The 4 inner planets -- Mercury, Venus, Earth and Mars -- share several features in common. Astronomers contact them the “terrestrial planets” because they have actually solid, rocky surface roughly similar to desert and mountainous areas on the earth. The inner planets are much smaller 보다 Jupiter, Saturn, Uranus and also Neptune, and they all possess steel cores.

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Inner planets are much smaller than the outer planets, and also are rocky through an steel core.


Astronomers theorize that the very early solar system developed as a ring of products surrounding the sun. Heavier elements such together iron and nickel condensed reasonably close to the sun, conversely, substances such together hydrogen, methane and water condensed in colder regions aside from that out. The terrestrial planets formed as clumps that rock and also heavy facets from the inner ring the materials gathered due come gravitational attraction; in a comparable way, the external band of gaseous substances developed the external planets.


Compared come the 4 gas gigantic planets that make up the external solar system, the inside planets all have actually diminutive sizes. The the four, planet is the largest, with a diameter of 6,378 kilometers (3,963 miles) at the equator. Venus is a close second at 6,051 kilometers (3,760 miles). Mars is lot smaller through a 3,396-kilometer (2,110-mile) diameter, and also Mercury is the smallest terrestrial planet, measure up 2,439 kilometers (1,516 miles) across.


The terrestrial planets all have rocky surfaces that function mountains, plains, valleys and other formations. The temperatures of the inside planets are low enough that rock exists mainly as a solid in ~ the surface. To different degrees, they additionally have meteor affect craters, back the thick atmospheres that Venus and Earth protect them from most meteors, and also weathering and other factors wipe out all yet the many recent craters. Mars has an extremely low atmospheric pressure, and Mercury has virtually none, therefore craters are an ext common on these planets.

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Astronomers think all four of the terrestrial planets possess an stole core. During their at an early stage formation, the planets were hot blobs of molten metals and other elements; being heavier, many of the iron and also nickel finished up top top the inside through lighter elements such together silicon and also oxygen creating the outside. Geologists have concluded the the earth iron core is partially liquid and also partly solid by observing the habits of earthquake tide traveling v the earth. Researchers speculate that the various other terrestrial planets may additionally have partly liquid cores.


Chicago native John Papiewski has actually a physics degree and also has been writing because 1991. He has added to "Foresight Update," a nanotechnology news from the Foresight Institute. He additionally contributed to the book, "Nanotechnology: molecule Speculations on global Abundance." Please, no rectal calls/emails!