The Sairecabur volcano (5971 m), in the Atacama Desert, is a high-altitude extreme environment with high daily temperature variations, acidic soils, intense UV radiation, and low availability of water. Four different species of yeasts were isolated from this region using oligotrophic media, identified and characterized for their tolerance to extreme conditions. rRNA sequencing revealed high identity (>98%) to Cryptococcus friedmannii, Exophiala sp., Holtermanniella watticus, and Rhodosporidium toruloides. To our knowledge, this is the first report of these yeasts in the Atacama Desert. All isolates showed high resistance to UV-C, UV-B and environmental-UV radiation, capacity to grow at moderate saline media (0.75–2.25 mol/L NaCl) and at moderate to cold temperatures, being C. friedmannii and H. watticus able to grow in temperatures down to −6.5°C. The presence of pigments, analyzed by Raman spectroscopy, correlated with UV resistance in some cases, but there is evidence that, on the natural environment, other molecular mechanisms may be as important as pigmentation, which has implications for the search of spectroscopic biosignatures on planetary surfaces. Due to the extreme tolerances of the isolated yeasts, these organisms represent interesting eukaryotic models for astrobiological purposes.

Exoplanet discovery has made remarkable progress, with the first rocky planets having been detected in the central star's liquid water habitable zone. The remote sensing techniques used to characterize such planets for potential habitability and life rely solely on our understanding of life on Earth. The vegetation red edge from terrestrial land plants is often used as a direct signature of life, but it occupies only a small niche in the environmental parameter space that binds life on present-day Earth and has been widespread for only about 460 My. To more fully exploit the diversity of the one example of life known, we measured the spectral characteristics of 137 microorganisms containing a range of pigments, including ones isolated from Earth's most extreme environments. Our database covers the visible and near-infrared to the short-wavelength infrared (0.35-2.5 μm) portions of the electromagnetic spectrum and is made freely available from biosignatures. astro.cornell.edu. Our results show how the reflectance properties are dominated by the absorption of light by pigments in the visible portion and by strong absorptions by the cellular water of hydration in the infrared (up to 2.5 μm) portion of the spectrum. Our spectral library provides a broader and more realistic guide based on Earth life for the search for surface features of extraterrestrial life. The library, when used as inputs for modeling disk-integrated spectra of exoplanets, in preparation for the next generation of space-and ground-based instruments, will increase the chances of detecting life.biosignatures | spectral library | reflectivity | extremophiles | pigments I n the last decade, the field of exoplanet research has transitioned rapidly from detection to detection and characterization, with the first rocky exoplanets detected in the central star's liquid water habitable zone. Much of the excitement of this research in both the astrobiology community and the general public is motivated by the quest to discover a second genesis of life. The great distances that separate us from even the most nearby stars dictate that all measurements of the exoplanet must be made through remote sensing techniques for the foreseeable future. Thus, it is critical for us to determine the types of biosignatures that we should be looking for when designing the next generation of ground-and space-based instruments that will observe these planets at high spectral and possibly spatial resolutions.Since the mid-1960s a primary life-searching strategy has been to look for a specific combination of an oxidizing and a reducing gas in the exoplanetary atmosphere, such as the O 2 and CH 4 in our atmosphere, because this is a thermodynamically unstable situation suggesting that an active agent such as life is responsible for the chemical disequilibrium (1, 2). Of particular interest, both from an observational and modeling perspective, is to complement those indirect life detection studies with surface features that are direct properties of the organisms themselves (3).Alt...

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A critical aspect of human space exploration and eventual settlement is the ability to construct habitats while minimizing payload mass launched from Earth. To respond to this challenge, we have proposed the use of fungal bio-composites for growing extra-terrestrial structures, directly at the destination, significantly lowering the mass of structural materials transported from Earth and minimizing the need for high mass robotic operations and infrastructure preparations. Throughout human history, the construction of habitats has used biologically produced materials, from bone and skins to wood and limestone. Traditionally, the materials are used only post-mortem. Currently, the idea of working with living biological organisms, and the phenomenon of growth itself, is of increasing interest in architecture and space applications. Here, we describe the use of mycelium-based composites as an alternative, biological approach for constructing regenerative and adaptive buildings in extrem environments and extraterrestrial habitats. It is a continuation of our research program initiated under the auspices of the “Myco-architecture Off Planet” NASA NIAC Team. These composites, which are fire-resistant, and insulating, do not consist of volatile organic compounds from petrochemical products and can be used independently or in conjunction with regolith, could employ the living biological growth in a controlled environment, for the process of material fabrication, assembly, maintenance, and repair, providing structures resilient to extra-terrestrial hazards. Here we outline the potential and challenges of using bio-composites for Earth and space applications. We describe how these might be addressed to make this biological approach feasible, providing new, growing materials for designing and building sustainable habitats, both on Earth and for long-duration space missions.