"Based on its density, scientists think GJ 1214b is made up of about three-quarters liquid water with a solid core of iron and nickel and an atmosphere of hydrogen and helium—not unlike Earth."<p>what<p>This is either terrible writing or terrible science (on the author's part, not the scientists', I would imagine). About 70% of the Earth's <i>surface</i> is water, but only a fraction of a percent of Earth's mass is water. (<a href="http://bit.ly/7Gfk8V" rel="nofollow">http://bit.ly/7Gfk8V</a>, total water volume from <a href="http://en.wikipedia.org/wiki/Water#Water_on_Earth" rel="nofollow">http://en.wikipedia.org/wiki/Water#Water_on_Earth</a>). And the Earth's atmosphere is definitely not primarily hydrogen and helium.
Using Gmm/r^2 we find that it should have almost exactly the same gavitaional pull as earth at the surface (89% g). That's neat. Means we could have a boat with a sealed cabin at the right pressure and sail around the ocean with basically normal gravity.
OT, but can we send a damn probe to Europa already? I want to know if there's liquid oceans there, and if so, do they harbor life? It's in our freaking solar system, for crying out loud!
Link to original article in Nature: <a href="http://dx.doi.org/10.1038/nature08679" rel="nofollow">http://dx.doi.org/10.1038/nature08679</a> (for those who have access)