EARTHSC 1121 Lecture 5: 1/24

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Present Day Accretion
~40,000 metric tons of extraterrestrial matter is accreted by the Earth every year
~110 tons/day
Mostly dust
Something with a 1 meter diameter falls every year
Something the size of an SUV falls ~every decade
Every few 10s of thousands of years, something the size of a football field hits the Earth.
No one has been killed by a meteorite.
Meteor Crater; AZ
~50,000 years ago
130 meters across; 300,000 ton iron-nickel meteorite
Silica glass at the bottom of the crater--there was so much heat that the
quartz in the soil was melted.
Shoemaker-Levy 9 (89)
Jupiter pulled comet apart→ string of comets that got strung out, passed around the
Sun, and Shoemaker & Levy saw this and were able to predict that it would crash back
into Jupiter, which it did.
When you hit a planet really hard with a large object, you create a lot of heat.
Peekskill Fireball
Altoona, PA
Early evening on October 9,1992
Hit a car! The owner kept it.
Parents were filming a football game and actually caught the fireball on video.
Dinosaur Extinction
Not the only extinction event in Earth’s history.
Many of the other extinction events had to do with a meteorite impact.
Used to think the dinosaur extinction (65,000,000 years ago) caused by volcanic flows
(in western India), not a meteorite. In the 80s, evidence of a meteorite impact
manifested.
It looks like the meteorite impact occurred very soon after the volcanism occurred.
Meteorite impact and volcanism appear to have happened on exact opposite sides of the
world.
Why study meteorites?
Discover processes that were happening in the early solar system before and during the
planetary formation process
Tied into this class because:
Primary constraint on the overall composition of the planet
Primary way to constrain the age of the Solar System
Study the earliest geological processes (like volcanism!) in the solar system
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