Infrared spectroscopy of microbially induced carbonates and past life on Mars

Abstract

A number of evidences, as the past presence of water, a denser atmosphere and a mild climate, suggest that on early Mars environmental conditions should have been favourable to the emergence of life. Therefore, if life actually developed on Mars a few hundreds of million years ago, or even more recently, some biomarkers may still be present.In several previous papers, based on laboratory analysis, we have investigated the modifications induced by thermal processing in the mid-infrared spectra of carbonate samples, in the form of fresh shells and fossils of different ages, skeletal remains of already complex terrestrial life, whose biotic origin is not questionable. In this way we have been able to develop a spectroscopic method for discriminating biotic samples from their abiotic counterparts.In this work we show that our method can be successfully applied also to microbialites, i.e. bio-induced carbonates deposits, and particularly to stromatolites, the laminated fabric of microbialites, some of which are among the most primitive and oldest traces of biological activity on Earth. This result is of valuable importance since such primitive living organisms can be considered good analogues for putative martian life forms.