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Geologic maps are foundational products for natural hazard assessments but developing them for submarine areas is challenging due to a lack of physical access to the study area. In response, submarine geomorphologic maps are used to provide geologic context and spatial information on landforms and related geo-hazards for risk management. These maps are generated from remotely sensed data, e.g. digital elevation models (DEMs), which introduce unique hurdles to submarine mapping. To address this issue, we produced a workflow for applying planetary geologic mapping methods to submarine data. Using this, we created an onshore-offshore geomorphologic map of the Christiana-Santorini-Kolumbo Volcanic Group, Greece. This product can be used to enhance hazard assessments on Santorini, which is a tourist hot-spot at high risk for volcanically- and seismically-induced hazards. We present this workflow as a tool for generating uniform geomorphologic map products that will aid natural hazard assessments of submarine environments.

Proxima Centauri b provides an unprecedented opportunity to understand the evolution and nature of terrestrial planets orbiting M dwarfs. Although Proxima Cen b orbits within its star's habitable zone, multiple plausible evolutionary paths could have generated different environments that may or may not be habitable. Here we use 1D coupled climate-photochemical models to generate self-consistent atmospheres for evolutionary scenarios predicted in our companion paper (Barnes et al., 2016). These include high-O2, high-CO2, and more Earth-like atmospheres, with either oxidizing or reducing compositions. We show that these modeled environments can be habitable or uninhabitable at Proxima Cen b's position in the habitable zone. We use radiative transfer models to generate synthetic spectra and thermal phase curves for these simulated environments, and instrument models to explore our ability to discriminate between possible planetary states. These results are applicable not only to Proxima Cen b, but to other terrestrial planets orbiting M dwarfs. Thermal phase curves may provide the first constraint on the existence of an atmosphere, and JWST observations longward of 7 microns could characterize atmospheric heat transport and molecular composition. Detection of ocean glint is unlikely with JWST, but may be within the reach of larger aperture telescopes. Direct imaging spectra may detect O4, which is diagnostic of massive water loss and O2 retention, rather than a photosynthesis. Similarly, strong CO2 and CO bands at wavelengths shortward of 2.5 {\mu}m would indicate a CO2-dominated atmosphere. If the planet is habitable and volatile-rich, direct imaging will be the best means of detecting habitability. Earth-like planets with microbial biospheres may be identified by the presence of CH4 and either photosynthetically produced O2 or a hydrocarbon haze layer., Comment: 93 pages, 36 figures, 3 tables. Submitted to Astrobiology

The search for spectroscopic biosignatures with the next-generation of space telescopes could provide observational constraints on the abundance of exoplanets with signs of life. An extension of this spectroscopic characterization of exoplanets is the search for observational evidence of technology, known as technosignatures. Current mission concepts that would observe biosignatures from ultraviolet to near-infrared wavelengths could place upper limits on the fraction of planets in the galaxy that host life, although such missions tend to have relatively limited capabilities of constraining the prevalence of technosignatures at mid-infrared wavelengths. Yet searching for technosignatures alongside biosignatures would provide important knowledge about the future of our civilization. If planets with technosignatures are abundant, then we can increase our confidence that the hardest step in planetary evolution--the Great Filter--is probably in our past. But if we find that life is commonplace while technosignatures are absent, then this would increase the likelihood that the Great Filter awaits to challenge us in the future., Comment: 13 pages, 2 figures

Inner Solar System bodies with absent or extremely tenuous atmospheres such as Mercury and several high-eccentricity Near Earth Objects (NEOs) are subject to a wide range of surface temperatures. Here we show how the thermal expansion induced by strong diurnal insolation variations affects the thermal infrared spectra of felsic-rich to mafic-rich regoliths. 1400-700 cm−1 spectra of granular plagioclase-pyroxene mixtures were measured in the laboratory at four temperatures between 425 K and 725 K, simulating different daily surface temperatures within the Solar System. At the same time, we describe for the first time how two minerals with different thermal expansion coefficients combined in the same granular sample appear in a non-ambient (i.e., non-298 K) thermal infrared spectrum. The spectra of plagioclase-rich analogues appear to be dominated by felsic features regardless of the daily surface temperature, and do not exhibit any of the short-wavelength absorptions of pyroxenes. When detectable, on the other hand, the 870-cm−1 pyroxene absorption, which is not affected by thermal variations, functions instead as a proxy for the solid-solution composition (i.e., the Mg-Fe relative contents). In contrast, indications of the plagioclase solid solution occurring at ambient temperatures (i.e., Ca-Na relative contents) disappear at temperatures over 525 K. Christiansen feature position and spectral contrast, which show a clear dependency on composition even at high temperatures, require an accurate reproduction of the shallow thermal gradient in order to be used as indices. In general, in order to decipher planetary hyperspectral data, surface temperature acquisition seems to be a prerequisite, as well as a comparison with analogue spectra obtained under realistic environmental conditions.

This manuscript presents a review of data used by planetary geomorphologists and the software tools needed to prepare, process, and analyze those data, along with an example of doing so. Visible image capture and the photometric and geometric processing of those images are reviewed, as are laser altimetry data, and terrain data derived from images via stereogrammetry. Image processing, geographic, and geospatial software tools are discussed.

International audience; Basin-edge lobate scarps are a sub-type of tectonic shortening structure on the surface of Mercury that have formed at the edge of volcanic units that fill or partly fill impact basins. We have performed a global survey of these features and find that they are widespread in basins across the planet. We obtained model ages from crater size–frequency distribution analysis for a subset of our surveyed basins, for both the smooth plains infill and for the last resolvable tectonic activity on the associated basin-edge scarps. Our results indicate that some of these lobate scarps were still accumulating strain in the late Mansurian (approximately 1 Ga). From a photogeological assessment, we find that the orientations of these basin-edge lobate scarps are similar to those reported for the global population of lobate scarps in earlier studies, appearing to align ∼north–south at low latitudes and ∼east–west at higher latitudes. However, reassessing these landforms’ orientation with artificially illuminated topographic data does not allow us to rule out the effect of illumination bias. We propose that these landforms, the result of crustal shortening in response to global contraction, formed along the interface between the basin floor and the smooth plains unit, which acted as a mechanical discontinuity along which shortening strains were concentrated.

Dunes, dune fields, and ripples are unique and useful records of the interaction between wind and gran- ular materials – finding such features on a planetary surface immediately suggests certain information about climate and surface conditions (at least during the dunes’ formation and evolution). Additionally, studies of dune characteristics under non-Earth conditions allow for ‘‘tests” of aeolian pro- cess models based primarily on observations of terrestrial features and dynamics, and refinement of the models to include consideration of a wider range of environmental and planetary conditions. To-date, the planetary aeolian community has found and studied dune fields on Mars, Venus, and the Saturnian moon Titan. Additionally, we have observed candidate ‘‘aeolian bedforms” on Comet 67P/Churyumov- Gerasimenko, the Jovian moon Io, and – most recently – Pluto. In this paper, we hypothesize that the pro- gression of investigations of aeolian bedforms and processes on a particular planetary body follows a con- sistent sequence – primarily set by the acquisition of data of particular types and resolutions, and by the maturation of knowledge about that planetary body. We define that sequence of generated knowledge and new questions (within seven investigation phases) and discuss examples from all of the studied bod- ies. The aim of such a sequence is to better define our past and current state of understanding about the aeolian bedforms of a particular body, to highlight the related assumptions that require re-analysis with data acquired during later investigations, and to use lessons learned from planetary and terrestrial aeo- lian studies to predict what types of investigations could be most fruitful in the future.

Knowledge about the interior of our planet is mainly based on the interpretation of seismic data from earthquakes and nuclear explosions, and of composition of meteorites. Additional observations have led to a wide range of hypotheses on the heat flow from the interior to the crust, the abundance of certain noble gases in gasses vented from volcanoes and the possibility of a nuclear georeactor at the centre of the Earth. This paper focuses on a proposal for an underground laboratory to further develop antineutrinos as a tool to map the distribution of radiogenic heat sources, such as the natural radionuclides and the hypothetical nuclear georeactor., Invited talk presented at the International Symposium on Radiation Physics, Cape Town, 2003. Manuscript is submitted to Radiation Physics and Chemistry