Asteroids & Meteors
Lectures will be available at: homework.uoregon.edu/pub/elsa/haydock/
Asteroid Belt Basic
Characteristics
Estimated 1 million are ~1km or larger; millions
more are smaller
25+ asteroids are bigger than 200Km
Average size asteroid ~ 1 km
Observing Asteroids
Approximately 1km in size
Would cause catastrophic
damage on Earth.
More than 1 million are
this size (1Km) or
greater
~200 asteroids are
this size (100km) or
greater
This asteroid is 70 times
bigger than the one that
exploded over Russia
Largest Asteroids found
Big asteroid on
slide 3
Ceres was first & largest asteroid object discovered (1801).
Both differentiated
Ceres
Asteroid: Itokawa,
effectively a rubble pile
Mass
Mars-like densities (~3 g/cm3)
Size of all combined asteroids= ½ Moon
diameter
Question: Would this object be more or less
massive than Earth? Venus? Mars? Mercury?
Basic Characteristics
Question: Would this object be more or less
massive than Earth? Venus? Mars? Mercury?
Less! About 3
times the
mass of Ceres
or 1/10,000th
the mass of
Earth
Asteroid Belt Orbits
distance ranges from 2 ~ 3.5 AU with average
distance about 2.8AU
Asteroids are not evenly distributed in belt.
Jupiter pulled asteroids into specific orbits
resonant to Jupiter’s orbit.
Unlike Star Wars, the asteroid belt is not
densely populated. The large asteroid spacing is
vast – approximately 1 million kilometers. Thus
collisions with space craft are highly unlikely.
Dawn Mission
Determining why
these two objects in
the asteroid belt
evolve differently,
role of water in
planetary formation,
origins of solar
system. Currently,
Dawn is on its way to
Ceres.
Asteroid Belt Formation
Planetesimals moved too fast due to Jupiter’s
gravitational field. Instead of accreting into a
larger protoplanet, particles crash and break into
smaller pieces.
Trojan Asteroids: Share orbit of
Planet
These asteroids
share a planet’s
orbit at two
specific
gravitationally
stable points called
Lagrangian points
- the balance
between the pull
of the Sun and the
planet.
Jupiter, Neptune, Mars and even Earth have trojans asteroids.
Apollo Asteroids & NEAs
Objects in the asteroid belt can be pushed out
via gravity or collision. Those which have Earth
crossing orbits are called Apollos.
Near Earth
Asteroids
(NEA) come
within 0.3 AU
of Earth. They
don’t
necessarily
cross Earth’s
orbit.
Amor Asteroids
Asteroids
cross Mars’
orbit but not
Earth’s orbit.
Possible
Asteroids in
transition to
Apollos via
interaction of
Mars gravity
Energy of impact
Energy of meteor is product of mass and
speed2 (speed x speed)
10meter asteroid  0.2 Megatons (10 atom
bombs)
1 km asteroid  80,000-200,000 MT bomb
100 km asteroid 80-200 billion MT bomb
note: 1 MT = energy of 1 million tons of TNT
Meteor, Meteorite or
Meteoroids
Object size =
grain of sand
Speed = up to
250,000 km/hr
Meteor, Meteorite or
Meteoroids
The meteor streak comes from a grain
interacting with atmosphere.
Object heats and strips electrons from atoms
and molecules (ionization).
The electrons recombine with the air
molecules and emit light.
Meteors
Are usually 100km from surface of Earth
Fireballs are from grape sized objects
Meteor, Meteorite or
Meteoroids
Meteorite is the rock that sometimes
survives the journey and lands on the
ground.
2 major types:
Primitive: original rock from the formation of
Solar System
Processed: rock from a larger differentiated
body (underwent melting, etc)
Primitive Meteorite
Stony or Chondrite type
meteorite.
Usually old as solar System
(4.6 byo)
Sometimes contain amino
acids/ organic compounds
– these can only form past
the asteroid belt
More Primitive Meteorites
Selling
meteorite
is big
business
$1400!!!
Processed Meteorite
Iron type meteorite
“Willamette”
Meteor - found in
West Linn, Oregon largest meteorite
discovered in North
America
Iron meteorites are easy to spot because of
their shape.
Evidence of worship in different cultures.
Early human civilization first access to Iron.
Processed Meteorite
Pallasite type
meteorite is a
combination of stone
(olivine) and
Iron/Nickel
created from
core/mantle boundary
of possibly:
Earth from an impact
differentiated
asteroids
Martian Meteorite!
Ancient Mars meteor found in Antarctic
Meteor, Meteorite or
Meteoroids
A Meteoroid is the object flying in space
before it enters atmosphere
Originate from:
Comet debris (Meteor showers)
Collision of asteroids in space
Moon or Mars impacts
Meteor Showers
Showers occur when
Earth crosses orbit of
comet debris.
Some Notable Showers
Name
Date
Comet
Origin
Geminids
Dec 14
1862 III
Perseids
Aug 12
Halley
Orionids
Oct. 21
P/TempelTuttle
Leonids
Nov 17
3200
Phaethon