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 80,000-200,000 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.
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 141862 III PerseidsAug 12Halley OrionidsOct. 21P/Tempel- Tuttle LeonidsNov 173200 Phaethon Some Notable Showers