Viruses are the most numerically abundant biological entities on Earth. As ubiquitous replicators of molecular information and agents of community change, viruses have potent effects on the life on Earth, and may play a critical role in human spaceflight, for life-detection missions to other planetary bodies and planetary protection. However, major knowledge gaps constrain our understanding of the Earth's virosphere: (1) the role viruses play in biogeochemical cycles, (2) the origin(s) of viruses and (3) the involvement of viruses in the evolution, distribution and persistence of life. As viruses are the only replicators that span all known types of nucleic acids, an expanded experimental and theoretical toolbox built for Earth's viruses will be pivotal for detecting and understanding life on Earth and beyond. Only by filling in these knowledge and technical gaps we will obtain an inclusive assessment of how to distinguish and detect life on other planetary surfaces. Meanwhile, space exploration requires life-support systems for the needs of humans, plants and their microbial inhabitants. Viral effects on microbes and plants are essential for Earth's biosphere and human health, but virus-host interactions in spaceflight are poorly understood. Viral relationships with their hosts respond to environmental changes in complex ways which are difficult to predict by extrapolating from Earth-based proxies. These relationships should be studied in space to fully understand how spaceflight will modulate viral impacts on human health and life-support systems, including microbiomes. In this review, we address key questions that must be examined to incorporate viruses into Earth system models, life-support systems and life detection. Tackling these questions will benefit our efforts to develop planetary protection protocols and further our understanding of viruses in astrobiology.

Liquid water on Mars might be created by deliquescence of hygroscopic salts or by permafrost melts, both potentially forming saturated brines. Freezing point depression allows these heavy brines to remain liquid in the near-surface environment for extended periods, perhaps as eutectic solutions, at the lowest temperatures and highest salt concentrations where ices and precipitates do not form. Perchlorate and chlorate salts and iron sulfate form brines with low eutectic temperatures and may persist under Mars near-surface conditions, but are chemically harsh at high concentrations and were expected to be incompatible with life, while brines of common sulfate salts on Mars may be more suitable for microbial growth. Microbial growth in saturated brines also may be relevant beyond Mars, to the oceans of Ceres, Enceladus, Europa and Pluto. We have previously shown strong growth of salinotolerant bacteria in media containing 2 M MgSO heptahydrate (~50% w/v) at 25 °C. Here we extend those observations to bacterial isolates from Basque Lake, BC and Hot Lake, WA, that grow well in saturated MgSO medium (67%) at 25 °C and in 50% MgSO medium at 4 °C (56% would be saturated). Psychrotolerant, salinotolerant microbes isolated from Basque Lake soils included and , which were identified by 16S rRNA gene sequencing and characterized phenetically. Eutectic liquid medium constituted by 43% MgSO at -4 °C supported copious growth of these psychrotolerant isolates, among others. Bacterial isolates also grew well at the eutectic for K chlorate (3% at -3 °C). Survival and growth in eutectic solutions increases the possibility that microbes contaminating spacecraft pose a contamination risk to Mars. The cold brines of sulfate and (per)chlorate salts that may form at times on Mars through deliquescence or permafrost melt have now been demonstrated to be suitable microbial habitats, should appropriate nutrients be available and dormant cells become vegetative.

Low-latency teleoperations (LLT), or "telepresence" allows for the control of almost any asset in essentially real-time and has significant potential to address potential planetary protection concerns and to enhance astrobiology exploration activities on both robotic and human missions to Mars and elsewhere in the solar system. LLT can assist with the search for extraterrestrial life and help mitigate planetary protection concerns as required by the UN Outer Space Treaty. LLT can help by allowing for real-time exploration of areas that may otherwise not be conducive to direct human contact. Crew members can search for, acquire, and robotically manipulate samples in real-time and engage in precise measurements and experiments without requiring the crew to be present in dangerous or otherwise problematic conditions or environments. LLT operations can be particularly effective in studying "Special Regions" - areas of astrobiological interest that might be adversely affected by forward contamination from humans or spacecraft contaminants during activities on Mars. Similarly, LLT can aid in addressing concerns about backward contamination that could impact mission implementation for returning Martian samples and crew to Earth.

It is well established that any properly conducted biophysical studies of proteins must take appropriate account of solvent. For water-soluble proteins it has been an article of faith that water is largely responsible for stabilizing the fold, a notion that has recently come under increasing scrutiny. Further, there are some instances when proteins are studied experimentally in the absence of solvent, as in matrix-assisted laser desorption/ionization or electrospray mass spectrometry, for example, or in organic solvents for protein engineering purposes. Apart from these considerations, there is considerable speculation as to whether there is life on planets other than Earth, where conditions including the presence of water (both in liquid or vapor form and indeed ice), temperature and pressure may be vastly different from those prevailing on Earth. Mars, for example, has only 0.6% of Earth's mean atmospheric pressure which presents profound problems to protein structures, as this paper and a large corpus of experimental work demonstrate. Similar objections will most likely apply in the case of most exoplanets and other bodies such as comets whose chemistry and climate are still largely unknown. This poses the question, how do proteins survive in these different environments? In order to cast some light on these issues we have conducted a series of molecular dynamics simulations on protein dehydration under a variety of conditions. We find that, while proteins undergoing dehydration can retain their integrity for a short duration they ultimately become disordered, and we further show that the disordering can be retarded if superficial water is kept in place on the surface. These findings are compared with other published results on protein solvation in an astrobiological and astrochemical setting. Inter alia, our results suggest that there are limits as to what to expect in terms of the existence of possible extraterrestrial forms as well to what can be achieved in experimental investigations on living systems despatched from Earth. This finding may appear to undermine currently held hopes that life will be found on nearby planets, but it is important to be aware that the presence of ice and water are by themselves not sufficient; there has to be an atmosphere which includes water vapor at a sufficiently high partial pressure for proteins to be active. A possible scenario in which there has been a history of adequate water vapor pressure which allowed organisms to prepare for a future dessicated state by forming suitable protective capsules cannot of course be ruled out.

A well-developed theory of evolutionary biology requires understanding of the origins of life on Earth. However, the initial conditions (ontology) and causal (epistemology) bases on which physiology proceeded have more recently been called into question, given the teleologic nature of Darwinian evolutionary thinking. When evolutionary development is focused on cellular communication, a distinctly different perspective unfolds. The cellular communicative-molecular approach affords a logical progression for the evolutionary narrative based on the basic physiologic properties of the cell. Critical to this appraisal is recognition of the cell as a fundamental reiterative unit of reciprocating communication that receives information from and reacts to epiphenomena to solve problems. Following the course of vertebrate physiology from its unicellular origins instead of its overt phenotypic appearances and functional associations provides a robust, predictive picture for the means by which complex physiology evolved from unicellular organisms. With this foreknowledge of physiologic principles, we can determine the fundamentals of Physiology based on cellular first principles using a logical, predictable method. Thus, evolutionary creativity on our planet can be viewed as a paradoxical product of boundary conditions that permit homeostatic moments of varying length and amplitude that can productively absorb a variety of epigenetic impacts to meet environmental challenges.

Earth-like civilizations generate heat from the energy that they utilize. The thermal radiation from this heat can be a thermodynamic marker for civilizations. Here we model such planetary radiation on Earth-like planets and propose a strategy for detecting such an alien thermodynamic electromagnetic biomarker. We show that astronomical infrared (IR) may be detected within an interestingly large cosmic volume using a 70 m-class or larger telescope. In particular, the Colossus telescope with achievable coronagraphic and adaptive optics performance may reveal Earth-like civilizations from visible and IR photometry timeseries' taken during an exoplanetary orbit period. The detection of an alien heat signature will have far-ranging implications, but even a null result, given 70 m aperture sensitivity, could also have broad social implications.

Hot Lake (Oroville, WA) is an athalassohaline epsomite lake that can have precipitating concentrations of MgSO salts, mainly epsomite. Little biotic study has been done on epsomite lakes and it was unclear whether microbes isolated from epsomite lakes and their margins would fall within recognized halotolerant genera, common soil genera, or novel phyla. Our initial study cultivated and characterized epsotolerant bacteria from the lake and its margins. Approximately 100 aerobic heterotrophic microbial isolates were obtained by repetitive streak-plating in high-salt media including either 10% NaCl or 2 M MgSO. The collected isolates were all bacteria, nearly evenly divided between Gram-positive and Gram-negative clades, the most abundant genera being , , and , and also were cultured. This initial study included culture-independent community analysis of direct DNA extracts of lake margin soil using PCR-based clone libraries and 16S rRNA gene phylogeny. Clones assigned Gram-positive bacterial clades (70% of total clones) were dominated by sequences related to uncultured actinobacteria. There were abundant clones related to bacterial sulfur metabolisms and clones of and . These epsomite lake microbial communities seem to be divided between bacteria primarily associated with hyperhaline environments rich in NaCl and salinotolerant relatives of common soil organisms. Archaea appear to be in low abundance and none were isolated, despite near-saturated salinities. Growth of microbes at very high concentrations of magnesium and other sulfates has relevance to planetary protection and life-detection missions to Mars, where scant liquid water may form as deliquescent brines and appear as eutectic liquids.