Metabolic Processes Preserved as Biosignatures in Iron-Oxidizing Microorganisms: Implications for Biosignature Detection on Mars

Iron-oxidizing bacteria occupy a distinct environmental niche. These chemolithoautotrophic organisms require very little oxygen (when neutrophilic) or outcompete oxygen for access to Fe(II) (when acidophilic). The utilization of Fe(II) as an electron donor makes them strong analog organisms for any potential life that could be found on Mars. Despite their importance to the elucidation of early life on, and potentially beyond, Earth, many details of their metabolism remain unknown. By using on-line thermochemolysis and gas chromatography?mass spectrometry (GC-MS), a distinct signal for a low-molecular-weight molecule was discovered in multiple iron-oxidizing isolates as well as several iron-dominated environmental samples, from freshwater and marine environments and in both modern and older iron rock samples. This GC-MS signal was neither detected in organisms that did not use Fe(II) as an electron donor nor present in iron mats in which organic carbon was destroyed by heating. Mass spectral analysis indicates that the molecule bears the hallmarks of a pterin-bearing molecule. Genomic analysis has previously identified a molybdopterin that could be part of the electron transport chain in a number of lithotrophic iron-oxidizing bacteria, suggesting one possible source for this signal is the pterin component of this protein. The rock samples indicate the possibility that the molecule can be preserved within lithified sedimentary rocks. The specificity of the signal to organisms requiring iron in their metabolism makes this a novel biosignature with which to investigate both the evolution of life on ancient Earth and potential life on Mars

Assessing long-term effects of artificial light at night on insects: what is missing and how to get there

Widespread and significant declines of insect population abundances and biomass are currently one of the most pressing issues in entomology, ecology and conservation biology. It has been suggested that artificial light at night is one major driver behind this trend. Recent advances in the gathering and analysis of long-term data sets of insect population and biomass trends, however, have mostly focused on the effects of climate change and agricultural intensification. We posit here that adequate assessment of artificial night at light that would be required to evaluate its role as a driver of insect declines is far from trivial. Currently its implementation into entomological monitoring programmes and long-running ecological experiments is hampered by several challenges that arise due to (i) its relatively late appearance as a biodiversity threat on the research agenda and (ii) the interdisciplinary nature of the research field where biologists, physicists and engineers still need to develop a set of standardised assessment methods that are both biologically meaningful and easy to implement. As more studies that address these challenges are urgently needed, this article aims to provide a short overview of the few existing studies that have attempted to investigate longer-term effects of artificial light at night on insect populations. To improve the quality and relevance of studies addressing artificial light at night and its effect on insects, we present a set of best practise recommendations where this field needs to be heading in the coming years and how to achieve it

Probing the Composition of Primitive Solar System Materials with a Compact Laser Mass Spectrometer

To contribute to and complement our understanding of the processes governing the formation,distribution, and evolution of primitive materials throughout the solar system, it will be critical toform connections between broad remote sensing spectroscopic surveys, laboratorymeasurements of analogs and samples delivered to Earth, and in situ measurements of thesurface composition on future primitive body missions. Recently, a laboratory prototypeemploying resonance two-step laser mass spectrometry [Getty et al., 2012] has been coupledto a cryogenic sample stage to enable measurements of analog samples that are relevant tothese fundamental questions. Analyses of mineral-aromatic mixtures and meteorite powderswill be presented. Our goals are twofold: (1) to conduct laboratory studies on solar systemanalog, meteoritic, and potentially returned samples to elucidate composition, and (2) toprovide a compact but capable analytical instrument for discovery-driven in situ interrogationof surface chemistry on a future mission, such as to a Trojan asteroid, comet, or icy moon

Structure and stability of Con(pyridine)m − clusters: Absence of metal inserted structures

A synergistic approach combining the experimental photoelectron spectroscopy and theoretical electronic structure studies is used to probe the geometrical structure and the spin magnetic moment of Con(pyridine)−m clusters. It is predicted that the ground state of Co(pyridine)− is a structure where the Co atom is inserted in a CH bond. However, the insertion is marked by a barrier of 0.33eV that is not overcome under the existing experimental conditions resulting in the formation of a structure where Co occupies a site above the pyridine plane. For Co2(pyridine)−, a ground-state structure is predicted in which the Co2 diametric moiety is inserted in one of the CH bonds, but again because of a barrier, the structure which matches the photoelectron spectrum is a higher-energy isomer in which the Co2 moiety is bonded directly to nitrogen on the pyridine ring. In all cases, the Co sites have finite magnetic moments suggesting that the complexes may provide ways of making cluster-based magnetic materials

The Gowdy T3 Cosmologies revisited

We have examined, repeated and extended earlier numerical calculations of Berger and Moncrief for the evolution of unpolarized Gowdy T3 cosmological models. Our results are consistent with theirs and we support their claim that the models exhibit AVTD behaviour, even though spatial derivatives cannot be neglected. The behaviour of the curvature invariants and the formation of structure through evolution both backwards and forwards in time is discussed.Comment: 11 pages, LaTeX, 6 figures, results and conclusions revised and (considerably) expande

Locally U(1)*U(1) Symmetric Cosmological Models: Topology and Dynamics

We show examples which reveal influences of spatial topologies to dynamics, using a class of spatially {\it closed} inhomogeneous cosmological models. The models, called the {\it locally U(1)$\times$U(1) symmetric models} (or the {\it generalized Gowdy models}), are characterized by the existence of two commuting spatial {\it local} Killing vectors. For systematic investigations we first present a classification of possible spatial topologies in this class. We stress the significance of the locally homogeneous limits (i.e., the Bianchi types or the `geometric structures') of the models. In particular, we show a method of reduction to the natural reduced manifold, and analyze the equivalences at the reduced level of the models as dynamical models. Based on these fundamentals, we examine the influence of spatial topologies on dynamics by obtaining translation and reflection operators which commute with the dynamical flow in the phase space.Comment: 32 pages, 1 figure, LaTeX2e, revised Introduction slightly. To appear in CQ

Communications: Chain and double-ring polymeric structures: Observation of AlnH3n+1 − (n=4–8) and Al4H14 −

A pulsed arc discharge source was used to prepare gas-phase, aluminum hydride cluster anions, AlnHm−, exhibiting enhanced hydrogen content. The maximum number of hydrogen atoms in AlnHm− species was m=3n+1 for n=5–8, i.e., AlnH3n+1−, and m=3n+2 for n=4, i.e., Al4H14−, as observed in their mass spectra. These are the most hydrogen-rich aluminum hydrides to be observed thus far, transcending the 3:1 hydrogen-to-aluminum ratio in alane. Even more striking, ion intensities for AlnHm− species with m=3n+1 and m=3n+2 hydrogen atoms were significantly higher than those of nearby AlnHm− mass peaks for which m\u3c3n+1, i.e., the ion intensities for AlnH3n+1− and for Al4H14− deviated from the roughly bell-shaped ion intensity patterns seen for most AlnHm−species, in which m ranges from 1 to 3n. Calculations based on density functional theory showed that AlnH3n+1− clusters have chain and/or double-ring polymericstructures

Manufacture of Gowdy spacetimes with spikes

In numerical studies of Gowdy spacetimes evidence has been found for the development of localized features (spikes) involving large gradients near the singularity. The rigorous mathematical results available up to now did not cover this kind of situation. In this work we show the existence of large classes of Gowdy spacetimes exhibiting features of the kind discovered numerically. These spacetimes are constructed by applying certain transformations to previously known spacetimes without spikes. It is possible to control the behaviour of the Kretschmann scalar near the singularity in detail. This curvature invariant is found to blow up in a way which is non-uniform near the spike in some cases. When this happens it demonstrates that the spike is a geometrically invariant feature and not an artefact of the choice of variables used to parametrize the metric. We also identify another class of spikes which are artefacts. The spikes produced by our method are compared with the results of numerical and heuristic analyses of the same situation.Comment: 25 page