MadSci Network: Earth Sciences

Re: Do other planets have layers?what are teh layers made of?

Date: Sun Aug 29 21:11:31 1999
Posted By: Diane Hanley, Geologist
Area of science: Earth Sciences
ID: 935700124.Es

Dear Alexandra,

Thank you for writing!   I assume that you are asking whether other planets 
have a core, a mantle and a crust like the earth has.   On Earth, the core 
is at the earth’s center and is composed of iron.  Surrounding the core is 
the mantle:  molten basaltic rock.  (The lava flows that often occur in 
Hawaii are basalt that has made it to the surface of the earth.)  The crust 
is the outer layer of the earth and is made of solid rock.

Planetary scientists are pretty sure that Mercury, Venus and Mars also have 
these layers.  Their cores are mostly made of iron and their mantles are 
probably made of similar basaltic material.  Their crusts are made up 
primarily of basaltic rock versus the Earth’s crust which has so many 
different rock types (granite, sedimentary rock, etc.) 

Mercury no longer has a molten mantle and is completely solid.  Venus 
probably still has a molten mantle because it’s entire surface is 
relatively recent in geologic terms, about 500 million years old.  (Earth 
is 4.6 Billion years old).  Mars may also still have a molten mantle but is 
fairly geologically inactive meaning it has no plate tectonics, earthquakes 
or active volcanoes.

Not just planets have a core, mantle and crust.  Several moons in our solar 
system have them!  The Moon has a core and mantle similar to Earth’s but 
the crust is basaltic rock.  Last but not least, the moons Titan, Triton, 
Titania and Ganymede have silicate cores (minerals containing the element 
silicon), mantles made of water and ice, and crusts of ice.

I recommend the following web site for good info on all of the planets and 
moons in our solar system. It also has information about the current space 
missions underway for Mars, Jupiter and Saturn.
	The Nine Planets, A Multimedia Tour of the Solar System  

Diane Hanley

Thomas R. Watters, 1995.  Planets, A Smithsonian Guide

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