- Industry: Astronomy
- Number of terms: 6727
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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 ...
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
Common particle type in lunar regolith; agglutinates consist of small rock, mineral, and glass fragments bonded together with glass.
Industry:Astronomy
A course-grained igneous rock consisting largely of the mineral olivine.
Industry:Astronomy
Term coined by William K. Hartmann in 1973 to describe the lunar-wide zone of fragmented material developed on the Moon by mixing of impact basin/crater ejecta (transported by ballistic trajectories) and local rock. Estimates of the thickness of this mixed zone are between 1. 5 to about 2. 5 kilometers.
Industry:Astronomy
The immense cloud of gas and particles of floating cosmic dust from which our Solar System (Sun and planets) condensed 4. 6 billion years ago.
Industry:Astronomy
A thin slice or rock, usually only 30 micrometers thick. Thin sections are used to study rocks with a microscope.
Industry:Astronomy
On the Moon, a mixture of very small dark orange and black glass balls which formed from quickly cooled lava droplets during a pyroclastic eruption.
Industry:Astronomy
The angular distance North or South from the Earth's equator measured in degrees on the meridian of a point; Equator being 0° and the poles 90° N and 90° S.
Industry:Astronomy
