- 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 ...
General term to describe the process of mass movement (or avalanche) of material downslope by falling, sliding, or flowing, under the force of gravity. It also describes the landform (pile of debris) produced.
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
Point in the elliptical orbit of a comet about the Sun in which it passes closest to the Sun.
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
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
An imaginary great circle in the sky drawn concentric to the Earth's equator.
Industry:Astronomy
The full range of frequencies, from radio waves to gamma rays, that characterizes light. The electromagnetic spectrum can be expressed in terms of energy, wavelength, or frequency (where the wavelength equals the speed of light divided by the frequency and energy equals Planck's constant times the frequency. )
Industry:Astronomy
An iron-oxide mineral (Fe<sub>2</sub>O<sub>3</sub>) that may be the cause of the red color on Mars. Courser-grained gray hematite has the same chemical formula as the red variety, but a different crystalline structure. The deposits of gray hematite found in the Terra Meridiani region of Mars may suggest that water once circulated through the region's rock layers.
Industry:Astronomy
A temperature scale that assigns the value 0° C to the freezing point of water and the value of 100° C to the boiling point of water at standard pressure. To convert Celsius to Fahrenheit: Multiply by 9, then divide by 5, then add 32.
Industry:Astronomy
