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ngc3314
2006-Jun-23, 02:01 PM
A paleontology email list just carried a link to a video (here (http://www.youtube.com/watch?v=3JHdYBet_4Q)) simulating a really big impact with Earth. No mere Chicxulub event, this looks more like the size of Ceres (with no Bruce Willis in sight). Narration is in Japanese, but for the rest of us, the visuals alone have some interesting bits. I was impressed with the feeling of impending doom as we watch the asteroid's shadow move across the Earth, reversing direction as it gets closer and closer so its apparent motion becomes faster than the Earth's rotation (even though I doubt the shadow edge would be sharp enough for some of those "Independence Day" shots over city skylines). The whole of Honshu basically peels up and crumples with the shock wave. The last human work seen is a ruined Greek-looking building on a hilltop surrounded by a boiling sea, as secondary impacts rocket in all around. Indeed, an impact of that magnitude would return the whole surface to a lava ocean.

antoniseb
2006-Jun-23, 02:24 PM
this looks more like the size of Ceres (with no Bruce Willis in sight).

Thank goodness the likelyhood of this happening anytime soon are pretty small. One thing that I would expect to happen that they didn't model here is that the seismic waves from the impact would travel around the world, and cause a major catastrophe on the opposite side of the planet before the fire storm could get there. That back-side event should blast a lot of material into Solar orbit.

X-COM
2006-Jun-23, 02:30 PM
I say that is high time that we get ourself an decant impact insurence. I am not only talking of ways to deflect incomming objects, nothing can deflect something of that magnitude. We need to spread from earth. The moon, Mars and many more moons further out, including astroids like the one we saw are just waiting out there. In time, if we work hard enough on it we may be able to reach the stars.

Vermonter
2006-Jun-23, 02:38 PM
That's pretty horrific imagery! I watched the video, and couldn't help think of how completely screwed we'd be if something even a fraction of that size nailed us. I wasn't able to understand the Japanese, but who needs words?

never
2006-Jun-23, 03:11 PM
Personally I dont't think it will happen 'cos it's already happened.
The current most widely accepted theory for the Moon’s creation is that a giant impact long ago caused some of the Earth to break off and form it. That theory was first put to scientists at Cornell University in 1974 by Bill Hartmann. Alastair Cameron, a top Harvard scientist agreed with him. This theory is similar but takes into account the differing faces of the Moon including the positron spectrometer images we now have of it’s far side showing the ancient St Pierre-Aitken Basin and the implications of that ancient, iron stained, giant impact crater which couldn’t have been created unless it was by something iron that was very large and moved the Moon a very great distance, very long ago. The larger impacts on the Moon’s surface generally belong to the earlier phases of its’ history. The biggest is the South Pole-Aitken Basin- the largest impact crater in the entire solar system. It is 1550 miles (2500 km) wide and 7.4 miles (12 km) deeper than its surroundings. The Moon is denser on the side opposite the crater because when it was hit its mass would have been squashed towards that side. The Earths’ pull has meant that the heavier near side has always presented itself to us in the past. This has resulted in us only relatively recently being able, thanks to satellite images, to see colour enhanced images of the ancient iron stained impact crater on the far side.

When the planets of this solar system condensed together the area they were situated in and the constituent elements and density within the clouds of gas and dust from which they formed would affect their eventual make up. The denser elements in the locality would cluster together and solidify first and the consequent increasing gravitational pull would continue to draw other matter towards the mass ending with the lightest elements such as hydrogen and oxygen around their surfaces. The planets are all different from each other in size and make up due to the differences in cloud and temperature in their locality when they formed. The dust and gas clouds from which they formed would shape into the orbital plane around the Sun due to them being colder and denser than the hot matter being ejected from the poles of the young Sun while it was spinning over. In traversing their orbital plane they have attracted and amassed whatever was closest, condensing into the planets as we now know them. Something large enough hitting the Earth during a crucial period of its’ formation when it was approximately five million years old would have dislodged the core as that’s the part which would have condensed together and solidified first.- Newtons’ Law would have applied. I believe that the solid iron core at the centre of our planet (spinning at a different rate from it’s molten surround) once collided with, dislodged and replaced the original one and sent it some distance away to become our Moon. Furthermore, that event has caused the planet we live on to develop in the way it has, providing the right conditions and ingredients for us to have arrived at the point we are now. The ancient Valhalla impact crater on Jupiter’s moon Callisto could also be studied and be seen as an indicator that some other moons were in fact once early planet cores that were knocked out and remained captured by gravity.

The Moon is only slightly larger than the solid iron core now at the centre of the Earth. This core had to have been formed in a different location to its present one otherwise it would have melted but because it was solid when it entered the Earth and heat radiates outwards it does not. It would have initially been spinning madly as a result of the collision and it would have drawn to it the densest molten elements of the existing Earth thus drawing iron away from the present crust. The subduction zones away from the solid core would mean that there was an ongoing variation in sinking and rising of various types of matter creating Earths’ peculiar varieties of crust. Both Moon and Earth have the same oxygen-isotope signature which led scientists to conclude that they were formed in the same location in space. Radiometric dating has shown that the Moon's crust formed between 20 and 30 million years after the Earth’s. However, the surface of the Moon has rock of varying ages and is classified in The Atlas of the Solar System, Moore, Hunt, 1997,(p.152), as having a 4,000 million year old highland regolith. The oldest sample of Moon rock is Anorthocite taken from the highest ground and has been dated at 4.6 billion years old. Therefore it makes more sense that the Moon was once the solid centre of the Earth in the early stage of its creation than if it had condensed spherically subsequent to the breakaway. Indeed, it would not be feasible for it have formed spherically after the breakaway when it’s near side has always faced the Earth. The age and size of the St Pierre- Aitken crater is so great that it alone should constitute proof of this. The Moon has also been shown to have some remnants of liquid hydrogen on its’ surface in deep areas hidden from the Sun. The side facing the Earth appears to have been subjected to more heat which would surely be occasioned when the Earth was undergoing vast fiery turmoil from the initial collision. In McNab/Youngers‘The Planets’ it states that Moon rock is the same as Earth rock but as if it had been roasted, boiling away the lighter elements like hydrogen and oxygen. The three large maria on the near side would be a result of that roasting. It would also have had most of the below surface magma pushed to the near side when the St Pierre –Aitken basin was formed on the far side opposite. Halle Rille, the so called river gorge, on its’ near side looks suspiciously like cracking as a result of that massive impact on the far side.

Einstein commented that if a new theory was not based on a physical image simple enough for a child to understand, it was probably worthless. He also pictured the planets as marbles rolling around a curved surface centred on the Sun. The image brought to my mind in visualizing the enormous collision would be similar to that of a snooker or pool ball sent spinning towards another which then moved slightly away, leaving the spinning ball in its’ place. Some might remember the striking image shown years ago on the news when during a famous boxing match a punch was thrown with such force that the sweat surrounding the mans’ head stayed suspended in mid air when the head was knocked backwards. Another seemingly opposite illustration could be if one was to picture the magician’s trick where the crockery stayed in the exact same position when the tablecloth was whipped from under it. One should see then that the cloak of spinning liquid, magma and gases surrounding the original core could well remain spinning in situ around the spinning solid interloper.

Since we know Appollo 11 measured the rate of drift away of the Moon to be 3.8 cms per year it may be possible to date the collision. As the earliest known age of Earth rock is 3.9 billion years old and earliest known fossil evidence is 3.8 billion years old I would estimate the impact must have happened approximately 4 billion years ago when the Earth was about 500 million years old and had a solid condensed core surrounded by magma, and other lighter elements like hydrogen and oxygen. As that original condensed core is now our Moon and has been found by seismic detectors to have only a very small iron core it should mean that the massive iron print of the impact crater photographed on the far side of the Moon has to be from the iron sphere which caused the impact and which is now spinning at the centre of our planet.

GDwarf
2006-Jun-23, 03:27 PM
I say that is high time that we get ourself an decant impact insurence. I am not only talking of ways to deflect incomming objects, nothing can deflect something of that magnitude. We need to spread from earth. The moon, Mars and many more moons further out, including astroids like the one we saw are just waiting out there. In time, if we work hard enough on it we may be able to reach the stars.
No, something that big can be deflected, if we find it early enough and spend money on the technology. The big downside, as Carl Sagan pointed out, is that if we have the technology to deflect it away from the Earth, we also have the ability to deflect it towards the Earth, and then all it takes is for one man with plenty of power who doesn't care about the consequences...

Vermonter
2006-Jun-23, 03:46 PM
Welcome to BAUT! Thanks for the info, as well.

Vermonter
2006-Jun-23, 03:47 PM
No, something that big can be deflected, if we find it early enough and spend money on the technology. The big downside, as Carl Sagan pointed out, is that if we have the technology to deflect it away from the Earth, we also have the ability to deflect it towards the Earth also, and then all it takes is for one man with plenty of power who doesn't care about the consequences...

Like Superman on a bad day...

antoniseb
2006-Jun-23, 03:58 PM
if we have the technology to deflect it away from the Earth, we also have the ability to deflect it towards the Earth also, and then all it takes is for one man with plenty of power who doesn't care about the consequences...

I disagree (sort of). The technology to deflect it is the technology to change it's path a total of at most 4000 miles over whatever time period we're interested in. If the object would otherwise not come within hundreds of millions of miles of the Earth, the job is hundred of thousands of times more difficult to accomplish, which one can presume will take a different scale of the technology and expense.

Ara Pacis
2006-Jun-23, 09:12 PM
Never, the Giant Impact Hypothesis (http://en.wikipedia.org/wiki/Giant_impact_hypothesis) I am familiar with does not describe such an event.

yuzuha
2006-Jun-23, 10:19 PM
That was also in in some show I saw on National Geo or Nature etc. AFAIK, the earth got hit with a glancing blow by a proto-planet that merged with the earth, spun off the moon and got rid of most of the water. Later, after life first formed, they think the earth was hit maybe 6 times by asteroid sized bodies, as in the video, that covered the earth with rock vapor (they showed the Amazon catching fire from the radiant heat of the atmosphere before the cloud of rock vapor even got there). I agree there would be circular shock waves on the opposite point, that would probably trigger massive flood basalt eruptions, but they were mainly showing the vaporized rock boiling away the oceans and melting the upper layer of rocks on the entire surface... after this video sequence it talks about the only life surviving on the planet would be extremophile bacteria that live in the rocks miles below the surface (with nice graphics of the heat flow in the earth's crust showing the narrow band of habitable temperatures between the surface and the mantle in the 100's or so years the top layer would take to cool enough for water to start condensing again) and mentioned that these extremophiles have relic genes for photosynthesis that are of no use when they live deep under ground.

There are the remains of really huge astroblemes in Sudbury Canada and Vredefort Africa that are about 2 billion years old as is the Bushveldt igneous complex in S Africa. The moon took one too http://antwrp.gsfc.nasa.gov/apod/ap960906.html

eburacum45
2006-Jun-25, 03:11 PM
Thats probably right. The impact with the ~Mars sized impactor is unlikely to have been the last major impact, although they probably decreased in frequency quite rapidly.
Life is thought to have had a foothold on our world around 3.8 billion years ago, so I doubt that our planet has had a Ceres-sized impactor since that time.

Roy Batty
2006-Jun-26, 12:57 PM
I'm having trouble imagining any man made object still being recognisable even within a minute of an impact of such a large object. Anyway, wouldn't tidal forces play recognisable havoc with both bodies some time before that impact? :)

publiusr
2006-Jun-28, 05:20 PM
No, something that big can be deflected, if we find it early enough and spend money on the technology. The big downside, as Carl Sagan pointed out, is that if we have the technology to deflect it away from the Earth, we also have the ability to deflect it towards the Earth, and then all it takes is for one man with plenty of power who doesn't care about the consequences...


It is easier to make an object miss than to carefully alter bodies to make them hit. Even so--it might not be such a bad thing.

Imagine a lot of carbon tethers linking two large bodies with the asteroids rotating at a certain speed one rotates with the direction of the Earth-the tether breaks and falls faily slowly. You have a nice big space-rock ready to be mined. Or they can be broken up and very wide sheets of material used to balluted them down.

Arneb
2006-Jun-28, 06:22 PM
The last human work seen is a ruined Greek-looking building on a hilltop surrounded by a boiling sea, as secondary impacts rocket in all around.

It's not only Greek-looking, it's Greek. This is a very good representation of the Temple of Poseidon on Cape Sounion, South of Athens, perched on the most wonderful promontory to see sunsets and moonrises in the world. Yes, that one! (http://antwrp.gsfc.nasa.gov/apod/ap050623.html)