Impact Craters
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  • 1.  
  • 2. Megan Grove
  • 3. A colored magnetic-anomaly map shows the Chicxulub impact crater, on the Yucatán Peninsula in Mexico. Scientists rely on such maps to help them study the crater, which is buried under more than half a mile (1 kilometer) of sediment. Anomalies (red, yellow, and blue) occur where the local magnetic field differs from the expected value (green). LiDAR works by shining a laser pulse at the ground and measuring the time delay of the returning light. The first light to get to you comes from the top of the canopy, and the last light to get back comes from the few photons that reached the ground before reflecting back. The distribution of light in between the first and last returns revealing details about the plant canopy structure. Nick
  • 4. Chicxulub Crater, third largest and possible dinosaur killer. The third largest impact crater lies mostly underwater and buried underneath the Yucatán Peninsula in Mexico. At 170km (105 miles) in diameter, the impact is believed to have occurred roughly 65 million years ago when a comet or asteroid the size of a small city crashed, unleashing the equivalent to 100 teratons of TNT. Likely, it caused destructive tsunamis, earthquakes and volcanic eruptions around the world, and is widely believed to have led to the extinction of dinosaurs, because the impact probably created a global firestorm and/or a widespread greenhouse effect that caused long-term environmental changes. nick
  • 5.
      • The principal criteria for determining if a geological feature is an impact structure formed by the hypervelocity impact of a meteorite or comet are listed below. The criteria can be divided into megascopic (overview – bird’s eye / satellite scale), macroscopic (can be seen easily seen with the naked eye) and microscopic (requires a microscope to see) features, as follows:
      • Presence of shatter cones that are in situ (macroscopic evidence).
      • Presence of multiple planar deformation features (PDFs) in minerals within in situ lithologies (microscopic evidence).
      • Presence of high pressure mineral polymorphs within in situ lithologies (microscopic evidence and requiring proof via X-ray diffraction, etc.).
      • Morphometry. On other planetary bodies, such as the Moon and Mars, we rely on the shape of the impact structure to determine its presence and type (simple versus complex, etc.). This is a megascopic quality (i.e., too big to be seen unaided by the human eye, thus requiring remote sensing, aerial photography, detailed mapping of multiple outcrops to assemble and view the typically km- or multiple km-size structure). On Earth, recognizing impact structures solely by their morphometry is complicated by two factors: (a) weathering, erosion, burial processes and tectonic deformation can obscure and/or destroy the original shape; (b) certain terrestrial features generated by means other than impact can have comparable circular form (e.g., volcanoes, salt diapirs, glacigenic features), such that a circular structure alone is not sufficient to claim impact structure status. Some buried craters have been revealed solely by geophysical techniques, although drill core is typically required to reveal macro- and microscopic evidence to prove an impact origin.
      • Presence of an impact melt sheet and/or dikes, and impact melt breccias that were generated due to hypervelocity impact (macroscopic). These bodies typically have a crustal composition derived by the fusion of target rocks (i.e., there is no mantle contribution to the melt). Such melts may be contaminated by meteoritic (projectile) components (the latter requires specialized geochemical analysis to detect the projectile components). Melt sheets may be overlain by so-called fallback breccias (referred to as “suevite” by some workers), and material blasted out of the crater may form ejecta blankets about the original central cavity. For large impact events, ejecta can be distributed globally. Impact melt sheets are recognized by careful mapping and rock sampling followed by microscopy and geochemical analysis.
      • Pseudotachylyte and Breccias: Pseudotachylyte is a rock type generated by faulting at either microscopic or macroscopic scales. However, pseudotachylytes are also associated with seismic faulting due to endogenic processes (e.g., earthquakes due to isostatic rebound and plate tectonics), so they are not exclusively impact generated. However, in association with features listed above, they can be a contributory criterion. Pseudotachylyte associated with impact structures may form in radial and concentric fault systems that help to define the megascopic structure of the crater. Pseudotachylytes can be included in a family of rocks referred to as breccias . Many different types of breccia can be developed as part of the impact process (including impact melt breccias listed in (5) above), but breccias can also form by endogenic processes. The interpretation of breccias therefore requires considerable care and experience. Moreover, they should not be considered diagnostic of impact, but rather contributory evidence.
      • revised estimates for these parameters indicate that the impactor was 1-3 km in diameter, had a mass of 1 billion tons, and the released energy during impact was 400 000 megatons TNT. 
      •  
      • Make points shorter and more direct. so condense each point. JTA   
    nick not going to say all , just key points
  • 6.   nick
  • 7. nick
  • 8.
      • The principal criteria for determining if a geological feature is an impact structure formed by the hypervelocity impact of a meteorite or comet are listed below. The criteria can be divided into megascopic (overview – bird’s eye / satellite scale), macroscopic (can be seen easily seen with the naked eye) and microscopic (requires a microscope to see) features, as follows:
      • Presence of shatter cones that are in situ (macroscopic evidence).
      • Presence of multiple planar deformation features (PDFs) in minerals within in situ lithologies (microscopic evidence).
      • Presence of high pressure mineral polymorphs within in situ lithologies (microscopic evidence and requiring proof via X-ray diffraction, etc.).
      • Morphometry. On other planetary bodies, such as the Moon and Mars, we rely on the shape of the impact structure to determine its presence and type (simple versus complex, etc.). This is a megascopic quality (i.e., too big to be seen unaided by the human eye, thus requiring remote sensing, aerial photography, detailed mapping of multiple outcrops to assemble and view the typically km- or multiple km-size structure). On Earth, recognizing impact structures solely by their morphometry is complicated by two factors: (a) weathering, erosion, burial processes and tectonic deformation can obscure and/or destroy the original shape; (b) certain terrestrial features generated by means other than impact can have comparable circular form (e.g., volcanoes, salt diapirs, glacigenic features), such that a circular structure alone is not sufficient to claim impact structure status. Some buried craters have been revealed solely by geophysical techniques, although drill core is typically required to reveal macro- and microscopic evidence to prove an impact origin.
      • Presence of an impact melt sheet and/or dikes, and impact melt breccias that were generated due to hypervelocity impact (macroscopic). These bodies typically have a crustal composition derived by the fusion of target rocks (i.e., there is no mantle contribution to the melt). Such melts may be contaminated by meteoritic (projectile) components (the latter requires specialized geochemical analysis to detect the projectile components). Melt sheets may be overlain by so-called fallback breccias (referred to as “suevite” by some workers), and material blasted out of the crater may form ejecta blankets about the original central cavity. For large impact events, ejecta can be distributed globally. Impact melt sheets are recognized by careful mapping and rock sampling followed by microscopy and geochemical analysis.
      • Pseudotachylyte and Breccias: Pseudotachylyte is a rock type generated by faulting at either microscopic or macroscopic scales. However, pseudotachylytes are also associated with seismic faulting due to endogenic processes (e.g., earthquakes due to isostatic rebound and plate tectonics), so they are not exclusively impact generated. However, in association with features listed above, they can be a contributory criterion. Pseudotachylyte associated with impact structures may form in radial and concentric fault systems that help to define the megascopic structure of the crater. Pseudotachylytes can be included in a family of rocks referred to as breccias . Many different types of breccia can be developed as part of the impact process (including impact melt breccias listed in (5) above), but breccias can also form by endogenic processes. The interpretation of breccias therefore requires considerable care and experience. Moreover, they should not be considered diagnostic of impact, but rather contributory evidence.
    • nick      same here condence JTA
    •  
    •  
    •  
  • 9.  
  • 10.  
  • 11. nick
  • 12. Megan Grove
  • 13. ~ Scattering of dust and debris into the atmosphere ~ Cause large fires (generated by hot debris thrown from the crater) ~ Tsunamis, and severe storms with high winds and highly acidic rain ~ Seismic activity, and perhaps even volcanic activity Megan Grove
  • 14. ~ Dust and debris thrust into the atmosphere can block most of the sunlight          - This would lower surface temperatures globally          - Those organisms dependent on photosynthesis would die out and Earth's oxygen levels would dramatically decrease both on land and in the oceans thus suffocating organisms unable to cope with lower oxygen levels. Megan Grove
  • 15. ~ The impact may cause chemical changes in the Earth’s atmosphere           - Increasing concentration of sulfuric acid, nitric acid, and fluoride compounds    ~ The heat from the impact’s blast wave would have incinerated all life forms within its path Megan Grove
  • 16.  
  • 17. nick
  • 18.
      • Spaceguard Survey
      • LINEAR (Lincoln Near Earth Asteroid Research
      • LONEOS (Lowell Observatory Near Earth Object Search)
      • Pan-STARRS
    Alex
  • 19.
    • Totals as of December 31, 2007
    •  
    • Observations to MPC     22,349,515
    • Asteroid Detections        5,370,805 
    • Asteroid Discoveries      225,957
    • NEO Discoveries            2019 
    • Comet Discoveries         236
    •  
    • The goal of LINEAR is to demonstrate the application of technology originally developed for the surveillance of Earth orbiting satellites, to the problem of detecting and cataloging near-Earth asteroids—also referred to as near-Earth objects (NEOs)—that threaten the Earth.
    Alex
  • 20.
    • LONEOS has the capability to scan the entire sky accessible from Flagstaff, Arizona, every month. The telescope is able to record objects to a magnitude limit near V=19.3 or about 100,000 times fainter than can be seen with the naked eye. As of 2004 July, LONEOS had submitted more than 2.8 million asteroid observations to the IAU Minor Planet Center. After 10 years of full-time operation, we estimate that LONEOS could discover 500 of the 1-km or larger NEOs and perhaps twice as many smaller ones, thus substantially increasing our knowledge of these bodies.
  • 21.
    • Went online December 6th, 2008
    • Located in Hawaii
  • 22.
      • 350m asteroid that will pass close to Earth in 2029
      • Chance of hitting keyhole
      • Possible impact in 2036 
    Alex
  • 23. Alex
  • 24. Source: B612 Foundation
  • 25.
      • Variety of Mitigation and Prevention options
      • Only theoretical, no current technology available
      • B612 Foundation
      • Deep Impact - Proved we can create technology needed
      • Don Quijote
    Alex
  • 26.  
  • 27.
    • http://pan-starrs.ifa.hawaii.edu/public/asteroid-threat/asteroid_threat.html
    • http://www.ll.mit.edu/mission/space/linear/
    • http://asteroid.lowell.edu/asteroid/loneos/loneos1.html
    • http://www.esa.int/SPECIALS/NEO/SEMZRZNVGJE_0.html
    • Morrison, David. 2006, "Asteroid and comet impacts: the
    •        ultimate environmental catastrophe", The Royal Society
    •        vol. 364, pp. 2041-2054 .