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----------------------------- 2389 - METEORS - we call them shooting stars.
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- Meteoroids are usually varying in size from a grain of sand to the size of a baseball. What astronomers have recently learned is that shooting stars leave a trail of dust in our atmosphere that eventually makes its way to the surface of the Earth. These dust particles are only 10 to 20 microns in diameter.
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- A micron is a micrometer, or a millionth of a meter, 10^-6 meters. 20 microns is half the width of a human hair. 350 microns is the length of a grain of salt. 5 microns is smoke. One large meteor can leave a 1000 tons of this dust in its trail.
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- Estimates are that 110,000 tons of meteoroids land on the Earth every year. That is equivalent to 300 tons a day. That is equivalent to 30 elephants falling out of the sky every day. Of course, they do not fall in one place and 70% of them would fall into the water. But, that much mass is being added to the Earth every day.
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- That is still a lot of dust and it certainly has the potential of changing Earth’s climate. A large screen of dust would act as a blanket trapping Earth’s heat near the ground raising the average temperature around the globe. This dust is also the cause of the formation of most rain clouds. Each dust particle falls to Earth with the raindrop that formed around it.
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- When the meteoroid hit’s the Earth’s atmosphere at 30,000 mph it heats up to 3,000 F degrees. The meteoroid is then called a meteor, and if it hit’s the ground it is called a meteorite.
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- Most people believe that the friction of the air causes the meteor to heat up. Actually, much like the blunt nosed space shuttle it is “ram pressure” that produces the heat. The air is compressed in front of the fast moving object causing the air to heat up much like a tire heats up when you pump up its pressure, compressing the air inside.
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- Often the heat is intense enough to vaporize the meteor. It is these vapor trails that we call “ shooting stars”. They become visible starting about 60 miles up. Some large meteors splatter into a “fireball” explosion. One very large meteor exploded over Tunguska, Siberia, in 1908. The explosion leveled hundreds of square miles of forest.
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- Meteoroids can be broken off pieces of asteroids or the dust off comets. In fact, asteroids are simply meteoroids that have coalesced together due to mutual gravity or collisions. Planets are simply asteroids that have coalesced together through the same process.
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- The gaseous planets are simply comets that have coalesced together in this way. Asteroids and comets are, in effect, minor planets. Meteoroids are, in effect, minor asteroids and comets.
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- The asteroid belt between Mars and Jupiter would be another planet except Jupiter’s gravity keeps the asteroids moving at 3 miles per second, too fast for them to coalesce.
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- Science fiction movies always portray the asteroid belt has a cluster of asteroids being dodged by the space ship as it maneuvers through the maze. Actually the average distance between asteroids in the belt is over 6 million miles. Space ship maneuvering in this real situation would not be nearly as action packed for the movies.
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- Whether a meteor hit’s the Earth or vaporizes in the atmosphere depends on its speed, the angle of entry, its size and its composition. If it does hit the ground it will blast out a crater 10 to 20 times its size.
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- There are 3 basic types of meteorites: iron, stony-iron, and stony. Obviously the iron meteorites have the best chance of surviving the denser atmosphere and hitting Earth. As broken pieces of asteroids the iron ones came from the center core and the stony ones came from the outer crust.
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--------------------- Iron meteorite: 91% iron, 8.5% nickel, 0.6% cobalt
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--------------------- Stony-Iron meteorite: 36% oxygen, 26% iron, 18% silicon, 14% magnesium, 1.5% aluminum, 1.4% nickel, 1.3% calcium.
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--------------------- Stony meteorite: : 49% oxygen, , 26% silicon, 7.5% aluminum, 4.7% iron 1.4% nickel, 3.4% calcium, 2.6% sodium, 2.4% potassium, 1.9% magnesium , and trace elements of iridium.
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- If 300 tons of this stuff falls on the Earth each year how long would it take to make the whole Earth?
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- 1.095*10^5 tons/year. The Earth weighs 6.585*10^21 tons. That would take 60,000,000 billion years. But, the Earth is only 4.5 billion years old. Obviously, a lot more and bigger meteors came together faster in the past. It would take an average of 1,460 billion tons / year of meteors to make the Earth. There must have been some major collisions in Earth’s early years of formation.
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- For the first 17 centuries meteors were thought to be acts of God. In 1807 a fireball meteor exploded over Connecticut and several meteorites rained down. After astronomers studied these meteorites and as well as the asteroids a new theory materialized that meteorites are bits of asteroids zipping around our solar system. The theory still holds today.
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- The largest meteorite recovered in the US fell on Nebraska in 1948. It weighed 2,360 pounds. A little over one ton. All meteorites would add up to 300 of these landing each day. Fortunately, there are many, many more than 300 and they are much, much smaller.
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- The Meteor Crater in Arizona occurred 20,000 to 50,000 years ago. It is 600 feet deep, a mile wide, and the rim rises up 150 feet above the surrounding plain.
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- Iridium is another heavy metal found in meteors. It is heavy and therefore settled at the center of Earth billions of years ago. So, when Iridium is found on the Earth’s surface it must have come from meteors. Discovering a layer of Iridium around the globe is what lead scientists to conclude that a giant meteor hit the Earth 65 million years ago and wiped out the dinosaurs.
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- When we witness meteor showers of hundreds of shooting stars emanating from one location in the night sky, the Earth is passing through the tail left by a comet that passed in the path of Earth’s orbit around the Sun.
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- Astronomers have identified 1000 Sun grazing comets to date. Some coming to within 500,000 miles of the Sun’s visible surface. Comets in a group have similar orbits and are thought to be fragments from a larger comet that has broken apart from the Sun’s gravity.
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- As the comet approached the Sun, the gas and dust was pushed off the comet by the Solar Wind, the charged particles emanating from the Sun. This becomes the comet’s tail that always points away from the Sun regardless of the comets direction in space. The dust particles form a yellowish tail and the ionized (charged) gas particles form the bluish tail.
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- When you see comets and shooting stars I the night sky, see them as embryos of planets on our solar system. You are simply standing on a bunch of meteoroids that have stuck together.
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- But one step in the miracle tale of how we got here. What a miracle you are even here reading this.
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- June 2, 2019
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--------------------- Sunday, June 2, 2019 ---------------------
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