I did an article for another media outlet a few years ago about one of the most interesting and least understood impact materials found at Barringer Crater better known to the public as Meteor Crater in Arizona.
Let’s take a trip back in time to 50,000 years ago and imagine that it is a pleasant morning. The animals many of which have since gone extinct were roaming the central plateau we now call Arizona. Without any warning, there appeared a blinding light that streaked across the sky accompanied by a boiling trail of fire and smoke. Did the animals raise their heads to look we will never know. The source of the light went into the ground and for the briefest of moments, there was nothing. Then a tremendous explosion tore open a hole in the ground and a firestorm roared across the landscape extinguishing all life for perhaps twenty miles. The earth tremor created was felt by all the land animals for maybe a hundred miles. A cloud of superheated material was rising above the newly formed crater and chunks of rock and asteroid were falling around the area out for miles. Nothing was alive moments later when the vaporized portion of the iron asteroid began to cool in the air and fall as a rain of trillions of tiny metallic droplets amounting to thousands of tons of the asteroid.
Fifty thousand years later there are still trillions of these tiny bits of melted asteroid in the soil around Meteor Crater. They are called iron spheroids and they were seen and ignored for several decades before their true significance as the major remaining mass of the asteroid was realized by Dr. H. H. Nininger. Daniel Barringer saw them in the soil around the crater. His partner Benjamin Tilghman saw them in the soil samples. Others saw the tiny magnetic particles and also took no real notice. However after the volatilization theory was proposed by Forest Ray Moulton, Nininger sought to prove it by finding the remaining mass of the asteroid in the soil around the crater. And he did find that a great amount of the asteroid could even after 50,000 years be accounted for by the tiniest of evidence in the dirt near the crater.
Not all the spheroids have survived to the present time. The ones on the outer edges of the fireball where there was oxygen were turned to iron oxide blew away and quickly rusted away. The iron spheroids with little or no nickel have also rusted away over time. The ones that remain are the ones formed where there was no oxygen in the mushroom cloud, and that have a much higher concentration of nickel and cobalt than was in the asteroid body itself. Once the asteroid was a vapor the gloves were off as far as the composition the spheroids could have. All the possible mixtures of the elements in the asteroid formed and fell as tiny droplets. They are called spheroids but they are not all spheres. They are roughly rounded shapes but many are more elongated than spherical. They are lumpy and bumpy and they are tiny.
I have worked with them many times over the last thirty or forty years and it is always work done under some kind of magnification with very good tweezers. I found that magnetized needles were a nuisance when sorting the spheroids. You could not drop them where you wanted after they were stuck to the point of the needle. You would have to knock them off with a tap and lose control of where they fell. Using nonmagnetic tweezers works far better though it is a one-spheroid at a time process with magnification. Maybe some kind of tiny electromagnet with a switch is something that I should make in the future. Then I could pick up groups at a time and drop them into the place where I want.
Let’s insert two weeks right here. That is the time it took for me to think about that last statement and then rummage around in my ancient electronic parts to find a soft ferrite rod from an old radio antenna coil. I stripped off the Litz wire that was on it took it to the lab and ground down one end on a diamond lapping disc into a much thinner rod with a flat tip about two millimeters in diameter. I wrapped regular copper wire on the rod and connected a battery for a test. I just put on a small number of turns to try the concept. I had already placed a magnet on one end to see if the other end would pick things up and it did. The ferrite rod should have permeability and coercivity values that would allow it to become magnetized when the coil was energized but lose that magnetism when the current stopped flowing. I could not use a sharpened nail or needle since they would become magnetic after energizing the electromagnet. I needed the core of the electromagnet to be of a material that could not become a permanent magnet. Ferrites come in all kinds. Hard ferrite materials for example are used to make the refrigerator magnets and the magnets in loudspeakers so I was hoping that the ferrite rod I had was of a soft enough variety to not hold magnetism. The images below show the steps of this fun project.
So now after a test using a magnet on the far end of the ferrite and a poor electromagnet as proof of concept, I went on to make a good coil of about three hundred turns of insulated copper wire. I added a push button switch and attached a battery. It is not very attractive visually but it is iron attractive when I push the switch. Here is an image of the finished electromagnetic tweezers. I don’t know what to call it but I suppose that name will work.
While I am on the topic of magnetism some of the Nininger spheroids are still attracted to each other after roughly eighty years since The Doctor separated them from the sluggets and bits of iron shale which were all collected together in the soil samples. About one out of twenty spheroids will stick to other spheroids and my fine pointed metal tweezers that have themselves never been near a magnet. I have to lightly tap these into the tiny bottles we use in our displays. The majority never had a composition that made holding magnetism possible. Other spheroids were very easily magnetized and have retained that brief magnetic exposure from decades ago for all this time and maybe forever.
Back to the iron spheroids themselves.
There is a size range for the spheroids and the larger ones are noticeably much bigger than the smallest ones. To weigh them I found it necessary to screen them with my geological sieves get the sample that I wanted and then take a thousand of those and put them on my milligram scale. Nininger’s separation is pretty good but there are some larger ones among his smaller ones. I took a sizing screen that would catch the few that were too large to be called small and let the rest pass through. I manually counted out ten piles of one hundred to arrive at my thousand to weigh. Simple division was used to determine the average weight of one spheroid. The same thing could be done with the larger spheroids to get their weight. However, I did not have a thousand of the large ones so I am using Nininger’s weight as my data point for the large size. I think I had an advantage over Dr. Nininger by having a variety of highly precise scales at my disposal. But then I don’t know what he had in the 1930s and 40s. I sold a scale years ago that would have been wonderful for the spheroid weighing work. It was a Mettler that came out of NASA and could weigh in one-hundredths of a milligram. But it was impractical for me as I had no stable base to place it on. The cars passing on the street and the people walking in the house moved the floor and desk enough to drive me insane when trying to get a true weight reading. A milligram scale is sufficient, especially using a sieved sample of one thousand. I should say at this point that I used the large quantity of Nininger-collected spheroids from my collection for this work and not the ones I found long ago when access to the area was permitted. Mine have not been separated and graded by size as the Nininger ones.
I have said that trillions of the spheroids were produced and that is a big number. They told us in high school that math would be something we would need. On TV and movies, they have joked that math would save us at some point in our lives. Two years ago I found myself needing to do some math. I had to be sure that I was safe writing that trillions of metallic spheroids remain in the soil around Meteor Crater today.
I have been very conservative actually in these calculations. By reducing greatly the amount that Nininger estimated was still around the crater. He determined his number by collecting a large number of equal-sized samples from the soil in a selected area near Meteor Crater. I recently read an article that greatly increased the amount far above Ninninger’s estimates so my numbers for the spheroids may even be much lower than their true abundance.
Dr. Nininger had sampled very carefully an area on the northeast of the crater and extracted the spheroids from his soil samples using a magnetic device of his manufacture. He states several different ranges for the tonnage. But while discussing the cobalt enhancement he wrote that 2,000 – 3,000 tons of spheroids were in just the two square miles used in his sampling. I took a middle-range figure of 2,500 tons and used a metric ton which is midway between an American short ton and an Imperial long ton for the unit in my calculations. Though I am pretty sure that Dr. Nininger used a regular American ton in the 1940’s.
The image shown here is one thousand sieved small spheroids. They weigh on average 0.88 milligrams each. Nininger determined the weight of the large ones he used for metallurgical analysis to be 2.778 milligrams each. The average of his large ones and my small ones is 1.829 milligrams. 2,500 metric tons equals 2.540 trillion milligrams and therefore using my average weight. More than 1.3887+ trillion spheroids are remaining in just the two square miles northeast of Meteor Crater. There is an obvious problem of taking the largest and the smallest and doing a straight average. It would be better to take a large number of sieved fractions and determine a truer distribution of the sizes and weights for each fraction of the whole sample. However for my purpose here the average is in this writer’s opinion close enough to illustrate the points of interest.
That was fun and maybe no one else has done this. I should copyright this info somehow. Actually, it is copyrighted right now. The spheroids as I said before had been seen and mentioned as magnetic particles in the soil around the crater since at least the 1905 work of Barringer and Tilghman. But they were looking for the whole asteroid and not interested in the tiny spheroids they considered to be of no value in the dirt. Tilghman dropped out of the joint endeavor of Standard Iron Company and was bought out by Barringer. Barringer spent the next couple of decades promoting and raising money for the exploration of the crater to find the gigantic mass of nickel-iron he believed was buried there. He began work at Meteor Crater as a man who was very well off financially. He had the mine in Arizona which was one of the largest discoveries of gold and silver ever in the state. By the end, after spending all he had on Meteor Crater he sold his home and property and moved the family into a rental. He managed to still send his sons to Princeton I think, but he was no longer wealthy. Here is what might have happened if he had just pulled a larger number of magnets through the soil around Meteor Crater as he cut the soil with plowing discs.
Taking Nininger’s tonnage of spheroids in his two-square mile sampling area and cutting his concentration in half to be super extra careful yields 750 tons of spheroids per square mile.
Using the often quoted area of 200 square kilometers (78 sq. miles) as the area where condensation and other products of the impact are concentrated. The total weight of spheroids in that whole area around Meteor Crater is even at my reduced level 58,500 tons.
Using the enhanced percentages of Nickel and Cobalt Nininger determined were in the spheroids as the composition it is possible to determine the value. The following easily possible numbers result. Remember I am using 1/2 Nininger’s concentration of spheroids to be conservative. The elemental analysis that Nininger got has also been confirmed by others since his time.
Nickel Amount and Value
10,237.5 tons of Nickel which equals 22,569,792 pounds of Nickel. At the known 1922 price of $0.42 per pound that is $9,479,312.64 that Barringer could have extracted from the area around Meteor Crater as a raw magnetic “ore.”
Cobalt Amount and Value
731.25 tons of cobalt which equals 1,612,128 pounds of cobalt with a price fixed by producers for years which was in 1937, $1.29 per pound or $2,079,645 give or take a little for any small difference in the 1922 price.
For a conservative total of over $11,000,000 that’s millions with an “m” in 1922. Talk about missing a resource. I have also said nothing about the “FREE” iron that would have been collected along with these more valuable and strategic metals. The iron amounted to around 48,000 tons. That’s about the weight of a WWII battleship. The spheroids even the least weathered are surrounded by a coating of iron oxide so whether all the weight would be available to smelt into iron ingots is a reasonable question to ask. Some certainly would have been recovered and with the amount available the smelting process might have been adjustable to permit getting the most material from the spheroids. Especially because there was no rock to be crushed and disposed of. And the slag would have been quite different from that in a regular smelting routine.
Barringer and everyone else since the beginning of investigations knew about the spheroids and other nickel-iron particles in the soil. Add to these amounts the thousands of meteorites that would also have been recovered if he just scrapped the soil into some type of collecting machine like a dry washer with magnets he would have been rich. Instead, Barringer spent $150,000 of his money and roughly $600,000 from outside investors looking for something that was not there. His buried star.
But it is not all Barringer’s fault. Meteor Crater was the first crater to be investigated as a place formed by an asteroid impact. The crater played tricks on him too. His drillings into the floor of the crater hit meteorite fragments in most of the original twenty-eight holes he drilled. He did not realize that those were small fragments that fell into the crater immediately after the explosion and were mixed and covered by fallback rock and lake deposits. The thousands of fragments buried under the crater floor and those found so far along with fragments remaining on the plain surrounding the crater represent only a tiny amount of the original asteroid. But Barringer could not know that or believe that. The presence of all the pieces his drill hit just led him to create new theories that always ended with an assumption that vast amounts of pure nickel-iron were buried at Meteor Crater. Barringer could probably never have conceived at the beginning of the work that the projectile had penetrated many hundreds of feet of rock before coming to rest and exploding. In 1920 Barringer signed a lease with United States Smelting Refining and Mining Co. to drill on the south rim down into the area of greatest uplift and deformation at the crater. Though unsuccessful at reaching the buried mass of nickel-iron because it was never there. The drill did hit masses of meteorite that were extraordinarily hard to drill through. They were as hard as the drill bits and progress was made at the expense of dulled and repeatedly resharpened drill bits with only a single inch of progress made in a whole day sometimes. But the explosion of the asteroid did send pieces of the nickel-iron everywhere even if the final surviving amount was small.
I looked for the most recent estimates for the mass of the asteroid that formed Meteor Crater and was not very happy with the results of that internet search. Some references are for several hundred thousand tons. I guess no one wants to try or maybe they can not work it out more closely. Years ago the value was near 150,000 tons. Nininger states at one point 200,000 tons. If we use the 150,000 amount and remember that they are thinking even bigger today then this simple math work will show clearly what happened. The Meteoritical Bulletin currently shows 30 tons for the amount of Canyon Diablo meteorites recovered from around the crater. If there were for example double that amount for all the fragments under the crater floor. And add some more for the fragments not yet found around the crater and further round it up to 100 tons of fragments this is the percentage of what survived the impact. Just 0.000666% of the impact mass. So to put the expression the other way, 99.99933% of the asteroid vaporized. Moulton was certainly right and his 1920 math was indisputable. Did Barringer finally realize that no asteroid metal remained, we won’t ever know. But he was disturbed by the report. Within a few days of the release of Moulton’s calculations, Daniel Barringer was stuck with a heart attack and died. It is reported that he was highly agitated by the vaporization theory and was scrabbling to try and rally supporters to his stubbornly held conviction that a great mass of asteroid was still buried. So maybe he never gave up his belief after all.
Today the iron spheroids from Meteor Crater are fascinating reminders of the power of cosmic impacts and of the immense heat released when something nearly twice the mass of the Queen Mary, iron, solid and compact hits the Earth at fantastic speed. Now for the commercial break. We have neat displays of Meteor Crater spheroids collected by H. H. Nininger for sale at Meteorites-For-Sale.com. They will make a wonderful addition to any collection of Meteor Crater meteorites, impactites, and materials.