2GG3 Lecture 30 Meteorite Impacts II F24 PDF

Meteorite Impacts II © Maureen Padden  Crater Formation Simple Craters: Form from a small impact. Complex Craters: Form from large impacts. Craters are less than 2km in diameter Craters are greater than 2km in diameter...

Meteorite Impacts II © Maureen Padden  Crater Formation Simple Craters: Form from a small impact. Complex Craters: Form from large impacts. Craters are less than 2km in diameter Craters are greater than 2km in diameter © Maureen Padden Crater Formation © Maureen Padden  Impact structures in Canada Manicougan Crater, Quebec: Pingualuit Crater, Québec; formed formed 215.5 million years ago approximately 1.4 million years ago Brent Crater, Ontario: formed 435 million years ago © Maureen Padden  Sudbury Impact Structure 60 x 30 km crater formed 1.85 Ga ago due to impact of a 10-15km wide asteroid © Maureen Padden  Sudbury Impact Structure Elliptical shape of Sudbury basin is due to deformation by a mountain- building collision; original crater originally circular and much larger. Decompression melting during impact carried metals to Earth’s surface. Ore deposits of nickel, copper, gold, and silver are common. © Maureen Padden Tunguska and Chelyabinsk, Russia Tunguska, Russia,1908: A 50–200 m asteroid exploded 5–10 km high; Released 10–15 megatons of energy Flattened 80 million trees No fatalities or injuries due to remote area Chelyabinsk, Russia, 2013: A 10 million kg, 17 m diameter meteoroid Explosion blew out windows and shook buildings Air blast felt over 100 km2 ~1,500 people injured from shattering glass © Maureen Padden Tunguska, Russia © Maureen Padden Tunguska Scale © Maureen Padden The End-Cretaceous Impact © Maureen Padden  Evidence of Asteroid Impact - the element iridium is very rare on Earth - Around the world, there is an enriched iridium layer in the rock layers marking the end of the Cretaceous - There are no dinosaur bones above this layer in Drumheller © Maureen Padden  End Cretaceous Asteroid Impact 65 million year old sediment layers with shocked quartz grains, spherules, huge angular blocks, and tsunami deposits found throughout eastern North America and Caribbean © Maureen Padden  Chicxulub Crater Lunar Planetary Institute Edge of buried crater marked by ring of cenotes leading to a cave system. Water is de ected by buried crater and this ow dissolves overlying limestones. © Maureen Padden fl fl Cretaceous Geography © Maureen Padden End-Cretaceous Climate Change © Maureen Padden Source: David A. Kring, “lmpact Events and Their Effect on the Origin, Evolution and Distribution of Life.” GSA Today v. 10, no. 8 (2000), p. 4.  End-Cretaceous Impact: Problems for Life Earthquake of monumental magnitude with numerous aftershocks – extrapolated impact magnitude of 11.3 Wildfires raged regionally or even globally Huge amounts of nitrogen oxides in atmosphere probably fell as acid rain, acidified surface waters Dust and soot in atmosphere blocked sunlight, inhibiting photosynthesis Dust settled but water vapor and CO2 remained in atmosphere = global warming for years ©McGraw-Hill Education © Maureen Padden  End-Cretaceous Impact: Problems for Life Tsunami up to 300 m high Bubble of steam up to 500 km3 volume blows rock and asteroid debris into upper atmosphere End-Cretaceous asteroid landed in shallow sea underlain by limestone – vaporized to contribute even more CO2 to atmosphere, raised temperature as much as 10 °C Co-occurred with Deccan flood basalt eruptions in India – began 250,000 years before Chicxulub impact and continued for another 500,000 years = one-two punch to life on Earth ©McGraw-Hill Education © Maureen Padden  Risk Assessment Torino Scale developed to assess impact risks. - frequency estimated from Moon craters - risk of impact is low, but probability of harm during a big impact skews the probabilities © Maureen Padden  Near-Earth Objects 90% of Near-Earth Asteroids (> 1 km) are not on a collision course - NASA now searching for 140 m “city-killers” - found more Potentially Hazardous Asteroids (PHAs) than previously thought (at least 1877 objects) © Maureen Padden Edge-on view of Near-Earth Asteroids (NEAs) and Potentially Hazardous Asteroids (PHAs) © Maureen Padden  What to do? Engineering ideas: 1) push the object by attaching rockets 2) vaporizing rock using sunlight and large mirror 3) breaking it into smaller pieces while in space 4) gravity tractor - heavy spacecraft nearby pulling it off-course Have we tried any of these things? Not until now…. © Maureen Padden  DART mission Double Asteroid Redirection Test - NASA mission to move an asteroid - arrived in fall 2022 - experiment to see if we can change path of extra-terrestrial objects before they hit us © Maureen Padden  DART mission Double Asteroid Redirection Test © Maureen Padden