Gradient-Based Turbulence Estimates from Multicopter Profiles in the Arctic Stable Boundary Layer

Boundary-Layer Meteorology - We explore the potential of a new method for the estimation of profiles of turbulence statistics in the stable boundary layer (SBL). By applying gradient-based scaling...     

Investigation of biological, chemical and physical processes on and in planetary surfaces by laboratory simulation

The recently established Arkansas-Oklahoma Center for Space and Planetary Science has been given a large planetary simulation chamber by the Jet Propulsion Laboratory, Pasadena, California. When completely refurbished, the chamber will be dubbed Andromeda and it will enable conditions in space, on asteroids, on comet nuclei, and on Mars, to be reproduced on the meter-scale and surface and subsurface processes monitored using a range of analytical instruments. The following projects are currently planned for the facility. (1) Examination of the role of surface and subsurface processes on small bodies in the formation of meteorites. (2) Development of in situ sediment dating instrumentation for Mars. (3) Studies of the survivability of methanogenic microorganisms under conditions resembling the subsurface of Mars to test the feasibility of such species surviving on Mars and identify the characteristics of the species most likely to be present on Mars. (4) The nature of the biochemical “fingerprints” likely to have been left by live organisms on Mars from a study of degradation products of biologically related molecules. (5) Testing local resource utilization in spacecraft design. (6) Characterization of surface effects on reflectivity spectra for comparison with the data from spacecraft-borne instruments on Mars orbiters.     

Low pressure and desiccation effects on methanogens: Implications for life on Mars

Conditions on the surface of Mars would appear to be too hostile for life as we know it. But the subsurface is another matter. If liquid water is present, even intermittently, life forms present would at least be protected from the lethal radiation bombarding the surface. However, life would have to contend with variations in pressure and possibly extended periods of desiccation. The research reported here involves both active metabolism (methanogenesis) at 400 and 50 mbar of pressure, pressures that would be found in the near subsurface of Mars, and survival following desiccation at both 1 bar (a pressure that would be found in the Martian subsurface) and 6 mbar (the lowest pressure at the surface and very near subsurface). The three methanogens tested for active metabolism, Methanothermobacter wolfeii, Methanosarcina barkeri and Methanobacterium formicicum, all demonstrated methane production at both 400 and 50 mbar on JSC Mars-1, a Mars soil simulant. Methane production at 50 mbar was much reduced compared to that at 400 mbar, most likely due to the greater stress at the lower pressure. In desiccation survival experiments, M. barkeri had survived 330 days of desiccation at 1 bar, while M. wolfeii and M. formicicum survived 180 and 120 days, respectively. Methanococcus maripaludis did not survive desiccation at all at 1 bar. At 6 mbar, M. wolfeii, M. barkeri and M. formicicum survived 120 days of desiccation while M. maripaludis survived 60 days. These results along with results from previous research would seem to indicate that there is no reason that methanogens could not inhabit the subsurface of Mars.     

A Surface-Layer Study of the Transport and Dissipation of Turbulent Kinetic Energy and the Variances of Temperature,Humidity and CO$$_$$

We discuss scalar similarities and dissimilarities based on analysis of the dissipation terms in the variance budget equations, considering the turbulent kinetic energy and the variances of temperature, specific humidity and specific CO\(_2\) content. For this purpose, 124 high-frequency sampled segments are selected from the Boundary Layer Late Afternoon and Sunset Turbulence experiment. The consequences of dissipation similarity in the variance transport are also discussed and quantified. The results show that, for the convective atmospheric surface layer, the non-dimensional dissipation terms can be expressed in the framework of Monin–Obukhov similarity theory and are independent of whether the variable is temperature or moisture. The scalar similarity in the dissipation term implies that the characteristic scales of the atmospheric surface layer can be estimated from the respective rate of variance dissipation, the characteristic scale of temperature, and the dissipation rate of temperature variance.     

Zero-valent iron on Mars: An alternative energy source for methanogens

Zero-valent iron, montmorillonite-like smectites, and CO₂ gas are known to exist on Mars, and work was performed to investigate the ability of methanogens to subsist on these materials. After 71 days of incubation at 55 °C, mean methane concentration as percent of headspace volume was 19.80 ± 1.76% (mean ± SE) for replicates containing elemental iron and 0.50 ± 0.15% for those lacking elemental iron.