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First Contact Could Be Tomorrow!


Nevenall

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Re: First Contact Could Be Tomorrow!

 

Looks like it's 2010 AL30.

 

Interesting that that orbit it shows crosses Venus's orbit too. One leg of the Inner Solar System Shuttle Bus Route? That's a really poorly-determined orbit, though.

 

If it's an iron, that size of object is about the same as the impactor that made Meteor Crater in Arizona. You don't want to be right under it when it hits, but as such things go it's modest impact.

 

So the the results from the impact calculator are wrong? It claims that a 50-ft iron asteroid would airburst 5 miles up.

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Re: First Contact Could Be Tomorrow!

 

Looks like it's 2010 AL30.

 

Interesting that that orbit it shows crosses Venus's orbit too. One leg of the Inner Solar System Shuttle Bus Route? That's a really poorly-determined orbit, though.

 

If it's an iron, that size of object is about the same as the impactor that made Meteor Crater in Arizona. You don't want to be right under it when it hits, but as such things go it's modest impact.

 

Is Wikipedia off in this case? It says Meteor Crater was probably caused by a nickel-iron object "50 meters (54 yards) across." 54 yards would be roughly 160 feet. The article says this object is merely 33 to 50 feet at the widest. That's one fifth to one third the size in one dimension, and thus (very roughly) 1/25 to 1/9 the volume.

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Re: First Contact Could Be Tomorrow!

 

So the the results from the impact calculator are wrong? It claims that a 50-ft iron asteroid would airburst 5 miles up.

 

Is Wikipedia off in this case? It says Meteor Crater was probably caused by a nickel-iron object "50 meters (54 yards) across." 54 yards would be roughly 160 feet. The article says this object is merely 33 to 50 feet at the widest. That's one fifth to one third the size in one dimension' date=' and thus (very roughly) 1/25 to 1/9 the volume.[/quote']

 

Both of these are related. The fate of an object this size when it encounters Earth depends on its composition. For a given size (and its size, not mass, that we estimate from the apparent brightness), an object that is iron-nickel throughout has a much larger mass and mechanical strength than a "rubble pile" asteroid of primitive stony material. The rubble pile will blow up in the atmosphere; it doesn't have the strength to survive the shock pressures it encounters as it comes in. And iron is much stronger and more massive, so not only might it survive passage, it'll make a nice big hole (since crater diameter scales with kinetic energy, and energy scales with mass) if it does. An iron will have a density up around 7 or 8 tons per cubic meter; the rubble pile might be a little less than 1. The last time I read up on this (10 or 12 years ago, I'm afraid), survival through the atmosphere depends in complicated ways on strength, incident velocity, and bolide size.

 

The number I've seen for Meteor Crater is an estimate of about 10 meters if it was a more or less pure nickel-iron, and that comes from the crater diameter-impact energy relation and an assumption about density, and an assumption about impact velocity. Iron-type material has been recovered around that crater. I would have to do a lot of backtracking of sources, but my guess is the Wikipedia number comes from a different but still plausible set of assumptions, so they aren't in as severe a disagreement as it looks at first.

 

With this object at hand, we know what its incident velocity will be, but we have little idea about composition (and hence strength) and if all we have is that H magnitude (which I can't believe, but the guys with the radar systems to image objects in deep space tend to be DoD types who aren't all eager to let the world know what they can do) then we don't have a very good handle on its size, either. That means there's a lot of slop for survival and crater estimates.

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Re: First Contact Could Be Tomorrow!

 

Well' date=' unless the aliens are now controlling all channels of information, or my powers are delayed in manifesting, I guess it was just a chunk of space rock.[/quote']

 

Yeah. Up until the point where you sneeze and are surprised by the fireball that ignites the sofa.

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Re: First Contact Could Be Tomorrow!

 

Hmmm' date=' there could be bad implications of that. Using comic book logic, Bad things always happen when you rocket the threat out into space.[/quote']

Well consider this:

If I was sent to Jupiter to remove my superpower negation field, suddenly all of you would have full use of their superpowers.

All of you.

From the upwardly noble to the sociopathically trollish, including the shortsightedly stupid. All of you.

How long do you think Planet Earth could survive the resulting melee? ;)

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