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While the meteorites were gaining recognition, the origin of the crater remained in doubt. G.K Gilbert, an eminent geologist of the time and the first to suggest meteoritic origin of lunar craters, concluded that the Canyon Diablo crater was the result of a steam explosion. This theory was a long time dying and was accepted by some as late as 1953.
Commercial interests were not so doubtful. In 1903, lawyer-mining engineer-geologist Daniel Barringer recognized the crater as a potential site for mining of iron and nickel. Barringer staked mining claims on the site and began a search for a huge iron mass.
Over the next twenty years Barringer spent more than $600,000 drilling dozens of drill holes in the crater floor looking for the large mass. When he did not find it there, he hypothesized that it might be buried under the south rim. A final hole did strike increasing metal before it had to be abandoned because of bad drilling conditions. Some claimed that the long sought mass had been discovered.
Even before Barringer began his final holes a controversy began on whether any large mass would ever be found. In 1908, George Merrill suggested that the meteorite may have vaporized on impact.
Barringer died in 1929 and the high cost and ambiguous results of Barringer's efforts led investors in his company to seek reexamination of the premise of a large buried mass. The company retained a well respected astronomer and ballistics expert, F.R. Moulton, to make calculations about the mass of iron that could be expected. Moulton's startling conclusion was that the high energy of the impact would vaporize and fragment the entire mass--there would be no large iron-nickel mass.
Eventually, students of the matter reached a consensus that indeed the mass had been mostly vaporized on impact. Drilling and geophysical studies supported this conclusion. In addition, Nininger found a large area of tiny spherical iron droplets north east of the crater.
Today the Crater is operated as a private tourist attraction by the Meteor Crater Enterprise. The crater itself still belongs to the Barringer family.
The
Impact and the Crater
The Meteor Crater is a huge hole--about three
quarters of a mile wide and 600 feet deep. So, what kind of a meteorite could
have made this hole? How heavy was it? How fast was it traveling? These questions
have been the subject of scientific speculation since the crater was first recognized
being the result of an impact.
From 1910 to the 1950s different scientists
estimated a mass varying between 5,000 and 5,000,000 tons. In 1963, a scientist
compared the crater to those made by nuclear tests. He calculated that an energy
of 1.7 megatons (1.7 million tons of TNT) would be required to produce the crater.
This energy would be delivered by a mass of 63,000 tons (a sphere about 80 feet
in diameter) traveling at 9 miles per second.
The resulting crater is 3400 feet across, is about 600 feet from rim to floor, and has a rim that rises 200 feet above the plain. From the air, the crater has a squarish shape. The speculation is that this results from the character of the preexisting rock formations. (Crater photo courtesy Calvin Hamilton.).
Click here to see a really big picture of the Canyon Diablo Crater. Click here to find more information on craters and links to other sites.
Where
Did the Meteorite Go?
If a 63,000 ton meteorite hit the earth in Arizona,
where is it now? As was noted above, Moulton calculated that most of the mass
would have been vaporized on impact. Harvey Nininger, a famous meteorite hunter
and well-respected student of meteorites, hypothesized that he would find evidence
of iron condensed after vaporization. He studied the area around the crater and
mapped a large are to the northeast of the crater were tiny spherical droplets
of condensed iron can be found. This is apparently where most of the mass is located.
The idea that the huge Canyon Diablo mass was blasted into small bits is supported
by the lack of large specimens. The largest Canyon Diablo recovered is the 639
Kg on display in the Meteor Crater Museum. Specimens over ten kilograms are rare
and those over 100 Kg are only a handful. The adjoining map gives a rough idea
of the distribution of the small specimens around the crater.


Minerals
of the Canyon Diablo
The mineralogy of Canyon Diablo meteorites depends
on whether they have been shocked by impact. While all of the specimens were shocked
to some degree, some specimens found around the crater rim show very different
mineralogy. The less altered mineralogy is typical of iron meteorites. The important
minerals are:
Kamacite--this
iron nickel alloy makes about 90 percent of specimens.
Taenite--the
other iron nickel constituents taentie and plessite make up 1 to 4 percent of
the material.
Schreibersite crystals occur as
skeletal blades. This is a very hard mineral that will ruin a saw blade unfortunate
enough to be put to the task of cutting a Canyon Diablo.
Troilite--this
iron sulfide occurs as nodules up to 50 mm across or as elongated lenses. Troilite
may be mixed with graphite, daubreelite, chromite, or base metal sulfides. Troilite-graphite
masses may make up about 8.5 % of specimens.
Graphite
occurs as large bodies within iron or in separate masses.
Cohenite,
an iron carbide, is common. This mineral is even harder than Schreibersite.
Haxonite,
chromite and silicates are also found.
The specimens that were subjected
to greater shock show partial melting, recrystallization, neumann banding and
other deformation. Perhaps the most well-known shock effect
is the transformation of graphite to diamond and lonsdaleite. These take the from
of tiny dark masses that become evident on sawing. A diamond blade will move aside
when it hits one of these.
Nininger estimated that about 30 tons of specimens had been collected. Other workers have estimated that 8,000 tons of iron are contained in the fine grained material around the crater. This leaves about 55,000 tons to speculate about. Some of it remains buried as Barringer's drilling showed. The largest part of it may have been vaporized and drifted far away. Some of it remains in the form of specimens in area surrounding the crater. Until the area was closed to meteorite hunting recently, hunters with metal detectors were still finding significant numbers of specimens.