What makes a planet habitable

When it comes to planetary habitability, it's what's inside that counts
Artist's impression shows a view of the surface of the planet Proxima b orbiting the red dwarf star Proxima Centauri, the closest star to the Solar System. Credit: ESO/M. Kornmesser

Which of Earth's features were essential for the origin and sustenance of life? And how do scientists identify those features on other worlds?

A team of investigators with array of expertise ranging from geochemistry to planetary science to astronomy published this week an essay in Science urging the to recognize the vital importance of a planet's interior dynamics in creating an environment that's hospitable for .

With our existing capabilities, observing an exoplanet's atmospheric composition will be the first way to search for signatures of life elsewhere. However, Carnegie's Anat Shahar, Peter Driscoll, Alycia Weinberger, and George Cody argue that a true picture of planetary habitability must consider how a planet's atmosphere is linked to and shaped by what's happening in its interior.

For example, on Earth, plate tectonics are crucial for maintaining a surface climate where life can thrive. What's more, without the cycling of material between its surface and interior, the convection that drives the Earth's magnetic field would not be possible and without a , we would be bombarded by cosmic radiation.

"We need a better understanding of how a planet's composition and interior influence its habitability, starting with Earth," Shahar said. "This can be used to guide the search for exoplanets and star systems where life could thrive, signatures of which could be detected by telescopes."

When it comes to planetary habitability, it's what's inside that counts
An artist's impression of the surface of the super-Earth Barnard's Star b. Credit: ESO/M. Kornmesser

It all starts with the formation process. Planets are born from the rotating ring of dust and gas that surrounds a young star. The elemental building blocks from which rocky planets form—silicon, magnesium, oxygen, carbon, iron, and hydrogen—are universal. But their abundances and the heating and cooling they experience in their youth will affect their interior chemistry and, in turn, things like ocean volume and .

"One of the big questions we need to ask is whether the geologic and dynamic features that make our home planet habitable can be produced on planets with different compositions," Driscoll explained.

The Carnegie colleagues assert that the search for extraterrestrial life must be guided by an that combines , laboratory experiments of planetary interior conditions, and mathematical modeling and simulations.

"Carnegie scientists are long-established world leaders in the fields of geochemistry, geophysics, , astrobiology, and astronomy," said Weinberger. "So, our institution is perfectly placed to tackle this cross-disciplinary challenge."

In the next decade as a new generation of telescopes come online, scientists will begin to search in earnest for biosignatures in the atmospheres of rocky exoplanets. But the colleagues say that these observations must be put in the context of a larger understanding of how a planet's total makeup and interior geochemistry determines the evolution of a stable and temperate surface where life could perhaps arise and thrive.

"The heart of habitability is in planetary interiors," concluded Cody.


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More information: "What makes a planet habitable?" Science (2019). science.sciencemag.org/cgi/doi … 1126/science.aaw4326
Journal information: Science

Citation: What makes a planet habitable (2019, May 2) retrieved 26 May 2019 from https://phys.org/news/2019-05-planet-habitable.html
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May 02, 2019
There are uncountable ways an earth must be to be inhabitable. One obvious one (perhaps the most important) that the article does not even mention is water. To have these thousands of ways all aligned in 1 earth is truly amazing.

But that is the "easy" part.

The hardest part is, how did life get placed here in the first place? And to additionally rely on the false theory of evolution to believe that the earth is how it is today, requires a faith that beyond me.

May 02, 2019
No sorry Bart nut we have no knowledge of "... There are uncountable ways an earth must be to be inhabitable. ..."

We know of one (singular) Living World. We know of three failed worlds sharing this goldilock's zone.

In your sentence above,
how do you intend to prove "uncountable"?
Unless you believe in an anthropocentric Universe?

Why "must" there be any other
Living Worlds?
Considering how early we are since the Biggest Banger?

Even random chance gives damn depressing odds for another earth or even an alien-life variant.

& no, organic-chemistry is only a predecessor to life.
It is not biology.

May 02, 2019
"& no, organic-chemistry is only a predecessor to life.
It is not biology."
More accurately, "rather simple organic chemistry with a few catalysts (enzymes) might lead to basic biochemistry blocks such as amino acids and nucleotides, which in turn can lead to life". The problem is of course the issue of the catalysts : you cannot have catalysts without some form of life to produce them, while it is still unknown (and a field of active research) if reactions leading to basic biochemistry can be self-catalyzed. A classic "chicken & egg" situation.

Catalysts generally *speed up* chemical reactions, they are not always required. Given enough time and a lot of trial & error, which life naturally had, perhaps more complex organic molecules gradually formed. Nature also has an inherent tendency to give rise to more complex properties (order from chaos), which spontaneously emerge. Of course this is still only a hypothesis.

May 03, 2019
The paper is trivial opinion - few references, no quantification - and looks like a vehicle for crap. E.g. the Sun blocks an estimated 90 % of CR, Earth atmosphere the rest - the magnetic field block solar ejecta and its ablation of the atmosphere. And the press release is crap, since it does not reflect the paper that more correctly refer to the solar wind instead.


May 03, 2019
Catalysts generally *speed up* chemical reactions, they are not always required. Given enough time


Responding to erroneous, superstitious claims? Yes, that is correct.

We now know that life evolved from hydrothermal vents providing bioservices (inorganics, biochemicals, replication) with no enzymes but mineral catalysts and natural RNA hot/cold cycling replication capability for the pathway between non life - half alive - life [ https://www.natur...l2016116 ; the half alive last common universal ancestor].

It did not take long compared to the current planet age, the integrated observations predicts less than 40 Myrs [ https://www.natur...8-0644-x ]. The upper limit has just been set by the minor position of biochemists, Benner predicts 145 Myrs due to forced ("bespoke") chemistry [ https://www.airsp...0971988/ ].

May 03, 2019
On news on geological bioservices, see here: https://phys.org/...rth.html . This adds another central metabolism, as well as ties to observed later genetics, to the bioservices of the Hadean environment.

Here, as well as for the Heller glycogenesis/pentose metabolism there is a catalyst: the Fe2+ that the anoxic ocean was permeated with.


May 03, 2019
I agree that, with the evidence collected, the latest experiments confirm a very high probability that Life began to organize & evolve as early as the Hadean Aeon.

I have accepted that life started sooner & faster than I had originally believed was possible.

Then spent the next four billion years encompassing every possible, even improbable niche. To reproduce & thrive in uncounted variations of biomes.

But, from where we are now? We can also look upon the bleak, neighboring landscapes of failure.

Perhaps small rocky worlds, orbiting stable stars in the zone. May be expected to have at least achieved the organic chemical precursors to biology? During their Hadean periods or soon after?

However, it took Earth Life billions of tears to evolve beyond the status of algae, lichens & slime.

& from what we can observe, right now, there is no reason to indulge in unreasonable expectations.

May 04, 2019
Scientists have created artificial life in computers and watched it grow and evolve, without a "guiding hand." Which suggests life started itself, and has grown and evolved sans any Guiding Hand(s). All we have to do is figure out how life started itself, and the issue will be settled.

May 04, 2019
There is one unique place in the Galaxy to which all evolved intelligent life will eventually explore: Sagittarius A*, the supermassive black hole at the center.

What's more, because all intelligent life will conclude this fact about all other intelligent life, the vicinity of Sagittarius A* will also be the meeting place for intergalactic embassies.

If we had good enough telescopes, we could probably see the embassy parties right now.

May 04, 2019
@torbjorn,

"The sun blocks an estimated 90% of CR, earth's atmosphere the rest"

Not sure if you are agreeing with that statement or using it as an example of a mistake in the paper?

The earth's magnetic field blocks a substantial portion of cosmic rays, which is why as you go north or south, the cosmic ray incidence increases. Around Iceland at sea level, it's basically the same as 30,000 feet at the equator.

May 04, 2019
What makes a planet habitable


Pubs.

May 04, 2019
four, sorry but videogames do not count as biology.
If you have a link, to an accredited, peer-reviewed source for your claim of scientists creating life in a computer simulation?
Please share it with us.

jax, evidently you are not considering the sheer volume od Space encompassing the Sag*A accretion disk.

In that environment? How easy it would be for travelers to miss each other while passing within a light-rear.

Consider how much radiation. across the spectrum, at enormous velocities, is being thrown out during this calm period.

I would think it makes much more sense that advanced technologies would use the Metal-Rich Clusters as meeting places. Certainly closer & safer.

All the energy coming out of the AD? Getting close would be like trying to hold a conversation while standing in the watershed of Niagra Falls.

May 04, 2019
@torbjorn,

"The sun blocks an estimated 90% of CR, earth's atmosphere the rest"

Not sure if you are agreeing with that statement or using it as an example of a mistake in the paper?

The earth's magnetic field blocks a substantial portion of cosmic rays, which is why as you go north or south, the cosmic ray incidence increases. Around Iceland at sea level, it's basically the same as 30,000 feet at the equator.
says JaxPavan

There is no mistake in either the article OR the paper. I downloaded the .pdf and examined it for the words "sun" and "blocks".
It appears to be Torbjorn's own mistake. Perhaps a little too much Swedish akvavit? Surprised he hasn't caught it.

Speaking of which:

In that environment? How easy it would be for travelers to miss each other while passing within a light-rear.
A LIGHT-REAR?

May 07, 2019
"...we could probably see the embassy parties right now."

And we all know what kind of wild, drunken parties those Vogons are famous for.

May 07, 2019
There are uncountable ways an earth must be to be inhabitable. One obvious one (perhaps the most important) that the article does not even mention is water
Well lets see... theres this:

"things like ocean volume"

-Oceans have water in them dont they? And this:

"stable and temperate surface"

-Temperate means water in liquid form, right?
But that is the "easy" part
No the easy part is just deciding that some god did it and disregarding the evidence. And also just not reading the article.
The hardest part is, how did life get placed here in the first place? And to additionally rely on the false theory of evolution to believe that the earth is how it is today, requires a faith that beyond me.
No thats also very easy too. Claiming that, since we dont have all the answers yet, then it must have been god.

Easy and also very slimy. Godders are so dense.

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