Mars Had an Ancient Impact Like Earth 167
quixote9 writes "The BBC reports on a set of Nature articles showing that Mars had an impact about four billion years ago by a huge asteroid. This was about the same time that a much bigger object slammed into the Earth, throwing material into orbit around our infant planet. This material is thought to have coalesced to form the Moon. 'It happened probably right at the end of the formation of the four terrestrial planets — Mercury, Venus, Earth and Mars,' said Craig Agnor, a co-author on the Francis Nimmo study. 'In terms of the process of the planets sweeping up the last bits of debris, this could have been one of the last big bits of debris.' There's a theory that having a big moon is important to the development of life, because the much bigger tides create a bigger intertidal zone, but people used to think having a huge Moon like ours was a once-in-a-universe event."
Hopefully. (Score:5, Interesting)
people used to think having a huge Moon like ours was a once-in-a-universe event.
And I should hope that they still think so, seeing as Mars does not have a huge Moon like ours... Despite evidence of an impact that COULD have created one, and yet didn't.
Re:Hopefully. (Score:4, Funny)
Re:Hopefully. (Score:5, Informative)
Not sure if that was a joke, but Pluto's composition is far too different from Mars for that to have been the case. Besides, singling out Pluto isn't really rational. Pluto was demoted from planetary status precisely because Pluto isn't that special. It's just one of a whole bunch of similar objects out in the Kuiper Belt.
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Re:Orbital mechanics (Score:4, Informative)
Re:Orbital mechanics (Score:5, Funny)
Or crossing Neptune very closely. And since we suspect that Triton was captured by Neptune as it was forming a couple with a similar body which got ejected away when Triton was captured, we can imagine that Mars' hypothetical Moon was that other body. Now who knows, Mars probably caught that asteroid that made this moon to protect its beloved Phaeton [wikipedia.org], who was ultimately destroyed by the mighty gravitational pull of the ruthless and jealous Jupiter who failed to capture Phaeton in the past despite his numerous attempts, and thus pulverized it to make Mars miserable in retaliation.
Meanwhile, in the solar system. Will Jupiter find out which of the other gas planets threw a Shoemaker-Levy 9 at him? What surprise lurks in the confines of the solar system for Mars' old moon? Are Pluto and Charon about to divorce? Find out in the next episode of Desperate Planets!
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Find out in the next episode of Desperate Planets!
Feh, if I'm going to watch something like that, I'm going to wait for the racier Swingsystem.
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"Will Charon leave Pluto for a real planet?"
Crap, that's what I should have said instead :-(
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That's no moon! It's a, um, what are they calling it these days, "Plutoid" ?
Re:Hopefully. (Score:4, Informative)
People used to believe the world was flat but we don't need to throw that crap into every story about mapping or GPS.
IF you RTFA then you'll find no mention of some freaking 'Huge' moon being necessary to life. I suspect whoever wrote the Slashdot summary read too much Issac Asimov from the 60's, and wanted to seem 'SMRT'.
Check it out here [mountainman.com.au]
Re:Hopefully. (Score:5, Interesting)
IIRC, one special that I saw suggested that while life might have formed in the absence of the Moon, it probably would have been confined to the oceans only.
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The fact is, no one knows how likely it is for a planet to develop life, or intelligent life. We can speculate, but it's a wild guess at best. There's just too much uncharted wilderness out there and we have only one positive event with which to draw conclusions.
Re:Hopefully. (Score:5, Interesting)
Depends on where in the timeline you're talking about. In the first 500 million years after the moon formed, it was so close to the Earth that the tides were 1 MILE high. Can you imagine a wall of water a mile high rolling tens or in some cases hundreds of kilometers inland several times a day? I think that probably had a signficant impact on the weather too, don't you? But who knows, maybe that was good for aiding the formation and establishment of simple life.
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well the fish would have had to evolve feet for that long arse walk back to the water when the tide went out.
it was a joke laugh.
Re:Hopefully. (Score:4, Interesting)
Extreme tides like that may well have helped spur the evolution of life. Proto-microbes washed onto shore and other materials washed back in. Think of it as a big huge mixing bowl.
Some of those microbes may just have gotten stranded. Most probably died. A few probably adapted, living in shallow pools or clinging to rocks.
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Damnit don't make me "google 1 mile in km"
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Duh!
</poe>
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people used to think having a huge Moon like ours was a once-in-a-universe event.
And I should hope that they still think so, seeing as Mars does not have a huge Moon like ours... Despite evidence of an impact that COULD have created one, and yet didn't.
That would make it a once-in-a-solar-system event. There's nothing to say this isn't a common occurrence elsewhere. Unless of course you've observed the complete planetary composition of many other solar systems, which no one else has.
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That would make it a once-in-a-solar-system event. There's nothing to say this isn't a common occurrence elsewhere. Unless of course you've observed the complete planetary composition of many other solar systems, which no one else has.
The point I was trying to make is that we need not adjust our likelihood estimate (whatever that may be) based on a supposed Martian impact, because in fact there IS no large moon around Mars. I think it's likely that somewhere, there is a planet with a Moon like ours.
Re:Hopefully. (Score:4, Insightful)
It means rare. I doubt it's never happened before, it's just a very rare set of events. The size of space (as noted so accuratly in hitchhikers) is big. Really big. That big makes the odds that one rock or the exact size will 'just happen to' hit a young planet of the exact size at the exact direction, while not destabalizing their orbits by increasing the mass.. blah blah... really long odds.
and to add life to that, add the odds that this planet is in the 'livable zone'... add to this the odds that it contains the right materials... add to this the odds that the right chemicals are accessable in just the right places at the right times... add to this that all of that happens at the right time in the planets life... add to that few enough asteroid strikes to prevent obliterating it every few thousand years (Jupiter saves our asses on this)... add to that a bit of luck.
Another effect of the 'really big' portion is that we have a nearly limitless number of chances for this ultra rare occurance to happen.
Of course, to us it seems like it has to happen all the time... I mean hell, we're sitting right here watching it!... but the 99.999~% of planets who were just off the mark will never talk to us about how they see the odds differently.
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And add to all of the above that somewhere else where all this has happened like here, there is a Slashdot site discussing this very matter.
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well ,Mars has two moons .So what responsible for that then ?
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Alien hellspawn invasion?
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no, Phobos was dropped from the sky in '61 and Deimos ejected from orbit a few dozens of years later
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No. The problem with estimating the likelihood of life and planetary formation as we have only seen a single example and not all that well.
It could be that in normal planet formation a planet our size almost always occurs at about this range with similar planets around it and that a large strike like one that formed the moon is a common byproduct of that formation. In fact if you are looking at the probabilities based on examples alone you could surmise this to be extremely likely.
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I think the idea is that if a period of large impacts is a typical stage in the development of a planetary system, rather than a freak and unpredictable accident, chances are significantly greater that it has happened somewhere else as well.
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There are several moons in this solar system bigger than our own, although they all happen to orbit gas giants, so big moons per se aren't unusual.
The "large impactor on Mars" analysis lends support to models of planetary system formation that predict that some really big impacts -- such as formed our Moon -- are quite likely late in the initial aggregation phase. The severe axial tilt (98 degrees) of Uranus is probably the result of a similar catastrophic impact early in its history.
For a very readable bo
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One word : Charon.
For the less-well astronomically-informed out there, Charon, the first-discovered moon of Pluto, is proportionately larger than Luna is in the Earth-Luna system. So, for almost 30 years, having a huge moon hasn't been a "once-in-a-universe e
once-in-a-universe? (Score:5, Insightful)
Re:once-in-a-universe? (Score:4, Funny)
Well, except the creation and the end of the universe ;)
Re:once-in-a-universe? (Score:4, Funny)
Re:once-in-a-universe? (Score:5, Insightful)
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Maybe it was the same collision (Score:1)
What is the evidence pro and con that Mars and Earth are the ones that actually collided, creating the Moon, and then they went spinning away from each other to settle in their current orbits.
Or maybe something big hit an earth which was bigger at the time and made three big pieces, Mars, Moon and Earth.
The composition of the three bodies are quite different so maybe that speaks against the possibility....
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What is the evidence pro and con that Mars and Earth are the ones that actually collided, creating the Moon, and then they went spinning away from each other to settle in their current orbits.
Had that happened, Mars's orbit would not be nearly so circular as it is.
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Now I wonder tho... just how close would they have to come to each other in order to have mingling gravity completely tear apart the surface of each... Mayhaps a collision isn't neces
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Yes, the currently available evidence points to Mars having a liquid core.
>Unless they were coming from very opposite directions and just barely nicked each other, they should have become one.
Consider off-center impacts and conservation of momentum. If the impactor is much bigger than a mere dinosaur killer, then something's going to keep going.
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Re:Maybe it was the same collision (Score:5, Informative)
Re:Maybe it was the same collision (Score:5, Informative)
The two colliding bodies generally merge. IE, "Earth" as we know it didn't really collide with some foreign object that went skipping off into space again. "Earth Mark I" was a somewhat different planet whose remains are still here with us, and it collided with a very large object (essentially a planet in it's own right) called Theia (or sometimes aka Orpheus). Those two would have merged and the collision throw up the debris that formed the moon (which is also made up of parts of both)
So there is no search for the object that hit Earth to form the moon. It's still here with us as part of the new Earth, and Theia/Orpheus is essentially our original planet as well; it's just easier to call the bigger planet involved in that collision "Earth" because, well, it was the bigger of the two.
The same is likely true of Mars - the object that struck it probably merged with it.
As an interesting note, it's also thought that a large impact must have struck Venus as well, and must have hit it hard enough to "flip" the planet, as Venus, compared to every other planet in the solar system, rotates "backwards". There were some BIG things floating around and colliding in the early Solar system.
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Yeah, Venus must have had some fairly...unique event to make it rotate backwards, cause that's just flatly impossible to happen by itself. Debris further away from the sun is moving faster than debris closer, and hence when they merge they're always going to rotating in the same direction. At least on average of the billions of collisions that make the planet. So something really big must have hit the mostly-formed Venus and done something near the end.
Whether things brushed it 'the wrong way' enough to ma
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Debris further away from the sun is moving faster than debris closer,
Really? Kepler's laws [wikipedia.org] of planetary motion (specifically the third law) state that the closer an object is to the sun, the faster the orbit.
If you assume a circular orbit [wikipedia.org], then velocity is calculated as sqrt(G*M/r). Therefore, the radius is inversely proportional to the square of the velocity -- for example, something with an orbital radius 4x that of a closer object will be moving half as slowly as the closer object.
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Debris further away from the sun is moving faster than debris closer,
Really? Kepler's laws [wikipedia.org] of planetary motion (specifically the third law) state that the closer an object is to the sun, the faster the orbit.
Only if you consider angular velocity. In strict distance traveled per unit time, the further away you are, faster you are moving.
This is why in orbital mechanics you add velocity to allow something to catch up to you, and reduce velocity if you want to catch up to something. It's totally counter-intuitive, but in the grand scheme, that's how it works.
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Only if you consider angular velocity. In strict distance traveled per unit time, the further away you are, faster you are moving.
This is only true if everything has the same period, which is not the case in orbital mechanics. When you are talking about stable orbits, the larger the orbit, the slower the object is moving (with respect to the object being orbited). If you don't believe me, check out the wikipedia pages for the planets -- you will see that the further out the planet is, the slower the speed at which the object orbits. It has nothing to do with angular velocity.
Let's take Venus and Earth, for example. Venus' [wikipedia.org] orbit
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The thing I find interesting about the whole debate, is that for as long as I can remember scientists have been vilifying Velikovsky for his theories about exactly this kind of thing, and now all of a sudden (like over the last five years or so), this kind of "Planets in Collision" theory has become the standard view.
Sure Velikovsky was a bit of a crackpot and the specifics of his theories are pretty much made-up, but he was the first person to take a look at the same evidence quoted in this article and evo
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The thing is that you can say anything and 99.9% of the stuff that is said by crackpots is rubbish. Sometimes by pure bloody chance one of them gets it right but that means absolutely nothing. It's like three people saying that a coin flip will be heads or tails or land perfectly on it's side. Sure one of those three people will be correct but that doesn't make his "prediction" any less useless.
Science as a result is based around evidence, theories, experiments and so on. You don't claim X is true simply be
Umm. (Score:5, Funny)
Sorry. Sorry. I had to do it. I'll just shut up now and go to work.
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http://xkcd.com/307/ [xkcd.com]
I don't buy this (Score:1)
Re:Impact Scale (Score:5, Informative)
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It is Imperial. [maybethiswillwork.com]
A slashdot first! (Score:3, Funny)
Someone actually spoke of a beowolf cluster without making a joke!
I hope I've remedied this...
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Well lucky for them they weren't looking for evidence of a scenario that _did_ vaporize Mars!
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lots of things can lead to fluctuations in pools (Score:5, Interesting)
i understand why tidal pools can be thought of as interesting chemical incubators for life with all of the heating and cooling, wetting and drying that goes on, but a lot of other completely common and normal processes that can take place on a moonless planet can also lead to such incubators as well. waves, daily temperature variations, seasonal fluctuations, geography, etc.
the moon does make us an interesting little quasi double planet system. but i think that that uniqueness does not go hand in hand with our planet's other unique trait, life. correlation is not causation looms large in my mind on this idea that the moon gave the earth life. no, the earth's chemical makeup, temperature, and atmospheric pressure putting us near water's triple point, with a lot of water around: that gave us life. every other detail seems secondary and not mandatory
Re:lots of things can lead to fluctuations in pool (Score:2)
I was under the impression that the importance of the moon was linked to the fact that it causes our planet to have cyclical seasons; namely the gravitational pull of the moon helps keep the poles more-or-less stable as opposed to having a more exaggerated wobble. This was from The History Channel's show "The Universe" so take it with a grain a salt...they end up talking about some wacky things on that show sometimes :)
The moon does a lot of different things... (Score:5, Informative)
There are several things that our extremely large moon does for us that make life much more comfortable.
#1 is of course tides that are more extreme than the sun could generate
#2 rotational speed. The moon has kept our rotation from slowing as much as it should have. Shorter day/night cycles are important for environmental management.
#3 atmosphere. The moon helped reduce the density of proto-earth's atmosphere. Without it we probably would resemble Venus.
#4 plate tectonics. The tidal influence on the crust heats up the mantel and keeps the plates from sealing
#5 protection. The moon intercepts a large percentage of the impacts destined for earth. This reduces the disruptions caused my meteor impacts. This was more pronounced earlier, when the moon was closer and when it was even more important (more meteors around)
#6 increased metal content. Since the moon is almost entirely light minerals, most of the metals that were in the original impact were left on earth which artificially increased the concentration of metal in the crust.
While I can think of other things that could help with one or two of these, I can't think of something that would satisfy all of these consistently for a few billion years.
What do you suggest as an alternative?
Re:The moon does a lot of different things... (Score:4, Informative)
Actually, the moon, by displacing a large portion of the mass, has prevented the earth from being as tidally locked to the sun as it should be.
Since the earth-moon system presents a profile to the sun that is constantly changing, the sun's gravity can't tidally lock the planet. Mercury is tidally locked. Venus almost is. Without the moon we would have have a day length of several months. Notice how Mars has a day a little longer than ours and Jupiter is at 15 hours for a day.
What you are thinking about is the tidal friction between the earth and moon. Yes, this ALSO slows down the earths rotation but it is a much slower process and provides benefits which I outlined in my prior post, namely plate tectonics and a molten interior.
Tell me, what else do you think is incorrect?
Re:The moon does a lot of different things... (Score:4, Informative)
Tidally locked means that one face (the denser one) of the satellite always faces the parent. Currently the moon is locked to the earth. In time the earth MAY lock on the moon but that is unlikely because the moon's orbit is gradually expanding (due to tides) and the effect is gradually decreasing. But I don't believe there is an example of a parent tidally locking on a satellite (Pluto and Charon are essentially orbiting each other therefore both are parents)
When compared to literally every other satellite system in the solar system except for Pluto-Charon, the moon is a gigantic proportion of the earth's mass. The primary protection from locking on the sun is because the mass distribution shifts. Therefore there isn't one "face" of the earth-moon system that is denser all the time.
The primary source for #3 and 4 is venus. Venus is almost the identical size. While venus has higher solar flux that doesn't explain the dramatically thicker atmosphere, lack of plate tectonics and much colder core. The moon is the only other difference. So it is either the large satellite or the impact that cased the differences.
#5 and 6 are related. We know that the moon is significantly less dense than earth. We know that the earth is denser than venus even though they should be almost identical. We know that the earth and moon have essentially identical isotope ratios. Since the moon is less dense it's radius is large in ratio to earths which creates a shield that blocked up to 20% of the impacts earth would have experienced. Since the earth has a over large percent of metals, they WOULD get distributed throughout the planet. Mostly to the core but also to the mantel and crust. Since it is higher than expected, the amount of metal in the crust is higher than expected. Metals are vitally important to life. Since the moon is metal poor and that the similar isotope ratios prove that the earth and moon are formed from the same mix, it is only reasonable to assume that the higher metal content came from the impact that created the moon.
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The accurately explains the content of the atmosphere, 95% CO2 and a mix of others. It does NOT explain why Venus has 100 times the atmosphere for a nearly identical planet.
All the calculations suggest that Earth's atmosphere SHOULD be much thicker than it is. The reason it isn't is because much of the proto-Earth atmosphere was blown away during the impact and the moon, especially early on when it was much closer, provided enough tidal effect on the atmosphere to let some of it escape thus reducing the o
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Current numbers say that the core should be Significantly cooler than it is even considering radioactive decay. Venus, almost the identical size as earth has not tectonic plates and it's core is approaching solid. The only difference is the moon. The moon causes the earth's crust to warp which generates heat. This is the same thing that Jupiter does to Io but on a much smaller scale. The internal (thermal) convection followed by slab pull is powered by the tides caused by the moon.
As for #6. Yes both
Re:lots of things can lead to fluctuations in pool (Score:2)
Life? Don't talk to ME about life! (Score:3, Interesting)
If there were no moon it would have happened differently.
There is no proof or even indication that it would or wouldn't have happened at all. Life must be pretty damned special* because we've found no indication of it elsewhere. We've had probes to most of our star's planets and not found any hint of life anywhere yet, we've had SETI running for a long time and no indication at all that there's anybody out there.
We don't even know how life started on earth. So far, we DO know that life is unique to Earth in
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I'm all for SETI, but the amount of time that we've been using SETI is ridiculously small considering the size of the universe, the time we have to deal with, and the fact that we're searching only limited bands of spectrum.
To offer a horrible analogy, SETI is like a team or researchers looking for an unknown bacteria up in the Himalayas by standing in a basement in Wichita, Kansas and shouting one time "Wher
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True, but the point stands that there is no indication whatever that there's any life anywhere but earth.
Personally, I'm of the opinion that we most likely will find life of some sort. I also suspect that we may run across sentient life and not only not realise it's sentient, but even that it's alive.
The late Chief Dan George's character in Little Big Man had an observation (that I'm surely not quoting exactly since it's been years since I've seen that movie): "The Indian thinks everything is alive; the peo
Once in a universe? (Score:5, Insightful)
Re:Once in a universe? (Score:4, Insightful)
Actually it's more like a twice-in-a-universe event... just look at Pluto and its moon.
Re:Once in a universe? (Score:5, Informative)
Pluto and Charon aren't formed the same way. Charon really isn't even a "moon" at all, since rather than it orbiting Pluto, the center of mass is well between the two of them, and instead they orbit each other. They were almost certain separate bodies that simply became gravitationally bound to each other.
As well, Charon, in the inner solar system, wouldn't make much of a moon at all. The higher heat would essentially turn it into a comet that would melt away much of it's surface area, and reduce it's already pretty low mass.
Though I'm not sure about "once in a universe" odds, for 1 very, very large rock to become gravitationally bound in a STABLE orbit around another, without the two impacting (or, this system forming as a result of an impact), does seem like it'd be incredibly rare. Again though, "seeming" incredibly rare is indeed a guess on my part, and our sample size isn't large enough to really determine just how common it is.
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Pluto and Charon aren't formed the same way.
It is actually quite possible that Charon formed in exactly the same way as the Earth-Moon system. See this abstract [harvard.edu]. Most modern planet formation simulations show that the end stage of formation involves collisions between large proto-planets. Whether or not any particular giant collision results in a satellite or not depends on the details such as impact velocities and angles. Double bodies such as Earth-Moon and Pluto-Charon are likely to be relatively common outcomes given what we know of planet fo
Re:Once in a universe? (Score:5, Informative)
I seem to recall that a mechanism had been proposed whereby the material for the colliding body collected at a Trojan point, from which is was dislodged once it reached sufficient size - after which collision with the proto-earth would be just about inevitable. If the mars collider formed in the same way then collision with a large body could be pretty much normal in our sort of system and the incidence of large moons might be very high indeed.
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It is interesting that there's evidence Earth was hit by a large impactor, forming the moon, Venus was hit by a large impactor, flipping it's spin, and now Mars was hit by a large impactor.
That's three for three for the large terrestrial planets.
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It might be surprising that all three planets were hit but such big impactors. It does make it more likely that large moons like ours could form if every planet gets routinely whacked by planet sized rocks.
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Pluto and Charon aren't formed the same way. Charon really isn't even a "moon" at all, since rather than it orbiting Pluto, the center of mass is well between the two of them, and instead they orbit each other. They were almost certain separate bodies that simply became gravitationally bound to each other.
No. The problem is that in a two body system, you have two states, already captured and continues to orbit indefinitely, or never captured and the objects escape from each other. This depends solely on the total energy of the system. Too high and the bodies escape each other. Any gravitation interaction that results in a paired system like that and doesn't involve a collision to dissipate kinetic energy, requires, a third body to siphon off the excess energy. There's no way to transition between unless on
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Next you're going to tell us that the earth-shattering kaboom was what made the dinosaurs go extinct.
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Actually, if you want to look at a sample size of 9 then you've got TWO large, unitary moons. Pluto's moon Charon is even bigger in relation to the planet than ours is.
Paging Capt. Obvious (Score:2)
I feel more educated now.
My god, he was right! (Score:2)
We can expect the heavens to rain manna from Mars upon us at any time.
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How's that? Velikovsky's principle claim was that Earth has come very close to Venus and Mars in historical times, and that Venus was ejected from the Sun (again, very recently) and is still hot from that.
Getting smacked by a large impactor during the formation of the solar system has pretty much nothing to do with Velikovsky's theories.
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Once-in-a-universe stats source: (Score:3, Funny)
"Billion Nagasaki bombs" as a value (Score:4, Funny)
From the article
I think after the first billion Nagasaki bombs, you just say "energy equivalent to being struck by the Moon".
Nit picking, I know, but how can you even wrap your mind around that number of atomic bombs?
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I notice that the unit we're using here is "Nagasaki bombs" or "bombs like the one dropped on Nagasaki in 1945". Clearly the solution to this problem is to build and drop some bigger bombs.
Well actually we've made and detonated bombs up to 4,000 as powerful as Hiroshima/Nagasaki bombs (different tech, same power). But I agree, at this point, nobody realises what it means anymore. I suppose that instead of Hiroshima bombs, we express astronomical collisions in Libraries of Congress of TNT.
Not exactly (Score:5, Interesting)
Mars Had an Ancient Impact Like Earth
No it didn't. Like Earth, Mars had an ancient impact, but the impact itself was decidedly NOT like the impact Earth experienced.
Earth's impact obliterated the Mars-sized object that impacted earth, leaving a ring of ejects circling the Earth. The ring coalesced into the moon. This didn't happen on Mars; Mars has no giant satellite, only two small moons.
Also, I saw a few different accounts, and not everyone is yet convinced that the disparity between Mars' poles was caused by a giant impact. The San Fransisco Chrinicle, for instance, says [sfgate.com] "Huge impact may have divided Mars surface".
An interesting, yet probably non-answerable question occurred to me - If an object did smash into Mars, rather than hitting pole-on as the theory says (and I'm no astrophysicist and can't even spell it properly), which seems improbable to mee, seeing as how all the orbits of all the crap circling the sun seem to lie on a plane, could it have struck Mars' pole and then hit the next planet in (Earth), causing its moon?If this could have happened, could life have been on Mars at he time but completely wiped out, with its remnant chemicals starting life over on Earth?
There have been meteorites that are Martians [wikipedia.org].
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Not new (Score:3, Interesting)
Where's the ejecta? (Score:4, Interesting)
If this is true (a glancing blow by a huge object), I'm confused as to where the debris ejected from the collision would have ended up? Certainly not everything would have ended up melding with the main planet, especially (again) if this was a glancing blow. I'd expect some sizable amount of mass to be blown into orbit, as happened in the Earth-Moon formation event.
Mars's two moons are incredibly tiny - IIRC more like smallish asteroids - so no coalescence of debris into a larger satellite as we have.
Someone more awake in astrophysics class maybe can help with this.
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Depending on how it hit the debris may have been put into a retrograde orbit which is less stable.
Mars is significantly smaller so it is not able to hold onto it's satalites as easily...it could have escaped.
The collision is smaller than the earth-moon collision. There may have been less matter kicked up.
If it was very glancing then any debris would have more than escape velocity anyway...
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I'm here ;)
Collision (Score:2)
valcano activity (Score:2)
I'm sticking to my belief that the core of the planet blew out through Olympus Mons. Just the mental image of the planet squirting out magma like a massive pimple is too cool to give up.
where's the picture (Score:2)
Where's the picture of the crater?
The Moon (Score:2)
The moon keeps the core of our planet from turning into a brick like Mars. It keeps the internal forces churning to keep it molten, keep volcano's active and to keep the gases coming out of the rocks and into the atmosphere.
Which is why we should make a big moon on Mar's to terraform it.
uh ... really? (Score:3, Funny)
First off, I don't care how hard that astroid hit, it's not sending stuff into space. If the entire earth was made out of TNT and you set it off, the gravity would pull everything right back together again (this is true according to Dr. Melvin A. Cook [wikipedia.org]).
Second, it would seem that from an analysis of the composition of the moon and the composition of the earth, that they really aren't made out of the same stuff.
Not too surprised (Score:2, Funny)
I mean, Mars is a lot closer to the vacuum cleaner planets. Jupiter is like a Hoover, Saturn like a Dyson and Neptune is one of those water vacuums you see on late night TV. That's why Uranus is lying on its side, its falling asleep watching Neptune.