Earth Impacts

1
Earth Impacts
2
Asteroids chunks of rock orbiting the Sun and
travel at 30-40km/hr. Most are less than 3km in
diameter and the majority are 100m to 1km in
diameter
3

• Most of the Asteroids orbit the Sun in an area
  between Mars Jupiter called the Asteroid Belt.
• Occasionally they are knocked out of their orbits
  by
• Collisions
• Gravitational tug of the Sun and planets.

4
(No Transcript)
5
Comets are comprised of ice and rock, thus they
are often called dirty snowballs.
6
Nucleus solid rock Coma dust and gas Tail
mixture of water, other gasses and dust that
forms as the comet nears the Sun
7
Comet Hyakutake
Most comets have heads less than 15 kilometers in
diameter and travel at speeds of 60 or 70
km/sec. The tail of the comet always points AWAY
from the Sun
8
They originate in the Kuiper Belt and the Oort
Cloud. It is a vast spherical region well
beyond the orbit of Pluto that surrounds the Sun.
It contains billons of comets.
9

• Comet Hale-Bopp (1997)
• It came within the Earths orbit but on the other
  side of the solar system. Its closest approach
  was still 200,000,000 miles away.
• Had it collided with the Earth the energy
  expended would have been tens to hundreds of
  times that of the dinosaur killing asteroid.

10
(No Transcript)
11
In 1992, as Comet Shoemaker-Levy neared Jupiter,
it was broken up into 21 pieces by the planets
strong gravitational field. In July 1994 the
fragments, all lt1km struck the planet one after
another over a period of 6 days.
12
Meteors are streaks of light in the sky that
occur when a meteoroid hits the Earths atmosphere
13
Meteoroids are pieced of rock that totally burn
up in the Earths atmosphere.
14
Meteor Showers
15
Meteor Showers occur when the Earth passes
through the path of a comet.
16
Meteorites a piece of rock that survives the
passage through the Earths atmosphere to collide
with the Earth.
17
The Peekskill Fireball

• Small Impacts
• The meteorites land fairly cool.
• Thus, they simply punch through what they hit.

1992
18
Moderate Sized Impact (1.5 2 km)

• Effects
• Kill ¼ of the worlds population
• Ignite fires within hundreds of kilometers of the
  impact site
• Smoke and dust would linger in the atmosphere
  cooling the temperatures
• Nitrogen in the atmosphere would react with
  oxygen forming acid rain
• Much of the ozone layer would be destroyed
• Earthquakes and tsunamis would increase
• Result agriculture would probably be wiped out
  for a year and freezes in subsequent summers
  would threaten crops.

19
Moderate Sized Impacts produce open craters.
Mars
20
Meteor Crater, AZ

• Formed 50,000 years ago
• 1.2 km across, 180m deep
• Iron meteorite 60m diameter

21
Large Impacts produce broad shallow craters when
the walls of a deeper crater collapse inward
producing a wider but shallower crater.
Manicouagan Crater, eastern Canada
22
Heat from the impact, vaporizes the asteroid and
the target materials. This melts the rock,
excavates a crater and blasts out rock and
droplets of molten glass. The result is a huge
fireball that heats and melts rock and burns
everything combustible.
23
Chicxulub Impact Site
65 million years ago, an object struck just off
the Yucatan Peninsula
24

• The asteroid or comet was 10-15km in diameter
• Left an crater 112 miles in diameter and 3,000
  feet deep

25
At Ground Zero An almost immediate flash
incineration occurred
26

• Calculations suggest that the associated tsunami
  was 200m high

27

• KT (Cretaceous Tertiary) Extinction
• The extinction of the dinosaurs was likely the
  result of this.
• Somewhere between 40-70 of all species went
  extinct at this time.

Exactly how this happened is still not completely
understood.
28
One theory The impact produced tidal waves,
volcanism and earthquakes. After being vaporized,
the carbon in limestone was liberated to the
atmosphere as CO2, and produced a "greenhouse
effect" and the temperature of the planet rose.
29
The sulfur from the evaporite rocks (CaSO4), was
liberated as SO2, and produced acid rain and
toxic gases. All these produced an ecological
catastrophe, mainly for plants, that are the base
of the food chain.
30
Another theory suggests The impact produced
earthquakes, tidal waves and global volcanism.
The impact ejected millions of tons of pulverized
rock and sent them into the atmosphere where they
were suspended for hours to months. This
blocked the sunlight and produced a "nuclear
winter" effect with the consequence of lowering
the global temperature and inhibiting the
photosyntesis process and collapsing most of the
ecosystems.
31
Yet another theory suggests Global wild fires
triggered by the atmospheric reentry of red-hot
debris from the impact are another possibility.
Dust and soot from the fires would blot out the
Sun so animals would freeze or starve to death.
32
KT boundary at Bug Creek, MT

• Dust and carbon soot (from worldwide fires) layer
  is about 1cm thick.
• This layer contains substantial iridium (from the
  asteroid)

33
(No Transcript)
34
There were other, smaller impacts at this time.
Why?
Manson Crater in Iowa, much smaller (35km in
diameter) than the Chicxulub Crater also occurred
65Ma.
35
Impact Structures on the Earth
36
Chances of an impact on with the Earth
The chance of impact with a small-moderate
asteroid is greater than the chance of you
winning the lottery
37

• Is there anything we can do about an asteroid or
  comet approaching the Earth?
• Some facts if the object were an asteroid
  traveling at 30km/hr
• By the time it was inside the Moons orbit it
  would be 3 hours from impact
• An hour from impact it would be as bright as
  Venus
• 15 minutes from impact it would appear as an
  irregular mass rapidly growing in size
• 3 seconds from impact it would enter the Earths
  atmosphere

38

• Some suggestions
• Blasting it into pieces with a nuclear bomb
• Attaching a rocket to deflect it

39
Near Miss? 6 Dec,1997 astronomers spotted an
astroid 1.5 km across In March 1998, calculated
that on 28 Oct 2028 it would come to within 2.5
times the distance to the Moon If it were to
collide with the Earth at 20 40 km/sec it would
be equivalent to 2 million Hiroshima-type atomic
bombs. If it struck the ocean, the resulting
tsunami would be 100m high and would obliterate
most of the coastal cities. If it hit on land,
the crater would be 30km across and darken the
sky for weeks or months with dust and vapor.