Dirk Schulze-Makuch

Locating potential biosignatures on Europa from surface geology observations.

We evaluated the astrobiological potential of the major classes of geologic units on Europa with respect to possible biosignatures preservation on the basis of surface geology observations. These observations are independent of any formational model and therefore provide an objective, though preliminary, evaluation. The assessment criteria include high mobility of material, surface concentration of non-ice components, relative youth, textural roughness, and environmental stability. Our review determined that, as feature classes, low-albedo smooth plains, smooth bands, and chaos hold the highest potential, primarily because of their relative young age, the emplacement of low-viscosity material, and indications of material exchange with the subsurface. Some lineaments and impact craters may be promising sites for closer study despite the comparatively lower astrobiological potential of their classes. This assessment will be expanded by multidisciplinary examination of the potential for habitability of specific features.

Search parameters for the remote detection of extraterrestrial life

Abstract Direct consequences of biological activity (biosignatures) and alterations of the geological environment due to biological processes (geosignatures) are currently known only for the planet Earth. However, geoindicators remotely detectable by robotic technology have revealed a number of sites in the solar system where conditions compatible with the support of life may exist. By focusing on a search for energy gradients, complex chemistry, liquids that may act as solvents, atmospheres, and indicators of geological differentiation, robotic exploration of the solar system and beyond should lead to fruitful targets in the search for extraterrestrial life. An analysis of all major solar system bodies for these parameters suggests that Mars, Titan, and the Galilean satellites should be given the highest priority in the search for extraterrestrial life in our solar system. Extending them to other bodies in the solar system, however, draws attention to Io, Triton, Titania, Enceladus, and Iapetus, among others, as worthy of greater attention.

Surfactant‐modified zeolite can protect drinking water wells from viruses and bacteria

Septic tanks, sewage effluents, and landfills can release microbial pathogens into groundwater. This problem is amplified in the so-called colonias along the U.S.-Mexico border and other low-income areas around the world that have no public sewage systems. The result is often outbreaks of groundwater-associated disease for which enteric viruses and bacteria, spread via a fecal-oral route, are responsible. However, due to difficulties and limitations in detection and surveillance of disease outbreaks, the causative agents for more than 50% of the outbreaks are unknown, though the clinical features suggest a viral etiology for most of those cases [U.S. Centers for Disease Control and Prevention, 1993]. Enteric pathogens such as E coli 0157:H7, Campylobacter, Enteroviruses, Hepatitis A virus, and caliciviruses have been responsible for groundwater-related microbial infections in humans. Inexpensive solutions to this problem are urgently needed. The recent threat of bio-terrorism and concerns about the safety of drinking water supplies further add to that urgency.

Correlation between microbiological and chemical parameters of some hydrothermal springs in New Mexico, USA

Discharge areas of hydrothermal springs are known to be inhabited by diverse types of microorganisms including archaea, prokaryotes and eukaryotes. A total of 11 hydrothermal samples from the Rio Grande rift and the Valles caldera in New Mexico were analyzed to investigate the correlation between chemical and microbiological parameters of hydrothermal waters. The sampled fluids are categorized into three chemical groups: (I) steam-condensing acid sulfate waters, (II) deep geothermal and derivative waters and (III) thermal meteoric waters. Analyses of the microbial phospholipid fatty acids and denaturing gradient gel electrophoresis of DNA show that acid sulfate waters were populated by thermoacidophilic organisms and had high biomass content. Mineralized deep geothermal and derivative waters exhibited a high degree of microbial diversity, but had low biomass content. Thermal meteoric waters are low in total dissolved solids, and exhibit very low biomass content and microbial diversity. DNA sequences from several previously unknown microbial species were detected. The results of this study support the hypothesis that microbes can be used as tracers for specific types of subsurface environments.

The Scaling of Hydraulic Properties in Granitic Rocks

Crystalline carbonates from 25 sites display an exponential increase of hydraulic conductivity with scale of measurement of 0.5 for porous-flow media, between 0.5 and 1.0 for dual-porosity media and about 1.0 for fracture- and conduit-flow media. Granitic rocks from 3 sites were analyzed for variations of hydraulic properties (hydraulic conductivity and transmissivity) to determine whether they follow the same trend as fractured crystalline carbonates do. Granitic rocks from two of the sites show a definite increase of hydraulic properties with scale of measurement while data are lacking to obtain a significant relationship for the third site. When establishing a scale relationship, transmissivity appears to be a more suitable parameter for granitic rocks than does hydraulic conductivity. This is due to (1) a correlation of hydraulic conductivity to depth which was observed at two sites, and (2) the presence of transmissive fractures outside the well screen that allow additional discharge to the borehole. More data are needed to verify whether the relationship found for fractured crystalline carbonates is also valid for granitic rocks because of the larger local variations in hydraulic conductivity and transmissivity for granitic rocks.