Earth-like planets have Earth-like interiors

Well, I can't say I'm surprised:

Every school kid learns the basic structure of the Earth: a thin outer crust, a thick mantle, and a Mars-sized core. But is this structure universal? Will rocky exoplanets orbiting other stars have the same three layers? New research suggests that the answer is yes - they will have interiors very similar to Earth.

Here's the rest of the story. user link on phys.org

I'll keep watching this.

Ja, when I was a school kid, we were taught that:

Earth has multiple layers. A crunchy outer shell, a chocolately middle layer, a chewy nougat, and a caramel center, packed with peanuts.

We might have watched a lot of candy bar commercials as kids, too, Ja? Blitzball.

From a chemical perspective, this makes total sense:

Earth's principal chemical elements are actually oxygen and silicon (not just quartz, SiO2, but the vast majority of all common minerals on earth include silicon and oxygen), plus the iron of Earth's core. The differentiation of mantle and core is something that's inevitable to happen from a certain size. Thing is, these elements are not only common in our own solar system, but they're also common elsewhere in the universe (oxygen is the third-most common element in the universe, after hydrogen (most common) and helium (second most-common). Therefor, planets elsewhere - if they are rocky, they should have a similar interior composition. I.e. they are not gaseous, like Jupiter and Saturn in our solar system, and not surrounded by a vast mantle of high-pressure "ice" (which seems to be the case with Uranus and Neptune: technically these are more interlopers between an ocean planet and a gas giant, than actual gas giants, in particular because they seem to be lacking a mantle of metallic hydrogen).

What's still a bit of a question mark is where exactly all the water on Earth came from? Was it mostly from outgassing, or was it mostly brought in from outside by comets, or a combination of both?

My hunch is that it probably came mostly from outgassing. It seems unlikely that the sheer amount of water would come from a bombardment of comets.

On Tuesday, February 9th, 2016 at 9:14 am, Jovian said:

I'm not convinced on that, especially because there's a few other oddieties about Earth that cannot be readily explained. One issue is that we have gold (as well as platinum and other platinum group elements) in Earth's crust, which we shouldn't have, because gold and platinum are so-called "siderophile" (Greek for "iron-liking" ) elements. Normally, you would expect Earth's crust and mantle to be extremely depleted in these elements. What is even more bizarre is that the relative concentrations match up with the primordial concentrations for in the so-called chondrites, a type of meteorites that are not only are old, but have the chemical composition to the "raw building material" for Earth and the other planets in our solar system - although in much lower concentration. The conclusion there is that a large amount of material must have rained down onto the early earth (as well as onto the moon and the other rocky planets - this event is also called the "Late Heavy Bombardment"), which leaves also the possibility open that a large amount of water was also brought in simultaneously.