Finding Potentially Hazardous Asteroids

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Finding Potentially Hazardous Asteroids

• Nick Kaiser
• (with lots of help from Jim Heasley, Dave Tholen
  and Rob Jedicke)
• IfA Open House
• 04/26/03

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Outline

• The asteroid hazard
• How do asteroids become hazardous?
• What can be done about it?
• What is the IfA doing about it?
• Pan-STARRS

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The asteroid hazard

• The historical record
• From air-bursts to mass extinctions

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Celestial Bombardment!

• Craters on
• Moon, Mercury,
• Venus, Mars
• And
• EARTH !!!

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Celestial Bombardment!
Celestial Bombardment on the Moon!
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Earth Has Been Hit Before!

• Asteroid crater in Canada
• seen from space

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Earth Has Been Hit Before!

• Meteor crater in Arizona was formed about
  50,000 years ago. The impacting iron meteorite
  had a mass of 1 million tons and diameter of 50
  meters. The impact blast was equivalent to a 20
  megaton nuclear weapon and produced a crater over
  1 km in diameter.

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Earth Has Been Hit Before!

• In 1908 a blast equivalent to a 15 megaton
  bomb occurred near the Tunguska river in Siberia.
  It occurred about 8 km over the Earths surface,
  flattening trees over a thousand square
  kilometers. The object was a stony body with a
  mass of 100,000 tons.

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When the last Big-One Hit

• The impact that is thought to have killed off
  the dinosaurs -- the Chicxulub crater, which is
  off the Yuchatan peninsula in the Gulf of
  Mexico--was produced by an object 10-15 km in
  diameter, resulting in a crater 200 km in
  diameter.

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Honolulu Advertiser October 10, 2002
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It Can Happen Again!

• Public awareness of the danger from celestial
  impacts was heightened by the break up of comet
  Shoemaker-Levy 9 after a close pass by Jupiter.
• On its next orbit, the fragments collided with
  Jupiter producing atmospheric explosions.

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It Can Happen Again!

• Impact of comet segments
• on Jupiter observed with
• IfA UH 88 telescope and
• infrared camera

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It Can Happen Again!

• Even more recently, CNN and other news agencies
  reported that on March 8, 2002 asteroid 2002 EM7
  passed within 288,000 miles of Earth.
• This object is slightly larger than the Tunguska
  impactor and could have caused considerable
  damage had it hit the planet.
• 2002 EM7 came out of our blind spot, coming from
  the direction of the Sun. We didnt see it until
  after it had passed!

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known asteroids in solar system
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The asteroid collision rate
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risk from asteroids
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Summary of risk

• Mass extinctions
• every few tens of millions of years
• Global catastrophes
• million year events
• Regional damage/tsunamis
• 1000MT impacts every 70,000 years
• Tunguska events
• one per 1000 years
• Bottom line
• You are as likely to die from an asteroid strike
  as to die in an air crash

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Collision risk from sub-km size asteroids

• Most of risk comes from km size objects and
  larger
• Very infrequent but very damaging
• Smaller objects can be damaging too
• Asteroid strikes in the ocean will generate big
  waves
• But will they cause much damage?
• Or will they break with little damage on the
  continental shelf?

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Los Angeles Basin
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How do asteroids become harmful

• Most asteroids reside in the main belt between
  mars and jupiter and are harmless
• But gravitational jostling can push asteroids
  onto unstable orbits
• These orbits then evolve, becoming elliptical and
  entering the inner solar system.
• Once on such an orbit, they last about 100M
  years, after which time they either get ejected
  or collide with a planet or with the sun

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What can be done to reduce the risk?

• Asteroid collisions are one of many natural
  hazards
• But we can do something about it
• Go out and find all the potentially hazardous
  objects and see if they are actually hazardous
• If they all turn out to be safe then the risk
  will have been eliminated
• If not..

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Mandate by U.S. Congress

• 1991 U.S. Congress directed NASA to conduct
  workshops on how potentially threatening
  asteroids could be detected, and how they could
  be deflected or destroyed.
• 1994 House Comm. on Science/Technology directed
  NASA and DoD to identify and catalogue within 10
  years orbits of all comets and asteroids 1km
  crossing orbit of Earth

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Modern Existing Searches

• Among the active search programs in the U.S.
  are
• Spacewatch (Kitt Peak in Arizona)
• NEAT (JPL using USAF Maui telescopes)
• LINEAR (Lincoln Labs at White Sands, NM)
• LONEOS (Lowell Observatory)
• IfA UH88

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Killer Asteroids and new
solar system objects
Detection with UH 88
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What is the IfA doing?

• Pan-STARRS - a new telescope facility
• 4 smallish (1.8m) telescopes, but with extremely
  wide field of view
• Can scan the sky rapidly and repeatedly, and can
  detect very faint objects
• Project led by IfA with help from Air Force, Maui
  High Performance Computer Center, MITs Lincoln
  Lab and Science Applications International Corp.

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Optical design
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Pan-STARRS numbers

• 4 telescopes
• 4 billion pixels
• 10 terabytes per night
• 30 petabytes in 10 years
• 30,000,000,000,000,000 bytes!

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Pan-STARRS Asteroid Search Strategy

• Pan-STARRS will target potentially hazardous
  objects
• Objects that may become actually hazardous in
  100 years

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Potentially Hazardous Asteroids
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Pan-STARRS capability

• Pan-STARRS will become operational in 2006
• By that time, the existing search programs will
  have found 70-80 of the 1km size objects, but
  will be running out of steam
• Pan-STARRS will push the completeness for km size
  objects to near unity
• And will find most of the objects with diameter
  300m
• Pan-STARRS will also do lots of other science,
  ranging from the formation of the solar system to
  the fate of the Universe as a whole.