The National Aeronautics and Space Administration (NASA) Astrobiology Institute (NAI) conducted two “Workshops Without Walls” during 2010 that enabled global scientific exchange—with no travel required. The second of these was on the topic “Molecular Paleontology and Resurrection: Rewinding the Tape of Life.” Scientists from diverse disciplines and locations around the world were joined through an integrated suite of collaborative technologies to exchange information on the latest developments in this area of origin of life research. Through social media outlets and popular science blogs, participation in the workshop was broadened to include educators, science writers, and members of the general public. In total, over 560 people from 31 US states and 30 other nations were registered. Among the scientific disciplines represented were geochemistry, biochemistry, molecular biology and evolution, and microbial ecology. We present this workshop as a case study in how interdisciplinary collaborative research may be fostered, with substantial public engagement, without sustaining the deleterious environmental and economic impacts of travel.
With the recognition of an increasing potential for discovery of extraterrestrial life, a diverse set of researchers have noted a need to examine the foundational ethical principles that should frame our collective space activities as we explore outer space. A COSPAR Workshop on Ethical Considerations for Planetary Protection in Space Exploration was convened at Princeton University on June 8–10, 2010, to examine whether planetary protection measures and practices should be extended to protect planetary environments within an ethical framework that goes beyond “science protection” per se. The workshop had been in development prior to a 2006 NRC report on preventing the forward contamination of Mars, although it responded directly to one of the recommendations of that report and to several peer-reviewed papers as well. The workshop focused on the implications and responsibilities engendered when exploring outer space while avoiding harmful impacts on planetary bodies. Over 3 days, workshop participants developed a set of recommendations addressing the need for a revised policy framework to address “harmful contamination” beyond biological contamination, noting that it is important to maintain the current COSPAR planetary protection policy for scientific exploration and activities. The attendees agreed that there is need for further study of the ethical considerations used on Earth and the examination of management options and governmental mechanisms useful for establishing an environmental stewardship framework that incorporates both scientific input and enforcement. Scientists need to undertake public dialogue to communicate widely about these future policy deliberations and to ensure public involvement in decision making. A number of incremental steps have been taken since the workshop to implement some of these recommendations. Key Words: Planetary protection—Extraterrestrial life—Life in extreme environments—Environment—Habitability. Astrobiology 12, 1017–1023.
The Cuatro Ciénegas Basin (CCB) is a rare oasis in the Chihuahuan Desert in the state of Coahuila, Mexico. It has a biological endemism similar to that of the Galapagos Islands, and its spring-fed ecosystems have very low nutrient content (nitrogen or phosphorous) and are dominated by diverse microbialites. Thus, it has proven to be a distinctive opportunity for the field of astrobiology, as the CCB can be seen as a proxy for an earlier time in Earth's history, in particular the late Precambrian, the biological frontier when prokaryotic life yielded at least partial dominance to eukaryotes and multicellular life. It is a kind of ecological time machine that provides abundant opportunities for collaborative investigations by geochemists, geologists, ecologists, and population biologists in the study of the evolutionary processes that structured Earth-based life, especially in the microbial realm. The CCB is an object of investigation for the identification of biosignatures of past and present biota that can be used in our search for extraterrestrial life. In this review, we summarize CCB research efforts that began with microbial ecology and population biology projects and have since been expanded into broader efforts that involve biogeochemistry, comparative genomics, and assessments of biosignatures. We also propose that, in the future, the CCB is sanctioned as a “Precambrian Park” for astrobiology. Key Words: Microbial mats—Stromatolites—Early Earth—Extremophilic microorganisms—Microbial ecology. Astrobiology 12, 641–647.
The EPOXI Discovery Mission of Opportunity reused the Deep Impact flyby spacecraft to obtain spatially and temporally resolved visible photometric and moderate resolution near-infrared (NIR) spectroscopic observations of Earth. These remote observations provide a rigorous validation of whole-disk Earth model simulations used to better understand remotely detectable extrasolar planet characteristics. We have used these data to upgrade, correct, and validate the NASA Astrobiology Institute's Virtual Planetary Laboratory three-dimensional line-by-line, multiple-scattering spectral Earth model. This comprehensive model now includes specular reflectance from the ocean and explicitly includes atmospheric effects such as Rayleigh scattering, gas absorption, and temperature structure. We have used this model to generate spatially and temporally resolved synthetic spectra and images of Earth for the dates of EPOXI observation. Model parameters were varied to yield an optimum fit to the data. We found that a minimum spatial resolution of ∼100 pixels on the visible disk, and four categories of water clouds, which were defined by using observed cloud positions and optical thicknesses, were needed to yield acceptable fits. The validated model provides a simultaneous fit to Earth's lightcurve, absolute brightness, and spectral data, with a root-mean-square (RMS) error of typically less than 3% for the multiwavelength lightcurves and residuals of ∼10% for the absolute brightness throughout the visible and NIR spectral range. We have extended our validation into the mid-infrared by comparing the model to high spectral resolution observations of Earth from the Atmospheric Infrared Sounder, obtaining a fit with residuals of ∼7% and brightness temperature errors of less than 1 K in the atmospheric window. For the purpose of understanding the observable characteristics of the distant Earth at arbitrary viewing geometry and observing cadence, our validated forward model can be used to simulate Earth's time-dependent brightness and spectral properties for wavelengths from the far ultraviolet to the far infrared. Key Words: Astrobiology—Extrasolar terrestrial planets—Habitability—Planetary science—Radiative transfer. Astrobiology 11, 393–408.
Mars for Earthlings (MFE) is a terrestrial Earth analog pedagogical approach to teaching undergraduate geology, planetary science, and astrobiology. MFE utilizes Earth analogs to teach Mars planetary concepts, with a foundational backbone in Earth science principles. The field of planetary science is rapidly changing with new technologies and higher-resolution data sets. Thus, it is increasingly important to understand geological concepts and processes for interpreting Mars data. MFE curriculum is topically driven to facilitate easy integration of content into new or existing courses. The Earth-Mars systems approach explores planetary origins, Mars missions, rocks and minerals, active driving forces/tectonics, surface sculpting processes, astrobiology, future explorations, and hot topics in an inquiry-driven environment. Curriculum leverages heavily upon multimedia resources, software programs such as Google Mars and JMARS, as well as NASA mission data such as THEMIS, HiRISE, CRISM, and rover images.
Two years of MFE class evaluation data suggest that science literacy and general interest in Mars geology and astrobiology topics increased after participation in the MFE curriculum. Students also used newly developed skills to create a Mars mission team presentation. The MFE curriculum, learning modules, and resources are available online at http://serc.carleton.edu/marsforearthlings/index.html. Key Words: Mars—Geology—Planetary science—Astrobiology—NASA education. Astrobiology 14, 42–49.
There is concern in many developed countries that school students are turning away from science. However, students may be choosing not to study science and dismissing the possibility of a scientific career because, in the junior secondary years, they gain a false view of science and the work of scientists. There is a disparity between science as it is portrayed at school and science as it is practiced. This paper describes a study to explore whether engaging in science through astrobiology outreach activities may improve students' understanding of the nature and processes of science, and how this may influence their interest in a career in science. The results suggest that the students attending these Mars research–related outreach activities are more interested in science than the average student but are lacking in understanding of aspects of the nature of science. A significant difference was detected between pre- and posttest understandings of some concepts of the nature of science. Key Words: Science education—School science—Creativity—Nature and processes of science—Attitudes—Astrobiology. Astrobiology 12, 1143–1153.
The OMEGA/Mars Express hyperspectral imager identified gypsum at several sites on Mars in 2005. These minerals constitute a direct record of past aqueous activity and are important with regard to the search of extraterrestrial life. Gale Crater was chosen as Mars Science Laboratory Curiosity's landing site because it is rich in gypsum, as are some desert soils of the Cuatro Ciénegas Basin (CCB) (Chihuahuan Desert, Mexico). The gypsum of the CCB, which is overlain by minimal carbonate deposits, was the product of magmatic activity that occurred under the Tethys Sea. To examine this Mars analogue, we retrieved gypsum-rich soil samples from two contrasting sites with different humidity in the CCB. To characterize the site, we obtained nutrient data and analyzed the genes related to the N cycle (nifH, nirS, and nirK) and the bacterial community composition by using 16S rRNA clone libraries. As expected, the soil content for almost all measured forms of carbon, nitrogen, and phosphorus were higher at the more humid site than at the drier site. What was unexpected is the presence of a rich and divergent community at both sites, with higher taxonomic diversity at the humid site and almost no taxonomic overlap. Our results suggest that the gypsum-rich soils of the CCB host a unique microbial ecosystem that includes novel microbial assemblies. Key Words: Cuatro Ciénegas Basin—Gale Crater—Gypsum soil microbial diversity—Molecular ecology—Nitrogen cycle. Astrobiology 12, 699–709.
Lava caves contain a wealth of yellow, white, pink, tan, and gold-colored microbial mats; but in addition to these clearly biological mats, there are many secondary mineral deposits that are nonbiological in appearance. Secondary mineral deposits examined include an amorphous copper-silicate deposit (Hawai‘i) that is blue-green in color and contains reticulated and fuzzy filament morphologies. In the Azores, lava tubes contain iron-oxide formations, a soft ooze-like coating, and pink hexagons on basaltic glass, while gold-colored deposits are found in lava caves in New Mexico and Hawai‘i. A combination of scanning electron microscopy (SEM) and molecular techniques was used to analyze these communities. Molecular analyses of the microbial mats and secondary mineral deposits revealed a community that contains 14 phyla of bacteria across three locations: the Azores, New Mexico, and Hawai‘i. Similarities exist between bacterial phyla found in microbial mats and secondary minerals, but marked differences also occur, such as the lack of Actinobacteria in two-thirds of the secondary mineral deposits. The discovery that such deposits contain abundant life can help guide our detection of life on extraterrestrial bodies. Key Words: Biosignatures—Astrobiology—Bacteria—Caves—Life detection—Microbial mats. Astrobiology 11, 601–618.
The release and oxidation of ferrous iron during aqueous alteration of the mineral olivine is known to reduce aqueous solutions to such extent that molecular hydrogen, H2, forms. H2 is an efficient energy carrier and is considered basal to the deep subsurface biosphere. Knowledge of the potential for H2 generation is therefore vital to understanding the deep biosphere on Earth and on extraterrestrial bodies.
Here, we provide a review of factors that may reduce the potential for H2 generation with a focus on systems in the core temperature region for thermophilic to hyperthermophilic microbial life. We show that aqueous sulfate may inhibit the formation of H2, whereas redox-sensitive compounds of carbon and nitrogen are unlikely to have significant effect at low temperatures. In addition, we suggest that the rate of H2 generation is proportional to the dissolution rate of olivine and, hence, limited by factors such as reactive surface areas and the access of water to fresh surfaces. We furthermore suggest that the availability of water and pore/fracture space are the most important factors that limit the generation of H2. Our study implies that, because of large heat flows, abundant olivine-bearing rocks, large thermodynamic gradients, and reduced atmospheres, young Earth and Mars probably offered abundant systems where microbial life could possibly have emerged. Key Words: Serpentinization—Olivine—Hydrogen—Deep biosphere—Water—Mars. Astrobiology 11, 711–724.
After the realization of the International Space Station, human exploratory missions to Moon or Mars, i.e. beyond low Earth orbit, are widely considered as the next logical step of peaceful cooperation in space on a global scale. Besides the human desire to extend the window of habitability, human exploratory missions are driven by several aspects of science, technology, culture and economy. Mars is currently considered as a major target in the search for life beyond the Earth. Understanding the history of water on Mars appears to be one of the clues to the puzzle on the probability of life on Mars. On Earth microorganisms have flourished for more than 3.5 Ga and have developed strategies to cope with so-called extreme conditions (e.g., hot vents, permafrost, subsurface regions, rocks or salt crystals). Therefore, in search for life on Mars, microorganisms are the most likely candidates for a putative biota on Mars and the search for morphological or chemical signatures of life or its relics is one of the primary and most exciting goals of Mars exploration. The presence of humans on the surface of Mars will substantially increase this research potential, e.g., by supporting deep subsurface drilling and by allowing intellectual collection and sophisticated in situ analysis of samples of astrobiological interest. On the other hand, such long-duration missions beyond LEO will add a new dimension to human space flight, concerning the distance of travel, the radiation environment, the gravity levels, the duration of the mission, and the level of confinement and isolation the crew will be exposed to. This will raise the significance of several health issues, above all radiation protection, gravity related effects as well as psychological issues. Furthermore, the import of internal and external microorganisms inevitably accompanying any human mission to Mars, or brought purposely to Mars as part of a bioregenerative life support system needs careful consideration with regard to planetary protection issues. Therefore, before planning any human exploratory mission, the critical issues concerning human health and wellbeing as well as protection of Mars in its pristine condition need to be investigated.
Mars; Human exploratory missions; Astrobiology; Search for extraterrestrial life
Spectral characterization of super-Earth atmospheres for planets orbiting in the habitable zone of M dwarf stars is a key focus in exoplanet science. A central challenge is to understand and predict the expected spectral signals of atmospheric biosignatures (species associated with life). Our work applies a global-mean radiative-convective-photochemical column model assuming a planet with an Earth-like biomass and planetary development. We investigated planets with gravities of 1g and 3g and a surface pressure of 1 bar around central stars with spectral classes from M0 to M7. The spectral signals of the calculated planetary scenarios have been presented by in an earlier work by Rauer and colleagues. The main motivation of the present work is to perform a deeper analysis of the chemical processes in the planetary atmospheres. We apply a diagnostic tool, the Pathway Analysis Program, to shed light on the photochemical pathways that form and destroy biosignature species. Ozone is a potential biosignature for complex life. An important result of our analysis is a shift in the ozone photochemistry from mainly Chapman production (which dominates in Earth's stratosphere) to smog-dominated ozone production for planets in the habitable zone of cooler (M5–M7)-class dwarf stars. This result is associated with a lower energy flux in the UVB wavelength range from the central star, hence slower planetary atmospheric photolysis of molecular oxygen, which slows the Chapman ozone production. This is important for future atmospheric characterization missions because it provides an indication of different chemical environments that can lead to very different responses of ozone, for example, cosmic rays. Nitrous oxide, a biosignature for simple bacterial life, is favored for low stratospheric UV conditions, that is, on planets orbiting cooler stars. Transport of this species from its surface source to the stratosphere where it is destroyed can also be a key process. Comparing 1g with 3g scenarios, our analysis suggests it is important to include the effects of interactive chemistry. Key Words: Exoplanets—Earth-like—M-dwarf—Photochemistry—Biosignatures. Astrobiology 13, 415–438.
Main sequence M stars pose an interesting problem for astrobiology: their abundance in our galaxy makes them likely targets in the hunt for habitable planets, but their strong chromospheric activity produces high-energy radiation and charged particles that may be detrimental to life. We studied the impact of the 1985 April 12 flare from the M dwarf AD Leonis (AD Leo), simulating the effects from both UV radiation and protons on the atmospheric chemistry of a hypothetical, Earth-like planet located within its habitable zone. Based on observations of solar proton events and the Neupert effect, we estimated a proton flux associated with the flare of 5.9 × 108 protons cm−2 sr−1 s−1 for particles with energies >10 MeV. Then we calculated the abundance of nitrogen oxides produced by the flare by scaling the production of these compounds during a large solar proton event called the Carrington event. The simulations were performed with a 1-D photochemical model coupled to a 1-D radiative/convective model. Our results indicate that the UV radiation emitted during the flare does not produce a significant change in the ozone column depth of the planet. When the action of protons is included, the ozone depletion reaches a maximum of 94% two years after the flare for a planet with no magnetic field. At the peak of the flare, the calculated UV fluxes that reach the surface, in the wavelength ranges that are damaging for life, exceed those received on Earth during less than 100 s. Therefore, flares may not present a direct hazard for life on the surface of an orbiting habitable planet. Given that AD Leo is one of the most magnetically active M dwarfs known, this conclusion should apply to planets around other M dwarfs with lower levels of chromospheric activity. Key Words: M dwarf—Flare—Habitable zone—Planetary atmospheres. Astrobiology 10, 751–771.
Fueled by the rapid pace of discovery, humankind's ability to understand the ultimate causes of preventable common disease burdens and to identify solutions is now reaching a revolutionary tipping point. Achieving optimal health and well-being for all members of society lies as much in the understanding of the factors identified by the behavioral, social, and public health sciences as by the biological ones. Accumulating advances in mathematical modeling, informatics, imaging, sensor technology, and communication tools have stimulated several converging trends in science: an emerging understanding of epigenomic regulation; dramatic successes in achieving population health-behavior changes; and improved scientific rigor in behavioral, social, and economic sciences. Fostering stronger interdisciplinary partnerships to bring together the behavioral–social–ecologic models of multilevel “causes of the causes” and the molecular, cellular, and, ultimately, physiological bases of health and disease will facilitate breakthroughs to improve the public's health.
The strategic vision of the Office of Behavioral and Social Sciences Research (OBSSR) at the National Institutes of Health (NIH) is rooted in a collaborative approach to addressing the complex and multidimensional issues that challenge the public's health. This paper describes OBSSR's four key programmatic directions (next-generation basic science, interdisciplinary research, systems science, and a problem-based focus for population impact) to illustrate how interdisciplinary and transdisciplinary perspectives can foster the vertical integration of research among biological, behavioral, social, and population levels of analysis over the lifespan and across generations. Interdisciplinary and multilevel approaches are critical both to the OBSSR's mission of integrating behavioral and social sciences more fully into the NIH scientific enterprise and to the overall NIH mission of utilizing science in the pursuit of fundamental knowledge about the nature and behavior of living systems and the application of that knowledge to extend healthy life and reduce the burdens of illness and disability.
The study of the origin of life covers many areas of expertise and requires
the input of various scientific communities. In recent years, this research
field has often been viewed as part of a broader agenda under the name of
“exobiology” or “astrobiology.” In this review,
we have somewhat narrowed this agenda, focusing on the origin of modern terrestrial
life. The adjective “modern” here means that we did not speculate
on different forms of life that could have possibly appeared on our planet,
but instead focus on the existing forms (cells and viruses). We try to briefly
present the state of the art about alternative hypotheses discussing not only
the origin of life per se, but also how life evolved
to produce the modern biosphere through a succession of steps that we would
like to characterize as much as possible.
In plants, sensitive and selective mechanisms have evolved to perceive and respond to light and gravity. We investigated the effects of microgravity on the growth and development of Arabidopsis thaliana (ecotype Landsberg) in a spaceflight experiment. These studies were performed with the Biological Research in Canisters (BRIC) hardware system in the middeck region of the space shuttle during mission STS-131 in April 2010. Seedlings were grown on nutrient agar in Petri dishes in BRIC hardware under dark conditions and then fixed in flight with paraformaldehyde, glutaraldehyde, or RNAlater. Although the long-term objective was to study the role of the actin cytoskeleton in gravity perception, in this article we focus on the analysis of morphology of seedlings that developed in microgravity. While previous spaceflight studies noted deleterious morphological effects due to the accumulation of ethylene gas, no such effects were observed in seedlings grown with the BRIC system. Seed germination was 89% in the spaceflight experiment and 91% in the ground control, and seedlings grew equally well in both conditions. However, roots of space-grown seedlings exhibited a significant difference (compared to the ground controls) in overall growth patterns in that they skewed to one direction. In addition, a greater number of adventitious roots formed from the axis of the hypocotyls in the flight-grown plants. Our hypothesis is that an endogenous response in plants causes the roots to skew and that this default growth response is largely masked by the normal 1 g conditions on Earth. Key Words: Gravity—Multicellular life—Spacecraft experiments—Spaceflight. Astrobiology 11, 787–797.
Epigenetics is one of the most rapidly expanding fields in the life sciences. Its rise is frequently framed as a revolutionary turn that heralds a new epoch both for gene-based epistemology and for the wider discourse on life that pervades knowledge-intensive societies of the molecular age. The fundamentals of this revolution remain however to be scrutinized, and indeed the very contours of what counts as ‘epigenetic' are often blurred. This is reflected also in the mounting discourse on the societal implications of epigenetics, in which vast expectations coexist with significant uncertainty about what aspects of this science are most relevant for politics or policy alike. This is therefore a suitable time to reflect on the directions that social theory could most productively take in the scrutiny of this revolution. Here we take this opportunity in both its scholarly and normative dimension, that is, proposing a roadmap for social theorizing on epigenetics that does not shy away from, and indeed hopefully guides, the framing of its most socially relevant outputs. To this end, we start with an epistemological reappraisal of epigenetic discourse that valorizes the blurring of meanings as a critical asset for the field and privileged analytical entry point. We then propose three paths of investigation. The first looks at the structuring elements of controversies and visions around epigenetics. The second probes the mutual constitution between the epigenetic reordering of living phenomena and the normative settlements that orient individual and collective responsibilities. The third highlights the material import of epigenetics and the molecularization of culture that it mediates. We suggest that these complementary strands provide both an epistemically and socially self-reflective framework to advance the study of epigenetics as a molecular juncture between nature and nurture and thus as the new critical frontier in the social studies of the life sciences.
epigenetics; imaginaries; molecularization; plasticity; responsibility; social policy
A conspicuous biomorphic ovoid structure has been discovered in the Nakhla martian meteorite, made of nanocrystalline iron-rich saponitic clay and amorphous material. The ovoid is indigenous to Nakhla and occurs within a late-formed amorphous mesostasis region of rhyolitic composition that is interstitial to two clinopyroxene grains with Al-rich rims, and contains acicular apatite crystals, olivine, sulfides, Ti-rich magnetite, and a new mineral of the rhoenite group. To infer the origin of the ovoid, a large set of analytical tools was employed, including scanning electron microscopy and backscattered electron imaging, wavelength-dispersive X-ray analysis, X-ray mapping, Raman spectroscopy, time-of-flight secondary ion mass spectrometry analysis, high-resolution transmission electron microscope imaging, and atomic force microscope topographic mapping. The concentric wall of the ovoid surrounds an originally hollow volume and exhibits internal layering of contrasting nanotextures but uniform chemical composition, and likely inherited its overall shape from a preexisting vesicle in the mesostasis glass. A final fibrous layer of Fe-rich phases blankets the interior surfaces of the ovoid wall structure. There is evidence that the parent rock of Nakhla has undergone a shock event from a nearby bolide impact that melted the rims of pyroxene and the interstitial matter and initiated an igneous hydrothermal system of rapidly cooling fluids, which were progressively mixed with fluids from the melted permafrost. Sharp temperature gradients were responsible for the crystallization of Al-rich clinopyroxene rims, rhoenite, acicular apatites, and the quenching of the mesostasis glass and the vesicle. During the formation of the ovoid structure, episodic fluid infiltration events resulted in the precipitation of saponite rinds around the vesicle walls, altered pyrrhotite to marcasite, and then isolated the ovoid wall structure from the rest of the system by depositing a layer of iron oxides/hydroxides. Carbonates, halite, and sulfates were deposited last within interstitial spaces and along fractures. Among three plausible competing hypotheses here, this particular abiotic scenario is considered to be the most reasonable explanation for the formation of the ovoid structure in Nakhla, and although compelling evidence for a biotic origin is lacking, it is evident that the martian subsurface contains niche environments where life could develop. Key Words: Biomorph—Clays—Search for life (biosignatures)—Martian meteorites—Hydrothermal systems. Astrobiology 14, 651–693.
To improve the method of automated retrieval of surveillance-related literature from a wide range of indexed repositories.
The ISDS Research Committee (RC) is an interdisciplinary group of researchers interested in various topics related to disease surveillance. The RC hosts a literature review process with a permanent repository of relevant journal articles and bimonthly calls that provide a forum for discussion and author engagement. The calls have led to workgroups and society-wide events, boosted interest in the ISDS Conference, and fostered networking among participants.
Since 2007, the RC has identified and classified published articles using an automated search method with the aim of progressing ISDS’s mission of advancing the science and practice of disease surveillance by fostering collaboration and increasing awareness of innovations in the field of surveillance. The RC literature review efforts have provided an opportunity for interprofessional collaboration and have resulted in a repository of over 1,000 articles, but feedback from ISDS members indicated relevant articles were not captured by the existing methodology. The method of automated literature retrieval was thus refined to improve efficiency and inclusiveness of stakeholder interests.
The earlier literature review method was implemented from March 2007 to March 2012. PubCrawler  (articles indexed in Medline) and Google Scholar  search results were sent to the RC via automated e-mail. To refine this method, the RC developed search strings in PubMed , Embase , and Scopus , consisting of over 100 terms suggested by members. After evaluating these methods, we found that the Scopus search is the most comprehensive and improved the cross-disciplinary scope. Scopus results allowed filtering of 50–100 titles and abstracts in fewer than 30 minutes each week for the identification of relevant articles (Figure).
Journal titles were categorized to assess the increased range of fields covered; categories include epidemiology, agriculture, economics, and medicine (51 categories total).
Since implementing the new method, potentially relevant articles identified per month increased from an average of 19 (SD: 13; n= 31) to 159 (SD: 63; n= 3). Both methods identified articles in the health sciences, but the new search also captured articles in the life, physical, and social sciences. Between March 2007 and March 2012, articles selected were classified into an average of 10 different categories per literature review (SD: 4; n= 31) versus an average of 33 categories (SD: 5; n= 3) with the updated process.
The new search method improves upon the previous method – it captures relevant articles indexed in health science and other secondary databases beyond Medline. The new method has resulted in a greater number of relevant literature articles, from a broader range of disciplines, and in reduced amount of preparation time as compared to the results of the previous search method. This improvement may increase multi-disciplinary discussions and partnerships, but changes in online publishing pose challenges to continued access of the new range of articles.
Disease surveillance literature; ISDS Research Committee; Literature search
As part of an empirical study investigating how life scientists think about ethical and societal implications of their work, and about life science research in general, we sought to elucidate barriers that scientists might face in considering such implications.
Between 2005 and 2007, we conducted a study consisting of phone interviews, focus groups, and a national survey of life scientists at biomedical research institutions. The study population included graduate students, postdoctoral fellows, faculty, clinical instructors, and research staff. We analyzed data through qualitative and quantitative methods.
In analyzing the data, we found that life scientists do, in fact, face barriers to considering ethical and societal implications of research. We categorized these barriers as falling into four broad domains: (1) lack of awareness of ethical and societal implications; (2) lack of relevance of such concerns to their specific research; (3) self-confidence in their ability to resolve such concerns; and (4) aspects of the daily practice of science itself.
Life science researchers experience elements inherent in their training and in the conduct of science as barriers to thinking about ethical and societal implications related to their work. These findings suggest areas in which research ethics educators, bioethicists, and the scientific community can focus their efforts to improve social and ethical accountability in research.
Bioethics; qualitative methods; quantitative methods; empirical research
Microbial mats are self-sustained, functionally complex ecosystems that make good models for the understanding of past and present microbial ecosystems as well as putative extraterrestrial ecosystems. Ecological theory suggests that the composition of these communities might be affected by nutrient availability and disturbance frequency. We characterized two microbial mats from two contrasting environments in the oligotrophic Cuatro Ciénegas Basin: a permanent green pool and a red desiccation pond. We analyzed their taxonomic structure and composition by means of 16S rRNA clone libraries and metagenomics and inferred their metabolic role by the analysis of functional traits in the most abundant organisms. Both mats showed a high diversity with metabolically diverse members and strongly differed in structure and composition. The green mat had a higher species richness and evenness than the red mat, which was dominated by a lineage of Pseudomonas. Autotrophs were abundant in the green mat, and heterotrophs were abundant in the red mat. When comparing with other mats and stromatolites, we found that taxonomic composition was not shared at species level but at order level, which suggests environmental filtering for phylogenetically conserved functional traits with random selection of particular organisms. The highest diversity and composition similarity was observed among systems from stable environments, which suggests that disturbance regimes might affect diversity more strongly than nutrient availability, since oligotrophy does not appear to prevent the establishment of complex and diverse microbial mat communities. These results are discussed in light of the search for extraterrestrial life. Key Words: Cuatro Ciénegas—Metagenomics—Microbial mats—Oligotrophic—Phosphorus limitation—Stromatolites. Astrobiology 12, 659–673.
The Cuatro Ciénegas Basin (CCB) has been identified as a center of endemism for many life-forms. Nearly half the bacterial species found in the spring systems have their closest relatives in the ocean. This raises the question of whether the high diversity observed today is the product of an adaptive radiation similar to that of the Galapagos Islands or whether the bacterial groups are “survivors” of an ancient sea, which would be of interest for astrobiology.
To help answer this question, we focused on Firmicutes from Cuatro Ciénegas (mainly Bacillus and Exiguobacterium). We reconstructed the phylogenetic relationships of Firmicutes with 28 housekeeping genes and dated the resulting tree using geological events as calibration points.
Our results show that marine Bacillus diverged from other Bacillus strains 838 Ma, while Bacillus from Cuatro Ciénegas have divergence dates that range from 770 to 202 Ma. The members of Exiguobacterium from the CCB conform to a much younger group that diverged from the Andes strain 60 Ma and from the one in Yellowstone 183 Ma. Therefore, the diversity of Firmicutes in Cuatro Ciénegas is not the product of a recent radiation but the product of the isolation of lineages from an ancient ocean. Hence, Cuatro Ciénegas is not a Galapagos Archipelago for bacteria but is more like an astrobiological “time machine” in which bacterial lineages survived in an oligotrophic environment that may be very similar to that of the Precambrian. Key Words: Firmicutes—Cuatro Ciénegas—Precambrian—Molecular dating—Western Interior Seaway. Astrobiology 12, 674–684.
The discovery of large (>100 u) molecules in Titan's upper atmosphere has heightened astrobiological interest in this unique satellite. In particular, complex organic aerosols produced in atmospheres containing C, N, O, and H, like that of Titan, could be a source of prebiotic molecules. In this work, aerosols produced in a Titan atmosphere simulation experiment with enhanced CO (N2/CH4/CO gas mixtures of 96.2%/2.0%/1.8% and 93.2%/5.0%/1.8%) were found to contain 18 molecules with molecular formulae that correspond to biological amino acids and nucleotide bases. Very high-resolution mass spectrometry of isotopically labeled samples confirmed that C4H5N3O, C4H4N2O2, C5H6N2O2, C5H5N5, and C6H9N3O2 are produced by chemistry in the simulation chamber. Gas chromatography–mass spectrometry (GC-MS) analyses of the non-isotopic samples confirmed the presence of cytosine (C4H5N3O), uracil (C5H4N2O2), thymine (C5H6N2O2), guanine (C5H5N5O), glycine (C2H5NO2), and alanine (C3H7NO2). Adenine (C5H5N5) was detected by GC-MS in isotopically labeled samples. The remaining prebiotic molecules were detected in unlabeled samples only and may have been affected by contamination in the chamber. These results demonstrate that prebiotic molecules can be formed by the high-energy chemistry similar to that which occurs in planetary upper atmospheres and therefore identifies a new source of prebiotic material, potentially increasing the range of planets where life could begin. Key Words: Astrochemistry—Planetary atmospheres—Titan—Astrobiology. Astrobiology 12, 809–817.
Spore-forming bacteria are of particular concern in the context of planetary protection because their tough endospores may withstand certain sterilization procedures as well as the harsh environments of outer space or planetary surfaces. To test their hardiness on a hypothetical mission to Mars, spores of Bacillus subtilis 168 and Bacillus pumilus SAFR-032 were exposed for 1.5 years to selected parameters of space in the experiment PROTECT during the EXPOSE-E mission on board the International Space Station. Mounted as dry layers on spacecraft-qualified aluminum coupons, the “trip to Mars” spores experienced space vacuum, cosmic and extraterrestrial solar radiation, and temperature fluctuations, whereas the “stay on Mars” spores were subjected to a simulated martian environment that included atmospheric pressure and composition, and UV and cosmic radiation. The survival of spores from both assays was determined after retrieval. It was clearly shown that solar extraterrestrial UV radiation (λ≥110 nm) as well as the martian UV spectrum (λ≥200 nm) was the most deleterious factor applied; in some samples only a few survivors were recovered from spores exposed in monolayers. Spores in multilayers survived better by several orders of magnitude. All other environmental parameters encountered by the “trip to Mars” or “stay on Mars” spores did little harm to the spores, which showed about 50% survival or more. The data demonstrate the high chance of survival of spores on a Mars mission, if protected against solar irradiation. These results will have implications for planetary protection considerations. Key Words: Planetary protection—Bacterial spores—Space experiment—Simulated Mars mission. Astrobiology 12, 445–456.
Evidence for the widespread occurrence of extraterrestrial halite, particularly on Mars, has led to speculations on the possibility of halophilic microbial forms of life; these ideas have been strengthened by reports of viable haloarchaea from sediments of geological age (millions of years). Raman spectroscopy, being a sensitive detection method for future astrobiological investigations onsite, has been used in the current study for the detection of nine different extremely halophilic archaeal strains which had been embedded in laboratory-made halite crystals in order to simulate evaporitic conditions. The cells accumulated preferentially in tiny fluid inclusions, in simulation of the precipitation of salt in natural brines. FT-Raman spectroscopy using laser excitation at 1064 nm and dispersive micro Raman spectroscopy at 514.5 nm were applied. The spectra showed prominent peaks at 1507, 1152 and 1002 cm−1 which are attributed to haloarchaeal C50 carotenoid compounds (mainly bacterioruberins). Their intensity varied from strain to strain at 1064-nm laser excitation. Other distinguishable features were peaks due to peptide bonds (amide I, amide III) and to nucleic acids. No evidence for fatty acids was detected, consistent with their general absence in all archaea.
These results contribute to a growing database on Raman spectra of terrestrial microorganisms from hypersaline environments and highlight the influence of the different macromolecular composition of diverse strains on these spectra.
Raman spectroscopy; extremely halophilic archaea; halite; astrobiology; fluid inclusions; carotenoids; bacterioruberins; Martian subsurface
Iron (oxyhydr)oxide microbial mats in modern to ∼100 ka tufa terraces are present in a cold spring system along Ten Mile Graben, southeastern Utah, USA. Mats exhibit morphological, chemical, and textural biosignatures and show diagenetic changes that occur over millennial scales. The Jurassic Brushy Basin Member of the Morrison Formation in the Four Corners region of the USA also exhibits comparable microbial fossils and iron (oxyhydr)oxide biosignatures in the lacustrine unit.
Both the modern spring system and Brushy Basin Member represent alkaline, saline, groundwater-fed systems and preserve diatoms and other similar algal forms with cellular elaboration. Two distinct suites of elements (1. C, Fe, As and 2. C, S, Se, P) are associated with microbial fossils in modern and ancient iron (oxyhydr)oxides and may be potential markers for biosignatures. The presence of ferrihydrite in ∼100 ka fossil microbial mats and Jurassic rocks suggests that this thermodynamically unstable mineral may also be a potential biomarker.
One of the most extensive sedimentary records on Mars is exposed in Gale Crater and consists of non-acidic clays and sulfates possibly of lacustrine origin. These terrestrial iron (oxyhydr)oxide examples are a valuable analogue because of similar iron- and clay-rich host rock compositions and will help (1) understand diagenetic processes in a non-acidic, saline lacustrine environment such as the sedimentary rocks in Gale Crater, (2) document specific biomediated textures, (3) demonstrate how biomediated textures might persist or respond to diagenesis over time, and (4) provide a ground truth library of textures to explore and compare in extraterrestrial iron (oxyhydr)oxides, where future explorations hope to detect past evidence of life. Key Words: Biogeochemistry—Mars—Biosignatures—Diagenesis—Iron oxides. Astrobiology 14, 1–14.