meteor explosion over Chelyabinsk, Russia, 2013
undetected house sized meteor, atmospheric friction slowed and heat it until it exploded above Chelyabinsk, light form explosion greater than the Sun, shockwave shattered building windows causing many inj and shook building, hot cloud of gas, dust, and asteroid fragments on ground
energy in Earth’s movement
Earth moves around the Sun at 108000 km/h, any head on collision with large object would create large amts of E and potential for harm
extraterrestrial debris
1. sources
2. types of meteors
- mainly fragmented asteroids (rocks) from the asteroid belt (between Jupiter and Mars) and comets (ice and rock) from Kuiper belt (beyond Neptune, orbiting solar sys) or Oort Cloud (spherical, beyond Kuiper, unpredictable motion)
- Meteoroids are pieces of asteroids and comets in space, fireballs or meteors blaze through Earth’s atmosphere, meteorites hit Earth’s surface
rates of meteoroid influx
1. rate
2. entering atmosphere
3. bolide
- many meteoroids enter Earth’s atmosphere every day, smaller meteoroids occur more frequently
- atmosphere is dense enough to heat meteoroid to glowing shooting star, many vaporize before reaching surface, burn and glow, creating shock waves or sonic boom as air is compressed
- meteoroid that explodes in atmosphere
cosmic dust
small enough meteroid to be unaffected by atmopshere, setteles on surface as gentle rain, collected from filtering dredged sea floor sediments, melting tons of Antarctic or Greenland ice, rooftop rain gutters
finding meteorites
- deserts, farm fields, Antarctica and Greenland ice sheets where dark meteorites stand out against light coloured or sparsely vegetated ground
- Antartica is best place since meteorites are preserved by cold, no rain thus no carbonic acid or plant chemicals to dissolve rocks, ice flows and concentrates meteorites at bends where they’re easier to find
comets
elliptical orbit around the sun, mass of ice, frozen CH4, dust, and rock material (coma) around nucleus, producing ion tail of gas that melts and is ionizedand dust tail of dust as it nears the sun
crater formation
- simple crater: form from small impact, craters less than 2km in diameter, melts rock upon impact
- complex crater: large impacts, greater than 2 km, central uplift from rebound E, melt flows around it creating rings
Sudbury impact structure
2nd largest existing crater, 2 billions years ago 10-15 km asteroid created a 60 x 30 km circular crater called Sudbury basin, elliptical shape due to deformaiton by continental-continetal collision, decompression melting of igneous rock during impact concentrated metals into ore deposits of copper, gold, nickel, silver
tunguska, Russia, 1908
large asteroid exploded at 5-10 km high and released 10-15 megatoms of E, flattened boreal forests, massive wildfires, no fatalities or injuries due to remote area
Yucatan Peninsula end cretaceous meteorite impacts, 66 mil yrs ago
1. overview
2. Chicxulub crater
- 14 km diameter asteroid struck surface, marking end of Mesozoic Er and Age of Dinosaurs
- impact created 150 diameter Chicxulub crater partially in Gulf of Mexico, buried edge marked by ring of cenotes (compressed features with ground water, leading to cave system, flow of dissolved overlying limestones creating circular area)
end cretaceous meteorite impacts, 66 mil yrs ago: mass destruction
- impact gen earthquake with Mw 11.3
- heat released spread lots of wildfires globally, gen lots of ash and nitrogen oxides in atmopshere for acid rain acidifed surface waters
- soot and dust from meteorite in atmosphere blocked sunlight, inhibiting photosynthesis, large GHE by CO2 and water vapour remaining in atmosphere
- gen mega tsunami 1.5 km high from impact and falling debris, felt across entire globe
- co-occured with Deccan flood basalt eruptions in India, devastating to life on earth
near Earth objects
mapping asteroids near Earth to determine probabilty of risk of collison, 90% near-Earth asteroids not on collision course, NASA searching for 140m city killer, Potentiall Hazardous Asteroids high risk more than thought
Torino scale
assess probability of event and corresponding impact risks, frequency estimated from Moon craters, large events really rare and globally catastrophic
how to deal with meteorite impacts
1. engineering course
2. DART mission
- push object by attaching rockets, vaporizing rock using sunlight and large mirror, breaking it into smaller pieces while in space, gravity tractor heavy spacecraft nearby pulling it off course
- NASA experiment to see if we can change the path of extra-terrestrial object before it hits Earth
