Earth-like planets have Earth-like interiors

February 8, 2016
Credit: Harvard-Smithsonian Center for Astrophysics

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.

"We wanted to see how Earth-like these are. It turns out they are very Earth-like," says lead author Li Zeng of the Harvard-Smithsonian Center for Astrophysics (CfA).

To reach this conclusion Zeng and his co-authors applied a computer model known as the Preliminary Reference Earth Model (PREM), which is the standard model for Earth's interior. They adjusted it to accommodate different masses and compositions, and applied it to six known rocky exoplanets with well-measured masses and physical sizes.

They found that the other planets, despite their differences from Earth, all should have a nickel/iron core containing about 30 percent of the planet's mass. In comparison, about a third of the Earth's mass is in its core. The remainder of each planet would be mantle and crust, just as with Earth.

"We've only understood the Earth's structure for the past hundred years. Now we can calculate the structures of planets orbiting other stars, even though we can't visit them," adds Zeng.

The new code also can be applied to smaller, icier worlds like the moons and in the outer solar system. For example, by plugging in the mass and size of Pluto, the team finds that Pluto is about one-third ice (mostly water ice but also ammonia and methane ices).

The model assumes that distant exoplanets have chemical compositions similar to Earth. This is reasonable based on the relevant abundances of key chemical elements like iron, magnesium, silicon, and oxygen in nearby systems. However, forming in more or less metal-rich regions of the galaxy could show different interior structures. The team expects to explore these questions in future research.

The paper detailing this work, authored by Li Zeng, Dimitar Sasselov, and Stein Jacobsen (Harvard University), has been accepted for publication in The Astrophysical Journal and is available online.

Explore further: What kinds of stars form rocky planets?

More information: "Mass-Radius Relation for Rocky Planets Based on PREM," Li Zeng, Dimitar Sasselov & Stein Jacobsen (Harvard University), 2016, accepted for publication in the Astrophysical Journal arxiv.org/abs/1512.08827

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8 comments

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Torbjorn_Larsson_OM
4 / 5 (6) Feb 08, 2016
A short but sweet paper. The averaging used could be discussed since it log-transforms a disparate result into a weighted average, but the statistics seem to capture the most common outcome.
wduckss
3 / 5 (4) Feb 08, 2016
The laws are a universal. Conditions, where are realized laws, are not.
Whydening Gyre
5 / 5 (3) Feb 08, 2016
The laws are a universal. Conditions, where are realized laws, are not.

Aren't universal laws the descriptor of conditional state parameters universally?
wduckss
1 / 5 (2) Feb 09, 2016
The laws are a universal. Conditions, where are realized laws, are not.

Aren't universal laws the descriptor of conditional state parameters universally?


The body of a certain mass always becomes a star, but it can be achieved and with less mass along other effects (binary system, a strong influence of gravity, the faster the rotation). The law is the same, conditions are not.
Earth and Venus have a molten core, Uranus and Saturn have no ..
Nik_2213
5 / 5 (3) Feb 09, 2016
But what about the mega-impact that gave us the Moon ? Didn't that skew the proportions ??
wduckss
1 / 5 (3) Feb 10, 2016
The influence of the moon and the influence of the Sun, determine the Earth, Venus determine the sun.

A normal occurrence in the universe (which I classify under the effects of "binary" system).
SHREEKANT
1 / 5 (3) Feb 12, 2016
"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.".

2nd OPINION:

Because the main source of these elements is supernova blast. I have already given new hypothesis for the formation of Solar system on the basis of Dark atom & Dark energy.

I ALREADY explained on 24th, July' 2015 that ATOMIC COMPOSITION & CERTAIN CONDITION also decide the composition heavenly bodies.

Reference:

Kindly refer to the SLIDES OF MY ORAL PRESENTATION IN VIETNAM ON 24TH, JULY' 2015 in an International Science conference on "Planetary System – a synergistic view" [19th- 25th July' 2015]

Title : "REGENERATION OF STAR & FORMATION OF SOLAR SYSTEM - Potter Man's concept"

https://disqus.co...kant_74/

For details comments:

www.swarajgroups....ike.html
antigoresockpuppet
not rated yet Feb 13, 2016
Nik_2213

5 / 5 (2) Feb 09, 2016
But what about the mega-impact that gave us the Moon ? Didn't that skew the proportions ??


Yeah. Earth doesn't have an earth-like interior. It's like saying someone looks like Michael Jackson. MJ dosn't look like MJ and it wasn't a natural process. So, just what is the point?

SHREEKANT 1 /5 (2) 20 hours ago
"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.".

2nd OPINION:
- blah, blah, blah -


3rd OPINION:
Chup Kar, Badir!

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