Fun Science

  • >Impact Show all

    Approximately 50,000 years ago, on a continuous plain extending for miles in the high desert plateau of Northern Arizona, out of the northeastern sky, a pinpoint of light grew rapidly into a brilliant fireball. This body was probably broken off from an asteroid during an ancient collision in the main asteroid belt (between the planets, Mars and Jupiter) some half billion years ago. Hurtling about 26,000 miles per hour, it was on a rendezvous course with earth. In seconds, it passed through the earth's atmosphere with little loss of velocity or mass.

    In a blinding flash, a huge iron-nickel meteorite or dense cluster of meteorites, estimated to have been about 150 feet across and weighing several hundred thousand tons, struck the rocky plain with an explosive force greater than twenty million tons of TNT. Traveling at supersonic speed, this impact generated immensely powerful shock waves in the meteorite, the rock and the surrounding atmosphere.

    In the air, shock waves swept across the level plain devastating all in the meteor's path for a radius of several miles. In the ground, as the meteorite penetrated the rocky plain, pressures rose to over twenty million pounds per square inch, and both iron and rock experienced limited vaporization and extensive melting. Beyond the affected region, an enormous volume of rock underwent complete fragmentation and ejection.

    Watch an animation of how scientists think the meteor collision occured.

  • >Making The Crater

    The result of these violent conditions was the excavation of a giant bowl shaped cavity. In less than a few seconds, a crater was carved into this once flat rocky plain. During its formation, over 175 million tons of limestone and sandstone were abruptly thrown out to form a continuous blanket of debris surrounding the crater for a distance of over a mile. Large blocks of limestone, the size of small houses were heaved onto the rim. Flat lying beds of rock in the crater walls were overturned in fractions of a second and uplifted permanently 150 feet.

    Fragments of rock and iron-nickel, some as large as a few feet across, were thrown several miles away. In some of the shocked meteorites, the intense pressures transformed small concentrations of graphite into microscopic sized diamonds.

    A dense hot cloud rose high above the crater carrying with it droplets of molten iron-nickel, pieces of molten rock, and abundant rock debris. This material rained down as fallout until the cloud drifted away and dissipated to the surrounding area. Meteorite fragments that separated early from the main mass during its passage through the atmosphere continued to fall at lower velocities on the crater and surrounding area during and immediately after the impact.

    Prior to impact, less than a percent or so of the meteorite was lost due to atmospheric heating and ablation as it plummeted to earth. During impact, however, it is believed that a small percentage was vaporized, whereas the majority was melted. Any meteorite material that did not vaporize or melt was intensely fragmented and either thrown out during excavation or mixed with the fragmented rock that remained in the crater.

    Watch an animation of how scientists think the meteor collision occured.

    About half is thought to be present in very small to microscopic iron-nickel spherules and fragments scattered through out the Breccia lens beneath the crater floor. As a result of the impact, the crater floor was 700 feet deep; it is now approximately 550 feet deep. The crater is over 4,000 feet across and 2.4 miles in circumference.

  • >Discovery

    There is evidence of the crater being referenced by Native Americans in the area; however a man named Franklin, who served as a scout for General Custer, wrote the first report of the crater in 1871. For years the crater was referred to as Franklin's Hole. Later, local settlers named it Coon Butte, and it was thought to be just another extinct volcano, possibly part of the Hopi Buttes volcanic field located in the northeast. In 1886, a sheepherder found iron-nickel meteorites in the area; but believing them to be silver he did not report his findings until 1891. Eventually, such discoveries led to the suggestion, by some, that the crater was a result of a giant meteor impact.

    During that year, the chief geologist of the United States Geological Survey, G.K. Gilbert briefly visited and explored the crater. He had earlier correctly concluded that the bulk of the craters on the moon were formed by impacts. However, he interpreted the field evidence at Meteor Crater incorrectly and concluded it had volcanic origin. Although this idea held fast for the next two decades, a major change in scientific thinking was about to occur.

    In 1902, Daniel Moreau Barringer, a Philadelphia mining engineer, became interested in the site as a potential source for mining iron. He later visited the crater and was convinced that it had been formed by the impact of a large iron meteorite. He further assumed that this body was buried beneath the crater floor. Barringer formed the Standard Iron Company and had four placer mining claims filed with the Federal Government, thus obtaining the patents and ownership of the two square miles containing the crater. This was ten years before Arizona became the 48th state.

    In 1903, Barringer came to meteor crater and spent the next twenty-six years attempting to find what he believed would be a giant iron meteorite. His work and scientific research were carried on with great perseverance and bitter disappointment. Since the crater is roughly circular, it was natural at that time to assume that the body that formed it lay beneath its center. Consequently, the first shaft was started where the low, white mounds of pulverized Coconino sandstone can still be seen on the crater floor. A few small meteoritic fragments were reported in the shaft, but unfortunately, the pulverized sandstone beneath the water table turned to quicksand and prevented mining to a depth where the main body was supposed to lie.

    After the initial exploration, Barringer conducted some simple experiments and discovered that a rifle bullet fired into thick mud, even at a low angle, generally produces a circular hole. This was an important clue- could the meteorite have penetrated at an angle and is buried off center? Looking at the south crater wall you will see as did Barringer, that the rock is noticeably uplifted. Sandstone and limestone beds, which once were deeply buried, are now more than 250 feet above their pre-impact levels; in fact, they are higher than anywhere else in the crater.

    This observation, coupled with the fact that many meteorite fragments had been found on the northeast side of the crater, led Barringer to conclude that the mass had come in at an angle from that direction and buried itself beneath the south rim of the crater.

  • >Mining

    Looking again at the south crater wall, you will see a notch with a streak of red debris running down the slope. Drilling was started at that notch and at a depth of 1,250 feet Barringer reported increasing numbers of oxidized meteorite fragments. At times, hours passed with no progress in deepening the hole and eventually the drill bit jammed completely. Barringer interpreted this to be caused by meteorite debris.

    The drill bit was permanently stuck, the drill cable broke. Funds were exhausted, and the exploration was abandoned in 1929. Although Barringer died later that year, he lived to see his theory of the impact origin of the crater begin to be increasingly accepted by the scientific community.

  • >Modern Development

    In 1941, the Barringer family entered into a lease with the Bar T Bar Ranch Company, a cattle operation that started in the 1880's and owns or leases the surrounding lands. In 1955, Bar T Bar Ranch Company formed a separate corporation, Meteor Crater Enterprises, Inc., and entered into a long-term lease with the Barringers.

    All the facilities at Meteor Crater were built, maintained, and are staffed by the Enterprises. Today the Barringers still own the land and both the Barringer family and the owners of the Enterprises regard the property as a public trust. Each year they both make substantial contributions to science and education; through grants, scholarships, and special awards.

  • >Scientific Discovery

    Modern geological and geophysical exploration techniques have largely replaced the earlier method of digging shafts and rotary drilling. New approaches include the use of seismic, gravity, magnetic, and electrical field techniques.

    Recently, cosmic ray spallation procedures were used to arrive at a more accurate age of the crater and C14 dating techniques have been used to address erosion and climactic issues. Advanced microscopic, x-ray, and other laboratory procedures are used to study the shocked rocks, meteorite material and their histories.

    Dr. Eugene Shoemaker, Ed Chow, and Don Milton, all of the U.S. Geological Survey, discovered two important minerals at Meteor Crater: coesite and stichovite. Both are high-pressured polymorphous forms of silica, or silicon dioxide (SiO2), altered to very dense crystalline states by extremely high pressures equivalent to more than 20,000 times atmospheric pressure, or 300,000 pounds per square inch.

    Although coesite and stichovite can be produced in the laboratory, they had not been identified in nature. Since the Meteor Crater research, both minerals have been identified at a number of other geological features called astroblems. The existence of these two highly pressurized minerals is now part of the diagnostic criterion used to prove that these sites are indeed ancient meteorite craters.

    In recent years, work has been completed at Meteor Crater in the fields of terrestrial impact craters, cratering mechanics, planetary studies, and astronaut training. From 1964 through 1972, the U.S. Geological Survey and NASA provided extensive science training at Meteor Crater for the Apollo astronauts, under the guidance of Dr. Eugene Shoemaker and Dr. David Roddy, both with the Branch of Astrogeology of the U.S. Geological Survey.

    This training was particularly significant because scientists were extremely interested in what materials lay on the lunar surface as well as what was beneath the surface. The cratering process ejects material that actually originates below the surface of the crater, therefore, when our astronauts went to the moon, they knew they should be able to collect material on ejecta blankets that originated beneath the crater regions- a valuable sampling technique learned at Meteor Crater.

  • >Fingerprints from Space

    Photographs of our moon, the other planets and their satellites clearly show that the craters were the result of meteorite, asteroid and comet impacts. Decades of research on the earth's surface now show that it has been the target of numerous collisions, both large and small.

    Today, Mother Nature continues her process of slow but inevitable erosion by wind, water and heat. Fortunately for science and all of us, Meteor Crater shape has changed relatively little since its formation 50,000 years ago.

    The crater walls have been only slightly modified by erosion and, in places, still exhibit some original fallout from the debris cloud. The rim crest has been lowered by erosion less than a few tens of feet, and still stands some 150 feet above the surrounding plane. The majority of the ejecta blanket is still present. Most craters on earth have been leveled by erosion. Although there are many larger terrestrial impact sites, Meteor Crater is the first proven and best-preserved impact site on earth.

    This feature, named Meteor Crater or Barringer Meteorite Crater, represents the most basic type of impact crater in the solar system. In 1968, Meteor Crater was designated a Natural Landmark by the Department of the Interior.

    At Meteor Crater, we are attempting to illustrate collision and impact processes, which played a dominant role in the development of our planets, satellites, asteroids and comets. The geological and planetary records are clear: collisions, ranging in size from microscopic to gigantic events, have occurred since the beginning of the solar system, and will continue to occur. Indeed, the very course of life on earth has been affected by this endless bombardment. No less can be expected in the future!

  • >B612 Foundation Movie with Ed Lu