IMPACTS

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IMPACTS
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IMPACTS
Pg. 62 SOME INTERESTING STUFF ABOUT IMPACTS When
we look at the Moon we see the record of impacts
on its surface. Moon formed nearly 4.5 billion
ya (YEARS AGO) intense impacts till 3.9 billion
ya From space debris - earth must have been
equally impacted. Only a few impact craters
(astroblems) survive - why? Plate tectonics
destroys them. Moon has no plate tectonics Astro
star and blema wound fancy term for impact
crater IS IT STILL HAPPENING TODAY? YES -
Shooting stars, meteor showers. If hit earth
meteorite
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IMPACTS

• PG. 62-63
• WHERE DOES SPACE DEBRIS COME FROM?
• 1. Asteroids-small bodies orbiting the sun
• Asteroid Belt - between inner and outer planets
• orbit the Sun
• b) small (lt 600 mi diameter) rocky metallic and
  icy mass
• If all came together would create a planet only
• about 1/2 size of Moon
• may have been the 10th planet but gravity of
  Jupiter so
• strong could not combine to make that
  planet-interfered
• with suns gravity causes conflict and too
  energetic
• field for accretion to occur

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IMPACTS

• PG. 62-63
• WHERE DOES SPACE DEBRIS COME FROM?
• 1. Asteroids-small bodies orbiting the sun
• e) rarely collide but when do may cause orbital
  path to change and likely they could collide with
  planets
• Apollo and Amor asteroid groups orbits intersect
  Earths orbit- possibility of collision
• ND pg. 457 fig. 16.7

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IMPACTS
PG. 62-63 WHERE DOES SPACE DEBRIS COME FROM? 1.
Asteroids-small bodies orbiting the
sun ADD NEAR-Shoemaker Space Craft Near Earth
Asteroid Rendezvous-NEARasteroids that come
within 121 million miles of Earth Spent about a
year orbiting and collecting images and data
WHY? Landed on Eros just to see if they could.
WHY?
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IMPACTS

• PG. 62-63
• WHERE DOES SPACE DEBRIS COME FROM?
• 1. Asteroids-small bodies orbiting the sun
• recently determined that they are numerous small
  bodies (Ida and Dactyl) weakly held together not
  always one solid piece
• h) they may be able to absorb large amounts of
  energy without being destroyed - so much for
  destroying an asteroid on a collision path!-Could
  explain this

Could be
Could ALSO be
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IMPACTS

• Pg. 63
• 2. Comets
• ice and rock debris - see tail as frozen outer
  portion
• turns to vapor producing gasses and dust.
• Tail lines up with solar wind so always away
  from
• the Sun
• DEMO
• b) small - up to 10 mi diameter
• c) trillions of them out there - most in Oort
  cloud

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IMPACTS
Pg. 63 2. Comets ADD
Kuiper Belt Oort Cloud
Contain short-period orbit cometslt200years Contain long-period orbit cometsgt200 years
Flattened disk image link Spherical image link
Comets are dirty snowballs Comets are dirty snowballs
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IMPACTS
Pg. 63 2. Comets d.) many have eccentric orbits
which bring them closer to Sun (and Earth) and
then track far outside Neptunes orbit e.)
Halleys comet is most famous - last visit 1986
76 year return interval
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IMPACTS

• Pg. 63
• LOTS OF METEOROIDS GET TO EARTH
• Up to 100 billion meteoroids enter Earths
• atmosphere EVERY 24 hours-
• What happens to them?
• Most are small - and most burn up
• shooting stars are burning meteoroids
• (lt 1mm in size)
• a) burn due to atmospheric friction
• b) some deflected back to space
• c) hit Earths atmosphere is like hitting a
  solid
• (water is deadly if you jump from great heights)
• This causes destruction on impact with the
  atmosphere.

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IMPACTS

• Pg. 63
• LOTS OF METEOROIDS GET TO EARTH
• If large enough (gt.04 ounce) when hit the ground
  we
• call them meteorites
• Can create a sonic boom when enter atmosphere
• hear on Earth if meteoroid is gt basketball size!
• Oh yeah, and can cause injuries if fall on you
• YOU HAVE GOT TO BE KIDDING ME
• 1954 an 8.5 lb. meteorite crashed through womans
• House bounced off several walls and hit her.
• Doesnt happen often but when it does
• BIG global impact

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IMPACTS

• Pg. 64
• IMPACT SITES
• METEOR CRATER, AZ - Barringer Crater
• Near Winslow AZ
• Crater is 0.6 miles wide and 600 feet deep with a
  rim
• rising 100-200 feet.
• Why an impact site? How do we know? Evidence?
• 1) steep-sides and closed
• 2) rim rocks tilted back
• 3) inverted stratigraphy (rock layers)
• 4) huge blocks of rock outside or crater
• crater floor is shattered

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IMPACTS

• 6) meteorite material collected from floor
• 7) high Temp. and high Pressure - fused sand
  (tektites) and shatter cones and shatter cone in
  situ
• What else could make a round circular crater-like
  thingy?
• volcano and solution cavity (subsidence) but no
  evidence for either
• DRAWING/DEMO BEFORE AND AFTER SUBSIDENCE/SINKHOLE
• Age- 50,000 years old
• Meteorite 130 feet across
• Trees leveled, wildfires and dust darkened sky.
• Rock material vaporized by heat energy.
• Twice energy as Mt.St. Helens eruption.

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Pg. 65 K/T (Cretaceous/Tertiary) Event (dinos
die) 1) Evidence in clays at boundary iridium
actual plot 2) shocked quartz grains 3) melted
sand spherules - tektites 4) microscopic diamonds
commonly in meteorites 5) fire layers-post impact
fires 6) ratio of iridium/osmium similar to
meteorites basically the same idea as
1 Impact Site - Chicxulub off Yucatan
Tsunami sediments related to Chicxulub found in
Mexico, TX and NJ and Carolinas! Another link
IMPACTS
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IMPACTS
Pg. 65 An Ancient Impact site in Chesapeake Bay
Evidence Presence of tektites shape- defined
by ejecta and seismic data Age 35.5 million
years old EFFECT caused a topographic low
rivers drained toward
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IMPACTS

• Pg. 65
• Tunguska, Siberia 1980
• meteorite exploded 5 miles above ground
• WHY?-probably icy and stoney NOT metallic
• 2) Blast heard over 600 miles away!!
• 37 miles away a person burned and thrown 7 feet
• in air by blast
• 4) people 300 miles away knocked down
• 5) fires seen 12 miles away
• 6) Forest leveled about 80 million of them
• overall very nasty - luckily no one lived close
• to the area! CONSIDER THIS What if it would
  have
• happened over a highly populated area
• Meteor was between 165-100 feet in diameter

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IMPACTS
Pg. 65 COULD THIS HAPPEN TODAY - sure First
Remember NEAR-Shoemaker project WHAT ARE WE
DOING ABOUT IT? NASA has 3 funded programs to
address NEO - near earth objects ADD SIMPLY
they are cataloguing and assessing any
potentially dangerous asteroids/meteors Things
we could do 1.) shoot it with a nuclear warhead.
problems? 2.) Use focused solar energy to nudge
out of the way. 3.) Towing/pushing with space
craft. Problems? THE TRUTH Early Detection is
key. Interesting Article
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IMPACTS
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