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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."
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.
In astrology, Jupiter is considered the "greater benefic," the planet that bestows fortune, luck, and positive benefits.
Just sayin'.
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 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!
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)
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.
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 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.
... is the fact that eventually we have to get off earth and learn how to survive in the hostile universe anyway.
With all due respect, as much as I want mankind to go into space there's nothing to suggest earth will become uninhabitable in the next few million years. Not unless we destroy it, but in that case there's not much hope we'll be capable of interstellar travel either. On that angle, who cares if that happens this century or this millennium? We could easily have spent another million years on the ape stadium, shaving off a few centuries means nothing.
The odds that any interstellar "manned" spacecraft would be anything like today's manned mission is highly unlikely. More likely what we're doing now is like testing the extreme conditions of cross-continent horse-and-buggy rides when the solution is a jet plane. I'm guessing we'll send something like space probes that'll thaw or build embryos on site with nursing robots to form new colonies, sending fully grown people is just insanely inefficient in so many ways.
You may think that's inhumane, but I think it's the only humane thing. Imagine being second generation plus on a ship in the dark void of space, only seeing pictures and videos of earth while you're trapped on a tin can because your ancenstors decided to make you a pawn in colonizing a new planet. Plus, then they'd also be real people that quite possibly, or even probably, will die at some point from ship failure. A probe on the other hand may only produce humans if all flags are green.
Live today, because you never know what tomorrow brings
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.