Appendixes



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Signs of Life: A Report Based on the April 2000 Workshop on Life Detection Techniques Appendixes

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Signs of Life: A Report Based on the April 2000 Workshop on Life Detection Techniques This page in the original is blank.

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Signs of Life: A Report Based on the April 2000 Workshop on Life Detection Techniques A Glossary and Acronyms GLOSSARY Abiotic Originating without the participation of a living system. Aerogel A nearly transparent, very lightweight material made primarily from silica; the world's lightest solid, weighing as little as three times the weight of air and exhibiting superb insulating properties. Aerosol A fine aerial suspension of liquid (mist, fog) or solid (dust, fume, smoke) particles. Anaerobe An organism that lives and reproduces in the absence of dissolved oxygen, instead using oxidants such as iron and sulfur compounds in energy metabolism. Anoxic Lacking oxygen or other oxidizing agents. Archaebacteria A group of prokaryotic microorganisms that are only distantly related to eukaryotes and the other prokaryotes and are members of the domain Archaea. Autotroph An organism that can make its own energy without requiring previously formed organic material from the environment. Biogenic Of biological origin. Biopolymer A large molecule having a repeating structural feature assembled by a living system from building blocks; proteins (built from amino acids) and DNA (built from nucleotides) are two examples. Carbonate A mineral having the carbonate ion, such as calcite (calcium carbonate), siderite (iron carbonate), and magnesite (magnesium carbonate).

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Signs of Life: A Report Based on the April 2000 Workshop on Life Detection Techniques Catalyst A substance that enhances the rate of a chemical reaction by lowering its activation energy, without itself being changed. Chemoautotrophic Producing organic matter by using the energy obtained from oxidation of certain chemicals; using carbon dioxide as the only source of carbon. Chemolithotrophic Capable of generating metabolically useful energy by the oxidation of inorganic compounds. Chert A hard sedimentary rock made up of very-fine-grained or amorphous silica. Chirality Handedness; a property of an object. An object is chiral if it cannot be superimposed on its mirror image. Diagenesis All of the changes that occur to a fossil (or more generally any sediment) after initial burial; includes changes that result from chemical and physical as well as biological processes. Eh A measure of the oxidative potential of the environment. Enantiomers A pair of objects (molecules, crystals) that are non-superimposable mirror images of each other. Enantiopurity In a mixture of enantiomers, the ratio of one enantiomer to the other. Eukaryote An organism having a membrane-bound nucleus and usually other organelles. FastDNA ML A program to analyze the relationships between nucleic acid sequences. Fluorogenic Capable of producing a new moiety that generates fluorescence. Flow cytometry A process of automated cell analysis that utilizes detection of cells flowing in a fluid stream. Fossiliferous Referring to any rock (usually sedimentary) that contains fossils. Fractionation Separation of a complex mixture into fractions, each of which is enriched in one of the components of the mixture. Gas chromatography Chromatographic technique in which the stationary phase is a solid or an immobile liquid and the mobile phase is gaseous. The gaseous samples are separated based on their differential adsorption to the stationary phase. Genomics The science that studies the entire genetic content of an organism. Heterotrophic Using only organic matter for energy and growth. Hydrolase Any member of the class of enzymes that catalyze the cleavage of a chemical bond with the addition of water.

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Signs of Life: A Report Based on the April 2000 Workshop on Life Detection Techniques Levorotatory A term used to describe an optically active substance that rotates the polarization of plane-polarized light in a left-handed (counterclockwise) direction. Lipid An organic molecule that is not soluble in water and often forms membranes. Lipopolysaccharide A composite of lipids and sugars, found in biological membranes from terrean organisms. Lithobiont An organism inhabiting hard rock substrates. Magnetic biomineralization The formation of magnetic bodies by biological action. Metabolism The processes or chemical changes in a cell by which food is built up (anabolism) into living protoplasm and by which protoplasm is broken down (catabolism) into simpler compounds with the exchange of energy. Methanogenesis The biological production of methane. Microautoradiography The technique of obtaining photographic images of microscopic samples by using neutron, x, or gamma radiation emitted from the sample. Monomer A building block of a polymer, including a biological polymer. Amino acids are monomers of polypeptides (proteins) and nucleotides are monomers of nucleic acids. Muramic acid A component of bacterial cell walls. Nanopore A pore in a membrane barrier, defined by having a diameter of several nanometers or less. Oligotroph A microorganism specifically adapted to grow under conditions of low nutrient supply. Organic Derived from living systems; more recently, given the fact that all known living systems contain carbon in reduced form (i.e., not carbonate), “organic” has come to mean “containing reduced carbon.” Peptides Any of various natural or synthetic compounds containing two or more amino acids linked by the carboxyl group of one amino acid and the amino group of another. Phylogeny Ordering of species into higher taxa and the construction of evolutionary trees based on genetic relationships. Pigment Coloring matter in cells and tissues. Planetesimals The planetary bodies that formed the building blocks of all solar system planets and satellites. Prion A small proteinaceous infectious agent that resists inactivation by procedures that modify nucleic acids.

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Signs of Life: A Report Based on the April 2000 Workshop on Life Detection Techniques Ribosome A minute, round particle composed of RNA and protein found in the cytoplasm of living cells and active in the synthesis of proteins. Self-assembly A process by which biomolecules such as proteins, nucleic acids, and lipids aggregate into more complex structures. Tholin The reddish tar-like organic residue created in simulations of the action of ultraviolet radiation on gases typically found in planetary environments in the outer solar system. Vesicle A microscopic volume defined by a boundary structure; examples include selfassembled vesicles bounded by a membranous lipid bilayer, and small cavities formed in volcanic rock by entrapment of a gas bubble during solidification. ACRONYMS ADP Adenosine diphosphate. AMP Adenosine monophosphate. ATP Adenosine triphosphate. CHONS Containing carbon, hydrogen, oxygen, nitrogen, and sulfur. CT Computerized tomography. DAPI 4',6-Diamidino-2-phenylindole; a DNA dye that fluoresces (“blue”) when exposed to ultraviolet light and is used to stain the nuclear or background DNA of the cell in FISH assays. DNA Deoxyribonucleic acid; the genetic biopolymer of most terrean organisms. EDX Electron diffraction. EDXA Energy-dispersive x-ray analyzer. EELS Electron energy-loss spectrometry. EM Electron microprobe. ESEM Environmental scanning electron microscopy. ESI Electrospray injection; a way of generating ions for mass spectrometry that involves making droplets of a solution containing the analyte and evaporating it. FA Fluorescent antibody. FISH Fluorescent in situ hybridization; the detection of highly specific DNA probes that have been hybridized to either interphase or metaphase chromosomes using fluorescence microscopy.

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Signs of Life: A Report Based on the April 2000 Workshop on Life Detection Techniques GC-MS Gas chromatography-mass spectrometry; an analytical tool that separates molecules by chromatography and then analyzes them for their mass. IDP Interplanetary dust particle. IR Infrared. LSCM Laser scanning confocal microscope. MALDI Matrix assisted laser desorption and ionization; a way of elevating large molecules into the gas phase to permit their analysis in a mass spectrometer that involves embedding these in a matrix, and then putting energy into the matrix to sputter it and the molecule of interest into the “gas phase.” MPN Most probable number. mRNA Messenger RNA. PCR Polymerase chain reaction. rRNA Ribosomal RNA. RNA Ribonucleic acid. S Svedberg; a unit of sedimentation coefficient, equal to 10−13 second. SAED Selected area electron diffraction. SEM Scanning electron microscopy; images objects as small as 1 nanometer. SIMS Secondary ion mass spectrometry. SNC meteorites Three small classes of basaltic meteorites (shergottites, nakhlites, and chassignites) thought to have been ejected from Mars 's surface during an impact. TEM Transmission electron microscopy. TOF Time of flight; a type of mass spectrometry that assesses the mass of an ion by the time that it takes to move in an electric field. TPF Terrestrial Planet Finder. UV Ultraviolet. XAFS X-ray absorption fine structure. XRD X-ray diffraction. XRF X-ray fluorescence.