- 産業: Astronomy
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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 ...
Tektites are small beads of silica glass that are usually black but can also be shades of brown or green. People used to think they came from the Moon, but now we know they are from the Earth. Tektites formed during impacts on Earth when plumes of vapor and melted rock pierced the atmosphere. The impact debris traveled briefly through space before reentering the atmosphere--spreading the tektites over huge areas called strewnfields. The largest tektites, which are found on land, are several centimeters across. The smallest, which are found in layers of deep sea sediments, are only micrometers across.
Industry:Astronomy
The naturally occurring nuclear reactions in stars that make the elements heavier than hydrogen and helium. See also supernova.
Industry:Astronomy
Term describing the chemical composition of an igneous rock composed almost entirely of magnesium-rich and iron-rich minerals (e.g., olivine, pyroxenes) and minimal silica.
Industry:Astronomy
Term applied to molten rock in the interior of a planet or moon. When it reaches the surface, magma is called lava.
Industry:Astronomy
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.
Industry:Astronomy
Sediment on the surface of the lunar highlands; composed of broken rock and mineral fragments, and glass produced by impact.
Industry:Astronomy
Elements that are not incorporated into common rock-forming minerals during magma crystallization, hence they become enriched in the residual magma and in the rocks finally formed from it. Examples are: potassium, rubidium, strontium, hafnium, thorium, uranium, and lanthanum, samarium, europium, and the rest of the rare earth elements (REE).
Industry:Astronomy
The region of space between the orbits of Mars and Jupiter, from 2. 1 to 3. 3 AU, where most asteroids are found.
Industry:Astronomy
The description of the physical characteristics of rocks including color, mineral compositions, grain sizes, grain shapes, texture or fabric (relationship between grains).
Industry:Astronomy
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
