Glossary - ACS Symposium Series - ACS Publications - American

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Glossary Abyssal plain Flat or gently sloping areas of the deep ocean floor generally covered with fine-grained sediments. Achondrite Meteorite from an asteroid that has gone through the process of differentiation. Adiabatic A term in thermodynamics that describes a process that occurs without exchange of heat. Aerosol Sub-microscopic dispersions or suspensions of liquid droplets or solid particles in a gas. AGE see Asymptotic Giant Branch Alkali-feldspar A feldspar with a chemical composition of or between the endmembcrs NaAlSi 0 and KAlSi 0 . 3

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Amphibole A group of chain silicates. The simplest chemical formula for an amphibole is CaaMgsSigC^iOH^. Ankerite A sedimentary rock composed of calcium, iron, magnesium, and manganese carbonates. Apatite A group of phosphate minerals with the general formula Ca (P0 ) (X) where X is F,C1, or OH. 5

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Aphelion The point in the elliptical orbit of a planet farthest from the sun. Archean Terrestrial geologic eon that extends from the Hadean (3.8 Ga) until 2.5 billion years ago. Asymptotic Giant Branch Stars (AGE) A period of stellar evolution. They are named for their place in a region on the Hertzsprung-Russell Diagram dominated by evolving low to medium-mass stars (0.6-10 solar masses).

391 Zaikowski and Friedrich; Chemical Evolution across Space & Time ACS Symposium Series; American Chemical Society: Washington, DC, 2008.

392 Astronomical Unit (AU) An astronomical unit of length equal to the average distance between the Earth and the Sun. 1AU = 149.6xl0 km. 6

^417 see Astronomical Unit.


Baryon Subatomic particles made of three quarks. Protons and neutrons are both baryons. Biotite A common phyllosilicate (sheet silicate) mineral with the general formula K(Mg, Fe)3AlSi O (F, OH) . 3

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Chalcophile An element that tends to follow sulfur's behavior during geochemical processes, cf. lithophile and siderophile C Class Star Red giant stars where there is an excess of carbon in the atmosphere. Carbon stars are near the end of their lives. Centaur An icy asteroid that orbits between Jupiter and Neptune. Chondrite Meteorite from an undifferentiated planetary body, most likely an asteroid. Unaltered varieties generally contain chondrules or chondrule fragments. Chondrule Spherical millimeter-sized silicate droplet formed by melting and quenching prior to incorporation into undifferentiated meteorites. Circumstellar Envelope (CSE) The circumstellar environments around a masslosing giant star. Clathrate Well-defined chemical compounds consisting of a caged (trapped) molecular species contained in a lattice of a second type of molecule. CNO cycle A catalytic fusion cycle that converts H to He in stars. Corundum An oxide mineral with the formula A1 0 . 2

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CSE see circumstellar envelope. 2

D Abbreviation for Deuterium ( H). dex (decimal exponent) A logarithmic unit used in astronomy. For example, -O.XX dex equals 10" . oxx

Zaikowski and Friedrich; Chemical Evolution across Space & Time ACS Symposium Series; American Chemical Society: Washington, DC, 2008.

393 Differentiation Melting and fractionation of a planetary body into layers of different chemical composition, e.g. core, mantle and crust. In this process highdensity materials sink and low-density materials float. Dolomite A sedimentary rock composed of calcium magnesium carbonate.


Dwarf star A star on the main-sequence of the Hertzsprung-Russell diagram. Also known as main-sequence stars. Our Sun is a main-sequence star. Eccentricity A measure of the departure of an orbit from a circular path. Endmember A mineral that is at a pure compositional end of a mineral series. Minerals are solid solutions of varying chemical composition rather than having an exact chemical formula. For example, olivine contains endmembers fayalite (Fe Si0 ) and forsterite (Mg Si0 ), but actual olivine compositions are generally charge-balanced solid solutions between these: e.g. Fe .75Mgi. SiO or Feo.ioMg! SiO . cf. olivine, fayalite, forsterite. 2

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Enstatite The Mg-rich pyroxene group endmember mineral with the formula MgSi0 . 3

Fayalite The Fe-rich olivine group endmember mineral with the formula Fe Si0 . 2

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Feldspar A group of aluminum silicate minerals. Feldspars compose many of the rock-forming minerals found in the Earth's crust. Ferrosillite The Fe-rich pyroxene group endmember mineral with the formula FeSi0 . 3

Forsterite The Mg-rich olivene group endmember mineral with the formula Mg Si0 . 2

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Ga A unit of time equal to one billion (10 ) years. In geological or cosmological contexts, one can often assume that "ago" is implied if not explicitly stated. Garnet A group of silicate minerals with the general formula X Y (Si0 ) where X is a divalent cation and Y is a trivalent cation. 3

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Greenalite An iron-rich phyllosilicate mineral found in banded iron formations. Hadean Terrestrial geologic eon that extends back to the Earth's formation until about 3.8 billion years ago.


394 Hematite Oxide mineral with the formula Fe 0 . 2

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Hornblende A general term for an amphibole group chain silicate. Illite A phyllosilicate (layered silicate) with a structure of parallel silicate tetrahedral sheets. Each sheet has the general formula Si 0 . Downloaded by UNIV OF CALIFORNIA SANTA BARBARA on May 28, 2018 | https://pubs.acs.org Publication Date: February 15, 2008 | doi: 10.1021/bk-2008-0981.ch024

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Interstellar medium (ISM) The matter (gas and dust) that exists between the stars within a galaxy. IOM see Insoluable Organic Matter. Isochron A set of data points on an isochron plot that all fall on a single line and represent a single radiometric age. ISM see Interstellar Medium. Kuiper belt An area of the solar system extending from the orbit of Neptune (-30 AU) to 50 AU from the Sun. Lithophile An element that tends to follow (be concentrated in) the silicate portions of a rock during geochemical processes, cf. calcophile and siderophile. 30

Me Mass of the Sun: 1.99xl0 kg. 6

Ma A unit of time equal to one million (10 ) years. In geological or cosmological contexts, one can often assume that "ago" is implied if not explicitly stated. M Class Star The most common class of stars. These are red dwarf stars and are relatively small and cool. Magnetite A ferrimagnetic mineral with chemical formula Fe 0 . 3

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Metallicity A measure of the proportion of elements in a star other than hydrogen or helium. In astronomy, chemical elements other than hydrogen and helium are called metals. Meteor Light that results from the entry of a meteoroid or micrometeoroid from space into the Earth's atmosphere. Meteorite A fragment of a planetary body that reaches the surface of another planetary body.


395 Meteoroid A fragment dislodged from a planetary body that is traveling in space. Mineral Naturally occurring inorganic elements or compounds with crystalline structure.


Molecular cloud An interstellar cloud whose density and size permits the formation of molecules. Monte Carlo method A nondeterministic computational method for simulating the behavior of complex physical and systems. Montmorillonite A phyllosilicate mineral that typically forms microscopic crystals making a clay. It is the main constituent of the volcanic ash weathering product, bentonite. Nierite A mineral with the formula Si N . 3

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Nova A cataclysmic nuclear explosion. Nuclear cross section A model used to characterize the probability that a nuclear reaction will occur. Nuclear cross section is measured in units of barns with one barn equal to 10" cm . 24

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Nucleosynthesis The formation of unstable and stable isotopes in stars. Olivine A magnesium iron silicate mineral with the common solid solution endmembers forsterite and fayalite. Osbornite A mineral with the formula TiN. Parsec (pc) A unit of length used in astronomy that stands for parallax of 1 arcsecond. In more common units: 3.09χ 10 km or 2.063x 10 A U . 13

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Plagioclase A series of minerals within the feldspar family with endmember chemical compositions ranging from NaAlSi 0 to CaAl Si 0 . 3

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Phyllosilicate A class of minerals with a parallel or layered silicate sheet structure. Mica is a common example. Photosphere The region where an astronomical object stops being transparent to light. For stars, this is the visible "surface".


396 Pillow basalts Igneous rocks formed when basaltic lavas flow directly into water before solidifying. p-process The proton (p) capture process is a nucleosynthetic process responsible for the production of the proton-rich isotopes with masses A>100. Pyroxene A class of chain silicate minerals with the general formula XY(Si,Al) 0 . X and Y can be a wide range of charge-balancing cations (typically Fe, Mg, Ca, Na).


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Quartz A silicate mineral having the formula Si0 . 2

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RQ Radius of the Sun: 6.96x10 m. RG see Red Giant Star. Red Giant Star Red giants are stars of 0.4 to 10 times the mass of the Sun which have exhausted the supply of hydrogen in their cores and switched to fusing hydrogen in a shell outside the core. The Sun is expected to become a red giant in about five billion years. Retrograde motion Orbital or rotational motion that is clockwise as seen from north of the ecliptic. For example, Triton is in retrograde orbit around Neptune and Venus is in retrograde rotation. Riebeckite A sodium-rich member of the amphibole mineral group. r-process The rapid (r) neutron capture process is a nucleosynthetic process where nuclei are bombarded with a large neutron flux to form highly unstable neutron rich nuclei that rapidly decay to form stable nuclei. Most elements heavier than Fe are formed by the r-process. S Class Star These stars are classified by the presence of zirconium oxide lines, and reside between the Class M stars and Class C stars in spectral type. Siderite A mineral with the formula FeC0 . 3

Siderophile An element that tends to follow iron's behavior during geochemical processes. Siderophiles are enriched in the Earth's core. cf. calcophile and lithophile. Silicate A compound containing silicon and oxygen.


397 Sinoite A mineral with the formula Si N 0. 2

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Spinel A group of minerals named after the namesake mineral MgAl 0 . They have the general formula X Y 0 where cation X occupies tetrahedral sites and Y cations occupy octahedral sites. 2


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s-process The slow (s) neutron capture process is a nucleosynthetic process where the rate of neutron capture by nuclei is slow relative to the rate of radioactive beta-decay. Stilpnomelane An iron-rich phyllosilicate mineral often found in association with iron ores. Stromatolite Lithified sedimentary structures thought to result from the growth or activity of microorganisms. 3

Τ Abbreviation for Tritium ( H). Titanite A calcium titanium silicate mineral with the formula CaTiSi0 Sometimes called sphene.

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TNO see Trans-Neptunian Object. Trans-Neptunian Object (TNO) Any object in the solar system that orbits the sun at a greater average distance than Neptune. Troilite The mineral name for iron(II) sulfide: FeS. Trojan Asteroids that orbit 60° ahead of or behind a larger object. They do not collide with the larger because they orbit within one of the two Lagrangian points of stability. Turbidite Geological formations formed from underwater avalanches. Zircon A mineral with the formula ZrSi0 . 4


Glossary - ACS Symposium Series - ACS Publications - American

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