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Is Jupiter Earth's Cosmic Protector?
Hugh Pickens writes "Last Sunday, an object, probably a comet that nobody saw coming, plowed into Jupiter's colorful cloud tops, splashing up debris and leaving a black eye the size of the Pacific Ocean — the second time in 15 years that this had happened, after Comet Shoemaker-Levy 9 fell apart and its pieces crashed into Jupiter in 1994, leaving Earth-size marks that persisted up to a year. 'Better Jupiter than Earth,' say astronomers who think that part of what makes Earth such a nice place to live is that Jupiter acts as a gravitational shield, deflecting incoming space junk away from the inner solar system where it could do to humans what an asteroid apparently did for the dinosaurs 65 million years ago. 'If anything like that had hit the Earth it would have been curtains for us, so we can feel very happy that Jupiter is doing its vacuum-cleaner job and hoovering up all these large pieces before they come for us,' says Australian amateur astronomer Anthony Wesley, who first noticed the mark on Jupiter. But others say the warm and fuzzy image of the King of Planets as father-protector may not be entirely accurate. In 1770, Comet Lexell whizzed by the earth, missing us by a cosmic whisker after passing close to Jupiter. The comet made two passes around the Sun and in 1779 again passed very close to Jupiter, which then threw it back out of the solar system."
It's a bit like saying one speck of dust is protecting another speck of dust from other, smaller dust, as they swirl around an eddy of warm air in a coliseum.
Is Jupiter Earth's Cosmic Protector?
If this is true, it gives us another criteria to look for in distant solar systems that we suspect may harbor life or that we would like to colonize: a large shield planet in the same system capable of leaving the smaller world to develop uninterrupted.
It is interesting to wonder if our odds increase or decrease on being hit when there is a large massive body in our solar system. Like the article and summary say, some objects that would not have come close could be put on course for earth via Jupiter's gravitational forces. Who knows, maybe massive bodies like Jupiter pull more space debris into our system and make it more hostile than if it were just the earth orbiting the Sun?
My work here is dung.
Sorry for the dangling preposition in the subject, but regardless of whether or not Jupiter acts as a magnet for dangerous astral bodies, I wonder how risky it is to leave that job to Jupiter.
We have seatbelts in cars despite the mandatory brakes which are installed. We have random personal screenings at the airport even though we have a standardized process of metal detection and baggage scanning. We should not just sit idly without a comet/asteroid detection and elimination system just because Jupiter is catching the big ones for us.
We've been hit before. I don't want to get caught in the slamming door. How about some information, please!
... is the fact that eventually we have to get off earth and learn how to survive in the hostile universe anyway.
Now if Jupiter were like my boss, it would fling those comets at the earth with the message: "This issue is escalating rapidly. I need you to work on this today; send me status before you leave."
That Jupiter really sucks?
In astrology, Jupiter is considered the "greater benefic," the planet that bestows fortune, luck, and positive benefits.
Just sayin'.
The Earth will eventually be wiped out, obviously. We can't get lucky forever.
We'd better spread outselves out.
The current STS-127/Expedition 20 mission has shown us that troubleshooting a malfunctioning urine-recycling toilet and a tripped circuit breaker on a carbon scrubbing unit are far easier to fix in LEO than out father, especially considering how critical both systems are to a more distant mission.
Up, Up, Down, Down, Left, Right, Left, Right, B, A, START
The Earth has not yet faced a galaxy coming straight at it.
This reminds me of that anti-tiger rock I keep in my sock drawer?
That rock is so good, damn tigers are dieing out in India. Maybe Jupiter has similar effect on galaxies?
Mit der Dummheit kämpfen Götter selbst vergebens
Is it actually more likely for a body to be directed away from Earth than to Earth by Jupiter? I mean, it seems that a body not destined for Earth could otherwise hit if affected by Jupiter's gravity sufficiently.
Jupiter is the only planet in our system close enough to the sun and with a deep enough gravity well for them to have a barycenter (common orbital center) outside the sun's surface. That sort of wobbly orbital mechanics has far more effect on trajectories of small bodies than a nice, neat set of concentric circular orbits. The sun-Jupiter system will be more likely to cause fluctuations that result in small interlopers to get thrown out of the system or sucked into one of their gravity wells. Seeing the result on Jupiter is rare. Seeing it at the sun is more common. Between the two they're going to suck up far more than hit elsewhere.
But their influence is only the majority of a chaotic multi-body system. Just because they account for the most hits doesn't mean they take them all and nothing gets through elsewhere. Of course some will miss the big guys and hit (or nearly so) some of the others. That's the nature of a chaotic system of orbital mechanics. They are not exerting influence in an intentional manner, rather a deterministic but fairly unpredictable manner.
To assume a certain thing always happens because it has happened, and also to say it not accurate because there is an exception, is the sort of low caliber absolutist thinking that's common in "modern" science reporting. I have no doubt the parties credited with these viewpoints understand quite well the situation, and the apparent controversy is a function of the author of TFA.
"I may be synthetic, but I'm not stupid." -- Bishop 341-B
I don't want to get caught in the slamming door. How about some information, please!
We have reason to believe that you have fallen a victim to weapons of psychological warfare.
For your own good, turn of your audio and video receiving devices as well as any audio or video player and go get some sleep.
Mit der Dummheit kämpfen Götter selbst vergebens
Why not correct your dangling preposition rather than apologize for it?
the far side is much more cratered than the front side which shows how the Earth
...which is much larger than the moon, protects the moon from impacts more than the other way around.
"You're right," Fisheye says. "I should have set it on 'whip' or 'chop.'"
He just had a bad day.
After realizing what he did, he flicked that comet as far away from Earth as possible. And he said he was sorry.
The comet was never seen again. Lexell, after conducting further work in cooperation with Pierre-Simon Laplace, argued that a subsequent interaction with Jupiter had further perturbed its orbit, either placing it too far from the Earth to be seen or perhaps ejecting it from the Solar System altogether.
Mit der Dummheit kämpfen Götter selbst vergebens
It makes me wonder if, over time, all that added gravitation might not start to degrade the orbit somewhat, to say nothing of a possible single large impact.
Stop making sense!!!
the planets orbit in a plane, and the origin of most comets is in the outer solar system. Therefore, over time, Jupiter has indeed cleaned up many comets for the Earth.
We have to get our eggs off this speck of dust.
I find it amazing and worrisome that an object that size can get so close to Earth and hit Jupiter without astronomers learning about it until after the fact. To me, it is an indication that current near-earth object surveillance systems are not worth much.
Well, kind of, but look at it this way. If the Moon was a lone planet, it'd get craters everywhere equally. But it's not a lone planet, instead it has a bigger body always on the same side of it. Therefore, that there should be more impacts on the opposite side tells you that asteroids are quite attracted to Earth and that the Moon catches a lot of the when its on their way.
You just got troll'd!
Are you sure about that? Because while it surely attracts asteroids away from the Moon, it always attracts asteroids towards the couple to begin with. So are you really sure that the Moon is getting less than it would if it was alone?
You just got troll'd!
If the word logically doesn't offend you in that context. The largest temple in Rome was that of Jupiter Optimus Maximus on the Capitoline Hill (Wiki). So the Romans at least worshiped deities of some real world benefit.
/s
Jonti Horner and BW Jones have written a series of papers on this, summarized in this Astronomy and Geophysics article The first paper deals with the Asteroids. The second, in press, considers the Centaurs The third, of perhaps most relevance to this discussion, considers the Oort Cloud objects.
(To simplify the simulations, Earth was inflated to one million times its actual size. A juicy target indeed)
With Shoemaker-Levy I could understand how Jupiter could catch a comet, but what I don't understand is that the comet subsequently can run into Jupiter. I mean, shouldn't it continue orbiting around Jupiter just like the other moons around Jupiter do?
Bert
This is the exact reason we need thermonuclear hydrogen bombs stationed in outer space, ready to shoot: Unlike the dinosaurs, we don't have to be sitting ducks, we have the ability to defend ourselves against incoming comets. The problem with stationing bombs in outer space is an issue of trust: people down here still haven't figured out how to live in peace and leave each other alone, the UN is still not a functioning body of world government, people still play the "I don't trust you, I'll kill you before you kill me"- game, and call it self defense. So there is a distinct possibility that bombs stationed in outer space are directed back at Earth by people who are mad at each other, and can't just take it like a man, or can't stop dishing it out so others have to take it like a man. Possibly the bombs could be stringed out and stationed very far, into solar orbit past Mars near the asteroid belt, and Earth could carry many layers of inner defense shields, that stop any stray bombs that are hijacked, with some finite reaction time still left. The good part about having the bombs(and their observatories) extremely far is that the farther the comet is deterred by a minute angle on its path, the less effort is needed. So the benefit to risk ratio is better, because a bomb hitting Earth would only cause a localized damage, compared to the same force being able to deter an object the size of our moon by that 1 degree on its path to just miss Earth. The downside of going very far, is that it's easy to have stringed out objects in a solar orbit in a plane, as a circle, but it's hard to cover a sphere, like GPS does, because the paths might cross, and minute gravitational fluctuation might cause some of the objects to collide. Maintaining very many bombs that are far, compared to the much fewer required that are very close is also an issue, especially from a hijacking standpoint. A few bombs hijacked and hitting Earth would cause a local catastrophy, but if all the bombs that are very far are hijacked simultaneously, and redirected to Earth, that could be worth than the problem they are meant to defend against. A possible best solution is having habitable outer space stations, http://en.wikipedia.org/wiki/O'Neill_cylinder, cylinders that provide artificial gravity on the inner surface by rotation/centrifugal force, and are built triple layered gradual vacuum against air diffusion/leaks, and extremely heavy walled to protect from outer space radiation to replace Earth's atmosphere (this means complete artificial lighting/farming/silicon solar panels, except a very few lead glass windows. In such case you don't keep all your eggs in one basket - whether there is a major asteroid hit, or a global nuclear war wiping out all life on the planet, we would still have people and plants and animals, we would still have Life to come back and reseed and repopulate the planet. Life would not die. Such space stations traveling to the region of Mars then could take on the job of watching for comets and taking care of them, and though there is a distinct possibility of interstellar war between such space stations, at least having the technology and ability to live in a space station in pure vacuum/cold/intense radiation, whether that space station is landed on Earth, under water in Earth's oceans, under the clouds of Venus, behind Jupiter, or far past Pluto running on nuclear fuel alone, each of these give Life and humanity a better chance to survive. All it takes is at least a few people to make it after a global catastrophy. The real danger is making robots smarter than us that hunt us down and exterminate us. Back in the old days there was such a thing as defense - walls, trenches, fortifications. These days, because of technology, the only defense is attack: the equilibrium of mutually assured destruction. Yes we did gain the ability to beat the odds that dinosaurs couldn't, but we also gain the ability to destroy all life within a few months. As technology progresses, our ability
OK, I think I fail orbital mechanics - however, it seems that since the moon's face is tidally locked to earth (near side of the moon I guess is the colloquial) - that since the moon spends an equal amount of time "closer" to the asteroid field than Earth as it does "farther" from the asteroid field than Earth (meaning that the moon spends 1/2 of its time "sunside" of Earth) that asteroids ENTERING the moon's orbit region from farther out would have equal chance of impacting either face - EXCEPT for the influence of Earth's gravity probably either causing those rocks to impact Earth or at least redirecting them away from the moon.
...and that's why we still get hit by meteors every now and then. But listen, what you're saying only really applies to something coming straight at the solar system from outside and managing to hit one of the planets. Do you realise how unbelievably unlikely this is? The majority of the things that hit planets are wandering about in our solar system. Over a (very) long period of orbiting, the weak gravitational effects can play a considerable role in deflecting meteors.
That's something which seems to be ignored in the mention of Lexell's comet: if something passes quickly by Jupiter, it will not be affected, but if takes an inwardly-spiraling orbit - and think about it. That's more likely to be one that collides with something - then it's given sufficient time to be affected.
--
The whole notion that some body that is on the other side of the sun from us half the time is protecting us doesn't really work in my mind. It seems that it only works if you imagine the universe is laid out on a line. Put the Sun at zero, the Earth at 3 and Jupiter at 10 and then anything heading your way from >11 has to get past Jupiter first. In reality we can't even rely on foreign objects coming in along the ecliptic.
We don't do that because the likelihood of somebody abusing the weapons to kill us is substantially higher than the risk of being killed by an impact. Further more you're assuming that we'd get it right, and let's face it we tend to be kind of hit or miss on things like that. We were able to more or less successfully fight the ozone layer problem, but pretty much completely refuse to do anything about global climate change.
I'm not sure what makes you so sure that there'll be much left by the time a space object becomes a risk or that we'll be able to spot it in the first place. Many of those meteors move pretty damn fast.
the earth has had several mass extinctions in the past, the most recent was 65.5 million years ago when it is believed a meteor impacted the earth causing the demise of the dinosaurs, there
there was a few others that may or may not been caused by cosmic impacts
Politics is Treachery, Religion is Brainwashing
It tells you nothing about how "attracted" asteroids are to the earth, it tells you that a lots of asteroids on target for the near side of the moon, hit th earth instead.
To provide evidence that the Earth attracts asteroids (which it obviously does, you know gravity and all) you would need to see more craters on the far side of the moon then you see on a once side of a similarly sized body in a similar obit that does not have a larger body nearby to do the attracting.
Well it depend if you buy in the rare earth hypothesis or not. It might be interesting to do a mathematical model of the solar system and throw a few large objects towards the Earth and see how Jupiter plays its role. I believe this was part of the hypothesis by Ward and Brownlee.
Views expressed do not necessarily reflect those of the author.
i was under the impression that Jupiter was our protector, isn't that prevalent theory in science today? didn't Carl Sagan talk about this in Cosmos?
unless drugs have totally fried my brain- isn't Jupiter's mass (gravitational pull) what causes the huge asteroid field between Mars and Jupiter?
i had better dust off those Cosmos tapes and find my bong...
"You can kill the revolutionary, but you can't kill the revolution."-- Fred Hampton
It would be a lot more painful.
Only a programmer well versed in orbital mechanics could make it "interesting." The average slashdot commenter apparently isn't.
see http://jontihorner.com/index.php?p=1_10_Publications> Horner, J., & Jones, B. W for the results of (non-brain-dead) modeling.
So are you really sure that the Moon is getting less than it would if it was alone?
Nope.
"You're right," Fisheye says. "I should have set it on 'whip' or 'chop.'"
I had always thought that had something to do with the earths gravity smoothing out the craters over time. Does anybody know if any actual research has been done on this?
it tells you that a lots of asteroids on target for the near side of the moon, hit th earth instead.
lol, wtf?? Asteroids don't absolutely have to hit something you know, if they don't hit something they most likely won't hit anything.
You just got troll'd!
Not everywhere, only in the "seas", so that's irrelevant.
You just got troll'd!
Wrong. Both sides of the moon have had the same level of impact, and the 'far' side is not facing the asteroids any more than the 'near' side. The earth-moon system rotates in space and the moon rotates around the earth so both faces are in the direction of the asteroids all the time.
The 'near' side of the moon only looks smoother because mare lava flows have smoothed it out somewhat. It's just chance that put those flows on the side we see.
Fun fact: if the earth had no weather, it would look just like the moon in terms of impact craters. The earth is much bigger and has actually been hit more often. But our weather has eroded most of them.
Sig for hire.
The absolute worst possible outcome is that we have made so many other species extinct by that time that there is no stable ecological niche for humans and we go extinct too. I'm not arguing that this is particularly likely, but it's definitely worse than your worst case, unless you were counting subsistence 'living' with population = 0. However, adding that to your list of consequences with a small probability (0.5% or so) shouldn't make any difference to you. In fact, adding it with a very large probability (99,99995% or so), given your 'logic', doesn't make any difference either, so carry on.
Just as a hint, real logic means, if you introduce different facts, you just might reason to a different result. Your real, if unstated 'logic' is 'If it's not me it hurts, it's not a tragedy'. Since you didn't state it openly, but a bunch of unconnected claims you call logic, you don't have to be concerned that someone would point out that you are a sociopath, using an entirely emotional argument to provide pseudo-justification for being a rat-bastard who has basically told every single person reading this you don't care if their loved ones and descendants live or die.
Who is John Cabal?
for the dinosaurs, they were dying out before it hit and others survived well beyond the collision. Moreover, one cannot state with certainty that a similar event might mean to humans. It would depend where it hit and the response. In some sense it might stop us from our dangerous current course where significant opinion welcomes easily seen disaster. Some blinded by myopic short term interests and others believing, at least some humans, are special and will be protected by their deity of choice. A cosmic event might cause some to rethink was is really important not just for themselves, but for the species. But perhaps not, the survivors may just believe some strayed enough that wholesale punishment has been inflicted upon nearly all. Therefore, their deity (and their's alone) must be placated.
If the latter becomes the predominant voice, at least we can be consoled the planet might not go the way of Venus.
I think I speak for all of us Jupiterian slashdotters when I say I have a problem with that statement.
Maybe. But I find a bit scary that nobody noticed in space the large "object" before it crashed into Jupiter.
Slashdot, fix the reply notifications... You won't get away with it...
Exactly how does "which then threw it back out of the solar system" disprove the theory?
A rigorous experiment would probably involve comparing lots of roughly moon sized objects, in isolated orbits, in tidally locked orbits around larger bodies, and in orbits where they don't keep one face pointed at a nearby larger body.
But, there's something else to consider for our specific, real moon, besides orbital mechanics. There were probably a lot more hits in the early era of the solar system (more rocks then, a lot of what we see is the result of most rocks having been used up). In that era, the Moon probably still had a molten core. Tidal effects from Earth might mean more lunar lava erupted on the side facing us, and more of the craters there were covered with fresh material.
That's an old (1810 to 1950's) theory that was just assumed for a lot of textbooks, and not necessarily the one Selenographers today prefer, but it's not a rejected or disproven idea, just one that there's little interest in doing more work on to make it more rigorous. It got a bit of a nudge from Russian photos of the far side and from the same sort of observations by the Apollo missions in the early and late sixties, respectively, and then all the researchers decided working on it more would probably require someone digging some holes on the moon, so it's simply languishing unless somebody goes back.
Who is John Cabal?
Wrong. Both sides of the moon have had the same level of impact
Wrong, the far side has about 1.67 times more recent impacts than the near side (citation).
The 'near' side of the moon only looks smoother because mare lava flows have smoothed it out somewhat. It's just chance that put those flows on the side we see.
No, we don't know that, there surely is a reason other than chance, we just don't know for sure what it is yet. Also, not all of it was covered by lava flows, and you can tell these areas look different from the far side. Well at least they look different to me.
Fun fact: if the earth had no weather, it would look just like the moon in terms of impact craters.
I'll assume that you chose the word weather instead of atmosphere for a reason, not too sure why, but the Earth is geologically active and has an atmosphere (assuming you weren't talking about there not being an atmosphere) then it would look more like Venus. And Venus doesn't have so many visible craters. Yeah, there's quite a difference between a body that died over 3 billion years ago and one that's still active, radiating and erupting.
You just got troll'd!
Yeah, and I like turtles, but that has nothing to do with what's being talked about.
You just got troll'd!
There is also conjecture that earth's atmosphere was initially "seeded" by major cometary impacts, without which our kind of life could not have developed. So over the entire history of our planet, (if this is true) cometary impacts have not been completely negative from a human perspective.
The whole "Jupiter shield" idea is myth. There's no reason to assume that Jupiter will throw more junk into wider orbits than into tighter ones more likely to hit the earth.
From the Wikipedia article on Jupiter (assuming it is correct): "Jupiter is 2.5 times more massive than all the other planets in our Solar System combined â" this is so massive that its barycenter with the Sun actually lies above the Sun's surface (1.068 solar radii from the Sun's center). Although this planet dwarfs the Earth (with a diameter 11 times as great) it is considerably less dense. Jupiter's volume is equal to 1,317 Earths, yet is only 318 times as massive." http://en.wikipedia.org/wiki/Jupiter Surface Area: 6.21796Ã--1010 km2 = 121.9 Earths So this would only make sense that it had a much greater surface area (122x) than earth to be hit or had a 122% better chance of getting smacked compared to our own.
Architectural Renderings
Wanted to type "dying", typed diing, spell checker corrected to dieing, didn't preview text myself...
It happens.
I remember once I mistyped "Queue" as "Que", to which someone replied "Que?"... we laughed... good times.
Mit der Dummheit kämpfen Götter selbst vergebens
The fact that the far side has more craters than the near side seems to be pretty good evidence that the planet that happens to always be on the near side might just be stopping some of the ones that would have otherwise hit the near side.
Or do you have some other explanation? Magical faeries that teleport things out of the way maybe?
Why would asteroids be coming towards the Moon FROM EARTH?
By being pulled by Earth into a near Earth miss and going forth to hit the Moon right in the kisser. The "near" side faces the rest of the universe too, just a few degrees of arc are occupied by Earth.
You just got troll'd!
You're right in that the Earth keeps asteroids away from the near side, but why you fail to understand how the Earth makes it rain on the Moon's far side puzzles me.
Just picture from left to right the following : a bunch of asteroids, the moon's far side, the moon's near side, the Earth. The Earth pulls the asteroid towards itself. The moon is in the away and catches the space rock rain like a space umbrella.
You just got troll'd!
There are several different energy gathering systems that we know how to operate in an energy positive manner (i.e., the energy output could be used to create an identical system+energy). This makes the complete consumption scenario rather unlikely.
Nerd rage is the funniest rage.
What about when we're between Jupiter and the sun? Then the pull from each would put us pretty much square in the path of whatever's coming, wouldn't it? No wonder people are so scared of syzygies.
if they don't hit something they most likely won't hit anything.
An astutely profound observation. Absolutely profound.
HSJ$$*&#^!#+++ATH0
NO CARRIER
The point is that not only does Jupiter protect the terrestrial planets now, but that Jupiter has protected Earth from the birth of the solar system. This is one reason that Earth isn't yet another gas giant.
The recent controversial redefinition of the word "planet" (http://en.wikipedia.org/wiki/IAU_definition_of_planet) discusses this "vacuum cleaner" effect as the third of three criteria:
Jupiter is by far the largest planet and has by far the largest such effect. A lot of the reasoning in the comments has caused one to question how well Astro 100 courses are being taught, but perhaps it is ok to venture one simple statement for why Jupiter preferentially protects the inner solar system. The comets that threaten us originate in the distant Oort Cloud (http://en.wikipedia.org/wiki/Oort_cloud). They visit the inner solar system, but their orbits all begin far outside. It is thought that external perturbations play a role in causing them to plunge inwards. Jupiter (to oversimplify outrageously) stands between us and the bombardment.
Fundamentally this is the famous "three body problem". The equations describing Newtonian gravity are straightforward to solve for two bodies, and impossible to solve precisely for three or more. Relativistic corrections add a bit of spice. As a result planetary mechanics requires numerical integration.
The solar system is full of neat resonances and points of stability such as the Lagrangian points. Jupiter's Trojan asteroids (http://en.wikipedia.org/wiki/Trojan_(astronomy)) cluster at L4 and L5 and are thought to be as numerous as those in the main belt. Our Moon's tidal locking is a) imperfect (since the orbit is rapidly growing (http://en.wikipedia.org/wiki/Moon#Orbit_and_relationship_to_Earth), and b) simple compared to resonances (http://en.wikipedia.org/wiki/Orbital_resonance) between other bodies.
lol, wtf?? Asteroids don't absolutely have to hit something you know, if they don't hit something they most likely won't hit anything.
Or more seriously, I mentioned what would be evidence of that, I don't think the crater differences on the sides are of the moon do - they seem to be more simply explained by the earth blocking the near side from some impacts.
Jupiter clears out a path of asteroids and comets by being so massive that it attracts them to itself to either fling it to an orbit in the asteroid belt or out to the Oort Cloud or takes a hit from it to prevent it from cluttering up the solar system.
If it wasn't for Jupiter and other gas giants, we'd have more comets and asteroids getting near the inner planets, so Saturn, Uranus, and Neptune are Soccer Goalies as well.
But they don't always stop everything, just a majority of it.
Early on when our solar system was being formed, there were a lot of collisions with Earth and our Moon, and some say some of the collisions helped life to form and evolve, but in later years fewer and fewer collisions happened until we have the modern day.
Remember, Slashdot does not have a -1 disagree moderation, and no, troll, flamebait, and overrated are not substitutes.
Yes, and so is the Moon, as its cratered far side will show you (the far side is much more cratered than the front side which shows how the Earth attracts asteroids towards the far side and away from the near side).
Next question?
Wait.....seriously? The Dark Side of the Moon is cratered more than the Light Side because of how Earth attracts asteroids?
How about.....since the light side is always facing the Earth, the Earth protects the light side from bombardment. It is a lot tougher for an asteroid to go around the Earth and strike the light side (Which is always facing the Earth) than it is to merely barrel into the dark side.
Last Sunday, an object, probably a comet that nobody saw coming, plowed into Jupiter
First, I'd like to apologize for being slightly off-topic.
I wonder why pretty much all astronomy sources are unwilling to state with certainty that Jupiter has a rocky core. It's only natural that more solid material has fallen into the atmosphere than has been captured in orbit. It's not like the comets and meteorites will 'orbit' for very long within friction of the atmosphere, so the only place for solid matter to go is the center.
Low odds of an intercept. Now multiply that by thousands of orbits the body will make. The important factor is not that Jupiter will immediately intercept every body; just that a typical body will be more vastly more likely to be intercepted first by Jupiter than the Earth.
We had 5 major mass extinctions in the past, but the most recent one isn't in the past at all but is happening right now. It began slowly with the rise of Man, but ramped up exponentially with the industrial revolution. Compared to previous extinction events, it's by far the worst of them by many orders of magnitude.
This astronomic loss of biodiversity isn't so much about high-profile rhinos and tigers and cute pandas, but about the almost unseen microbiota and microfauna throughout the biosphere, upon which all of our food and even our own bodies depend. It very rarely makes the news (not sexy enough), but we may not pull out of this one.
Apparently we don't need a big rock to hit us at all. We seem to be totally self-sufficient at achieving extinction.
"The question of whether machines can think is no more interesting than [] whether submarines can swim" - Dijkstra
(Pyongyang, NK) A defiant North Korea announced the launch of a projectile the size of several soccer fields (football fields in the U.S.) that struck Jupiter today. As it descended into Jupiter's cloud tops it was transmitting data and broadcasting the "Song of General Kim Il-sung" and "Song of General Kim Jong-Il", about Kim Jong-Il and his father.
North Korea's neighbors condemned the launch as "unfortunate". The U.S. State Department declined to comment, although in another display of his ability to mitigate, President Obama has invited Kim Jong-Il to meet him on Jupiter for a beer.
is dat somthin on which we shud bet our existence?
it can be made to work.
http://www.accountkiller.com/removal-requested
Maybe. But I find a bit scary that nobody noticed in space the large "object" before it crashed into Jupiter.
Hmm... no one saw it coming, and no one saw it leave. All we know is that it left a gaping hole in the side of Jupiter. It must have been space ninjas...
(There is supposed to be a Sarcmark® here, but my $1.99 check hasn't cleared, yet...)
The Moon always shows the same side to earth. It's obvious that that side will always be more protected.
Blocking? As in, just being an umbrella, an obstacle in the way? Considered that Earth occupies less 2 degrees of the Moon's field of view, that would account for a very small difference, something a couple of orders of magnitude too small to explain the discrepancy in impacts.
You just got troll'd!
Don't worry, we are well on the way of blowing the planet to smitherines ourselves. No amount of protection from Jupiter is going to stop our self-destruct sequence!
~Ami
Chicago Web Design
lol, dark side and light side?
And what you're saying is pretty much what I said, except you left out the part where the Earth does all the attracting and the Moon gets in the way. Although maybe it's not what you're saying, I'm not sure :
It is a lot tougher for an asteroid to go around the Earth and strike the light side
Are you saying that the problem is the size of the Earth, not its gravitational pull? If you do then you need a serious reality check on how small the Earth looks from the Moon/compared to the distance between the two. The Earth isn't much of a physical obstacle at all.
You just got troll'd!
Yeah... that's the reason I compared geologically active Earth with geologically active Venus. You were supposed to get that.
You just got troll'd!
Right, the problem is that most people in the thread don't see to understand how it's by having the Earth pull all those asteroids towards itself that it makes rocks rain on the far side of the Moon. It seems that some people believe that the Earth only acts by somehow covering physically that side of the moon, like a sort of umbrella.
You just got troll'd!
Why? The orbital mechanics of that aren't obvious to me. If the speed of the impactors was much larger than the escape speed from the Earth, then a physical blocking approach would make sense. But the relative speed of the impactors should in fact be comparable to the escape speed from Earth, so Earth's gravity will make a significant different in the trajectories. In that case, I can see a case for Earth *focusing* impactors on the Moon after they make close passes of Earth.
Sure, the far side is more cratered. And if you set up that dichotomy on the Moon without having it oriented that way, the less-cratered side would probably turn to orient towards Earth, in solar-system timescales. So that orientation may be misleading. What you need to show us is that the excess impacts on the far side have happened since the Late Heavy Bombardment. I don't think that this is the case. (In fact, the Lunar Highlands on the nearside are as heavily cratered as the far side is. This strongly suggests that the nearside wasn't struck less often, it was just resurfaced when the mare formed.)
You're assuming linear trajectories. In the solar system, EVERYTHING is moving along a curve. Nothing hurls straight at a standstill Earth only to have the moon swing through its path and take the hit instead, which is what you seem to be arguing. All objects in the solar system are being carried by the sun's gravity and thus are at varying-sized elliptical orbits, so it is not too difficult to imagine numerous parabolic paths sliding between Earth and its moon to impact it on the inner side.
It's not a lie. It's the truth with lossy compression.
And if you set up that dichotomy on the Moon without having it oriented that way, the less-cratered side would probably turn to orient towards Earth, in solar-system timescales.
You're wrong, and I won't even bother to try to understand your twisted logic.
What you need to show us is that the excess impacts on the far side have happened since the Late Heavy Bombardment.
I have already, thank you
I don't think that this is the case.
Wrong again. Don't mean to troll (wait, I actually do), but debating on astronomical topics on Slashdot is like shooting a dead guy in a barrel. I mean look at this whole discussion, it wasn't even supposed to cause controversy, but people have such misconceptions about astronomy that it turns into a huge debate where I'm practically alone trying to explain how it works to people who don't understand how gravity works/that the Earth is very small compared to the Earth-Moon distance/have misconceptions that just elude my grasp and are completely oblivious to their gaping ignorance on the topic.
You just got troll'd!
Well, for the time being and the foreseeable/coming future, i'm HAPPY to be covered by our massive JUPITER than massive URANUS.... From a software/hardware perspective, Jupiter is a better, smoother sheathe, but URANUS is ringed, chunky and reflective (if not coarse) for our (viewing) pleasure....
Previously: "Linux... Toward the Sunrise..." Now: "Linux... Toward the-- No, now, part of Every Sunrise"
and what it tells is: there isn't much money in astronomy.
So how does your "the earth sucks in asteroids that hit the moon" work then?
Since half of those sucked in asteroids will be coming from the non-moon side of the earth, missing the earth and smacking into the moon's near side.
Of course the near-side being hotter is a more likely explanation than either of these. But the earth as a shield still seems to make more sense than the earth as a vacuum cleaner.
Since half of those sucked in asteroids will be coming from the non-moon side of the earth, missing the earth and smacking into the moon's near side.
That's a good point, but do you think that it makes it as likely to happen as an asteroid just falling straight on the far side? No, and here's why : an asteroid coming from behind the Earth (from a lunar point of view) is quite likely to make a L turn or U turn when it nearly misses the Earth and thus never get anywhere near the Moon, like, cross the lunar orbit more than 90 degrees away from where the moon is.
But the earth as a shield still seems to make more sense than the earth as a vacuum cleaner.
What's really amazing is that you would consider a "shield" of less than 2 degrees of arc more likely to protect the near side of the Moon than having the Earth's strong gravitational pull make the asteroids' hyperbolic orbits look like a U turn and thus pretty much send a number of them back where they came from. Actually if it helps to think of the Earth as a sort of gravitational lens, and the asteroids' trajectories as rays of light, then you can see that from a random angle the "image" of the Moon would seem squished, and therefore harder to hit. It surely explains the 1.67 difference ratio I mentioned earlier. Well that's if you can picture how a gravitational lens makes non-aligned objects behind look, I know I can.
Of course the near-side being hotter
lol, hotter, wtf?? Seriously, what are you talking about.
You just got troll'd!
The near side has a much higher concentration of radioactive elements (plus a thinner crust), hence more recent lava flows removing craters.
I forgot to say that some wild westerns do end with the heroes "riding off into the sunset"