The Possibility of "Pure" Planets

[MrModesty]

"Pure" planets?

What is the likelihood of a planet being almost entirely one element? Is it possible to have a planet that is purely water?

 

[Vanadium 50]

Water is not an element.

 

[MrModesty]

Water is not an element.

Thanks for not answering my question.

Regardless of whether water is an element or not, the question remains the same. Is it possible for a planet to be purely anything? I'm sure it is very rare, if not almost impossible, but have we discovered planets that are predominantly one element/chemical? It seems that with the size and diversity of the universe, it has to be possible. Is there anyone thing that prevents this from happening?

 

[Arch2008]

Well in the early universe there was only hydrogen and some helium with a dash of lithium. So if you somehow had a lone, low-mass globular cluster that was totally without giant stars that convert hydrogen into the other elements, then it would remain mostly hydrogen (at least for a while). Then you might get some hydrogen gas giant exoplanets around whatever stars did form. IMHO, this would be very unlikely, but possible.
A “purely water” exoplanet would have to be small or the core water would separate into hydrogen and oxygen due to the temperature.

 

[Vanadium 50]

You need to better define your question. Does "Almost entirely" mean >90%? >99? >99.9%? Also, what does "purely anything" mean?

Jupiter is composed of 90% hydrogen and 10% other elements (by number of atoms). Pure water is 67% hydrogen and 33% other elements (again, by number of atoms). So I could argue that Jupiter is at least as "pure" as your example. Nevertheless, I don't think you will agree with that. So you will need to carefully specify what exactly you mean.

 

[mjacobsca]

What is the likelihood of a planet being almost entirely one element? Is it possible to have a planet that is purely water?

It seems highly unlikely, except for the previously mentioned gas giants which are mostly hydrogen. Perhaps a planet can form an iron core like the Earth and then have its outer core sheared off by some catastrophe? Or melted off?

The heavier elements typically find their way into stellar nurseries due to supernovae, and this means a pretty good mix of heavier elements are all intermixed, having been formed in layers in the star prior to the explosion, and formed from the explosion itself. It would probably be difficult for these to just separate into individual elements naturally. I'm sure there may be cases with higher concentrations of iron or silicon due to a succession of similar stars creating similar elements, but I doubt you'd ever see 100%.

I think the closest thing you have in the universe is a neutron star, which is just one big pile of neutrons.

 

[clm321]

I think the closest thing you have in the universe is a neutron star, which is just one big pile of neutrons.[/QUOTE]

almost made of entirely nuetrons, also has some protons and electrons that didnt combined

 

[qraal]

I think the closest thing you have in the universe is a neutron star, which is just one big pile of neutrons.

almost made of entirely nuetrons, also has some protons and electrons that didnt combined[/QUOTE]

If you know that then you know more than the people who study them. Our knowledge of nuclear matter in such conditions is seriously lacking - that's why every new observation of neutron star radii, for example, gives us new insights into what's going on inside.