Talk:Late Heavy Bombardment
|WikiProject Solar System / Moon||(Rated C-class, High-importance)|
|WikiProject Geology||(Rated C-class, Mid-importance)|
|WikiProject Astronomy||(Rated C-class)|
- 1 Re-adding of the critisims section
- 2 Mya
- 3 Yet another scenario
- 4 Noble gas proof
- 5 Nice model
- 6 Wait a minute...
- 7 What's so late about the "Late" Heavy Bombardment?
- 8 "million" or "billion" years ago
- 9 "Artist's" impression
- 10 Overly cautious
- 11 Fifth gas giant hypothesis Section
- 12 Role of LHB in supplying earth with water
- 13 There's Gold in them thar LHB
Re-adding of the critisims section
I notice this section has been re-added. I had originally removed this because the later data suggests that the "single impact" theory does not hold water. Given that some of these meteors are assumed to have come from the dark side, the "lower bound" at the same figure is extremely strong evidence that the Apollo rocks are genuine and not derived from Imbrium. The same argument is strong evidence against the second claim as well. Further progress in geochronology has pretty much ruled it out anyway, something that is covered (in passing) in one of the other refs I posted. I'm all for leaving these comments in, but the way the are presented leaves much to be desired. I believe the "back and forth" of history presents a valuable insight into thr workings of real-world science, and that separating the arguments breaks this chronology. For instance, the single impact concern now appears later than the evidence that is used to counter it. To the reader this suggests that the evidence in question does not have an answer (an astute reader might notice this, but that's not the point), and further it seems confusing because that line of argument predates the meteor information. I'm also a little worried about the wording of this section, because it seems to suggest something is "amiss" in the fact that the meteors date to a spread of times, but this is precisely what one would expect, it's the "lower bound" that is so interesting, for exactly the same reason that the "lower bound" is so interesting here on Earth. Maury 12:47, 7 March 2007 (UTC)
- Many respectable scientists do not believe the cataclysm hypothesis, and that is why I added an up to date reference by Bill Hartmann (he is one of the founders of the "crater chronology" method). I thought that the way it was written in the previous version misleadingly would lead someone to believe that the scientific community now believes that the case is nearly closed, which, as a lunar scientist myself, I can say it is not. Recently, even some of the dynamicists are beginning to question whether the data actually require a cataclysm. Perhaps we could have a "history of the cataclysm hypothesis" section, but I think that such a controversial topic also needs an "evidence for" and "against" section as well. When I get some more time, I will add more references. I am somewhat busy in real life right now preparing for the upcoming lunar and planetary science conference. Lunokhod 13:33, 7 March 2007 (UTC)
- Well I'm sure that "respectable scientists do not believe", but that's a hopeful sign. My concern is really about the presentation. Perhaps we could return to the historical overview layout, and then add another section called "ongoing debate" or something similar? Maury 16:57, 7 March 2007 (UTC)
- This is not meant as a challenge, Lunokhod, merely a request for information: can you give a pointer in the technical literature to doubts among the dynamicists? I recently heard a talk by one pushing the cataclysm idea. BSVulturis 22:19, 19 October 2007 (UTC)
- I think we should keep this in prospective; You will always find orders of magnitude of greater information supporting a new idea than information trying to debunk it. I don't think we should compare "believers" vs. "non-believers", or talk about *who* believes or does not, as that should hold some importance in a logical argument over what is true. I think we should describe the hypothesis, and describe logical reasoning as to why it may be wrong, like everywhere else on Wikipedia. Science is not a faith. The reader can form their own conclusions, but only if we provide them with the actual thinking out there on the subject. I think which great mind thinks it is right or wrong is trivia. An article describing a hypothesis should just describe how it may be right and how it may be wrong, and list evidence, not a celebrity list. Onexdata (talk) 16:30, 25 July 2012 (UTC)
Does "Mya" stand for "million years ago"? If so, we should explain that somewhere, and remove the "a" in contexts where the "ago" is not appropriate. If not, what does it stand for? --Doradus 18:00, 9 July 2007 (UTC)
- Point taken, fixing... Maury 20:52, 9 July 2007 (UTC)
Yet another scenario
- Jupiter migrated inwards and disrupted the asteroid belt to throw boulders around.
This they base on careful asteroid counting, but on the other hand they cathegorically dismiss most earlier time lines based on crater counting in the outer solar system ... Said: Rursus ☻ 17:32, 4 August 2008 (UTC)
- Eahgmgrrlmbl... compatible with the gas giant migration scenario, but nothing else. Said: Rursus ☻ 17:57, 4 August 2008 (UTC)
Noble gas proof
isn't a proof – just an important argument – this site argues that the current overabundance of noble gases is best explained if earth was bombarded by circa 0.5% of KBO:s alongside the asteroid material. Said: Rursus ☻ 19:57, 4 August 2008 (UTC)
The Possible Causes section needs rework (the first two sections say the same thing), and will be linked in content-wise to the corresponding section in Nice model, which is under construction. Iridia (talk) 07:51, 22 March 2009 (UTC)
- Ok, now the sentences are closer to their refs, fixing the problem that was the original source of my thought that they said similar things. Iridia (talk) 08:17, 22 March 2009 (UTC)
Wait a minute...
The "second criticism" states that it is a problem that the oldest rocks at from 4.1 bya. However, this is only a problem if it is assumed that the Moon formed earlier than this, which is not mentioned (and needs to be). Someone got a ref for this argument? Maury Markowitz (talk) 20:44, 7 July 2009 (UTC)
What's so late about the "Late" Heavy Bombardment?
Isn't this a pretty early period of the earth? Or was there also an "Early Heavy Bombardment" at some prior time? Please explain why it is called "Late" at all. -- 22.214.171.124 (talk) 07:35, 16 June 2010 (UTC)
- As far as I understand this, it's called 'late', because the apparent sudden increase in the rate of bombardment by asteroids/comets does not fit with the expected gradual reduction in impacts following the formation of the planets/moons, see here . Mikenorton (talk) 09:00, 16 June 2010 (UTC)
"million" or "billion" years ago
I notice a conflict between two wikipedia articles and am guessing it is merely a mistake of one letter for another.
In this article "Late Heavy Bombardment" - it is stated that this cataclysmic event occurred "4.1 to 3.8 billion years ago."
However, according to the article "Timeline of evolution" this event occurred 3.9 MILLION years ago.
- As I see them, these two articles are in agreement - one saying 4.1 to 3.8 billion, the other one saying 3900 Ma (million years). Mikenorton (talk) 21:26, 5 July 2011 (UTC)
The picture File:Lunar cataclysm.jpg, described as an "artists's" impression of the moon during the Late Heavy Bombardment, is too artistic and has very little in common with reality. It was extremely improbable that there were two impacts on the Moon at the same time even in that time, in fact there were quite long periods beween individual impacts. The article says that on the Earth "serious environmental damage would occur about every 100 years". The Moon is even smaller, so the rate of impacts would be significantly lower too. Therefore I consider the picture very misleading, no matter how impressively drawn it is. Jan.Kamenicek (talk) 17:39, 9 January 2012 (UTC)
- Very good point but observing even a single impact is still highly unlikely using your "once every 100 years" measurement. A drawing of a red moon would be silly and would convey nothing. I think the artist used 2 impacts to show that the moon was bombarded, and not struck a single time. This image is attempting to indicate a very large (chronologically speaking) event, I think the illustration is trying to describe it in a single image, not so much trying to depict a "snapshot" of what you might see at any particular time during the event. Onexdata (talk) 08:58, 22 July 2012 (UTC)
This article is very informative, but I think could probably push the Nice model a bit more, and probably be a bit more confident (though clearly not 100%) that the LHB does exist. In particular, I'd dispute "The evidence for this event comes primarily from the dating of lunar samples, which indicates that most impact melt rocks formed in this rather narrow interval of time" in the intro. It's true that the Apollo samples led to the original formulation of the hypothesis, but this is now substantially supported by dating of impact ages for lunar meteorites, as well as impact-resetting of general meteorites, and of ALH84001 - this is noted later in the article, but is a bit misleading up front (see, e.g., Strom et al., 2005, Science v.309). In the criticisms section, the first concern has largely been addressed by thinking about the wider meteorite population (note the reference date is 1998). It's valid to note, but is by no means a watertight argument. The second argument is more sound, but is presently uncited, and again may well not apply to the meteorite dating.
There also needs to be a line somewhere in the article that makes it clear that the LHB isn't meant to be envisioned as an "on/off" event with a well defined end, but rather (under the Nice model, and probably the others too) would give a gradual (~exponential) tailoff. Hence the statement "Nevertheless, the ages do not "cluster" at this date, but span between 2.5 and 3.9 Ga," which as placed at the moment is very disparaging about the hypothesis, is in fact completely compatible with it.
I think my basic point is that from my knowledge of the planetary community, most people would regard the LHB as pretty likely (even though not 100% proven), and that if it does exist, it's almost certainly through the Nice model or a variant of it - due to its wide-ranging explanatory power. Those other hypotheses are decidedly "niche", and we should be noted as such. The article doesn't really reflect these two things. DanHobley (talk) 22:03, 17 May 2012 (UTC)
- I disagree. I actually think this article is too biased in support of LHB theory. I just took an astrophysics course that covered the formation of the Earth in great detail, and my professor stated that Late Heavy Bombardment is highly controversial at best. The majority of the astrophysics community views the theory to be a solution without a problem, or an unlikely idea without evidence. As you said, the theory arose from the dates of the Apollo samples, all of which were taken from the moon surface, not from deep drilling, and all of which were taken from a single, incredibly small sample area, and all were inside a single large impact crater. He pointed out if this single sample were taken on Earth, the rock dates would indicate absolutely nothing, and anyone who went as far as suggesting a theory that contradicts all known evidence from the sample would be labeled a quack.
- Also, the Apollo samples actually coincide very nicely with the oldest dates found on Earth, and this actually supports the more widely accepted view that the moon may have had a Hadeon eon like the Earth, and indeed, all peer reviewed accretion models shows massive objects the approximate size of the moon or larger that accrete over what is accepted as the Hadeon eon would have gained incredible temperatures due to impact energy unless the accretion particles were gases (and moon and Earth makeup show this is false). So their surfaces would have been very high temperature molten rock while they accreted in the period in which we currently believe they did. This would reset rock dating, which explains why we find modern meteorites with dates older than 3.9 billion years, because they arrive from space sometime after the hadeon eon and were made up of protoplanetary formations, but we do not find any Earth or moon rocks older than 3.9 billion years.
- Indeed, this evidence is the actual basis of existing theory of the Earth's history. It is called the Hadeon eon and standard accretion. The Late Heavy Bombardment is a theory that arose out of the dating of a single moon sample as you say, and does not answer any questions the scientific community has, it is simply a minority view of something highly unlikely that may have happened with extremely little evidence to support the claim.
- Suggesting that there was some unlikely event to explain the finding of rock dates that were actually predicted by standard accretion theory is adding complexity without any reason. There is no reason for it to become widely accepted unless there are findings that are not explained by existing theory.
- In my personal view, it is akin to suggesting gravity exists because of an acting force. Perhaps that is true, but we discovered a theory that explains that gravity can exist without an acting force, (just as standard accretion theory explains all known rock dates without LHB theory).
- There should be supporting evidence of an unlikely event that cannot be answered with another theory, but indeed, existing theory, as far as I am aware, also explains any evidence people use to support LHB theory. The simplest answer is usually right. Onexdata (talk) 09:01, 22 July 2012 (UTC)
Fifth gas giant hypothesis Section
In this section, we blithely tell people that Jupiter lost angular momentum, and so went further from the Sun. This is bit like applying the brakes to go faster. An orbit with less angular momentum is closer to its parent, not further away. One must add energy to do lifting. Wayne Hardman (talk) 01:06, 9 September 2012 (UTC) Quite right, angular momentum obviously increases with an increasing orbit . And the planet is refered to as both a gas giant and an ice giant. Usualy giant planets are one or the other. — Preceding unsigned comment added by 126.96.36.199 (talk) 08:04, 19 March 2013 (UTC)
- Y'know how water is soft but it really hurts to jump from the high board? Well a planet the size of Jupiter or Saturn has so much pressure at the bottom of its atmosphere (space probes are squashed like a bug only a fraction of the way into the atmosphere) that solid surface (ice) or virtual surface (gas) is immaterial (Radar reflection surface due to density gradient). (Surface of the Sun is "soft" gas and plasma but still a collision if you jit it.) Since both planets have clouds of Ammonia, Methane, etc. we can assume perhaps a liquid surface, however He/H2 would probably be above critical point (temp and pressure) before that. All of these are made up of frozen what-we-call gases, they do fit the "gas giant" moniker. Interesting to note that Jupiter like Earth are the only planets that radiate more energy than they recieve from the Sun. Like the movie "2001", interesting to see if sending a nuclear weapon would ignite it. Shjacks45 (talk) 08:36, 11 October 2013 (UTC)
Role of LHB in supplying earth with water
I think that there should be a section on the postulated importance of the LHB in supplying the earth's water, as referred to at . As I understand it, it is thought that very little water would have survived the conditions on the early earth, and comets during the LHB may have been crucial in providing the water to fill the oceans and make plate tectonics and advanced life possible. I could have a go at this, but it is probably better done by an editor more expert than me. Dudley Miles (talk) 23:00, 25 November 2012 (UTC)
- Elemental distribution of Earth is different than Solar System. Earth has a Iron-Nickel core based on indirect data and dearth of expected Iron and Nickel. In fact there is a underrepresentation of Ferrophilic and Carbide forming elements (elements that can alloy with Iron like Carbon, Hydrogen, Chromium, Thorium, et al). Carbon and Hydrogen dissolved in molten Iron will react exothermically with Iron Silicate (Mantle Olivine) generating more Iron and Water and Carbon Dioxide. Water and Carbon Dioxide at high pressure (above the critical point) liquify rock although Magma formation is supposed to be an upper mantle thing. Just a thought. Shjacks45 (talk) 10:10, 11 October 2013 (UTC)
There's Gold in them thar LHB
See http://www.sciencedaily.com/releases/2011/09/110907132044.htm Assuming ferrophilic heavy metals were lost to the core and redeposited in the crust via LHB. Explanation for differing elemental abundance for Earth versus the rest of the Solar System in Abundance of the chemical elements. Of course Earth and Jupiter are the only two planets that emit more energy than input by the Sun. Higher amount of radioactive elements on Earth (assume Jupiter is "cold fusion", don't laugh, its got a few million PSI) mean fission products add to rare metals and gases (consider He3/He4 is higher on Earth than System or Sun). Another source noted that concentration of Gold and Noble metals in rock samples is higher than rocks older than 3.8 Billon years old. Of course this suggests a Gold rush for Moon dust? Shjacks45 (talk) 09:58, 11 October 2013 (UTC)