The Mystery of the Tunguska Fireball

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Asteroid Collision and Prevention
Strategies Presented by Stephanie Floyd
The Mystery of the Tunguska Fireball By
Surendra Verma
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Background

• Object hit Tungus region of Central Siberian
  Plateau
• June 30, 1908
• Large object most likely a stony meteorite from
  an asteroid
• Objects brightness comparable to noonday sun.
• Exploded mid-air? 5-10km above ground
• Energy blast ? 10-20 megatons
• First expedition 1928 by Soviet Mineralogist,
  Leonid Kulik

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Are we going to be hit by another Tunguska-like
object again?

• Probability of an asteroid impact, small or big
  1 in 20,000 years.
• Impact of 50- 75m object (suggested size of
  Tunguska object) 1 in 1,000 yrs
• ?wipe out large city
• Interval between impacts of giant asteroids
  (16km) 100 million yrs
• ? destroy an entire continent trigger mass
  extinction

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Most affected countries

• Population lost China, Indonesia, India, Japan,
  U.S.
• Economic loss U.S., China, Sweden, Canada,
  Japan.
• Top 10 countries at highest general risk
• China, Indonesia, India, Japan, US,
  Philippines, Italy, UK, Brazil and Nigeria.

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Near-Earth Objects

• Comets and asteroids nudged by the gravitational
  attraction of nearby planets into orbits near
  Earth.
• Potentially Hazardous asteroids
• gt150m
• Approach Earth to within 7.5 million km
• Finding out the material composition of the
  object is also necessary before deciding which
  strategy is appropriate.

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Short-term prevention strategies

• Nuclear Weapons
• Fire nuclear missiles at the asteroid to vaporize
  it
• Only thermonuclear weapons would be powerful
  enough to destroy a 1km asteroid
• Nuclear pulse propulsion
• Numerous small nuclear explosions near asteroid
• Wont fracture object just alter its
  trajectory

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Long-term preventative methods

• Gravitational Tractor
• Unmanned spacecraft hovering over asteroid
• Spacecraft gravitationally pulls asteroid into
  non-threatening orbit
• External Pulsed Plasma Propulsion(EPPP)
• nuclear-powered spacecrafts that expel jets of
  plasma could
• The Unmanned space tug would attach to asteroid
  surface and slowly push it to alter trajectory

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Apophis asteroid

• Weighs 25-50 million tons
• 2029- will pass closer to Earth
• 2036 collision course with Earth
• ?2013- Mission Apex

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What's being done?

• SENTRY programme Established in 2002 by NASAs
  Jet Propulsion Lab. (JPL)
• Monitoring systems of NEO (near-earth objects)
• Program website http//neo.jpl.nasa.gov/risk/

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NEOMAP

• Near Earth Object Mission Advisory Panel
• Developing methods to detect NEOs discover more
  about them.
• ?Don Quijote Mission

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NASAs future goals

• Discover at least 90 of all NEOs of gt1km
• Dawn mission meet with asteroids Vesta and Ceres
  in 2011 and 2015

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• An asteroid or comet impact is the greatest
  natural threat to the long-term survivability of
  mankind - Robert Gold, Johns Hopkins University