National Academies Press: OpenBook

The Astrophysical Context of Life (2005)

Chapter: Appendix C: Glossary

« Previous: Appendix B: Related Reports and Programmatic Activities
Suggested Citation:"Appendix C: Glossary." National Research Council. 2005. The Astrophysical Context of Life. Washington, DC: The National Academies Press. doi: 10.17226/11316.
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C
Glossary


Aitken Basin

Largest impact basin known, located in the Moon’s southern polar region

alpha decay

Radioactive decay of a nucleus by the emission of an alpha particle, the nucleus of a helium-4 atom

amino acid

Class of basic molecules that make up proteins

apoptosis

Cell death

Archean

Period in Earth’s history from 3.8 to 2.5 billion years ago, when life arose

Argyre

Major impact basin on Mars

asteroid

Rocky fragments left over from the formation of the solar system

astrosphere

Zone of interaction between a star and its interstellar environment


beta decay

Radioactive decay of a nucleus by the emission of an electron (or positron) and an electron antineutrino (or electron neutrino)

biosphere

Life zone of Earth, which includes all living organisms and all organic matter that has not yet decomposed

bolide

Meteor that often explodes as a fireball


carbonaceous chondrite

Stony meteorite that contains carbonaceous compounds

Chicxulub

Impact basin in Mexico, which was created at the end of the Cretaceous and the beginning of the Tertiary

chirality

Degree to which an object is different from its mirror image

chromosphere

Visually transparent layer above the Sun’s visible photosphere

Suggested Citation:"Appendix C: Glossary." National Research Council. 2005. The Astrophysical Context of Life. Washington, DC: The National Academies Press. doi: 10.17226/11316.
×

clay

Generic term for an aggregate of hydrous silicate particles less than 4 µm in diameter

comet

Relatively small planetary body similar to an asteroid but composed largely of ice

cosmic rays

High-energy particles originating outside Earth

cross strand exchange

Process in which bases along one double helix strand separate and link across to a separate double helix and vice versa


Darwin

European Space Agency’s large infrared-wavelength space interferometer

Deep Impact

NASA mission to collide a spacecraft to create a deep crater in Comet Tempel 1

Deinococcus radiodurans

Gram-positive aerobic bacteria, the most radiation-resistant organism known

dichroism

Differential absorption of left- and right-hand circularly polarized light in a material

DNA

Deoxyribonucleic acid, the molecule that carries genetic information

DOE

U.S. Department of Energy

dose

Absorbed amount of radiation

dose rate

Rate at which tissue absorbs radiation

double-strand break

Break in both strands of the DNA molecule, usually caused by oxidative stress or certain forms of radiation

D-ribose

Right-handed form of a five-carbon sugar, found in all living cells


early stars

Stars that formed primarily from hydrogen and helium and are deficient in heavier elements

endogenous

Organic matter synthesized on Earth and necessary for the appearance of life (see exogenous)

exogenous

Organic matter delivered from space and necessary for the appearance of life (see endogenous)

Exploration Initiative

U.S. multiagency Vision for Space Exploration


field reversal

Periodic reversal of the magnetic field of a star or planet

flare star

Star that sporadically flares in brightness by an order of magnitude or more


gamma ray

Most energetic form of electromagnetic radiation

gamma-ray burst

Energetic cosmic event that produces a burst of gamma rays


habitable zone

Radial zone in which certain parameters thought to be necessary for life are met

Hadean

Era in Earth’s history 4.5 to 3.8 billion years ago, before life is thought to have arisen

Suggested Citation:"Appendix C: Glossary." National Research Council. 2005. The Astrophysical Context of Life. Washington, DC: The National Academies Press. doi: 10.17226/11316.
×

heliosphere

Huge magnetic bubble created in interstellar space by the outrushing solar wind and associated magnetic field

Hellas

Major impact basin on Mars

Herschel

European Space Agency’s far-infrared and submillimeter telescope project, due to launch in 2007

homochirality

Molecules possessing structure with the same handedness

hypermutable

Genes that have a high rate of mutation


impact basin

Large crater produced by a meteorite impact

in silico

Relating to processes that occur in computer simulations

in vitro

Relating to processes that occur in a laboratory

in vivo

Relating to processes that occur in living matter

isotope

Atoms of a chemical element whose nuclei have the same atomic number, Z, but different atomic weights due to different numbers of neutrons


K-T boundary

Boundary between the Cretaceous and Tertiary periods, about 65 million years ago

Kuiper Belt

Area of the solar system extending from within the orbit of Neptune (at 30 AU) to some 50 AU from the Sun


Lake Acraman

Large meteor impact crater in South Australia

L-enantiomer

Molecule with left-handed chirality

L-isomer

Molecule with left-handed chirality

Long-Duration Exposure Facility

NASA experiment involving a satellite that was retrieved after several years to determine the effects of long-term exposure to space

L-ribose

Left-handed form of a five-carbon sugar

LUCA

Last Universal Common Ancestor (of life)


magma chamber

Underground pocket containing molten rock

meiosis

Reproduction through cell division

metals

To astronomers, any element except hydrogen or helium

mtDNA

Mitochondrial DNA


NAI

NASA Astrobiology Institute

NASA

U.S. National Aeronautics and Space Administration

NSCORT

NASA Specialized Centers of Research and Training

NEO

Near-Earth object, an asteroid or comet that comes relatively close to Earth

NIH

U.S. National Institutes of Health

NSF

U.S. National Science Foundation

Suggested Citation:"Appendix C: Glossary." National Research Council. 2005. The Astrophysical Context of Life. Washington, DC: The National Academies Press. doi: 10.17226/11316.
×

obliquity

Angle between the plane of a planet’s orbit and that of the planet’s equator

Oklo

Series of natural fission reactors that were active in the Oklo Valley of Gabon, Africa, about 1.5 billion years ago

Oort Cloud

Spherical cloud of comets with semimajor axes between 1,000 and 50,000 AU

oxygen radical

Oxygen atom with an unpaired electron. Radicals are powerful oxidizing agents that can cause structural damage to proteins and nucleic acids.


panspermia

Hypothesis that life originated elsewhere in the universe and migrated through space to Earth and, potentially, elsewhere

photosynthesis

Biochemical process by which the energy of light is converted into chemical energy in plants, algae, and certain bacteria

phototroph

Organism that uses light as its main source of energy

phylogenetic

Of or related to the evolutionary development of a group of genetically related organisms

placer deposit

Alluvial deposit of sand and gravel representing stream beds

planetesimal

Small rocky and icy object that existed at an early stage in the development of the solar system

polymerase

Enzymes that catalyze the polymerization of nucleic acids

polyols

Polyhydric alcohols or sugar alcohols

polysaccharides

Polymers made up of chains of simple sugars. Examples include starch, cellulose, and glycogen

protein

Complex, high-molecular-weight organic compound that consists of amino acids joined by peptide bonds

Pseudomonas fluorescens

Common nonpathogenic, gram-negative bacteria that produces a soluble greenish fluorescent pigment, particularly under conditions of low iron availability

P-T boundary

Geologic boundary between the Permian and Triassic periods, about 250 million years ago

pyrimidine dimer

Two adjacent pyrimidine nucleotides, usually thymine, in which the pyrimidine residues are covalently joined by a cyclobutane ring. These dimers stop DNA replication.

pyrimidines

Organic compounds with a heterocyclic ring: two nitrogen atoms taking the place of carbon atoms at positions 1 and 3 relative to each other around the six-member ring


radiolarians

Single-celled organisms that form protective skeletons, usually made of silicon dioxide

ram pressure

Force per unit area required to stop the solar wind flow

Suggested Citation:"Appendix C: Glossary." National Research Council. 2005. The Astrophysical Context of Life. Washington, DC: The National Academies Press. doi: 10.17226/11316.
×

redox state

Chemical reaction environment determined by the balance of negatively and positively charged atoms

replication

Reproduction from a template

ribose

Five-carbon sugar

RNA

Ribonucleic acid, a molecule involved in transcription of the instructions in DNA. Some theorize that RNA was the precursor to DNA.


single-strand break

When one strand of the DNA molecule is broken, usually by oxidative stress or certain forms of radiation

solar flare

Eruption of hot gas and radiation from the Sun’s photosphere

solar neighborhood

Sun and nearby stars

Stardust mission

NASA mission to return dust from Comet Wild 2

subduction

Geologic process by which one tectonic plate is forced under another

Sudbury

Ancient impact basin in northern Canada

supernova

Stellar explosion


tars

Complex hydrocarbons with high viscosity and melting point

tectonics

Theory that Earth’s lithosphere exists as separate and distinct plates that float on a fluid-like asthenosphere

Titan

Largest moon of Saturn

TPF

NASA’s Terrestrial Planet Finder

transition elements

Elements located in groups IB to VIIIB of the Periodic Table. They have many of the characteristics of metals.


ultraviolet

Electromagnetic radiation more energetic than visible light

UVB

Ultraviolet sunlight that penetrates the ozone layer and reaches Earth’s surface

UVC

Ultraviolet sunlight with shorter wavelength than UVB that is filtered out by Earth’s ozone layer


VPL

Virtual Planetary Laboratory, hosted by Caltech and the Jet Propulsion Laboratory

volatile

Substance with a low evaporation temperature

Vredefort

300-km impact crater in South Africa, formed about 2 billion years ago


x ray

Electromagnetic radiation more energetic than ultraviolet light

Suggested Citation:"Appendix C: Glossary." National Research Council. 2005. The Astrophysical Context of Life. Washington, DC: The National Academies Press. doi: 10.17226/11316.
×
Page 70
Suggested Citation:"Appendix C: Glossary." National Research Council. 2005. The Astrophysical Context of Life. Washington, DC: The National Academies Press. doi: 10.17226/11316.
×
Page 71
Suggested Citation:"Appendix C: Glossary." National Research Council. 2005. The Astrophysical Context of Life. Washington, DC: The National Academies Press. doi: 10.17226/11316.
×
Page 72
Suggested Citation:"Appendix C: Glossary." National Research Council. 2005. The Astrophysical Context of Life. Washington, DC: The National Academies Press. doi: 10.17226/11316.
×
Page 73
Suggested Citation:"Appendix C: Glossary." National Research Council. 2005. The Astrophysical Context of Life. Washington, DC: The National Academies Press. doi: 10.17226/11316.
×
Page 74
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In 1997, the National Aeronautics and Space Administration (NASA) formed the National Astrobiology Institute to coordinate and fund research into the origins, distribution, and fate of life in the universe. A 2002 NRC study of that program, Life in the Universe: An Assessment of U.S. and International Programs in Astrobiology, raised a number of concerns about the Astrobiology program. In particular, it concluded that areas of astrophysics related to the astronomical environment in which life arose on earth were not well represented in the program. In response to that finding, the Space Studies Board requested the original study committee, the Committee on the Origins and Evolution of Life, to examine ways to augment and integrate astronomy and astrophysics into the Astrobiology program. This report presents the results of that study. It provides a review of the earlier report and related efforts, a detailed examination of the elements of the astrobiology program that would benefit from greater integration and augmentation of astronomy and astrophysics, and an assessment of ways to facilitate the integration of astronomy with other astrobiology disciplines.

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