The Cosmic Perspective Chapter 12 Lecture 27

Jupiter nudges the asteroids through the influence of

Orbital Reasonance

Can an asteroid be pure metal?

Yes, it must have been the core of a shattered asteroid

Did a large terrestrial planet ever form in the region of the asteroid belt?

No, because Jupiter prevented one from accreting

What does Pluto most resemble?

a comet

How big an object causes a typical shooting star?

a grain of sand or a small pebble

Which have the most elliptical and tilted orbits?

Oort cloud comets

Which are thought to have formed farthest from the Sun?

Kuiper belt comets

About how often does a 1-kilometer object strike the Earth?

every million years

What would happen if a 1-kilometer object struck the Earth?

It would cause widespread devastation and climate change.

Measuring Asteroid Properties

Size

Shape

Mass

Density

Composition

Size

few to hundreds of km radius

Shape

potatoes to spheres

Mass

how to measure

Density

Low like Rubble Piles

Composition

Spectra of Rocky vs Metallic vs Carbon Rich

What causes these 'gaps' in the asteroid belt?

Orbital resonances

orbital Resonances & the asteroid belt

resonances with Jupiter stir up asteroid belt:

makes orbits elliptical,

causes collisions, clears gaps

•Prevented a terrestrial planet from forming there

•Most original mass accreted onto other planets

Rules for Resonances

similar in mass = a bit elliptical

Massive = Hardly ever changes, other orbit can get VERY elliptical

Types of Metorites

Primitive

Processed

Primitive Meteorites

Raw materials from solar nebula

Most Stony with some metals

Some dark carbon rich some with water

Primitive Meteorites characteristics

Stony with metallic flakes

Carbon rich with H2O

Where do PRIMITIVE METEORITES come prom

Inner and outer regions of asteroid belt

The remains of the birth of solar system

Processed Meteorites characteristics

Iron rich like earth's core

Stony like earth's mantle or crust

Processed Meteorites

Significantly changed since solar system formation

Some metallic like terrestrial planet cores

From a differentiated body

Others are rocky, mantle-like, some basalts

Where do PROCESSED METEORITES come from

Once part of a larger object

From core of shattered Asteroid

From Mantle, crust, or surface of astroid

History of an Iron Meteorite

1) Iron formed in stars/stellar explosions

2)The solar nebula formed

3)Rock and metal condensed

4)Particles accreted into a small terrestrial world (but rock & metal were mixed together)

5)Differentiation separated rock & metal

6)A collision shattered the object

7)Orbital resonances nudged the fragments onto collision courses with Earth

8)An iron meteorite fell to Earth*