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Earth Sterilizing Impact

Civilization Threatening Impact. Mass Extinction Impact. Earth Sterilizing Impact. EROS Asteroid 433. KLEOPATRA Asteroid 216. Terrestrial Impact Frequency. Hiroshima. year. Tunguska. century. Tsunami danger. ten thousand yr. Global catastrophe. million yr. K/T. billion yr.

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Earth Sterilizing Impact

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  1. Civilization Threatening Impact Mass Extinction Impact Earth Sterilizing Impact

  2. EROS Asteroid 433

  3. KLEOPATRA Asteroid 216

  4. Terrestrial Impact Frequency Hiroshima year Tunguska century Tsunami danger ten thousand yr. Global catastrophe million yr. K/T billion yr. 0.01 1 100 10,000 million 100 million TNT equivalent yield (MT)

  5. What Happens When an Impact Takes Place? • Bolides (up to 5 MT) • Great fireworks display, no damage • Tunguska-class (15 MT) impact • Damage similar to large nuclear bomb (city-killer) • Average interval for whole Earth: 100 yr. • Minor risk relative to other natural disasters(earthquakes, etc.) • Larger local or regional catastrophes (e.g. 10,000 MT) • Destroys area equivalent to small country • Average interval for whole Earth: 100,000 yr. • Moderate risk relative to other natural disasters • Global catastrophe (> 1 million MT) • Global environmental damage, threatening civilization • Average interval for whole Earth: 1 million years • Major risk relative to other natural disasters

  6. Types of Craters

  7. Physics of Cratering • There are general forms of impact craters: • simple and complex • Simple craters: • Bowl shaped pits, usually less than 5km in diameter • Raised circular rim and a nearly parabolic interior • Depth to diameter ratios are between 1/5 and 1/3 • Floored by a pool of broken rock ( breccia ) mixed with shocked debris and impact melt. • There is usually evidence of melting that has drained back into into the crater over time.

  8. Physics of Cratering • Complex Craters: • These types of craters have a more complicated morphology than simple craters • At a transition diameter of 2 to 4 km, gravity causes the walls of the complex crater to slump downward and inward. • This movement creates a complex structure with a central peak or peak ring and a shallow depth to diameter ratio of between 1/10 and 1/20. • The central peak or peak ring is formed by the initial rebound from the compressional shock of the impact. • Slumping of the rim further modifies and enlarges the crater

  9. Barringer Meteor Impact Crater Location: 35 deg N, 111 deg W Diameter: 1.186 km Age: 49,000 years First recognized impact crater on Earth

  10. Wolf Creek Crater, Western Australia: The location of this crater is 19°10'S, 127°46'E. The rim diameter is 800 m Distance from the rim crest to the present crater floor is 60 m. The age is approximately 10,000-20,000 years. This is classified as a simple crater and Meteorite fragments have been recovered from the crater floor, attesting to its origin.

  11. Manicouagan Crater Northern Quebec, Canada Location: (Lat 51 23N, Long 68 42W). Diameter is about 100 km, with an inner ring which is lake with a diameter of 70 km The impact occurred 214 million years ago. The asteroid probably had a diameter of about 5 km and it may have produced a mass extinction. Landsat satellite photo

  12. Site of Impact Craters on Earth

  13. Fast Facts Related to Impact Craters on Earth • After its formation, the earth went through a period of intense bombardment by extraterrestrial bodies, at least 100 times higher than the present impact flux. • This bombardment period lasted from 4.6 to about 3.9 billion years ago. • Most of the terrestrial impact craters that ever formed, however, have been obliterated by other terrestrial geological phenomena. • Approximately 150 impact craters have been identified on Earth. • Almost all of these craters have been identified since 1950 and more are being discovered each year as the result of improvements in imaging technology from orbiting satellites. • Although the number of known impact craters on Earth is relatively small, the preserved sample is an extremely important resource for understanding impact phenomena and they provide the only ground-truth data currently available.

  14. Fast Fact Related to Impact Craters on Earth – cont. • The impact event known as the (K-T) event, is believed to have caused mass extinction on Earth because of the amount of material that was ejected into the atmosphere as the result of the impact. • From estimates of the terrestrial cratering rate, the frequency of K-T-sized events on Earth is of the order of one every 50-100 million years. • Smaller, but still significant impact events, occur on shorter time scales and will affect the terrestrial climate and biosphere to varying degrees. • Impacts are a random process not only in space but in time. • At the present, no systems or procedures are in place specifically for mitigating the effects of an impact.

  15. LINEAR NEO Search Systems

  16. Spaceguard Survey Progress • Spaceguard Survey originally proposed by NASA panel in 1992 • Additional support from US Congress in 1995 • Adopted as NASA goal in 1998 (in collaboration with USAF) • Survey Objective: Discover and track 90% of the Near Earth • Asteroids (NEAs) with diameter greater than 1 km within • ten years (by 2008) • Estimated number of NEAs larger than 1 km: approximately 900 • Number discovered through end of 2000: approximately 430 • Estimated completion date (to 90%): 2012 • Most NEAs discovered by MIT-Lincoln Lab LINEAR search system • Two USAF 1-m telescopes with NASA operating funds • Discovery rate approximately 5 / month • International program for follow-up and orbit determination • Threatening NEAs (if any) should be identified decades • before impact

  17. FOR MORE INFORMATION NASA Impact Hazard Website http:// impact.arc.nasa.gov NASA NEO Program Website http:// neo.jpl.nasa.gov

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