The Unseen Menace
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| (Part I) FOREWORD. Hmmm...thought the "empty-nester" and amateur astronomer as she opened the envelope. Normally, it was her habit to throw unsolicited junk mail, unopened, into the wastebasket, but this time something prevented her. Nestled among the contents of the envelope was a questionnaire. And even though it was now quite late on the Eastern Seaboard, the recipient quickly scanned the questions with interest. Suddenly, she spied the question she was hoping to find! How strange that this same question dealt with the subject she was writing an astronomy article on. Great! People are still concerned about this potential menace...she muttered as she turned off the kitchen light. Meanwhile, in the western half of the United States, the Sun had just disappeared behind the Rocky Mountains. In the twilight a small team of observers made their way to one of the few existing Spacewatch telescopes. Tonight, like so many other moonless nights, the objective of their mission would be to search for potential hazards from space, commonly referred to as, near-earth objects (NEO's). Such hazardous objects are asteroids and comets. The chilling and hair-raising Shoemaker-Levy 9 (SL9) comet impact with Jupiter, in the summer of 1994, was still very fresh in the minds of the team members. And everyone connected with the Spacewatch program wanted to do his or her very best to prevent such an awesome impact happening to Earth. However, since its inception, the Spacewatch program chronically suffered from the lack of funds and manpower, but this team, like their colleagues, firmly believed in its mission. But I think it is safe to say that tonight this little band of dedicated observers will not find the "big one" that might be headed for Earth. Even if they did, perhaps there would be ample time for the nations of the Earth to come together to pool both talent and resources. Working together they just might find a way to fend off the common menace that was moving relentlessly and unerringly towards them through the dark void and vastness of space. The Menace. Everyday, 24 hours a day, the Earth is being pelted by debris from outer space. The debris is the leftover of planetary formation and fragments of old comets. Fortunately for us, much of the debris range from micro-meteorites to large stony or stony-iron meteorites that, while they can cause a good deal of property damage, they are not so large as to bring civilization to an untimely end. But unless a person just happens to be in the path of an incoming meteorite, it is the unseen menace out in deep space that earthlings really need to concern themselves, especially, those objects of one half kilometer or more. It is these mammoth sized objects that are known to have racked enormous havoc and devastation not only upon the Earth, our Moon, and other planets and their satellites as well. Each year, the numbers of known NEO's steadily increase and along with it, the chance that Earth will suffer yet another blow. According to John and Mary Gribbin approximately one or two of these objects are discovered per month. Plus, there are approximately 2,000 known Earth-crossing asteroids (ECA's) along with a million objects between 0.1 and 1-km across. Now, add to these 500 million smaller objects 10-meters or less in size. To give you, the reader, a better idea of the seriousness of the situation, please refer to p. 192, of Gerrit L. Verschuur's fascinating and intriguing book, Impact! The Threat of Comets & Asteroids (1996). The orbits depicted represent only 115 known near-earth asteroids as of March 28, 1995! Please notice just how much potential peril our little world faces! Perhaps, the reader may recall some recent modern "close calls" that the Earth encountered on August 3, 1964, March 23, 1989, January 18, 1991, June 21, 1993, and March 15, 1994. And, may Heaven help us, when the year 2126 rolls around and the earth crossing comet Swift -Tuttle drops by (hopefully, NOT "in!") to pay it respects! Apparently the 24-kilometer diameter Swift-Tuttle comet is influenced by the gravitational pull of Jupiter and posses a threat for Earth for quite some time in the future. That is if it doesn't fall into the Sun or is thrown clear of our solar system. Calculations seem to indicate that the comet will make a close approach to Earth by some 23 million kilometers on August 5, 2126. Please remember that all it takes is one large asteroid or meteorite to gravitationally act upon another body, thereby, dislodging it from its normally harmless orbit, and send it hurling on a collision course toward Earth. Even a passing comet could very easily accomplish the same thing! In addition, some have even suggested that the passing of the fabled and elusive "death star," Nemesis could even play such a role! There are three groups of asteroids that bear watching: * The Apollo group is named for the first asteroid that was discovered to be an Earth crossing body. These asteroids actually cross the Earth's orbit when they are the closest to the Sun, but spend most of their time away from the Sun. The largest Apollo type asteroid is called Hephaistos and has a diameter of approximately 10-km. As of 1982 there were 30 known Apollo type asteroids. * The Aten group spends much of their time close to the Sun, but cross Earth's orbit when they are furthest from the Sun. As of 1982 there were 4 known Aten asteroids. * The Amor group may come close to the Earth's orbit, but does not cross it. The asteroids do come within 1.3 AU of our star. There are 23 known Amor type asteroids. And, as far as comets are concerned, Earth needs to keep the Kreutz family of comets under observation. These comets are known as 'sun-grazing' because they pass very close to the Sun. The sun grazers were named in honor of the German astronomer, Heinrick Kreutz, who first studied them and published his findings in 1891. The sun grazers are long period comets that come from beyond the boundaries of our solar system and pose a threat. Not only do they approach us from behind the Sun (and leave the same way), but also their small size makes them difficult to see. Apparently, in 1882, it took a total eclipse of the Sun in order to catch a glimpse of the first sun grazer! NOTE: Incidentally, the comet Ikeya-Seki is a member of the Kreutz family of comets. On August 30, 1979 the spacecraft Solwind took a photo of a comet before it careened into the Sun. In addition, other Solwind spacecraft have observed other sun grazing comets as well. QUERY: Okay, so a near-earth object has been spotted, what should earthlings expect? An object 10-meters in size would pose only a severe local threat. An object one half kilometer in diameter landing in the ocean would create a huge tidal wave (tsunami) that would reach far inland. But should impact occur over land, a huge crater will be gouged out of the earth followed by shock waves, earthquakes, and debris falling over a large area, followed by wild fires that had not been snuffed out by the aftermath of the impact. In addition, much of the lighter debris would be carried aloft into the atmosphere and would reduce incoming sunlight so vital to plant and animal life. Soon temperatures would begin to drop and depending upon the degree of damage, life might cease to exist. NOTE: Perhaps the reader will remember reading that after the eruption of Mount Pinatubo (June 12, 1991) that the average temperature, of the Earth, fell 0.5 degrees Celsius. This temperature drop lasted approximately two years and was caused by the 15 to 20 million tons of volcanic ash, dust, and sulfur dioxide spewed into the stratosphere. Lastly, an object 1 to 2-kilometers in diameter would cause global devastation. (Remember - the diameter of the Swift-Tuttle comet is 24 kilometers!) NOTE: In the book entitled, Comet and Asteroid Impact Hazards on a Populated Earth, by John S. Lewis (1999) the reader will find on pages 130 - 134 figures pertaining to the amount of destruction and costs involved. QUERY: What possible methods have been suggested to deal with a potential impact? So far, the following methods have been suggested - * Aiming a nuclear warhead at the object and blow it to smithereens has been suggested, but remember, Earth runs the risk of getting pelted with "smaller" debris! (Just HOW SMALL, is a VERY GOOD question!) * Or, the not so bad idea of equipping the incoming body with rockets so as to maneuver the body into a different path or orbit. * Better yet...once the object has been observed (if there is still plenty of time), send a rocket aloft so that it will meet the incoming object out in deep space and push the incoming object into a different orbit. * Or, a 'mass driver' might be used to throw pieces of rock or iron into space. Apparently, other methods were mentioned, in the March/April 1996 issue of Final Frontier an astronomy/space magazine, which I am sorry to say I do not have a copy. >From what I was able to learn, the magazine carried various suggestions, such as: the use of cables, mirrors, placing comet ice in the path of the incoming asteroid, and of course, the use of nuclear warheads. To Be Continued The Unseen Menace (Part I) FOREWORD. Hmmm...thought the "empty-nester" and amateur astronomer as she opened the envelope. Normally, it was her habit to throw unsolicited junk mail, unopened, into the wastebasket, but this time something prevented her. Nestled among the contents of the envelope was a questionnaire. And even though it was now quite late on the Eastern Seaboard, the recipient quickly scanned the questions with interest. Suddenly, she spied the question she was hoping to find! How strange that this same question dealt with the subject she was writing an astronomy article on. Great! People are still concerned about this potential menace...she muttered as she turned off the kitchen light. Meanwhile, in the western half of the United States, the Sun had just disappeared behind the Rocky Mountains. In the twilight a small team of observers made their way to one of the few existing Spacewatch telescopes. Tonight, like so many other moonless nights, the objective of their mission would be to search for potential hazards from space, commonly referred to as, near-earth objects (NEO's). Such hazardous objects are asteroids and comets. The chilling and hair-raising Shoemaker-Levy 9 (SL9) comet impact with Jupiter, in the summer of 1994, was still very fresh in the minds of the team members. And everyone connected with the Spacewatch program wanted to do his or her very best to prevent such an awesome impact happening to Earth. However, since its inception, the Spacewatch program chronically suffered from the lack of funds and manpower, but this team, like their colleagues, firmly believed in its mission. But I think it is safe to say that tonight this little band of dedicated observers will not find the "big one" that might be headed for Earth. Even if they did, perhaps there would be ample time for the nations of the Earth to come together to pool both talent and resources. Working together they just might find a way to fend off the common menace that was moving relentlessly and unerringly towards them through the dark void and vastness of space. The Menace. Everyday, 24 hours a day, the Earth is being pelted by debris from outer space. The debris is the leftover of planetary formation and fragments of old comets. Fortunately for us, much of the debris range from micro-meteorites to large stony or stony-iron meteorites that, while they can cause a good deal of property damage, they are not so large as to bring civilization to an untimely end. But unless a person just happens to be in the path of an incoming meteorite, it is the unseen menace out in deep space that earthlings really need to concern themselves, especially, those objects of one half kilometer or more. It is these mammoth sized objects that are known to have racked enormous havoc and devastation not only upon the Earth, our Moon, and other planets and their satellites as well. Each year, the numbers of known NEO's steadily increase and along with it, the chance that Earth will suffer yet another blow. According to John and Mary Gribbin approximately one or two of these objects are discovered per month. Plus, there are approximately 2,000 known Earth-crossing asteroids (ECA's) along with a million objects between 0.1 and 1-km across. Now, add to these 500 million smaller objects 10-meters or less in size. To give you, the reader, a better idea of the seriousness of the situation, please refer to p. 192, of Gerrit L. Verschuur's fascinating and intriguing book, Impact! The Threat of Comets & Asteroids (1996). The orbits depicted represent only 115 known near-earth asteroids as of March 28, 1995! Please notice just how much potential peril our little world faces! Perhaps, the reader may recall some recent modern "close calls" that the Earth encountered on August 3, 1964, March 23, 1989, January 18, 1991, June 21, 1993, and March 15, 1994. And, may Heaven help us, when the year 2126 rolls around and the earth crossing comet Swift -Tuttle drops by (hopefully, NOT "in!") to pay it respects! Apparently the 24-kilometer diameter Swift-Tuttle comet is influenced by the gravitational pull of Jupiter and posses a threat for Earth for quite some time in the future. That is if it doesn't fall into the Sun or is thrown clear of our solar system. Calculations seem to indicate that the comet will make a close approach to Earth by some 23 million kilometers on August 5, 2126. Please remember that all it takes is one large asteroid or meteorite to gravitationally act upon another body, thereby, dislodging it from its normally harmless orbit, and send it hurling on a collision course toward Earth. Even a passing comet could very easily accomplish the same thing! In addition, some have even suggested that the passing of the fabled and elusive "death star," Nemesis could even play such a role! There are three groups of asteroids that bear watching: * The Apollo group is named for the first asteroid that was discovered to be an Earth crossing body. These asteroids actually cross the Earth's orbit when they are the closest to the Sun, but spend most of their time away from the Sun. The largest Apollo type asteroid is called Hephaistos and has a diameter of approximately 10-km. As of 1982 there were 30 known Apollo type asteroids. * The Aten group spends much of their time close to the Sun, but cross Earth's orbit when they are furthest from the Sun. As of 1982 there were 4 known Aten asteroids. * The Amor group may come close to the Earth's orbit, but does not cross it. The asteroids do come within 1.3 AU of our star. There are 23 known Amor type asteroids. And, as far as comets are concerned, Earth needs to keep the Kreutz family of comets under observation. These comets are known as 'sun-grazing' because they pass very close to the Sun. The sun grazers were named in honor of the German astronomer, Heinrick Kreutz, who first studied them and published his findings in 1891. The sun grazers are long period comets that come from beyond the boundaries of our solar system and pose a threat. Not only do they approach us from behind the Sun (and leave the same way), but also their small size makes them difficult to see. Apparently, in 1882, it took a total eclipse of the Sun in order to catch a glimpse of the first sun grazer! NOTE: Incidentally, the comet Ikeya-Seki is a member of the Kreutz family of comets. On August 30, 1979 the spacecraft Solwind took a photo of a comet before it careened into the Sun. In addition, other Solwind spacecraft have observed other sun grazing comets as well. QUERY: Okay, so a near-earth object has been spotted, what should earthlings expect? An object 10-meters in size would pose only a severe local threat. An object one half kilometer in diameter landing in the ocean would create a huge tidal wave (tsunami) that would reach far inland. But should impact occur over land, a huge crater will be gouged out of the earth followed by shock waves, earthquakes, and debris falling over a large area, followed by wild fires that had not been snuffed out by the aftermath of the impact. In addition, much of the lighter debris would be carried aloft into the atmosphere and would reduce incoming sunlight so vital to plant and animal life. Soon temperatures would begin to drop and depending upon the degree of damage, life might cease to exist. NOTE: Perhaps the reader will remember reading that after the eruption of Mount Pinatubo (June 12, 1991) that the average temperature, of the Earth, fell 0.5 degrees Celsius. This temperature drop lasted approximately two years and was caused by the 15 to 20 million tons of volcanic ash, dust, and sulfur dioxide spewed into the stratosphere. Lastly, an object 1 to 2-kilometers in diameter would cause global devastation. (Remember - the diameter of the Swift-Tuttle comet is 24 kilometers!) NOTE: In the book entitled, Comet and Asteroid Impact Hazards on a Populated Earth, by John S. Lewis (1999) the reader will find on pages 130 - 134 figures pertaining to the amount of destruction and costs involved. QUERY: What possible methods have been suggested to deal with a potential impact? So far, the following methods have been suggested - * Aiming a nuclear warhead at the object and blow it to smithereens has been suggested, but remember, Earth runs the risk of getting pelted with "smaller" debris! (Just HOW SMALL, is a VERY GOOD question!) * Or, the not so bad idea of equipping the incoming body with rockets so as to maneuver the body into a different path or orbit. * Better yet...once the object has been observed (if there is still plenty of time), send a rocket aloft so that it will meet the incoming object out in deep space and push the incoming object into a different orbit. * Or, a 'mass driver' might be used to throw pieces of rock or iron into space. Apparently, other methods were mentioned, in the March/April 1996 issue of Final Frontier an astronomy/space magazine, which I am sorry to say I do not have a copy. >From what I was able to learn, the magazine carried various suggestions, such as: the use of cables, mirrors, placing comet ice in the path of the incoming asteroid, and of course, the use of nuclear warheads. To Be Continued Nancy L. Thomas Daytona Beach, FL USA (Part I) 6/3/2000 (Part II) 7/9/2000 Humble Before the Stars |