Pg. 62SOME INTERESTING STUFF ABOUT IMPACTSWhen 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 tectonicsAstro =star and blema =wound fancy term for impact crater

IS IT STILL HAPPENING TODAY? YES - Shooting stars, meteor showers. If hit earth= meteorite

PG. 62-63WHERE DOES SPACE DEBRIS COME FROM?

1. Asteroids-small bodies orbiting the sun

a)Asteroid Belt - between inner and outer planets orbit the Sun

b) small (< 600 mi diameter) rocky metallic and icy mass

c)If all came together would create a planet onlyabout 1/2 size of Moon

d)may have been the 10th planet but gravity of Jupiter sostrong could not combine to make that planet-

interfered with suns gravity causes “conflict” and too

energetic field for accretion to occur

PG. 62-63WHERE 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

f) Apollo and Amor asteroid groups’ orbits intersect Earth’s orbit- possibility of collisionND pg. 457 fig. 16.7

PG. 62-63WHERE DOES SPACE DEBRIS COME FROM?

1. Asteroids-small bodies orbiting the sun

ADDNEAR-ShoemakerSpace CraftNear Earth Asteroid Rendezvous-NEAR=asteroids that come within 121 million miles of Earth

Spent about a year orbiting and collectingimages and data WHY?

Landed on Eros just to see if they could. WHY?

PG. 62-63WHERE DOES SPACE DEBRIS COME FROM?

1. Asteroids-small bodies orbiting the sun

g)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

Pg. 632. Comets

a)ice and rock debris - see tail as frozen outer portionturns 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

Pg. 632. CometsADD

Kuiper Belt Oort Cloud

Contain short-period orbit comets<200years

Contain long-period orbit comets>200 years

Flattened disk image link

Spherical image link

Comets are “dirty snowballs”

Comets are “dirty snowballs”

Pg. 632. Comets

d.) many have eccentric orbits which bring themcloser to Sun (and Earth) and then track far outside Neptune’s orbit

e.) Halley’s comet is most famous - last visit 1986 ~76 year return interval

Pg. 63LOTS OF METEOROIDS GET TO EARTH1.Up to 100 billion meteoroids enter Earth’s

atmosphere EVERY 24 hours- What happens to them?

2.Most are small - and most burn up – shooting stars are burning meteoroids

(< 1mm in size)

a) burn due to atmospheric friction

b) some deflected back to space

c) hit Earth’s atmosphere is like hitting a solid(water is deadly if you jump from great heights)This causes destruction on impact with the atmosphere.

Pg. 63LOTS OF METEOROIDS GET TO EARTH3.If large enough (>.04 ounce) when hit the ground we

call them meteorites

Can create a sonic boom when enter atmosphere hear on Earth if meteoroid is > basketball size!

Oh yeah, and can cause injuries if fall on you

YOU HAVE GOT TO BE KIDDING ME1954 an 8.5 lb. meteorite crashed through woman’sHouse bounced off several walls and hit her.

Doesn’t happen often but when it does BIG global impact

Pg. 64IMPACT SITES

METEOR CRATER, AZ - Barringer CraterNear Winslow AZ Crater is 0.6 miles wide and 600 feet deep with a

rimrising 100-200 feet.

Why an impact site? How do we know? Evidence?

1) steep-sides and closed2) rim rocks tilted back3) inverted stratigraphy (rock layers)4) huge blocks of rock outside or crater5) crater floor is shattered

6) meteorite material collected from floor7) high Temp. and high Pressure - fused sand (

tektites) and shatter cones and shatter cone in situ

8)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 acrossTrees leveled, wildfires and dust darkened sky. Rock material vaporized by heat energy.Twice energy as Mt.St. Helen’s eruption.

Pg. 65K/T (Cretaceous/Tertiary) Event (dinos die)

1) Evidence in clays at boundary – iridium actual plot2) shocked quartz grains3) melted sand spherules - tektites4) microscopic diamonds commonly in meteorites5) fire layers-post impact fires6) 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

Pg. 65An Ancient Impact site in Chesapeake Bay

Evidence:

Presence of tektitesshape- defined by ejecta and seismic dataAge: 35.5 million years old

EFFECT: caused a topographic low= rivers drained toward

Pg. 65Tunguska, Siberia 19801)meteorite exploded 5 miles above ground

WHY?-probably icy and stoney NOT metallic2) Blast heard over 600 miles away!!3)37 miles away a person burned and thrown 7 feet

in air by blast4) people 300 miles away knocked down5) fires seen 12 miles away6) Forest leveled about 80 million of them7)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

Pg. 65COULD THIS HAPPEN TODAY - sureFirst Remember NEAR-Shoemaker project

WHAT ARE WE DOING ABOUT IT?NASA has 3 funded programs to address

NEO - near earth objectsADDSIMPLY: 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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