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 sizeWould cause catastrophic damage on Earth.

~200 asteroids are this size (100km) or greater

More than 1 million are this size (1Km) or greater

This asteroid is 70 times bigger than the one that exploded over Russia

Largest Asteroids found

Ceres was first & largest asteroid object discovered (1801). Both differentiated

Big asteroid on slide 3

Ceres

Asteroid: Itokawa, effectively a rubble

pile

MassMars-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 Orbitsdistance 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 FormationPlanetesimals 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

Near Earth Asteroids (NEA) come within 0.3 AU of Earth. They don’t necessarily cross Earth’s orbit.

Objects in the asteroid belt can be pushed out via gravity or collision. Those which have Earth crossing orbits are called Apollos.

Amor Asteroids Asteroids

cross Mars’ orbit but not Earth’s orbit.

Possible Asteroids in transition to Apollos via interaction of Mars gravity

Energy of impactEnergy 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

Speed = up to 250,000 km/hr

Object size = grain of sand

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.

MeteorsAre 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 SystemProcessed: 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 MeteoritePallasite type

meteorite is a combination of stone (olivine) and Iron/Nickel

created from core/mantle boundary of possibly:

Earth from an impactdifferentiated 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 spaceMoon or Mars impacts

Meteor ShowersShowers occur when Earth crosses orbit of comet debris.

Name Date Comet Origin

Geminids Dec 14 1862 III

Perseids Aug 12 Halley

Orionids Oct. 21 P/Tempel-Tuttle

Leonids Nov 17 3200 Phaethon

Some Notable Showers