- 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 ...
Mineral found in basalt; ranges from Mg<sub>2</sub> SiO<sub>4</sub> to Fe<sub>2</sub> SiO<sub>4</sub>.
Industry:Astronomy
An element with atomic number 2; symbol: He. It is the second most common element in the Sun and outer planets, but rare on the rocky planets.
Industry:Astronomy
General term referring to the layers of fragmental and loose, incoherent, or unconsolidated rock, mineral, and glass fragments of any origin (residual or transported) that accumulate on the surface. On the Moon, this blanket of debris is produced by impacts.
Industry:Astronomy
A hole or depression. Most are roughly circular or oval in outline. On Earth most natural craters are of volcanic origin. On the Moon most are of impact origin.
Industry:Astronomy
Term used to describe the layer of magma, hundreds of kilometers thick; thought to have covered the Moon 4. 5 billion years ago. The timing, duration, cooling rates, convection, partial melting, lateral and vertical chemical variations, and overturn of the lunar magma ocean are topics of continuing research.
Industry:Astronomy
Forces that alter the path of a comet, which are not caused by gravitational interaction with the Sun and planets. Typically this refers to uneven outgassing from vents on the comet, which serve to act like rocket nozzles.
Industry:Astronomy
Vast spherical swarm of comets orbiting our Solar System from roughly 2,000 to 100,000 AU. The Oort cloud, while roughly spherical at the largest radius, is wedge-shaped where it merges with the outer planet region in the vicinity of the Kuiper belt of comets. The cloud is divided into different regions of dynamical stability: the Kuiper belt (35-50 AU; affected by planetary perturbations), a dynamically inert region (50-2000 AU; not affected by gravity of planets or stars), the inner Oort cloud (2,000-15,000 AU; affected by galactic tidal forces), and the outer Oort cloud (15,000-100,000 AU; affected by stellar perturbations). The Oort cloud has never been observed, rather its existence is inferred from the careful analysis of the orbits of comets which come in from the cloud. Recent discoveries of objects in the Kuiper belt have confirmed its existence.
Industry:Astronomy
A course-grained igneous rock consisting largely of the mineral olivine.
Industry:Astronomy
Igneous rock, found in the lunar highlands, composed of plagioclase and olivine.
Industry:Astronomy
