has been a topic of intense past debate. However, a recent paper  reveals that this carbon indeed originated on Mars but through volcanic rather than biological processes. Using an array of sophisticated techniques, the team was able to demonstrate that some the macromolecules of carbon were solely the results of Martian magmatic activity, rather than contamination (from Earth or meteorites) or the remnants of ancient life on Mars itself.
According to the research group's leader, Andrew Steele, "These findings show that the storage of reduced carbon molecules on Mars occurred throughout the planet's history and might have been similar to processes that occurred on the ancient Earth." He adds, "Understanding the genesis of these non-biological, carbon-containing macromolecules on Mars is crucial for developing future missions to detect evidence of life on our neighboring planet."
For this study, the researchers conducted confocal Raman imaging spectroscopy on 11 Martian meteorites that spanned about 4.2 billion years of Mars history. Ten of the meteorites contained abiotic macromolecular carbon (MMC) phases detected in association with small oxide grains sealed within high-temperature minerals. The distribution of abiotic organic carbon in Martian igneous rocks is important for two primary reasons, 1) understanding the Martian carbon cycle, and 2) learning to detect possible past life on Mars. The occurrence of organic carbon within magmatic minerals found in the meteorites indicates that the Martian magmas favored precipitation of reduced carbon species during crystallization.
Figure: A red, green, and blue Ramon map of Red: spinel, Green: pyroxene, and Blue: reduced carbon. It shows the relationship between reduced carbon and spinel in Martian meteorites.
This work was supported by NASA Cosmochemistry grants NNX11AG76G, NNX10AI77G, the New Mexico Space Grant Consortium, and the Carnegie Institution.