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Different kinds of asteroid belts

You Need Just the Right Amount of Killer Asteroids to Promote Complex Life

Article Updated: 23 Dec , 2015

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An artist’s impression of the different configurations of asteroid belts that could occur. Image credit: NASA/ESA/A. Feild, STScI

Sure, asteroids can be planetary annihilators, scouring the surface of a world with fire and molten rock. But asteroids might also help seed a planet with the right ingredients to set up the conditions for life, and give that life encouragement to evolve more complex survival strategies.

As with all things, it’s just about balance. Too many asteroids, and you’ve got an unrelenting cosmic shooting gallery, raining fiery death from above. Too few asteroids, and complex life might not get the raw material it needs to get rolling. Life never gets that opportunity to really shake things up and evolve into more complex forms.

This conclusion comes from Rebecca Martin, a NASA Sagan Fellow from the University of Colorado in Boulder and Mario Livio of the Space Telescope Science Institute in Baltimore, Md. The researchers created a series of theoretical models based on observations of debris disks around other stars, as well as the Jupiter-sized planets discovered so far.

They found that only a fraction of the planetary systems out there have giant planets at the right locations to help create an asteroid belt of the right size. In fact, it looks like the Solar System might be rare and special when it comes to perfectly-sized asteroid belts.

“Our study shows that only a tiny fraction of planetary systems observed to date seem to have giant planets in the right location to produce an asteroid belt of the appropriate size, offering the potential for life on a nearby rocky planet,” said Martin, the study’s lead author. “Our study suggests that our solar system may be rather special.”

There are three potential models for asteroid belt formation in other star systems.

  1. A Jupiter-sized world migrates slowly inward, disrupting the asteroid belt before it can really form. All the potential asteroids are consumed or flung out into deep space. A potential Earthlike world is deprived of the chemicals (and catastrophic incentive) to evolve complex lifeforms. That’s bad
  2. No large Jupiter-sized world forms at all, allowing the solar system to create a massive asteroid belt. Material from this enormous asteroid belt would be too punishing to Earthlike worlds for complex life to stand a chance. Also bad.
  3. A Jupiter-sized world forms in the outer solar system, and only moves in a little, preventing an overly large asteroid belt from forming. There are still enough asteroids out there to seed an Earthlike world with chemicals and evolutionary encouragement, but not enough to set its progress back. That’s us!

To come to this conclusion, Martin and Livio created models of protoplanetary disks around various stars, and then watched what would happen with various Jupiter-sized planets. They compared their models to 90 protoplanetary disks that have been discovered so far by NASA’s Spitzer Space Telescope, and 520 giant planets found orbiting other stars.

So far, only 4% of the systems they’ve observed have the right combination of a compact asteroid belt with a Jupiter-sized planet nearby. This gives researchers a very specific configuration of asteroid belt and planetary arrangement to look for when searching for worlds that could contain complex life.

Original Source: NASA News Release

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IVAN3MAN_AT_LARGE
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IVAN3MAN_AT_LARGE
November 2, 2012 9:20 PM
Lawrence B. Crowell
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Lawrence B. Crowell
November 2, 2012 10:12 PM

I think it is also important that a Jovian planet not be too close to the star. If it is close this perturbs the orbit of any terrestrial planet that might be in the ~ 1AU orbital range.

LC

bfmorris
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bfmorris
November 2, 2012 11:48 PM

Well if a Jovian planet is too close then therefore it wouid have migrated in, thus there would already be a disrupted belt, correct?

Andrew Planet
Member
November 2, 2012 11:19 PM

Reformed killer asteroids promote life. Read all about it! Thanks, excellent article I really need to study and learn in detail. Retweeting for tomorrow for breakfast

Aqua4U
Member
November 2, 2012 11:46 PM

Reminds… We might be thankful for the ‘astronomical’ number of circumstances that led to life on this planet? Should we ever find highly evolved life elsewhere, it will no doubt be accompanied by a similar number of near miraculous circumstances? No wonder many have turned to religious or divine interpretation for our existence… Evolved lifeforms elsewhere might feel similarly so? I hope so.. it would breed benevolence and a respect for life. That would be better than the alternative…

TheDirtBoy
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TheDirtBoy
November 3, 2012 2:57 AM

Religion breeds benevolence and respect for life?!?! What planet do you live on? One quick look at any time in human history and it’s hard not to see a great deal of egotisim, ignorance, bigotry and violence caused directly by religion.

Aqua4U
Member
November 3, 2012 3:20 PM

My intent was not to tout religion, but to recognize instead how the realization that the incredible set of happenstance that lead to life on this planet, might lead to worship or at least be respected… here and elsewhere. Respect for life is not a religious tenant. Religion has been and is and will be, as you state, the source of much of mankind’s misery.

TheDirtBoy
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TheDirtBoy
November 4, 2012 5:05 AM

Life is rare and precious, agreed, but you don’t need a god to explain it’s existance and certianly not to respect that fact. If human history is anything to go by and one day we do meet an E.T. brandishing a belief in god may well start an interstellar holy war. Before we even consider moving out into the universe we need to shed ourselves of the superstitious nonsense that is religion and take responsibility for our own actions. besides, any “highly evolved life elsewhere” most likely won’t consider us to be highly evolved.

Torbjorn Larsson OM
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Torbjorn Larsson OM
November 3, 2012 1:27 PM
I find “Rare Earth” models based on bayesian reasoning daft. You can pick any number of factors specific for Earth and conclude Earth is unique. Similarly you can pick any number of factors specific for you and conclude you are unique. Say, very few children had your father and mother in common, and I’m sure you can think of dissimilarities to your siblings. That is not what astrobiology is based on. It looks at life and its constraints everywhere. We know humans, or species in general, are not uncommon. Similarly we can look for factors that are relevant for life and conclude that it is likely not uncommon. For example, to get life started we need energy, water… Read more »
Aqua4U
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November 3, 2012 3:31 PM

“…2-3 mass extinctions…”? More like 5 or possibly 6 mass extinctions, making our existence even more precarious and rare…. and that an evolved alien culture might reach the same conclusion.

Torbjorn Larsson OM
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Torbjorn Larsson OM
November 5, 2012 10:12 AM

Sorry, I meant large mass extinctions (and I couldn’t remember the exact number at the time). Those are the ones that wiped the diversity slate clean enough to speak of “independent worlds”. For established land animal ecology those are the last 3 of the “Big 5”.

The number of smaller mass extinctions is debated.

Lawrence B. Crowell
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Lawrence B. Crowell
November 4, 2012 2:50 AM
I did a Bayesian analysis of the possible orbital stability of an Earth mass planet at 1AU around other stars. I used known extrasolar system data and computed the Lyapunov exponents for the chaotic drift of these planets. Only one other planetary system produced a Lyapunov for a putative 1AU terrestrial mass planet comparable to Earth. Earth’s orbit is perturbed mostly by Jupiter, and the occurrence of Jovian planets is the critical factor.This was used as a Bayesian prior and I estimate there are only about 1000 planets in our galaxy comparable to Earth, This of course does not preclude other biologically active planets. For all we know Mars may have subsurface life in the liquid water at… Read more »
Torbjorn Larsson OM
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Torbjorn Larsson OM
November 5, 2012 10:07 AM

This shows how it isn’t relevant. We have already observed habitable planets at a larger frequency. Trying to specify characteristics for “an Earth analog” is open ended, while measures are unequivocal.

Lawrence B. Crowell
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Lawrence B. Crowell
November 5, 2012 5:46 PM
Most of these planets are around M-class stars which means they are likely tidally locked. I might be wrong, but I think this reduces the chances for those planets to be comparable to Earth. Also M-class stars do a fair amount of flaring. Also if there is a Jovian planet within a couple of AU of this planet the orbit of this planet is likely perturbed heavily. This means it is highly probable the orbit is rattled around and conditions are not terribly stable. While the Earth has exhibited a wide range of changes in its geological past these are actually fairly stable. Temperature variations are estimated to be within 15C, the content of the atmosphere has remained… Read more »
Torbjorn Larsson OM
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Torbjorn Larsson OM
November 6, 2012 9:48 AM

That is another discussion though.

Zoutsteen
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Zoutsteen
November 3, 2012 12:44 AM

Might I point out that Vesta and Ceres had its history, but not a destructive one.
An Earth like planet residing in a massive belt might actualy be more benificial towards evolving space travel than our Earthly enviroment, from an economical point of view.

Peter
Member
Peter
November 3, 2012 6:02 AM

I agree (I think) with Ivanman, we need an accompanying explanation of why and how an asteroid belt helps to encourage (initiate) life. That is definitely not part of my world view. Why is it we can form from the same protoplanetary disc but still need asteroidal content? Is that because our heavier elements have sunk into our molten earth before a crust is formed that can absorb an asteroidal impact and keep the new elements on the surface where they can mix with our atmosphere and atmospherics?

Torbjorn Larsson OM
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Torbjorn Larsson OM
November 3, 2012 1:17 PM
Nice prediction of persistent asteroid belts. The rest is less likely. Other models predicts the necessary scarceness of water and carbon on inner planets naturally from disk models. That model has been tested by the recent find of Mars initially having the same amount of water in its mantle. It is difficult to predict this same amount from an asteroid belt hammering Earth and Mars differentially due to the different distances and planetary sizes. And generally there is way too much of water and carbon in ordinary asteroids (~ 10 % average in the most common carbonecaous chondrites) for a planet with land and oceans and rocks (~ 0.05 % for Earth). A terrrestrial outside the snow line… Read more »
Super Earth
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Super Earth
November 5, 2012 3:17 PM

What’s wrong if there are too few asteroid impacts (as would happen with a gas giant-disrupted asteroid belt?

They cause mass extinctions. The less asteroids, the better (or I am missing something?).

And in the model that explain why the Earth is so dry, the few water that actually is on Earth is mainly from accretion (and posterior degassing from mantle) or from later asteroid and comet impacts?

Prism2Spectrum
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Prism2Spectrum
November 4, 2012 3:53 PM
~ “But asteroids might also help seed a planet with the right ingredients to set up the conditions for life, and give that life encouragement to evolve more complex survival strategies.” ___________________________ I hope I bend the line of that subject question by asking: Does the rubble belt (leftover material of Nebular Hypothesis), swarming fragments, and rogue objects, through violent impacts and crashing bombardments, play any role in explaining today’s superbly arranged World-System wrapping Earth in Life—one set-up for it (whether by endless chance, or no): chemical, mineral properties, Moon and oceans, continental masses and crustal mechanisms, life-enclosing-supporting spheres, above and below; ….? Break down the concept, like a grinding stream of asteroids hurtling around the Sun (the… Read more »
Torbjorn Larsson OM
Member
Torbjorn Larsson OM
November 5, 2012 10:17 AM

The speed with which life was established on Earth shows that it is an easy enough process on habitable planets (which we have many of).

Since it is a process, there is no question about cause and effect. Cosmology shows that the universe started out from elementary particles after inflation ended. Abiotic chemistry caused biotic chemistry.

Prism2Spectrum
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Prism2Spectrum
November 5, 2012 12:25 PM
You label Mr. Davies a “deist”, and promptly dismiss an observation by an accomplished physicist as unscientific (by inference), and imply its a statement of “religious” belief: “Deists believe in the existence of God without any reliance on revealed religion, religious authority or holy books.” That eliminates the “religion” label. ~ Mr. Davies ” is affiliated with the Institute for Quantum Studies. ~ “He is also an adviser to the Microbes Mind Forum.” [has nothing to do with deism or “religion” that I can read] ~ *His “inquiries have included theoretical physics, cosmology, and astrobiology; his research has been mainly in the area of quantum field theory in curved spacetime.” [Sounds like high- SCIENCE to me. I do… Read more »
Torbjorn Larsson OM
Member
Torbjorn Larsson OM
November 6, 2012 9:47 AM

– The observation of Davies religion was to predict his religious claim. (As much as you can predict individual behavior from individual’s behavior, so to speak.)

– Obviously Davies claim is religious, it says nature is not enough: “bheind it all”, “somebody”, “design”.

– Obviously deism is a religious position, it invokes superstition to predict nature. You are trying to equivocate between personal religious belief and organized belief. There are no deist churches is all, but there could be.

If you don’t get the two last points, which isn’t an opinion but a description of religion as it is usually defined, we can’t have a discussion.

Prism2Spectrum
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Prism2Spectrum
November 6, 2012 8:30 PM

The close minded will draw their automatic conclusions (based on bias?). The open-minded can judge for themselves.

justafan
Guest
November 4, 2012 11:41 PM

Do not the planets themselves derive from gravity upon the contents of the original belt? If so why the importance of asteroid hits later from the same belt contents.

IVAN3MAN_AT_LARGE
Member
IVAN3MAN_AT_LARGE
November 5, 2012 12:15 AM

During the initial stages of the Earth’s formation, it was molten and the heavy elements sank to the core of the Earth due to its gravity; consequently, this left the crust depleted of the essential elements needed for life, such as iron. However, these essential elements eventually came in from asteroids (and also water from comets) in the later stages of the Earth’s formation to enrich its crust.

Torbjorn Larsson OM
Member
Torbjorn Larsson OM
November 5, 2012 10:29 AM

Iron is siderophilic but it is also rock forming and was always retained in the crust as I understand it. It is many of the other transition elements that are depleted.

We now know the mantle contained enough hydrogen and oxygen to reconstitute today’s oceans when degassing and volcanism created the initial CO2 atmosphere.

We also know from hydrogen isotope ratios that comets could have supplied a minor part of water.

The participation of asteroids is an open question, I believe. In some core formation models they resupply all the depleted elements, in some others there was incomplete mixing in the first place.

IVAN3MAN_AT_LARGE
Member
IVAN3MAN_AT_LARGE
November 5, 2012 1:37 PM

Well, what I said also says so in the introduction of the paper (linked above):

[…]. Heavy elements, including some that are essential for life, were also probably delivered to the Earth’s crust through collisions. During the early times of formation the Earth was molten and its gravity pulled heavy elements to its core leaving the crust depleted of elements such as iron, gold and platinum. […].

Torbjorn Larsson OM
Member
Torbjorn Larsson OM
November 6, 2012 9:34 AM

Yes, the crust is relatively depleted of iron compared to the (iron!) core. But the question is if impactors delivered appreciable amounts.

IVAN3MAN_AT_LARGE
Member
IVAN3MAN_AT_LARGE
November 5, 2012 2:07 PM

Furthermore, referring to your link, it states there:

[…]. Manganese, iron and molybdenum do form strong bonds with oxygen but in the free state (as they existed on the primitive earth when free oxygen did not exist) can mix so easily with iron that they do not concentrate in the siliceous crust as do true lithophile elements. […].

Aqua4U
Member
November 6, 2012 3:16 AM
Laughs, chokes and makes a sheep-like bleating sound… We live and learn? Have we been down this path before? Recently I (re)read a Sci-Fi story by Ross Rocklynne entitled, ‘Time Wants a Skeleton’. It was written way back in 1941. In this story an astronaut, one Tony Crow, crash lands on a remote asteroid while chasing two criminals he hopes to capture. The asteroid he lands on is a remnant of an earlier collision between two much larger proto planets. The story follows a convoluted series of circumstances wherein Tony finds a skeleton in a cave with an emerald ring on it’s finger… ergo the title. Included in the story is time travel, cops and robbers, a genius… Read more »
Torbjorn Larsson OM
Member
Torbjorn Larsson OM
November 6, 2012 9:32 AM

We know from observing other systems, and from modeling our own, that disks are formed and then asteroids et cetera. It is also obvious from all available samples that they were never planets.

Hoofbeats, horses, zebras.

Aqua4U
Member
November 6, 2012 5:07 PM

Did you forget the sheep? Baaaaaaaah! Bleat-bleat!

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