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HOME Report Summary

Project ID: 339231
Funded under: FP7-IDEAS-ERC
Country: Germany

Mid-Term Report Summary - HOME (Habitability of Martian Environments: Exploring the Physiological and Environmental Limits of Life)

Our HOME (Habitability of Martian Environments) team of interdisciplinary researchers and students has been assembled and despite some start-up problems, we made major progress in our research areas. In order to determine the dry limit of life (on Earth and Mars) we put together a huge consortium of European and non-European investigators for the analysis of a wide variety of biological, geological, chemical, and environmental parameters in the Atacama Desert (see our project website In fact, this is the largest consortium with the broadest expertise that to date has undertaken research in this driest non-polar desert of Earth, which is one of the best analog sites to understand chemical, physical, and possible biological processes on Mars. We sampled along a moisture gradient including some of the most arid localities, but it became clear that even in the hyperarid core of the desert are still environmental niches, where life is metabolizing and growing. The soils in the Atacama are very low in biomass and organic compounds and thus are close to the detection limits of state-of-the-art technology, but by employing novel methods we are able to for example distinguish between external and internal DNA and ATP, and thus to evaluate whether microorganisms are still actively growing and reproducing, using the desert as a habitat, or are slowly dying at these locations. Our results also show that some organisms are using intriguing adaptation strategies, such as deliquescence, attracting water directly from the atmosphere and using dissolved salts as nutrients. A synthesis of earlier results was published by us suggesting the possible presence of remaining outposts of life on Mars. We plan to follow up with a flagship paper, which will include the whole consortium, and discuss our habitability results in the hyperarid core of the Atacama and how it relates to Mars.
We also conducted deliquescence studies in our laboratory to observe which salts can still stay in liquid form at different relative humidities or water activities. This is timely and critical research, relating to the discovery of Recurrent Slope Lineae on Mars, which are a potential habitat of life. We investigated in the laboratory salt-soil mixtures that resemble the ground material of Recurrent Slope Lineae and published those results. Currently we test the addition of selected microbes to salt-soil mixtures for evaluating whether they can be metabolically active in these geologically-analogous Martian soils or not. In addition to these laboratory experiments, we also test soils and microbes under Martian conditions in specialized Mars Simulation Chambers, including the attempt to proof metabolic activity of cyanobacteria under Mars near-surface conditions at our partner institution DLR, and testing of soils and microbes under Mars-simulated conditions on the International Space Station. We expect that these results dramatically change our understanding of Martian habitability.
One challenging but also rewarding aspect of our research has been the development of a Mars Soil Analyzer. During our investigation we noticed the intricate interactions between the soil media and any microbial organisms present. Thus, we decided to enhance the instrument´s ability to not only detect chemical and physical soil processes, mostly by using ion selective electrodes, but also biological activity within the soils. However, in order to avoid false positives, there is a need to use a sterilized control, especially since the goal is to carry the instrumentation on a future space mission to Mars. However, current sterilization methods are not ideal for our application, because they also alter the soil properties. Thus, we tested a different method, applying a low-temperature argon plasma to sterilize soil spiked with microbes. Although this method worked well with space assembly parts, it did not work well enough for soil sterilization, so we are currently testing an alternative novel pressure sterilization method.
The HOME team has been very active in presenting at conferences and publishing papers, many of them in high-impact journals. It speaks of our interdisciplinary team and our team effort that all participants of our HOME team are involved in these publications, and that our work involves so many colleagues from other institutions, all of which contribute to our effort with their time and resources.

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