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Could the Earth be an evaporated gas giant planet?
- anticensor 6y agoAFAIK Nitrogen in the initial atmosphere rules this out.
- perl4ever 6y agoIs there a succinct explanation of why some terrestial bodies in the solar system (Earth, Titan, Triton, Pluto) have mostly nitrogen atmospheres, but others (Mars, Venus) are mostly carbon dioxide instead? I mean, aside from specifics about each, what's the pattern that you would apply to an arbitrary planet?
- croddin 6y agoI think it is due the magnetosphere shielding from solar wind. Earth has a strong magnetosphere, while neither mars or venus do. For titan, wikipedia says "Titan spends 95% of its time within Saturn's magnetosphere, which may help shield it from the solar wind.", not sure about Triton and Pluto but they are much further from the sun so that probably helps solar wind not strip away as much nitrogen.
- Rooster61 6y agoA relative lack of effect from the solar wind, either through magnetic shielding (Earth, Titan) or sheer distance from the Sun (Triton, Pluto). Mars and Venus are both in the inner Solar System, and both have very weak magnetic fields.
- elihu 6y agoAccording to wikipedia, Venus' atmosphere is about 3.5% nitrogen and its pressure is about 91 atmospheres. So, technically Venus doesn't have a lack of nitrogen (it appears to have about 3 times as much as Earth), it has an extreme abundance of carbon dioxide. Something interesting I didn't know is that apparently Venus has almost no plain oxygen. Mars, on the other hand, doesn't have much nitrogen. Perhaps that's attributable to the relative lightness of N2, which would be more prone to float off into space than the somewhat heavier CO2.
- gnulinux 6y agoEarth atmosphere is 0.04% CO2. Why does Earth have such little CO2? Is maybe used by life on early Earth?
- perl4ever 6y agoIs that a rhetorical question? I assume it's something to do with: https://en.wikipedia.org/wiki/Limestone https://en.wikipedia.org/wiki/Limestone
- rozab 6y agoYep. https://en.wikipedia.org/wiki/Great_Oxidation_Event https://en.wikipedia.org/wiki/Great_Oxidation_Event
- mattkrause 6y agoI’m pretty sure we still have plants, though I admittedly haven’t been out of the house much. A lot of carbon was also captured during the aptly-named Carboniferous Period 360-300 million years ago. Woody plants had just evolved, but microbes that could break them down had not. Thus, coal. An earlier drop in sea levels also caused carbonate (as in limestone, dolomite, and iron ores) to precipitate out. The combination of these effects pushed oxygen levels about 50% above present, allowing very large animals to evolve.
- saagarjha 6y ago> Woody plants had just evolved, but microbes that could break them down had not. Thus, coal. Does this mean we’ll never have coal again?
- anticensor 6y agoWe will, but the balance is much more against coal now. We will have it consumed before it is replaced.
- mattkrause 6y ago
- pdonis 6y ago> Is there a succinct explanation of why some terrestial bodies in the solar system (Earth, Titan, Triton, Pluto) have mostly nitrogen atmospheres, but others (Mars, Venus) are mostly carbon dioxide instead? For Earth, the answer is simple: life. In the absence of life, a nitrogen-oxygen atmosphere is thermodynamically unstable. Our best current understanding is that the atmosphere of the early Earth, before life developed, was mostly methane and ammonia, which are commonly observed in the atmospheres of the outer planets and their satellites. Once life developed, the methane and ammonia were gradually chemically converted by life to water and nitrogen. For the others you mention, oxygen is not present, and the nitrogen is combined with methane (plus traces of carbon monoxide or carbon dioxide). I have not seen detailed thermodynamic calculations, but if there are very few oxygen atoms present, nitrogen plus methane should be thermodynamically stable. The unique feature of Earth as compared with these others would be the presence of a sufficient quantity of oxygen atoms to oxidize the nitrogen to ammonia in the early atmosphere before life developed. For Mars, it is close enough to the Sun and small enough to make its temperature too high for it to retain significant amounts of nitrogen or methane (it has traces of both, IIRC), so CO2, which is significantly heavier, is the only significant component left. For Venus, a significant amount of nitrogen gas is present (about four times as much as in Earth's atmosphere--Venus is significantly larger than Mars so its gravity can keep the nitrogen from escaping), but this is masked by the enormous amount of CO2 present (about 95 atmospheres worth), which AFAIK is believed to be due to all of the calcium carbonate in the surface rocks having been driven into the atmosphere due to a runaway greenhouse effect raising the temperature.
- neuronic 6y agoWhen solar system planets formed from stellar dust, do we assume that said dust was uniform in composition and merely position, solar dynamics and interplanetary dynamics such as collisions (formation of Moon) led to the differences in chemical composition? For example, it's the outer planets that are gas giants. Venus composition doesn't seem too different from Earth but it's much closer to Sol, so it's more exposed with much more energy absorbed etc.
- pdonis 6y ago
- T-hawk 6y agoIt's not a pattern of ratio or composition, it's a pattern of the quantity of each individual component. The individual quantities then constitute the composition. For CO2, the pattern is temperature. Titan, Triton, Pluto are well below CO2's freezing point so it stays on the surface as ice instead of atmosphere. At these temperatures, nitrogen is the heaviest abundant molecule that remains gaseous, followed by methane. If you're warm enough for gaseous CO2, you have it. The only exception is Earth and that's because plant life absorbed it and emitted O2 instead. For nitrogen, methane, argon, the pattern is mass. Only Venus and Earth have enough mass to hold on to those, compared to heavier CO2. Venus and Earth have similar quantities of those. Venus's excess of CO2 comes from temperature high enough to evaporate carbon and oxygen from rock compounds.
- saberdancer 6y agoTitan has enough mass to keep a decent nitrogen based atmosphere as well. It is probably closest to Earth with the exception that methane is a water analogue on Titan.
- perl4ever 6y ago"It is not apparent yet that such Rogue planets are regularly traded between star-systems and subsequently participate in serial evaporative events and the proposal may seem like a long shot, but on astronomical time scales the unlikely can become commonplace." It sounds a bit Velikofskian.
- mickfaraday 6y agoYes, Michael Lund of CalTech updated the Velikofskian hypothesis: https://arxiv.org/pdf/1903.12437.pdf https://arxiv.org/pdf/1903.12437.pdf
- deleted 6y ago[deleted]
- pdonis 6y agoThe fact that this paper appeared in April 2019 in a journal called "Acta Prima Aprilia" should give you a clue to how seriously to take it.
- tzs 6y agoThe fact that the paper uses “CalTech” was the big clue for me. Also check out the references at the end. Some big clues there too.
- hirundo 6y ago"The Chthonian process effectively selects for retainment of water and carbon dioxide, which are heavy and tend to rain back down upon condensing in the upper atmosphere." So earthlike planets would be more plentiful than otherwise. This could be a boon to scifi plots that entail conveniently breathable atmospheres. It would also tend to support the strong anthropic principle.
- mrfusion 6y ago> It would also tend to support the strong anthropic principle. How does it support that?
- hirundo 6y agoThe principle is: the universe has been fine-tuned in order to ensure that life arises. 1. The only forms of life that we know about are on a planet with plentiful water and carbon dioxide. 2. Planetary dynamics may favor the production of such planets by the evaporation of gas giants. Ergo, the rules of planetary dynamics appear to favor habitats for life as we know it. This appearance may be just an artifact of our limited survey of life in the universe, but it's all we have.
- dumbfoundded 6y agoI think you may be mixing up the causation. How probable our universe is, we'll never know (until we can see other universes). We do know that in this universe, life exists. Thus our universe has to be "fine-tuned" for us to exist because we do. As for the universe "favor"ing life, that doesn't really make sense either. I think it's safe to say the universe favors stars, gas giants, black holes but it's pretty hard to say the universe favors life when it's only given us ourselves as an example.
- bryanrasmussen 6y agoI suppose if the anthropic principle is correct that would mean there are many examples, it's just our problem that we are only familiar with one.
- hindsightbias 6y agoEmbedded link is very intersting https://wfirst.gsfc.nasa.gov/exoplanets_microlensing.html https://wfirst.gsfc.nasa.gov/exoplanets_microlensing.html
- daveslash 6y agoNo. At least, that was my knee-jerk thought, according to Betteridge's law of headlines. After reading through it, I do find it an intriguing hypothesis.
- retpirato 6y agoNO. If solar wind caused a gas layer to evaporate, Earth shouldn't have the atmosphere it does. This planet should be like those surrounding it. Those same solar winds/radiation would have made sure of that. The issue I have with this is the same issue I have with evolution. If conditions were not created to favor life why are we the only planet with any known life & which is perfectly suited to a variety of life? Do you really think that's a coincidence? Scientists are constantly coming up with one ridiculous theory after another to explain why no evidence of life has been found outside our planet instead of just acknowledging that this planet is unique because it was designed that way.
- rowanG077 6y agoHuh? No scientist claims to have ultimate knowledge of why there is life on earth. But to claim that Earth was created for life is leap too far. I mean we used to believe storms where conjured up by the gods because we didn't understand how they really are created. What you are saying is essentially the same. We don't know so it must have been created. You are essentially invoking the God-of-the-gaps fallacy.
- grayed-down 6y agoMaybe not created, but...tweaked?
- robbiep 6y ago... up until about 15 years ago we only knew of 9 planets so our sample size was pretty small
- saagarjha 6y agoAnd not all of them were even planets, either.
- dboreham 6y agoIt's a coincidence that a carbon lifeform like you is standing on a planet perfectly suited for carbon life, wondering at the chances of happening to be on the right kind of planet? I don't remember that scene from Hitchhiker's Guide, but it must be in there somewhere. The collolarry to the whale wondering why it is hurtling down towards the surface of a planet..
- valuearb 6y agoHow do planets migrate?
- tdy721 6y agoThrough the atoms of progenitor stars long since gone supernova. Probably neutron stars too! Or also by chance?
- valuearb 6y agoI know tidal curves have increase the moons orbit, I’m struggling to think of anything (outside massive collisions) that would cause planets to move closer to their stars, or move to new ones.
- nfg 6y agoOrbits can be quite unstable, for example read (one theory) or the early dynamics of the solar system: https://en.wikipedia.org/wiki/Nice_model https://en.wikipedia.org/wiki/Nice_model
- swebs 6y agoIf two planets were to pass close enough together, their orbits could become destabilized enough to essentially fling them.
- deleted 6y ago[deleted]
- anwar343 6y agoThe fact that this paper appeared in April 2019 in a journal called "Acta Prima Aprilia" should give you a clue to how seriously to take it.
- probably_wrong 6y agoDid you just copy pdonis' answer in this same thread word-for-word? https://news.ycombinator.com/item?id=22894412 https://news.ycombinator.com/item?id=22894412
- jacquesm 6y agoYes, standard trick of 'green' accounts that want to acquire some karma quickly: repost a good on-topic comment as a top comment. Flagged.
- bumblebritches5 6y agoI'm gonna go out on a limb and say no.
- pfarnsworth 6y agoHow can a captured planet ever maintain a stable, almost perfectly circular orbit around the Sun, at a plane that almost exactly matches the rest of the planets? It's impossible. The only way this can be explained is if all the planets were created together at the same time.
- echelon 6y agoThis argument seals the deal. The probability of getting that just right is vanishingly small.
- pfdietz 6y agoA planet formed in another star system would very likely have very different isotope ratios than one formed here. Earth has very similar isotope ratios for most elements to meteorites.