by apodman » Thu Aug 13, 2009 1:50 am
neufer wrote: http://en.wikipedia.org/wiki/Barringer_Crater wrote:The object that excavated the crater was a nickel-iron meteorite about 50 meters (54 yards) across ... It is believed that about half of the impactor's 300,000 tonnes (metric tons) bulk was vaporized during its descent, before it hit the ground.
http://en.wikipedia.org/wiki/Barringer_Crater wrote:Barringer, who in 1894 was one of the investors who made $15 million in the Commonwealth silver mine in Pearce, Arizona in Cochise County, Arizona, had ambitious plans for the iron ore. He estimated from the size of the crater that the meteorite had a mass of 100 million tons. The current estimate of 300,000 tons for the impactor is only three-tenths of one percent of Barringer's estimate.
I'm glad my antique hand-held calculator is powered by photons, else a guy could wear out some batteries checking facts to try to understand.
First, the back-of-the-envelope density calculation: A 50 meter sphere is about 65,450 cubic meters or 65,450,000,000 cubic centimeters. If it has a mass of 300,000 metric tons or 300,000,000 kilograms or 300,000,000,000 grams, it has a density of about 4.6 grams per cubic centimeter. This is less than the 7 or 8 grams per cubic centimeter I've seen quoted for iron-nickel meteorites, but it's close enough that the quoted size and quoted mass are in the same ballpark. Of course, if the 50 meter size is supposed to go with the 150,000 kilogram reduced mass, the discrepancy is greater.
Second, Barringer's number was a lot bigger than 300,000 metric tons (by a factor of more than 300), so "wow", that's quite a revision from the initial estimate to the current one.
Third, 150,000 metric tons (if half of the 300,000 ton impactor vaporized before impact with the solid ground as stated above) is a lot higher (by a factor of 5,000) than the Total Known Weight (30,000 kilograms or 30 metric tons) quoted in the other article. So I guess the Total Known Weight doesn't reflect the total estimated weight of the meteorite (which they didn't explain in the article so I would notice). So what does the 30,000 kilogram figure represent? I'm guessing it's total weight found and recovered, which might be useful for small meteorites but sounds like a less than useful number to give a hint of the mass of a large object that is mostly buried and/or melted into the Earth's crust.
[quote="neufer"][quote=" http://en.wikipedia.org/wiki/Barringer_Crater"]The object that excavated the crater was a nickel-iron meteorite about 50 meters (54 yards) across ... It is believed that about half of the impactor's 300,000 tonnes (metric tons) bulk was vaporized during its descent, before it hit the ground.[/quote][/quote]
[quote=" http://en.wikipedia.org/wiki/Barringer_Crater"]Barringer, who in 1894 was one of the investors who made $15 million in the Commonwealth silver mine in Pearce, Arizona in Cochise County, Arizona, had ambitious plans for the iron ore. He estimated from the size of the crater that the meteorite had a mass of 100 million tons. The current estimate of 300,000 tons for the impactor is only three-tenths of one percent of Barringer's estimate.[/quote]
[quote="neufer"][quote="[url]http://en.wikipedia.org/wiki/Canyon_Diablo_(meteorite)[/url]"]The Canyon Diablo meteorite impacted at Barringer Crater (Meteor Crater), Arizona and is known from fragments collected around the crater ... Total Known Weight (TKW) 30,000 kg.[/quote][/quote]
I'm glad my antique hand-held calculator is powered by photons, else a guy could wear out some batteries checking facts to try to understand.
First, the back-of-the-envelope density calculation: A 50 meter sphere is about 65,450 cubic meters or 65,450,000,000 cubic centimeters. If it has a mass of 300,000 metric tons or 300,000,000 kilograms or 300,000,000,000 grams, it has a density of about 4.6 grams per cubic centimeter. This is less than the 7 or 8 grams per cubic centimeter I've seen quoted for iron-nickel meteorites, but it's close enough that the quoted size and quoted mass are in the same ballpark. Of course, if the 50 meter size is supposed to go with the 150,000 kilogram reduced mass, the discrepancy is greater.
Second, Barringer's number was a lot bigger than 300,000 metric tons (by a factor of more than 300), so "wow", that's quite a revision from the initial estimate to the current one.
Third, 150,000 metric tons (if half of the 300,000 ton impactor vaporized before impact with the solid ground as stated above) is a lot higher (by a factor of 5,000) than the Total Known Weight (30,000 kilograms or 30 metric tons) quoted in the other article. So I guess the Total Known Weight doesn't reflect the total estimated weight of the meteorite (which they didn't explain in the article so I would notice). So what does the 30,000 kilogram figure represent? I'm guessing it's total weight found and recovered, which might be useful for small meteorites but sounds like a less than useful number to give a hint of the mass of a large object that is mostly buried and/or melted into the Earth's crust.