INFN-LNF Laboratori Nazionali di Frascati
A mineral found deep in Antarctic ice could be the key to trace the history of Martian ice caps.
An international research coordinated by a team of glaciologists of Milano-Bicocca University, in collaboration with Nasa Houston laboratory, the UK’s national synchrotron Diamond Light Source, the National Institute for Nuclear Physics, Rome Tre University and Hong Kong University, observed jarosite in deep Antarctic ice. The results are published in Nature Communications.
Jarosite is hydrous sulfate of potassium and ferric iron and it has been identified at several locations on Mars surface by Nasa rover Opportunity in 2004, suggesting the past existence of liquid water, necessary for the formation of this mineral.
Jarosite on Earth is a relatively common mineral although its presence is observed solely in particular environments, quite different from glaciers, like around mines, places with high rate of evaporation that enables the precipitation of salts and minerals and fumaroles. Up to now this mineral has never been associated to ice or glaciers on Earth.
Two scientists who contributed to this research, pointed out that jarosite on Mars could have formed inside ancient ice caps through the interaction between the mineral dust and acid substances of volcanic origin.
The hypothesis has been confirmed by the study of an 1600 m long ice core, that spans a range of 300000 years, drilled at Talos Dome in East Antarctica. This ice core was recovered between 2004 and 2007 in the framework of the TALDICE project, financed by the European Union with the support of the National Research Program in Antarctica. Thanks to different analytical techniques (X-ray absorption spectroscopy, X-ray fluorescence, scanning transmission electron microscopy) the formation of micrometric crystals of jarosite has been observed in the deepest part of the ice core. This result confirms that the mechanism at the basis of the jarosite formation is the transformation of mineral dusts trapped in the ice, below 1000 m depth at -10°C. At this depth liquid water is present in the form of concentrated acid solutions.
The discovery – states Giovanni Baccolo University of Milano-Bicocca – is destined to revolutionise the interpretation of the origin Martian jarosite deposits. Even if they are now disappeared, the ancient martian glaciers and the mineral dust trapped in these, left an evident geological trace, testifying the past climate evolutions.
The Frascati National Laboratory contributed from the very beginning of this research in 2003 with both the development of hardware and data analysis. In particular it was realized a ice manipulation system, i.e. a six degrees of freedom robot-based, for the alignment in vacuum of the ice samples with micrometric precision, an X-ray detector and a temperature control system to maintain the conditions for the analysis on ice. The same system was used to perform a study of Alpine ice using ice cores drilled on Monte Rosa.
Augusto Marcelli, INFN researcher and scientific expert of the Minister of Foreign Affairs, is co-author of this paper.