Shoemaker – Levy 9
Over 200 million Megatons of dynamite collide with Jupiter. In July 1994 Shoemaker – Levy 9 collided with Jupiter. What is Shoemaker – Levy 9, and how was it discovered? What is Jupiter, and why did Shoemaker – Levy 9 collide with it? Can an event like this happen to Earth? I will answer these questions in this report. But let me start by telling you what Shoemaker – Levy 9 is.
Shoemaker – Levy 9 is a comet, a small irregular mass made up of rocks and frozen gasses. Comets follow large orbits from around the Sun to the outer corners of our solar system. A comet is so fragile that if you could hold a piece of it in your hands you could pull it apart. Comets only become visible when they get close enough to the Sun for it’s heat to vaporize the comet’s gasses causing a long tail called the coma. The coma of a comet can be millions of miles long. The comets themselves are only between 20 and 750 kilometers wide. Like all other objects the comet follows the law of gravity. It’s orbit is decided by the largest object in the solar system, the Sun.
Shoemaker – Levy 9 was discovered photographically by Carolyn S. Shoemaker, Eugene M. Shoemaker, and David H. Levy on March 24, 1993. They used the Schmidt telescope at the Palomar Observatory in California. Shoemaker – Levy 9 was named for it’s discoverers and the nine indicates that it was the ninth short period comet discovered by this team. (A short period comet is a comet that has an orbit that lasts less than two hundred years.) Shoemaker – Levy 9 was confirmed by James V. Scotti of the Spacewatch Program at the University of Arizona. It was then given the designation 1993e by the International Astronomical Union’s Central Bureau for Astronomical Telegrams. This designation shows that Shoemaker – Levy 9 was the fifth comet discovered in 1993. On May 22, 1993 Bureau Director Brian G. Marsdon reported that Shoemaker – Levy 9 could very well hit Jupiter by October of 1993. On October 18, 1993 Paul W. Chodas and Donald K. Yeomans reported to the American Astronomical Society’s Division of Planetary Sciences that the probability of impact of Shoemaker – Levy 9 into Jupiter was greater than 99%. They stated that the fragments would hit over a period of several days in the month of July 1994. They also stated that the fragments of Shoemaker – Levy 9 would land on the night side of Jupiter at latitude 40 degrees south and the longitude 35 degrees, past the midnight meridian. What is Jupiter?
Jupiter is the largest of the nine planets in our solar system. It’s diameter is ten times that of Earth’s, and it’s mass is 300 times that of Earth’s. Jupiter is made up mostly of hydrogen and helium. It’s gravity is 2.4 times Earth’s gravity, and it rotates every nine hours and 55 minutes. Jupiter’s atmosphere is 89% hydrogen and 11% helium, and it’s clouds are made up of ammonia crystals. The ammonia crystal clouds are very colorful although it is not known why. Jupiter’s polar caps are dark, and across the rest of the planet are light and dark ovals. The most famous oval is known as The Great Red Spot, which is larger than Earth. Although The Great Red Spot’s color has brightened and faded, the oval has been there for over 160 years. Jupiter has 16 satellites the largest being Io. Two voyager spacecraft have in recent years discovered that Jupiter also has faint dust rings surrounding it. Now why did Shoemaker – Levy 9 collide with Jupiter?
As stated before a comet’s orbit is determined by the Sun. It will keep that orbit faithfully unless it passes too close to one of the nine planets which will then change it’s orbit with the planet’s gravitational pull. This is what happened to Shoemaker – Levy 9 when it got too close to Jupiter. Another effect of Shoemaker – Levy 9’s encounter with Jupiter’s gravitational pull was that it caused Shoemaker – Levy 9 to break up into many pieces. It is believed that it took Jupiter’s gravitational pull several decades to change the orbit of Shoemaker – Levy 9. The impact of Shoemaker – Levy 9 is the first time that scientists have discovered an object in space and been able to determine it’s consequences to a planet in more than seconds in advance.
If scientists had observed something like this before it would have been less amazing and less interesting. Fragment A struck Jupiter with a force of 225,000 megatons of dynamite creating a plume, which rose about 100,000 kilometers above Jupiter’s cloud tops. Fragments B, C, D, and E were similar to the impact of fragment A. Fragment F was very hard to detect. The biggest impact was from fragment G which struck with the force of about 6,000,000 megatons of dynamite, that is about 600 times the amount of all of the nuclear warheads in the world. The plume from fragment G rose about 3,000 kilometers above the clouds. The impacts from fragments G, K, and L created craters that were at least an Earth diameter across. The remaining fragments created craters of all different sizes. From watching the events of Shoemaker – Levy 9 scientists have learned more about comets, more about Jupiter, and more about the physics of high velocity impacts into planetary atmosphere. Will we ever get a closer look at this type of event? Hopefully, not!
Is there a chance of a space object colliding with Earth? Yes! Objects from space collide with Earth all the time. On October 9, 1992 a fireball was seen flying across the sky all the way from Kentucky to New York. This object was a 27-pound stony meteorite that fell in Peekskill, New York, punching a hole in the back of a car and then creating a small crater beneath it. Impacts into a Connecticut dining room and an Alabama bedroom are other well-documented cases. These were only minor impacts, however on February 12, 1947 about 150 tons of fragments reached the ground in Siberia, the largest weighing 3,839 pounds. There were 102 craters created greater than one meter in diameter the largest being 26.5 meters in diameter. This type of event happens on Earth about once in every ten years, however most of them are never reported because they occur at sea or in a remote area like Antarctica. There are even larger impacts than that on Earth, like the 1908 Tunguska Siberia impact in which an object weighing 2.2 billion pounds and 140 meters in diameter stuck Earth. The object’s impact was equal to 15 megatons of dynamite. It leveled about 2,200 square kilometers of Siberian forest. The largest object known to hit Earth happened approximately 65 million years ago near the Yucatan Peninsula in Mexico and is believed to have wiped out 70% of all life on Earth. It is estimated that an event like this occurs on Earth once every 50 to 100 million years.
This all sounds pretty scary, however no human in the past 1000 years has been known to be killed by a meteorite or comet. A person’s chance of being killed by one of these objects is nothing compared to being killed by lightening, volcanic eruptions, earthquakes, or hurricanes. I hope you have liked my report and I hope it has been informative.