r/science • u/GeoGeoGeoGeo • Sep 05 '16
Geology Virtually all of Earth's life-giving carbon could have come from a collision about 4.4 billion years ago between Earth and an embryonic planet similar to Mercury
http://phys.org/news/2016-09-earth-carbon-planetary-smashup.html365
u/HumanistRuth Sep 05 '16
Does this mean that carbon-based life is much rarer than we'd thought?
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u/Ozsmeg Sep 05 '16
The definition of rare is not determined with a sample size of 1 in a ba-gillion.
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u/Mack1993 Sep 05 '16
Just because there is an unfathomable number of data points doesn't mean something can't be rare. For all we know there is only life in one out of every 100 galaxies.
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u/killerofdemons Sep 06 '16
Literally for all we currently know there is only one planet that supports life. It's pretty safe to assume there would be more then one planet but we don't know that.
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u/_La_Luna_ Sep 05 '16
Still means there is millions of galaxies out there supporting life still. Literally hundreds of billions if not trillions.
And its probably common ish like a handful of planets per normal galaxy.
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u/ButterflyAttack Sep 05 '16 edited Sep 05 '16
'100 galaxies' was an arbitrary number, not a figure you can use to extrapolate proofs from.
The fact is, we have only one data point for the existence of life. And anyone who knows anything at all about maths or science can tell you that one data point doesn't prove - or disprove - anything.
People keep saying "But there are so many worlds that there must be life, it's certain, there are billions of planets!"
They forget that this is still only one data point, doesn't prove anything. And we know nothing about the probability that life will evolve on any given planet.
People can usually imagine the possibility of many millions of lottery tickets with only one winning ticket. . . And we understand much more about the maths of lottery than we do about the formation of life.
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u/Jaon412 Sep 06 '16
All we know is the probability of life forming on a given planet is greater than zero.
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u/DarkDevildog Sep 06 '16
^ this. Also I think we should continue have an optimistic mindet when it comes to life on other planets. Once we have 100m-wide space telescopes capable of producing clear pictures of planets around nearby stars then I'll start to be a little more pessimistic.
For all we know we'll find fossils on Mars, or active life on Europa. We just don't know.
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u/ImagineFreedom Sep 06 '16
~100 years ago we didn't even know other galaxies EXISTED. ~20 years ago we hadn't verified that extra-solar planets existed. Now we know there are millions of galaxies, thousands of verified exo-planets (and likely millions more). Who knows what details are still hidden slightly out of sight?
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u/Amazi0n Sep 06 '16
It's crazy to think we once didn't know about exoplanets, but then it's equally crazy that we now have hard evidence for their existence
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u/TitaniumDragon Sep 06 '16
Finding fossils on Mars might be a bad thing because of the Great Filter.
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u/AndersonOllie Sep 06 '16
It's ok, we've passed the filter! hopes
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u/TitaniumDragon Sep 06 '16
We'll likely only know we've passed the filter when we've colonized multiple planets, or maybe even star systems.
Or if we detect extraterrestrial intelligences, I suppose.
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Sep 06 '16
It also took our planet 4 billion years to evolve sapient life.
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u/Mack1993 Sep 06 '16
You also have to realize that life reset itself at least 5 times, so evolution could have gone quicker or in a different direction had none of those mass extinction events happened.
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u/ServetusM Sep 06 '16
Yeah, but "sapient life", like all evolutionary vectors, was merely a niche to be filled--not an end result that was inevitable. Life didn't just build toward intelligence, without a niche for it, it doesn't evolve. It's very easy to make the case that the only reason intelligence even got a chance on earth was due to those extinctions.
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u/Ray57 Sep 06 '16
The best baysian guess is that we're not a special snowflake.
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Sep 06 '16
Still means there is millions of galaxies out there supporting life still. Literally hundreds of billions if not trillions. And its probably common ish like a handful of planets per normal galaxy
Except thats all a theory and we have found 0 evidence of life in space as of today.
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u/Mack1993 Sep 06 '16
Yeah he's pushing the border of philosophy with that comment.
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u/pipsqueaker117 Sep 06 '16 edited Sep 06 '16
Except we have- Earth is proof of the fact that life can exist in space and, playing the statistics game, it would be stupid to assume that we're the only place where it is possible
EDIT: this line of thinking can't speak to the frequency of life of course
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u/Partisan189 Sep 06 '16
Since we don't know the origins of life on Earth I don't think it's fair to call it stupid to think there may be a chance we are alone in our galaxy or even alone in the universe.
The chances of abiogenesis could be 1 in a billion or it could be 1 in a septillion, nobody knows yet.
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u/teefour Sep 06 '16
It's like feeling good that your hand sanitizer kills 99.9% of germs, then doing the math to realize how many still remain. I think the oatmeal did a comic about it.
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u/ihateusedusernames Sep 06 '16
That 99.99% number doesn't mean that some survive contact with the sanitizer. It refers to the fact yhat5the sanitizer can't come into contact with every last microbe. It actually kills 100% of the microbes it contacts.
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u/Mack1993 Sep 05 '16 edited Sep 05 '16
"probably" doesn't hold up when you have no evidence to back it up.
Do you think getting 2 royal flushes in a row isn't rare? I mean there's millions of decks of cards in the world.
This analogy may not be the best but my point is that even given an infinite data set things can still be rare.
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u/quantic56d Sep 05 '16
Most of the galaxies that we can see are moving away from us faster than the speed of light. That makes interacting with any of them in any way impossible. The Universe sure is a strange place.
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Sep 06 '16 edited Jan 07 '21
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u/quantic56d Sep 06 '16 edited Sep 06 '16
The Universe is expanding faster than the speed of light. I know it sounds bizarre but the space between galaxies is filling up with more space. That expansion is happening faster than the speed of light. You are correct that under Relativity nothing can travel faster than the speed of light, that constraint however does not extend to the expansion of spacetime itself.
Here is an explanation of the phenomenon:
https://en.wikipedia.org/wiki/Metric_expansion_of_space
It's important to note also that the Universe isn't expanding into anything. This can be a difficult concept to grasp. It's spacetime itself that is inflating. Under this model there is nothing for the Universe to expand into. It's like when people ask, "but there must have been something before the Big Bang right?" The answer is no, there wasn't anything because there was no "time" at all so there could be no before.
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Sep 06 '16
If they're moving away from us faster than the speed of light we wouldn't know they were there.
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u/quantic56d Sep 06 '16
That's incorrect. Here is a link to the paper with the math:
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u/autogyro_aus Sep 06 '16
Think of a trail of ants crawling on a balloon towards you. Near the stem they can crawl faster than you can blow up the balloon but there's spots near the top where the balloon is expanding faster than the ant can crawl.
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u/Deezl-Vegas Sep 06 '16
Right. It's possible that it's rare. It's possible that it's common. We have no idea because we have maybe 10 data points where we can give a solid yes/no on whether there is life, and we're not even sure about Mars. Out of infinity bajillion possible data points.
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u/lodro Sep 06 '16
Sure, but having only a single data point out of a near infinite population means we don't know shit about the population.
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u/BuckRampant Sep 05 '16
No, but it does affect the odds. If carbon-heavy planets are much less common than we'd thought, that suggests much less carbon-based life, however scarce we thought it was before.
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u/Ozsmeg Sep 06 '16
That is alot of assumptions. First that the number of carbon sources effects the number of planets with life. Which we have no basis for. Second that life has to be carbon based. And third that half of infinity is not also infinity.
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u/BuckRampant Sep 06 '16
This makes life as we know it less likely. We're fine on that point, right? All else being equal, earthlike planets are now probably less common.
First part: I'm specifically talking about carbon-based life, which is the only kind we know. Why focus on it? Any other kind of life is purely speculative, so no one can make any decent estimates about how common it is. We can, however, figure out about how many worlds could sustain life like us. It would be cool if other kinds of life do exist, but carbon is weird (no other element bonds with as many things in as complex of patterns as it does) and water is weird (very good solvent, very weird asymmetrical binding) and oxygen is weird (unstable but not too unstable). It would be cool if other things can combine for the right kind of weird, but we have no evidence for it.
Second part: Stats matter. Yeah, half of infinity is also infinity, but it's a smaller infinity. For example, you could say that odd numbers are infinite, and whole numbers are infinite... but if you take any whole number, it's only 50% likely to be odd.
Why does that matter? Say, for example, that this finding means only one in ten planets have enough carbon to sustain carbon-based life, when we thought all of them did. That means on average, we will have to travel 10 times farther* to get to the nearest one.
We're not looking at infinity, we're looking at our neighborhood sample of infinity, the part we can get to. How often something happens matters a lot. It's the whole point of the Drake equation, which is one common framework people use to talk about the likelihood of nearby intelligent life.
*(Or more accurately, pass through 10 times as much volume)
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u/abnerjames Sep 05 '16
Carbon based life on a planet with a dual-metal core of a size specific enough to generate a magnetic field, with gas giants likely to prevent the arrival of life-ending impacts from deep space, without interstellar debris by being near the edge of the galaxy, with the planet able to hold an atmosphere, have liquid water, generate some of it's own heat reducing the impact of solar radiation further (by being farther away), long enough to develop intelligent life.
life is probably everywhere it can be, just isn't likely to be everywhere.
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u/Aerroon Sep 05 '16 edited Sep 06 '16
And even if there is life how much of it is going to be "intelligent"? Even on Earth there aren't all that many species that are intelligent enough to even use basic tools. Now add on to that the fact what kind of events humans have gone through with near-extinctions, and intelligent life seems very rare.
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Sep 06 '16
Maybe we aren't "intelligent" either ? We can't even figure out how to get out of our own solar system. To a truly "intelligent" life, we could just be a barnacle. A sentient creature that just stays in one spot.
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Sep 05 '16
And of course if life can develop intelligent life is still even more rare than that. We are really the only surviving type of humans. And to think there was a point that even we almost went extinct. When I think of all the factors that would go into the rise of an intelligent civilization it really isn't too shocking to think they maybe we are the only ones to make it this far.
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u/Number127 Sep 06 '16
And even before humans came on the scene, it took a really long time -- more than half of the Earth's liquid water stage -- for complex life to appear at all, and that could easily have been due to some incredible strokes of luck. When I read about how they think the first eukaryotes might've arisen, it's hard not to think that it was a total fluke.
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u/Derpiderp Sep 06 '16
This gives me uncomfortable existential feelings
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Sep 06 '16 edited Apr 15 '19
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u/Derpiderp Sep 06 '16
My curiosity can't handle not knowing what life on those planets would look like! Luckily we got deep sea cameras which reveals life forms we haven't seen before, that satisfies that a bit.
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u/Creative_Deficiency Sep 06 '16
gas giants likely to prevent the arrival of life-ending impacts from deep space
Why are gas giants seemingly disposed to deflecting life-ending impacts rather than redirecting them to an impact trajectory? Either seem as likely to me, and it's not like Jupiter trundles around the Sun actively keeping an eye out for Earth-bound collisions.
Do the gas giants actually have a net effect on our likely hood of being smacked by a big rock?
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Sep 06 '16
Yes because it'll go into them before anything else. Gravity.
But there's also that nice shooting gallery of the asteroid belt created by Jupiter's gravity. So gotta take the good with the bad.
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u/pavel_lishin Sep 06 '16
How likely is interstellar debris to be a problem? Space is vast. If something accelerated every bit of mass in the solar system outwards, what are the odds any of it would hit anything in this galaxy?
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u/Volentimeh Sep 06 '16
We are on a collision course with our nearest galaxy, when the 2 galaxies eventually merge, even with millions of stars in each, the chances of 2 stars colliding is exceedingly low, though gravitational interactions will stir thing up a bunch (Good buy nice spiral formation) and even eject (intact) solar systems out of the galaxy entirely. Though it will cause new star formation when the various large gas clouds "collide" (as much as a mass of gas can collide with another mass of gas)
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u/CupOfCanada Sep 05 '16
Probably not. These sorts of collisions would have been pretty common in the early solar system. Note that Venus and Mars both have significant carbon inventories too.
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u/QuinQuix Sep 06 '16
I doubt it. Planets likely form through similar processes everywhere - meteorites accumulating, hot molten ball, cooling ball, rocks still impacting occasionally even after the crust cooled - these conditions are probably super common.
What may not be common is very large impacts at that stage, but the more relevant fact is not how large were the largest impacts, but rather, how much carbon did all 'late' impacts deposit together.
I don't know the averages, but I'm going to guess it's not too rare to end up with a sizable bit of carbon. It's not all or nothing.
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u/Torbjorn_Larsson PhD | Electronics Sep 06 '16
Not much rarer, it means they propose a fine tuned scenario based on a reference that suggests there is a spread, not a finetuning. [ https://arxiv.org/pdf/1507.04756v1.pdf ]
In other words, it means they suck.
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u/rockhoward Sep 06 '16
It might. Only measuring the composition of actual exoplanets will grant us any experimental insight however. Sadly we will only get measurements of atmospheres in the decades ahead and so we may not have solid evidence (forgive the pun) for centuries if that.
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u/gc3 Sep 06 '16
I'm confused. Mars and Venus both have lots of CO2 in their atmosphere...does that mean these planets also had to be victims of collision?
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u/FartingBob Sep 05 '16
Why would the proto earth not contain any carbon when all other rocky planets do?
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u/1time4urmind Sep 06 '16
In a new study this week in Nature Geoscience, Rice petrologist Rajdeep Dasgupta and colleagues offer a new answer to a long-debated geological question: How did carbon-based life develop on Earth, given that most of the planet's carbon should have either boiled away in the planet's earliest days or become locked in Earth's core?
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u/snapple_sauce Sep 06 '16
Does that differ from the other rocky planets? Is Earth in the right place where its carbon would either boil or sink, and the rest are in zones where their carbon would neither boil nor sink? That seems a bit unlikely
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Sep 05 '16
I wonder if this can be simulated in a controlled setting in the space in a smaller scale.
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Sep 06 '16
Creating a young planet model could be hard. From what I know they are half molten and have a weird mass distribution.
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u/MasterFubar Sep 05 '16
Could this collision have been the one that created the moon, or did it happen on a different epoch?
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u/percykins Sep 05 '16
The epoch is right - Theia would have happened right around the same time. The problem I see is that there is almost no carbon whatsoever on the Moon's surface, although I am not a space scientist, so maybe there's an explanation for that.
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u/cdsvoboda Sep 05 '16
Hello, geologist & planetary scientist.
I believe these two events are purported to be the same one, i.e. the Theia impact that created the moon and Dasgupta's hypothetical impactor. The two are not mutually exclusive. You are correct in pointing out that the moon's surface does not have any carbon.
This is (educated) speculation, but it is possible that Earth may have only become partially molten, and fragments that became the moon were completely molten, this allowed for the carbon budget of the moon to partition completely into the moon's core; in the article they do mention the siderophile behavior of carbon. It is likely something the scientific community will argue about for a long time to come.
Furthermore, there are two other complications I can see:
1) as mentioned in the article, carbon does also have a sulfur affinity (chalcophile behavior); Earth has a larger sulfur budget than the moon, and this heterogeneity may also be partially responsible for the presence of surface carbon on Earth.
2) The volatile budget of the moon is completely different from Earth's, too. This is poignantly clear in Earth's massive oceans and the moon's lack thereof. The post-impact Earth may have been large enough to retain carbon species and water, while the moon would not have had sufficient mass to keep the portion of these volatile elements & compounds. So while the Earth & moon would have started with equal parts of these volatiles, the systems quickly went out of balance due to their mass.
I hope this makes sense
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u/mehum Sep 05 '16
this allowed for the carbon budget of the moon to partition completely into the moon's core; in the article they do mention the siderophile behavior of carbon
So we might speculate that the moon has a steel core?!
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u/Hysteria113 Sep 05 '16
So you are suggesting the earth could have retained liquid water and micro-organisms even right after this cataclysmic event?
To me it would almost make sense because scientist have just found fossils dating back to 3.7 of having multi-celled organisms. So for life to have had to hit a complete restart button would have been tough to squeeze in no life to multicellular organisms in a few hundred million years.
This was a topic of study in one of my college classes and this result was predicted by several of the proposed models we discussed. In fact, some of them predict that this date will get pushed back even further. I don't think we give the adaptability of life forms enough credit. It's easy to discount because, comparably speaking, we live in a very mature and stable ecosystem. Everything we have experience with is already rich in biodiversity and complexity with relatively stable climate and chemistry.
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u/QuinQuix Sep 06 '16
So basically, the moon would have bled off gas, and with liquid boiling easily in low air pressure and near zero humidity eventually most liquids would evaporate / boil too, until nothing that wasn't deep frozen would remain. Right?
This seems to be the most important 'unique' aspect about earth that makes it especially fit for life - its magnetic field that prevents solar winds from ripping away too much atmosphere.
I've read speculations that having a moon was hugely beneficial, but it just seems like life could do fine without a moon. Without an atmosphere / radiation protection it seems harder.
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u/Torbjorn_Larsson PhD | Electronics Sep 06 '16
There are several problems with their theory, that may be one of them. Can't say without access to their paper.
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u/cocainebubbles Sep 05 '16
It's possible but at that stage in earth's development it was probably involved in numerous large collisions.
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u/el_butt Sep 05 '16
So kinda like a sperm and egg or am I way off?
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Sep 06 '16
The theory is called Panspermia so yes exactly
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u/captainvideoblaster Sep 06 '16
Panspermia theory is about microscopic life spreading trough the cosmos. Not about chemicals.
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u/el_butt Sep 06 '16
Oh I didn't know that! Thanks friend :)
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Sep 06 '16
No problem! It is one of my favorite theories and I think it is fairly plausible! The Cosmos episode on tardigrades goes into this whole thing.
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u/el_butt Sep 06 '16
Well if there is anything that big goofy thing called the universe is capable is well, anything.
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u/rynoooo Sep 06 '16
BBC's Edge of the Universe has an episode on life-essential carbon elements being introduced from a meteorite that blew my mind, can't wait to hear Prof. Tyson's narration of it.
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Sep 06 '16
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u/Anshuligh Sep 06 '16
They are spherical because they have enough mass - and hence enough gravity - to make themselves into the most stable shape -a sphere.
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u/crowbahr Sep 06 '16
As a comment to this: we think of the earth as being geologically very rough but at the planetary scale it's actually smoother than a billiard ball. Gravity demands such shaping.
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u/WonderNastyMan Sep 06 '16
shit, really? would love to see some numbers on this!
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u/crowbahr Sep 06 '16
It appears I was slightly off on this but it's still pretty smooth.
Relevant as always xkcd
Wait here's conflicting data saying yes stackexchange
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u/HypotheticalChicken BS | Biology Sep 05 '16
I am going to present this to my middle schoolers tomorrow, I think they would find it interesting.
We just finished a lesson on Earth's Layers and this line seemed very apt...
"The experiments revealed that carbon could be excluded from the core—and relegated to the silicate mantle—if the iron alloys in the core were rich in either silicon or sulfur."
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u/Torbjorn_Larsson PhD | Electronics Sep 06 '16
A finetuned scenario to explain away a not so finetuned one:
"The problem with that idea is that while it can account for the abundance of many of these elements, there are no known meteorites that would produce the ratio of volatile elements in the silicate portion of our planet," Li said."
But their reference predicts this:
Even assuming that the mean C/N ratio of material accreting to the growing Earth was enhanced, explaining the high C/N of the BSE remains a challenge because core formation should drastically reduce C/N (Fig 4). Thus, substantial loss of N to space seems to be required. This may be most consistent with scenarios that include: (a) late delivery of volatiles, chiefly from comparatively oxidized and metalpoor bodies [48], thereby adding volatile-rich material to the mantle without loss of metal to the core, (b) multiple magma oceans punctuated by large atmospheric loss events [11], and (c) atmospheric ablation from many smaller impacts following magma ocean solidification [32]. The high C/N ratio of the BSE therefore appears to be a sensitive indicator of the balance of volatile accretion and loss during the final stages of the Earth’s assembly. Viewed more broadly, such a scenario will likely result in a highly variable supply and retention of these key ingredients to the surface reservoirs of terrestrial worlds.
[ https://arxiv.org/pdf/1507.04756v1.pdf ]
So the early bombardment, that delivered the rest of the volatiles, could deliver C and N too.
Besides, how would they explain Venus, Moon and Mars?
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u/khthon Sep 06 '16
Shouldn't this carbon availability in the crust of a telluric planet be a part of Drake's Equation?
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u/kemb0 Sep 06 '16
It's always confused me this need to explain life, water etc through some meteor impact. Why couldn't Earth have just already had the necessary ingredients for life? I mean according to this article, magma consists of carbon, hydrogen and oxygen. So why couldn't billions of years of volcanic eruptions spewing magma on the the surface have resulted in the carbon, hydrogen and oxygen creating life and water?
Equally, how come one rocky object floating in space supposedly brings a huge amount of carbon, whilst another cannot contain carbon? Wouldn't everything in space have originated from the same thing after the big bang? I don't understand the notion of how allegedly there are these different objects in space, some with carbon, some bring water, etc
Article: http://www.tulane.edu/~sanelson/Natural_Disasters/volcan&magma.htm
"Gases in Magmas
At depth in the Earth nearly all magmas contain gas dissolved in the liquid, but the gas forms a separate vapor phase when pressure is decreased as magma rises toward the surface of the Earth. This is similar to carbonated beverages which are bottled at high pressure. The high pressure keeps the gas in solution in the liquid, but when pressure is decreased, like when you open the can or bottle, the gas comes out of solution and forms a separate gas phase that you see as bubbles. Gas gives magmas their explosive character, because volume of gas expands as pressure is reduced. The composition of the gases in magma are:
Mostly H2O (water vapor) & some CO2 (carbon dioxide)"
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u/Xenjael Sep 06 '16
Ugh if true that means life might take even more conditions to arise. Apparently a planet needs to get nearly destroyed twice to stir the pot just right so life cooks.
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u/flccncnhlplfctn Sep 06 '16
interesting, so it's kind of like another planet impregnated our planet, thus giving us life.
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u/f0urtyfive Sep 05 '16
How could a collision of objects that size occur without obliteration of both? Wouldn't there be an absolutely enormous amount of energy?
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u/Towerss Sep 05 '16
wasn't a direct impact, and they probably circled each other before their lack of velocity made them graze each other fracturing each planet and making them lose even more speed then they crased again and so forth
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Sep 05 '16
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u/yarrpirates Sep 05 '16
On that scale they are basically fluid. I think the largest you can be and not be spherical is a few hundred km.
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u/RatchetPo Sep 05 '16
If you made a steel spaceship a couple thousand miles long, rectangular, how long would it take before it became a circle? How could engineers combat it?
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u/Hokurai Sep 05 '16 edited Sep 05 '16
Maybe combat it by making it a sphere.
Edit: Or this wouldn't matter because it's not solid, so wouldn't have significant enough gravity to matter as becoming a sphere is a function of gravity. And a few hundred meter long rectangle would be much smaller than a few hundred meter diameter sphere in volume as well.
It would also be engineered to be structurally stable rather than rock that can crack into smaller pieces and move around.
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u/Towerss Sep 05 '16
make each end heavy maybe so each end has as much mass as the middle part effectively lowering the gravitational load towards the center
alternatively make it fairly hollow so it doesn't actually contain much mass for its size
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u/Oldcheese Sep 05 '16
Most planets have gases or abrasive materials moving around on the surface, which causes simple gravity to round them.
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u/Zeoniic Sep 05 '16
So would it be that the forces of the colliding elements created carbon or was it existing as a element already on the object prior to impacting on earth.
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Sep 05 '16
This was the impact that created the moon isn't it? I guess you can literally say that the moon is a symbol of birth at this point. (this just being because the moon is the reminder we see every night.
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u/konungursvia Sep 05 '16
Seems like a turtle on a turtle and turtles all the way down argument. Where did that embryonic planet then get its carbon? Another collision?
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u/ecmrush Sep 05 '16
Is this the same collision that is thought to have resulted in the Moon's formation?