gas, ice and rock

[parallaxicality]

I really need a source for this, so if anyone can help me find one I'd be eternally grateful. when planetary scientists use the terms "gas", "ice" and "rock", which criteria are they using to differentiate them from each other? Is it material, or is it melting point? Are there any fixed limits on what constitutes a "gas", what constitutes "ice" and what constitutes "rock"?

[PraedSt]

I found this for you, it might help. It seems the presence of certain elements/compounds is required, rather than a particular state.

Astronomy expert/Gas giants

In fact the term “gas giant” was a bit of an arbitrary distinction, coined in 1952 by James Blish, a science fiction writer. While there is almost no distinction between gas and liquid on these planets, terrestrial scientists have stuck to a naming process that links elements to “gas”, “rock” and “ice” irrespective of their actual state. Silicates are termed rock, ice refers to water and ammonia, and helium and hydrogen are gas.

[parallaxicality]

Thanks. I really appreciate that. I think it might help.

[PraedSt]

if anyone can help me find one I'd be eternally grateful.

I've magnanimously decided not to hold you to that.

[slang]

James Blish, a science fiction writer

One well worth reading, IMHO.

[trinitree88]

Given a pressure and temperature....you can have "ices" of any pure substance if it fits in the phase diagram of that substance. On cold planets, far removed from their central star, the noble gases can ice up. Dust in the interstellar medium can be coated with various "ices" as it passes through gas clouds...kind of like tree ring growth, only ~ spherical in topology. pete

See:http://www.chemguide.co.uk/physical/...hasediags.html