2 research outputs found
Measurement of microbial activity in soil by colorimetric observation of in situ dye reduction: an approach to detection of extraterrestrial life
BACKGROUND: Detecting microbial life in extraterrestrial locations is a goal of space exploration because of ecological and health concerns about possible contamination of other planets with earthly organisms, and vice versa. Previously we suggested a method for life detection based on the fact that living entities require a continual input of energy accessed through coupled oxidations and reductions (an electron transport chain). We demonstrated using earthly soils that the identification of extracted components of electron transport chains is useful for remote detection of a chemical signature of life. The instrument package developed used supercritical carbon dioxide for soil extraction, followed by chromatography or electrophoresis to separate extracted compounds, with final detection by voltammetry and tandem mass-spectrometry. RESULTS: Here we used Earth-derived soils to develop a related life detection system based on direct observation of a biological redox signature. We measured the ability of soil microbial communities to reduce artificial electron acceptors. Living organisms in pure culture and those naturally found in soil were shown to reduce 2,3-dichlorophenol indophenol (DCIP) and the tetrazolium dye 2,3-bis(2-methoxy-4-nitro-5-sulfophenyl)-2H-tetrazolium-5-carboxanilide inner salt (XTT). Uninoculated or sterilized controls did not reduce the dyes. A soil from Antarctica that was determined by chemical signature and DNA analysis to be sterile also did not reduce the dyes. CONCLUSION: Observation of dye reduction, supplemented with extraction and identification of only a few specific signature redox-active biochemicals such as porphyrins or quinones, provides a simplified means to detect a signature of life in the soils of other planets or their moons
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Correlation Tracking for a Planetary Pointing and Tracking System
International Telemetering Conference Proceedings / November 14-16, 1978 / Hyatt House Hotel, Los Angeles, CaliforniaThe Planetary Pointing and Tracking System (PPTS) being developed at Jet Propulsion Laboratory is intended to provide precision pointing for science platforms on future autonomous planetary spacecraft. Future missions will impose very stringent platform pointing requirements due to low light levels and very high ground tracking rates. An integral part of PPTS is the correlation tracker, which has the potential to revolutionize autonomous guidance. The tracker provides two-axis pointing information concerning the position of the target body. It consists of a large-area charge-coupled device (CCD) imager and a microprocessor to control the CCD scanning function and data processing. The correlation tracker has three modes of operation: track, acquire and map. The track mode performs precision tracking of a target object. This is initiated after a target has been acquired. The map mode determes the centroidal coordinates, magnitude and size of bodies within the optical field of view. To improve precision pointing, various power spectra, such as shot noise and dark current, are derived. The probability of acquiring a target body is a function of signal-to-noise ratio and the noise equivalent angle. Derivations illustrating the application of these concepts are given. A discussion of mission analysis with the Uranian system as a representative example is provided.International Foundation for TelemeteringProceedings from the International Telemetering Conference are made available by the International Foundation for Telemetering and the University of Arizona Libraries. Visit http://www.telemetry.org/index.php/contact-us if you have questions about items in this collection