New instrument reveals recipe for other Earths

January 5, 2015
How do you make an Earth-like planet? The 'test kitchen' of Earth has given us a detailed recipe, but it wasn't clear whether other planetary systems would follow the same formula. Now, astronomers have found evidence that the recipe for Earth also applies to terrestrial exoplanets orbiting distant stars. Credit: David A. Aguilar (CfA)

How do you make an Earth-like planet? The "test kitchen" of Earth has given us a detailed recipe, but it wasn't clear whether other planetary systems would follow the same formula. Now, astronomers have found evidence that the recipe for Earth also applies to terrestrial exoplanets orbiting distant stars.

"Our solar system is not as unique as we might have thought," says lead author Courtney Dressing of the Harvard-Smithsonian Center for Astrophysics (CfA). "It looks like rocky exoplanets use the same basic ingredients."

Dressing presented the research today in a press conference at a meeting of the American Astronomical Society.

The key to the discovery was the HARPS-North instrument on the 3.6-meter Telescopio Nazionale Galileo in the Canary Islands. (HARPS stands for High-Accuracy Radial velocity Planet Searcher.) It is designed to accurately measure the masses of small, Earth-sized worlds. Those measurements are crucial to determine densities and therefore compositions.

"Our strategy for using HARPS-North over the past year has been to focus on planets less than two times the diameter of Earth and to study a few planets really well," explains Harvard astronomer David Charbonneau (CfA), who currently heads up the HARPS-North Science Team.

Most recently the team targeted Kepler-93b, a planet 1.5 times the size of Earth in a tight, 4.7-day orbit around its star. The mass and composition of this world were uncertain. HARPS-North nailed the mass at 4.02 times Earth, meaning that the planet has a rocky composition.

The researchers then compared all ten known exoplanets with a diameter less than 2.7 times Earth's that had accurately measured masses. They found that the five planets with diameters smaller than 1.6 times Earth showed a tight relationship between mass and size. Moreover, Venus and Earth fit onto the same line, suggesting that all these worlds have similar rock-iron compositions.

As for the larger and more massive , their densities proved to be significantly lower, meaning that they include a large fraction of water or other volatiles, hydrogen and/or helium. They also showed more diverse compositions rather than fitting into a single group like the smaller terrestrial worlds.

The team also noted that not all planets less than six times the mass of Earth are rocky. Some low-mass worlds with very low densities are known (such as the planets in the Kepler-11 system). But for typical close-in small planets, the chances are high that they share an Earth-like composition.

"To find a truly Earth-like world, we should focus on planets less than 1.6 times the size of Earth, because those are the rocky worlds," recommends Dressing.

Making Other Earths

Makes one small model planet

Ingredients:

1 cup magnesium1 cup silicon2 cups iron2 cups oxygen1/2 teaspoon aluminum1/2 teaspoon nickel1/2 teaspoon calcium1/4 teaspoon sulfurdash of water delivered by asteroids

Blend well in a large bowl, shape into a round ball with your hands and place it neatly in a habitable zone area around a young star. Do not over mix. Heat until mixture becomes a white hot glowing ball. Bake for a few million years. Cool until color changes from white to yellow to red and a golden-brown crust forms. It should not give off light anymore. Season with a dash of water and organic compounds. It will shrink a bit as steam escapes and clouds and oceans form. Stand back and wait a few more million years to see what happens. If you are lucky, a thin frosting of life may appear on the surface of your new world.

Explore further: 'Neapolitan' exoplanets come in three flavors

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metingunduz
not rated yet Jan 06, 2015
Well , several absolutely necessary ingredients missing from the recipe obviously ..! The first necessary ingredient is `habitability` with the existence of `effective protective magnetosphere` against cosmic radiation , without that you are doomed to perish at no time at that planet –just a matter of very short time indeed for any life form to disappear under strong cosmic radiation - . What it means you have to have liquid magma inside as well as volcanic activity so the liquid iron and nickel like magnet forming elements will be able to create strong magnetic field `MAGNETOSPHERE` around that planet with the help of strong magnetism coming from the nuclear fusion reactions of central star of that planet , so the deadly charged cosmic radiation coming from central star will be `effectively shielded` .
metingunduz
not rated yet Jan 06, 2015
Without this `protective shields existence` in any planetary body in our universe is doomed to be `inhabitable for any life form ` regardless of existence of other so called `ingredients` as well as liquid water . Simply because the molecules of genetic code `DNA ,RNA or other similar genetic code forming relatively –thermodynamically stable molecules - `have to maintain their code in a given generation time prior to duplication or reproduction `- in other words molecular code`s integrity – under the `cosmic radiation protected environment` so the `rate of mutation and structural damage to the code forming molecules like DNA and RNA – or other imaginable theoretical code forming molecules- WILL NOT EXCEED the optimum level of protection needed in order the life forms can survive .
metingunduz
not rated yet Jan 06, 2015
This optimum level of cosmic radiation is `utmost important` ingredient in any life forms existence . I am sure every body vividly remembers the `faulty` NASA backed `Mono Lake initial claim ` and experimental measurement error of extraterrestrial like form `arsenic` instead of `phosphorus` based back bone DNA like structure and life form of -bacteria- at the Arsenic laden Mono Lake of California .
Of course in reality Arsenic bond is NOT –thermodynamically- as stable as phosphorus bond to allow EVOLUTIONARY NECESSARY STABILITY OF THE GENETIC CODE so called `extraterrestrial life form` can exist and survive .
Exactly and similarly ; like the 'Thermodynamic bond strength ` –like arsenic vs phosphorus- at Mono Lake bacteria`s `faulty experiment since it turn out that the bond was indeed the `stable` phosphorus bond NOT `unstable` arsenic as it was claimed initially`.
metingunduz
not rated yet Jan 06, 2015
The punch line is :UNDER THE STRONG COSMIC RADIATION WITHOUT OPTIMUM SHIELDING AND PROTECTION by a `Strong enough magnetosphere` in any planetary body any `genetic code forming molecules` simply CAN NOT create and evolve as life forms ... Needles to say we as a species of `Homo Sapiens` can not survive on those planetary bodies without a strong and effective enough cosmic radiation shield ..
metingunduz
not rated yet Jan 06, 2015
Sorry to say this but ; I also realize that most `Astrophysicist and specialized engineers has no clue or knowledge `WHAT LIFE FORMS ABSOLUTE BASIC REQUIREMENTS ARE ` particularly when I read the `recipe` above that they have calculated they simply FORGOT the most important one ...They need some reality check and cold awakening I guess as well as `lessons on the basics of biology and life forms as well as molecular biology , termodynamics and evolution ` .
alfie_null
not rated yet Jan 06, 2015
Sorry to say this but ; I also realize that most `Astrophysicist and specialized engineers has no clue or knowledge `WHAT LIFE FORMS ABSOLUTE BASIC REQUIREMENTS ARE ` particularly when I read the `recipe` above that they have calculated they simply FORGOT the most important one ...They need some reality check and cold awakening I guess as well as `lessons on the basics of biology and life forms as well as molecular biology , termodynamics and evolution ` .

In your posts, you are missing the point of the article. I doubt there's anyone in the science community who would think life doesn't have a whole bunch of prerequisites. The article just focuses on two of them, planetary mass and composition.
Torbjorn_Larsson_OM
not rated yet Jan 06, 2015
@metingunduz: "several absolutely necessary ingredients missing from the recipe obviously".

You missed the point of the paper.

[Which is awesome by the way, they get a narrow recipe, they can test it and they can see that it mirrors the star corona Fe/Si and Mg/Si ratios meaning young stars and terrestrial planets are are the protoplanetary disk recipe with and without volatiles.]

It derives the necessary ingredients to make terrestrial planets with cores and mantles. The rest is irrelevant to the recipe.

Re habitability it is not the same as habitation, the former is (so far) a search filter to focus early science and the latter is an observational fact (see Earth). You mix these factors, geophysical conditions (say, liquid water stability) vs biological conditions (say, genetic molecule stability).

[tbctd]
Torbjorn_Larsson_OM
not rated yet Jan 06, 2015
[ctd]

And you are wrong on some of them. E.g. it is the Sun's magnetic field that mostly shields against cosmic rays (~ 90 % of the interstellar flux), most of the rest is shielded by the atmosphere (which is why they early saw CR was more intense as they got up in balloons).

The atmosphere may or may not be shielded by the geodynamo field, the jury is still out. Hydrogen is shielded, most likely. (Cf Venus vs Earth.) The rest, likely not.
metingunduz
not rated yet Jan 06, 2015
Well , if the subject matter was only - mass and composition- of any planet in our universe and especially if they were not talking `earthlike planet with life forms ` then there were no need to put the picture and implication of `earth look alike blue planet `with `green branch of fir tree` at the side of the dish ...They could have easily put Mars like `red and brown colored ball –so to speak- ` with no fir branch at the side of the dish ...Am I clear enough to describe the `intent` of the article with the picture they posted alongside the recipe which obviously imply earthlike planet with life forms ? When you say `Earth like` it means `Earth like` no other way around possible or even probable , to hand pick certain characteristics of our planet like it`s mass and composition ...

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