inner planet
–noun Astronomy. | any of the four planets closest to the sun: Mercury, Venus, the earth, or Mars. |
Origin: 1950–55
terrestrial planet
n. Any of the four planets, Mercury, Venus, Earth, or Mars, that are nearest the sun and have similar size and density. |
The American Heritage® Dictionary of the English Language, Fourth Edition
Copyright © 2009 by Houghton Mifflin Company.
Published by Houghton Mifflin Company. All rights reserved.
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Science Dictionary
inner planet
Any of the four planets Mercury, Venus, Earth, and Mars, whose orbits lie nearest the Sun. The inner planets are of similar size and have high densities compared to the larger gas giants among the outer planets. They are composed mostly of rock and metal and are relatively slow to rotate, with solid surfaces, no rings, and few moons. Also called terrestrial planet. Compare outer planet. See also inferior planet.
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The American Heritage® Science Dictionary
Copyright © 2002. Published by Houghton Mifflin. All rights reserved.
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