Originally Posted by James Nicoll

In article ,
Dan Birchall VE_TO_REPLY wrote:
(Alain Fournier) wrote:
What surprises me is its density, about 1870 kg/m^3, which
is consistent with 75% water and 25% rock. I'm no expert
in this area, but so much water (or other low density
liquid or solid) seems improbable to me.

I'm not a planetary scientist either, but I googled, and this
density is roughly comparable to that of our outer planets -
Neptune's density is 1760 kg/m^3, Pluto's is 2030 kg/m^3. The
planet's orbital radius and temperature would probably help shed
light on what elements would most likely be found there in solid,
liquid or gaseous forms.

The six most common elements in the universe are hydrogen,
helium, oxygen, carbon and neon*. If a world isn't massive/cold enough
to hold onto H2 (and given that neither helium nor neon will form
chemical compounds) the most common chemical compounds should
be made up of combinations of H, O and C. In other words, water
should be pretty common.


* From memory, by mass it's something like 70% H, 24% He, 11% O, 4.5% C
1% Ne.
--
http://www.livejournal.com/users/james_nicoll
http://www.cafepress.com/jdnicoll (For all your "The problem with
defending the English language [...]" T-shirt, cup and tote-bag needs)