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. ~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

Mass Mars-like densities (~3 g/cm 3 ) 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 1/10,000 th 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 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 impact Energy of meteor is product of mass and speed 2 (speed x speed) 10meter asteroid  0.2 Megatons (10 atom bombs) 1 km asteroid  80, ,000 MT bomb 100 km asteroid  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.

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. NameDateComet Origin GeminidsDec III PerseidsAug 12Halley OrionidsOct. 21P/Tempel- Tuttle LeonidsNov Phaethon Some Notable Showers