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COSMIC DEBRIS
To start:
1. “If it’s in the void, it’s a meteoroid. Above you soars a meteor. A meteorite is in you sight “
2. Watch the video clip provided in class.
A. A METEOROID is a chunk of rock and/or metal orbiting outside of the Earth’s atmosphere.
1. An ASTEROID is a meteoroid between Mars and Jupiter.
a. SIZE: microscopic to > 100km
i. Largest = CERES, diameter 1000km (600 miles)
b. MASS: total mass is thought to be a thousandth of the Earth’s.
c. NUMBER: more than 100,000 asteroids have been identified.
d. Asteroids do hit the earth—their orbits can be affected by Jupiter’s gravity such that a
collision course is created. About 700 Asteroids (called “Apollo” asteroids) exist within the
earth’s orbit.
e. Another group of asteroids is called “Trojan Asteroids”-- move within the same orbit as
Jupiter.
B.
A METEOR is the light produced when a meteoroid passes through the Earth’s atmosphere. (Friction
with air makes both the object and the air glow.)
Entry speeds are 1-40km/s. How fast is this in miles per hour?
1. The light begins 60-80 miles above the surface. Most particles have vaporized within fifty miles.
2. FREQUENCY: Estimated at Billions per day. Not visible during day, if particles are very small, or
if beyond 150 away.
3.
MASS—a few milligrams to 0.25g. Almost all vaporize on way trough the atmosphere, adding
perhaps hundreds of tons of matter to the earth daily.
4. A “Shooting Star” is a meteor.
C. A METEORITE is a meteoroid that reaches the Earth’s surface.
1. Most very small—largest = fifty tons.
2. Composition:
a. “stones”—similar to igneous rocks on earth. (make up 90% of meteorites discovered.
b. “irons”—iron and nickel
c. combination of the two.
3. It is hypothesized that meteorites are fragments of planetesimals that had enough mass to undergo
differentiation (we large enough and hot enough that molten metals sank to center, forming a core.
Later collisions tore apart the planetesimal, creating stones (crust), irons (core) and stony irons (from
boundary between core and crust.)
D. SIGNIFICANCE of Cosmic Debris
1. Radiometric dating show that asteroids are about 4.5BY old—supporting the nebular hypothesis on
the formation of the solar system.
2. Some structures in meteorites contain amino acids, the building blocks of proteins.
E. EXTRA FOR EXPERTS.
In 2005, the Japanese spacecraft Hayabusa landed on the asteroid, Itokawa. What did it learn?