Impact Events

Biggest Impact Events (21st Century)

• Chelyabinsk, Russia (2013)
• asteroid
• around 66 feet in diameter, 40,000 - 42,000 mph
• light brighter than the sun and generated intense heat that was felt from a fireball
• shallow entry angle into the atmosphere so it exploded 18.5 miles above the surface
• 26-33x more energy than the Hiroshima atomic bomb
• undetected before entry source direction was close to sun
• 1500 people injured (breaking glass), 7200 buildings damaged

Frequency of Large Events

• craters aren’t preserved forever so they’re hard to estimate
• look at the Moon and extrapolate back to Earth
  • 80x surface area = 80x impacts → 2400 impacts forming craters of >15 mile diameter

Near-Earth Objects

• asteroids (90% of total) or comets (10% of total) whose orbit makes it potentially hazardous to Earth
• 460 ft diameter or more would cause significant devastation
  • about 25,000 exist
  • none have a significant chance of hitting the Earth in 100 years
  • less than half of these have been found

Prevention of Impacts

• can we stop potentially hazardous asteroids/comets?

  • ideas:
  1. attach a rocket engine to the asteroid to drive it away from us
  2. use a big mirror to focus the sunlight on the asteroid and vaporize it
  3. scoop rock from it and toss it away so the asteroid’s size is less

• we have been able to land on asteroids before

  • ex: Japanese landed a spacecraft on a 1755 foot long asteroid traveling 56,000 mph in 2005