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World's Second Largest Meteorite Found?


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On 2/11/2020 at 2:04 PM, Bedrock Bob said:

Fun fact.

The speed at which an object collides with the earth's atmosphere may be greater relative to a point on earth. And the impact to The atmosphere may be slightly greater against the spin of the globe.

BUT

The explosion in the air that brings the object to terminal velocity will be greater. The speed at which an object hits the ground would not be.

An object that cannot slow to terminal velocity will vaporize. So any solid chunks left after bolide are all obeying the laws of physics and the crater they form is based on their mass, angle and speed. Their speed of impact would not be affected by the earth's rotation at all.

They all start at cosmic speeds and slow to terminal velocity before impact no matter which direction they are flying. Otherwise they detonate and never hit the surface.

Leastwise that is the way I understand it.

Actually,  meteorites hit the earth at different speeds, some melt the surrounding rocks and others don’t, and it is attributed to the speed and mass of the object:

Meteor crater formed by low velocity impact.https://www.nature.com/articles/434157a

 

http://www.impact-structures.com/impact-rocks-impactites/impact-melt-page-impact-melt-rocks-impact-glasses-and-congeners/

Edited by GotAU?
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3 hours ago, GotAU? said:

Actually,  meteorites hit the earth at different speeds, some melt the surrounding rocks and others don’t, and it is attributed to the speed and mass of the object:

Meteor crater formed by low velocity impact.https://www.nature.com/articles/434157a

 

http://www.impact-structures.com/impact-rocks-impactites/impact-melt-page-impact-melt-rocks-impact-glasses-and-congeners/

Absolutely they hit at different speeds. No argument there at all. 

Their speed is reduced to terminal velocity or they explode. After that point their speed is determined by aerodynamics, weight, and time in dark flight.

I see where orbital speed of the planet affects impact force. Good point. It probably makes the bolide more violent. So it stands to reason that large, durable pieces that withstood the explosion may make a bigger crater on impact than those going with the orbit of the planet. 

It also seems since the bolide would be more forceful that the "sweet spot" would be a smaller size window. 

It is a mighty complex calculation. If you say that the end result would be a bigger crater with all other things equal I certainly won't argue. But since it is such a complex calculation I suspect that your assertion might be over simplifying a bit. 

It is kind of like taking into account for coreolis when shooting long range. If you are comparing long shots in exactly the opposite directions east and west with all other factors equal the difference is real. But given the other variables in the solution coreolis may not even be a factor between 2 shots. 

The same with two meteorites. One may travel faster or slower and still make a larger crater. We just can't make the correlation between crater size and direction relative to orbit without the rest of the ballistic formula as well as a whole other set of factors related to the impact surface, size of impact or, angle, etc.

It is a great conversation! Thanks for having it!

 

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https://geology.com/records/largest-meteorite/

Apparently there was substantial iron oxide in soil when they excavated the Hoba which means it was much bigger then it is now. Just how much is hard to say.

The meteorite that created the Barringer Crater weighed about 4 million metric tons before entry, was 160 feet in diameter and left behind 30 tons of recoverable pieces.

It just makes me wonder how big Hoba originally was before entry. On the ground as it stands now, it's a 9ft by 9ft by 3ft square which is an unusual shape for a meteorite. The article seems to imply the shape is the reason why it didn't make much of a crater. I find it hard to believe it just fluttered down from the sky and plopped down on the ground. Does anyone really think aerodynamics played a part in why their isn't much of a crater. 60 plus tons is a lot of weight.😉

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21 hours ago, billpeters said:

The actual mass of Canyon Diablo before it struck the Earth was 8,578,642,193 pounds, or about 4 million metric tonnes.  The incoming bolide was 160 feet across with the average iron nickel mass of 500+ lbs per cubic foot, based on actual calculation of its components. The estimated recoverable mass of Canyon Diablo is a mere 30 metric tons, or 0.00077% of what hit the Earth.

 

Happy hunting,

billpeters

Is that .00077% figure approximate for all meteor (ite) entries or just the Diablo Canyon iron? Just curious about the size of meteors in general before they enter the atmosphere and hit the ground.

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38 minutes ago, Morlock said:

Is that .00077% figure approximate for all meteor (ite) entries or just the Diablo Canyon iron? Just curious about the size of meteors in general before they enter the atmosphere and hit the ground.

Two points.

I made a mathematical cubing error. The correct figures are the original "mass of Canyon Diablo before it struck the Earth was 603,185,779 pounds, or about 275,000 metric tonnes.  The incoming bolide was 160 feet across with the average iron nickel mass of 500+ lbs per cubic foot, based on actual calculation of its components. The estimated recoverable mass of Canyon Diablo is a mere 30 metric tons, or 0.011% of what hit the Earth."

And no, Canyon Diablo is not typical. Composition is a big determining factor is percent of recoverable meteorite material. Recoverable mass of most irons and pallasites will be in the 20% range, stoneys 10-15%, and carbons about 5%~. Of course, these are rough estimates.

billpeters

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Related, I came across this as the anniversary of Sikhote Alin just passed.  That fall created over 100 craters and I think it's cool that they worked backwards to figure out how the initial mass broke up.

 

EQodJqKU4AECsql.jpg

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That's a very interesting chart for sure. Makes me wonder how much time and patience it took to put that together. Too bad there's not an English version. 

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I found this online.

"The strewn field for this meteorite covered an elliptical area of about 1.3 km2 (0.50 sq mi). Some of the fragments made impact craters, the largest of which was about 26 m (85 ft) across and 6 m (20 ft) deep.[7] Fragments of the meteorite were also driven into the surrounding trees."

To me, that's a pretty small strewn field.

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