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Planetary Science Research Discoveries (PSRD) is an educational site sharing the latest research by NASA-sponsored scientists on meteorites, asteroids, planets, moons, and other materials in our Solar System. The website is supported by the Cosmochemistry Program of NASA's Science Mission ...
An element with atomic number 12; symbol: Mg. Magnesium is contained in the minerals olivine and pyroxene, and is very abundant in the mantles of the inner planets.
Industry:Astronomy
Large concentration of gas (roughly 75% hydrogen and 21-24% helium with trace amounts of other molecules), dust, and mineral grains. Our Solar System formed out of one approximately 4. 55 billion years ago.
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Common rock-forming mineral containing the carbonate ion, CO<sub>3</sub><sup>2-</sup>. Common carbonate minerals are calcite, CaCO<sub>3</sub>; siderite, FeCaCO<sub><sub>3</sub></sub>; magnesite, MgCO<sub>3</sub>; dolomite, CaMg(CO<sub>3</sub>)<sub>2</sub>; and ankerite, Ca(Fe,Mg,Mn)(CO<sub>3</sub>)<sub>2</sub>.
Industry:Astronomy
An element with atomic number 14; symbol: Si. Silicon is the most abundant element besides oxygen in planets, and forms the basis for silicate minerals such as olivine, pyroxene, and plagioclase.
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The splitting apart of a molecule into its consituent atoms. For example, the splitting of carbon monoxide into carbon and oxygen or the splitting of water into hydrogen and oxygen when struck by ultraviolet radiation.
Industry:Astronomy
The study of spectra. Every atom can only emit or absorb certain energies or wavelengths. Scientists use instruments called spectrometers to study the location and spacing of reflectance, emission, and absorption (spectral) lines in specific wavelengths to detect any atoms or molecules that may be present in a target material (such as minerals on the surface of the Moon or a planet).
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The standard unit of pressure is the pascal, abbreviated Pa, which is equivalent to 1 kg/m<sup>2</sup>. The pressure at the surface of the Earth is 100,000 Pa. Pressures inside planets are very large numbers, usually expressed as GPa (giga means billion).
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An imaginary great circle in the sky drawn concentric to the Earth's equator.
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The plane of a planet's orbit (or other Solar System object) is usually tilted with respect to the plane defined by the Solar System (the ecliptic). These 2 great circles intersect at 2 points. As the planet travels around its orbit, at one of the intersection points it will pass from below the ecliptic plane to above it (i. E. Northward). This point is called the ascending node.
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An abundant class of stony meteorites with chemical compositions similar to that of the Sun and characterized by the presence of chondrules. Chondrites come from asteroids that did not melt when formed and are designated as H, L, LL, E, or C depending on chemical compositions. The H, L, and LL types are called ordinary chondrites. The L chondrites are composed of silicate minerals (mostly olivine and pyroxene, but feldspar as well), metallic nickel-iron, and iron sulfide (called troilite). Most L chondrites are severely shocked-damaged, probably by a large impact on the asteroid in which they formed. The E type are called enstatite chondrites, a rare type that formed under very reducing conditions and are composed primarily of a magnesium silicate called enstatite. They are subdivided into the low-iron (EL) chemical group and the high-iron (HL) group. The C (or carbonaceous) chondrites contain water-bearing minerals and carbon compounds including a variety of organic molecules such as amino acids. Carbonaceous chondrites are the most primitive meteorites--primitive in a chemical way. For example, the CI group of carbonaceous chondrites are closest in composition to the photosphere (visible surface) of the Sun.
Industry:Astronomy
