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ESYS150 LECTURE 18 IMPACTS WITH SPACE OBJECTS

ESYS150 LECTURE 18 IMPACTS WITH SPACE OBJECTS. OUTLINE Impact scars and space objects Known impacts on Earth Environmental effects Events of the Twentieth Century Frequency of large events. IMPACT SCARS AND SPACE OBJECTS INTRODUCTION Comets and Asteroids.

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ESYS150 LECTURE 18 IMPACTS WITH SPACE OBJECTS

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  1. ESYS150 LECTURE 18 IMPACTS WITH SPACE OBJECTS OUTLINE Impact scars and space objects Known impacts on Earth Environmental effects Events of the Twentieth Century Frequency of large events

  2. IMPACT SCARS AND SPACE OBJECTSINTRODUCTIONComets and Asteroids Computer enhanced image of a comet. Earth moves through space occupied by comets and asteroids traveling on different paths. Will these paths cross and could a comet or asteroid destroy the human race

  3. IMPACT SCARS AND SPACE OBJECTSIMPACT SCARSMoon Few scars earth. Wiped away by plate motion and erosion Moon dead thus has a huge number of impact scars. Most occurred early in formation before 3.9Ba. Maria formed 3.8 - 3.2 Ba. Have many less impact craters. Craters formed by same processes active today.

  4. IMPACT SCARS AND SPACE OBJECTSSOURCES OF EXTRATERESTRIAL DEBRISMeteoroids, meteors and meteorites Meteoroids - pieces of asteroids and comets orbiting the sun Meteors - shooting stars blazing through Earth’s Atmosphere Meteorites - objects actually hitting the surface of the Earth. Either metallic (iron) or rocky (stony) Though most objects reaching atmosphere are stony. Iron meteorites are more common because stony meteorites (a) tend to break up in the atmosphere, (b) easily eroded and (c ) are difficult to detect.

  5. IMPACT SCARS AND SPACE OBJECTSSPOURCES OF EXTRATERRESTRIAL DEBRISAsteroids Solar system from the Sun to Jupiter in Astronomical units Asteroid belt of rocky and metallic objects lies between inner rocky planets and outer gaseous planets where 10th planet should lie. Most meteorites appear to come from the Asteroid belt.

  6. IMPACT SCARS AND SPACE OBJECTSSOURCES OF EXTRATERRESTRIAL OBJECTSAsteroids Asteroids occasionally collide and jump into an eccentric orbit. Clusters of Asteroids such as the Apollos and the Amors have orbits that intersect the orbits of Earth and Mars. They are possible sources for large meteorites that slam into the Earth’s surface

  7. IMPACT SCARS AND SPACE OBJECTSSOURCES OF EXTRATERRESTRIAL DEBRISComets Kuiper Belt - flattened disc of comets with orbits of < 200 years, orbits the Sun in a plane. Halley’s best known example Oort Cloud - vast encircling envelope of comets around the Sun. Has a spherical distribution. Orbits > 200years. Composition - ice and rocky debris (dirty snowball) Tail - created by gases and trapped dust released after sublimation intersecting with the Solar Wind Solar Wind - stream of sub-atomic particles streaming out of the Sun. Tail - lines up with solar wind moving out from the sun. Size - most comets less than 15 km in diameter

  8. IMPACT SCARS AND SPACE OBJECTSSOURCES OF EXTRA TERRESTRIAL OBJECTSKuiper Belt and Oort Cloud

  9. IMPACT SCARS AND SPACE OBJECTSSOURCES OF EXTRATERRESTRIAL MATERIALHalley’s comet Comes every ~76 years. Elongate elliptical orbit is steeply inclined to the Earth’s orbit. Seen 1910 and 1986.

  10. IMPACT SCARS AND SPACE OBJECTSRATES OF METEOROID INFLUXFrequency versus size of impacting space debris 1012 enter every day, almost all very small and burn up in atmosphere. Needs to weigh 350 tons to come through the atmosphere largely unaffected Cosmic dust (0.001 mm) so small . Not altered. Rains down on Earth Shooting stars (1mm) burn up in atmosphere. Glass drops to surface. Meteorites (1gm) melt in the atmosphere but some get through. Mostly iron composition

  11. KNOWN IMPACTS ON EARTHDISTRIBUTIONUS and Canada Meteorites weighing more than 350 tons not slowed down. 164 known impact craters in the world 57 in US and Canada

  12. KNOWN IMPACTS ON THE EARTHMETEOR CRATER ARIZONAClassic meteorite crater, 1 km wide, 185 m deep. Known to to be a meteorite crater for the following reasons: 1 Steep sides and closed, 2 Rim uplifted and tilted away from center 3 inverted piles of rock found outside the crater, 4 large blocks of limestone found outside crater, 5 Crater has 265 m of shattered rock, 6 Numerous pieces of nickel-iron found in the area and 7 High P/T rocks including fused sandstone and shatter cones. 30 m diameter meteorite about 50,000 years ago.

  13. KNOWN IMPACTS ON EARTHCRETACEOUS/TERTIARY BOUNDARY EVENTSection Gubbio, Italy Either side of the KT boundary have very different assemblages Boundary well exposed. Has clay layer with Iridium 300 x normal. Iridium common only in iron nickel meteorites. Found Iridium everywhere at KT boundary in cores.

  14. KNOWN IMPACTS ON EARTHTHE CRETACEOUS/TERTIARY BOUNDARY EVENTChicxulub structure Around world at K/T boundary found large amounts of Iridium. Rare on Earth. Common in meteorites. Suggested meteoritic collision with the Earth. Evidence suggested came down in the Caribbean. Circular gravity anomaly off the tip of the Yucatan Peninsula. PMEX had drilled exploratory holes in the area which had encountered shattered rock and glasses

  15. KNOWN INPACTS ON EARTHTHE CRETACEOUS/TERTIARY (K/T) BOUNDARY Chicxulub structure Geophysical surveys shoed circular structures at depth. Seismic data showed an inner and outer ring of 80 and 195 km diameter. Gravity and magnetic structures show some opening to the North west. Suggests a 10 km asteroid slammed into the Earth at a 20 - 30 degree angle 64.98 Ma

  16. ENVIRONMNETAL EFFECTS IMPACTSCRATER FORMING PROCESSComet or Asteroid hitting the Earth Large meteorites form complex craters • incoming meteoroid hits earth at speeds as high as 30km/sec 2 Impact shock creates high P & T that vaporizes most of the crater rock and the meteoroid

  17. ENVIRONMENTAL EFFECTS IMPACTSCRATER FORMING PROCESSComet or Asteroid hitting the Earth • The release wave following the shock wave causes the center to rise. • The fractured walls slide into the crater producing wider and shallower rim. Outer walls can have a diameter 100 times the depth.

  18. ENVIRONMENTAL EFFECTS IMPACTSPROBLEMS FOR LIFE FROM IMPACTS Impact of K/T asteroid had major effects on surface temperature. First, a fireball and hot gases that lasted many hours. Second, temperatures dropped to winter conditions as dust and ash blocked out sunlight. Third, after dust settled C02 remains aloft creating greenhouse warming of 10o C. Also have major 300 m tsunami and a huge steam bubble.

  19. EVENTS OF THE TWENTIETH CENTURYCOMET EXPLOSIONTunguska, Siberia 30 June 1908 Strange event in unpopulated Siberia. Massive fireball exploded 8 km above ground. Produced very bright light in northern Europe. Found all the trees in a 30 x 30 km area knocked down. No impact crater or even broken ground. 30 to 50 m meteorite exploded above ground. Expedition in 1958 found evidence of melted iron and silica rich rock. If over Washington do tremendous damage.

  20. EVENTS OF THE TWENTIETH CENTURYBIGGEST NEAR EVENTSRecent close calls 22 March 1989 - Asteroid 1989FC a 500m body, missed the Earth by less than 6hrs or 700,000 km. Would have created 7 km crater 19 May 1996 - 150 m Asteroid missed Earth by 700,000 km. Four times larger than the crater that made Meteor Crater, Arizona. ?? 2028 - in late 90’s was predicted that an Asteroid labeled 1997XF11 might hit the Earth in 2028. Near misses surprisingly high. About 50 house sized bodies pass between Earth and Moon every day. However, 50 m bodies burn up in Atmosphere. Only iron meteorites stay intact and they are uncommon.

  21. EVENTS OF THE TWENTIETH CENTURYBIGGEST NEAR EVENTSMeteor/Asteroid diameter, crater size and life Beyond 100 m diameter meteoroids have a devastating effect on life

  22. EVENTS OF 20TH CENTURY BIGGEST NEAR EVENTS Assessing Hazards Have Torino scale which assesses hazards on a 0 - 10 scale. Enables calm communication about the threats.

  23. FREQUENCY OF LARGE IMPACTSHOW OFTEN DO THEY OCCUR? Start by looking at moon. Maria 16% moons surface. Created 3.2 Ba. Find 5 craters > 50 km width and 24 craters > 25 - 50 km. One major impact every 110 million years. Comparing with the Earth. Earths surface 80 times that of Maria but land only 1/3 of earth’s surface. Would expect 720 impacts. Only have found 120. Most missing craters destroyed or buried. Odds extremely small that a large asteroid will hit Earth during our life time. However, so many will be killed when does hit this will skew statistics.

  24. FREQUENCY OF LARGE IMPACTSANNUAL RISK OF DEATH Over 2000 NEO’s. 25-50% will eventually hit the earth. Average time between impacts is 100,000 years. Risk being killed by impact is 1 in 20,000. High because a huge number of people 1.5 Billion will be killed in an impact.

  25. FREQUENCY OF LARGE IMPACTSCAN WE DO ANYTHING ABOUT THEM Have detected > 2000 NEO’s > 1 km in diameter. About 500 are NEA’s are potentially hazardous. I in 300 chance of one hitting Earth in 2880. Engineering action 1) Blow apart with Nuclear bomb 2) Attach rocket 3) Vaporize with sunlight 4) dig up rock mass. Is for sure going to happen but not in our life times.

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