Engineering topics
Nealson, K.
Publications and source records attributed to Nealson, K..
Biological iron isotopic fractionations in antarctic endolithis microbial communities
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Viking's experiments and hypothesis that Fe(VI) is a possible candidate as Martian oxidant
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Novel anaerobic thermoalkaliphilic bacterium Anaerobranca californiensis sp. nov., with dissimilatory reduction of sulfur, Fe(III) and other inorganic electron acceptors
A novel obligately anaerobic thermoalkaliphilic bacterium was isolated from the beds of alkaline hot springs located on the shore line of Paoha island of Mono Lake.
Application of Computer Tomography for Life Detection
Perhaps one of the most fundamentally difficult challenges facing those who would search for life is that of scale determination. Spatial scales of life on Earth range over more than 15 orders of magnitude in mass and volume, and more than 8 orders of magnitude in 2 dimensional space. If the distribution of life is sparse in comparison to the background on which it is found, then the choice of the right scale is critical to finding that life. But how does one identify the proper scale? To put this in other words, how does one recognize the "haystacks" in which the needles (biosignatures and evidence of life) might be most profitably searched for? The problem is further exacerbated when conditions get extreme because much of the life moves from the clement surface environment into the pores and more clement environments inside of rocks, minerals and soils. Once encased in their lithic homes, these microbes become nearly impossible to study by standard techniques because of the opacity of the rocks. It is this problem that we propose to address in the work proposed here. Computer Tomography (CT) has been a very valuable tool in medicine, where the best resolution available has typically been of the order of about 0.5 mm. However, to adapt the approach for life detection of microbial endoliths, the resolution needs to be moved to the micrometer and even submicrometer levels. Thus for the studies proposed here, we begin with a commercially available instrument that can yield resolution of approximately 10 micrometers. The rational for this is twofold: first, this is the "state of the art" in laboratory instruments; and second, that while the usual size of a microbial cell is about 1 micron, microorganisms tend to live in communities that usually exceed the 10 micrometer size range. The resolution also depends on the sample size itself, so having a small lab instrument into which small samples can be placed will be beneficial to the resolution. We have now used several different CT systems, beginning with the medical scanners (Arcadia CT group) for the detection of layered communities in sandstone rocks from Antarctica. Even this crude instrument was able to point to the areas of the rock that were dominated by microbial populations - this provides the critical first information that says, "Go back and look at these sites with other methods." We showed that without sample preparation or destruction it was possible to gain knowledge as to the presence of density differences suggestive of life.
Searching for life in the universe: lessons from the earth
Text of a talk to be presented at the German Society of Microbiology International meeting, keynote speech in astrobiology
Thermophiles from Mono Lake basin
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On the possibilty of clathrate hydrates on the Moon
One of the most important inferences of the Lunar Prospector mission data was the existence of subsurface water ice in the permanently shadowed craters near both lunar poles [Feldman et al., 1998]. We propose and substantiate an alternative explanation that hydrogen can exist in the shallow lunar subsurface in the form of clathrate hydrates: CH4 . 6H(2)o and/or CO2 . 6H(2)o.
Self-Sterilizating Properties of Martian Soil: Possible Nature & Implications
As a result of the Viking missions in 1970s, the presence of a strong oxidant in Martian soil was suggested. Here we present a testable, by near-term missions, hypothesis that iron (VI) contributes to that oxidizing pool.
Microbial Life in Areas with High Co(sub 2) Content Near Horseshoe Lake Model for Mars
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Endolithic Microorganisms in Mono Lake
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Organic Biosignatures in Antarctic Sandstone
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Application of Computer Tomography (CT) for Search of Life in Extreme Environments
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Hollow Cathode Ion Lasers for Deep Ultraviolet Raman Spectroscopy and Fluorescence Imaging
This article describes the development of hollow cathode ion lasers and their use in constructing an ultraviolet micro-Raman spectrograph with native fluorescence imaging capability.
Early Stellar Activity, Initial Redox Potential and the Habitability of Planets
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LIfe: Past, Present and Future
Molecular methods of taxonomy and phylogeny have changed the way in which life on earth is viewed -- they have allowed us to transition from a eukaryote-centric view of the planet to one that is peculiarly prokarote-centric, containing three kingdoms, two of which are prokaryotic unicells.
Evaluation of Meterorite Amono Acid Analysis Data Using Multivariate Techniques
The amino acid distributions in the Murchison carbonaceous chondrite, Mars meteorite ALH84001, and ice from the Allan Hills region of Antarctica are shown, using a multivariate technique known as Principal Component Analysis (PCA), to be statistically distinct from the average amino acid compostion of 101 terrestrial protein superfamilies.