Chapter 12 Remnants

Asteroids

What we see.

Orbits Inner Belt

Why no planet?

Orbital resonances by Jupiter

Collisions still grind the debris smaller and clean the belt out.

Special ones

Apollos or Near Earth Asteroids

Trojans 60deg ahead or behind Jupiter

Close-ups

Gaspara Mathilde Ida (and Dactyl) Eros

Eros orbit and landing

Itokawa

Size

close up picture

occultation

brightness and reflectivity

Mass

Flyby or another object

Moon [Ida and Dactyl] orbit

Density – loose ~1g/cm³ [Mathilde] more solid ~ 2.5g/cm³ [Eros]

Rotation from light curves

A variety of chemistry but most are

C Carbonaceous

S Silicate

M Metal

P dirty ice

D very dark ice

“Return samples” of asteroids aka

Meteorites

Terminology: meteors, meteoroids

Chemistry

Primitive

Carbonaceous Chondrites

Stony primitive

Processed

Iron

Stony-iron

How do they come from?

Primitives are primordial

Processed have been in parent bodies

History

A few are from Moon and Mars

Comets

West (1976), Hyakutake(1996), Hale-Bopp (1997)

Halley’s comet

NEAT motion

Structure Halley’s nucleus only 16x8km, density 1g/cm³

Tempel 1 and Deep Impact flash

Sample return from Wild 2 olivine

Growth and development

Holmes' coma expands

Origins Kuiper Belt and Oort Cloud

Pluto and the Kuiper Belt Objects

Pluto and Charon

Pluto discovered 1930

Orbit very eccentric and inclined

Charon discovered 1963

6 day orbit gave the masses and size so density about 2g/cm³

Formed by collision?

Very thin atmosphere which freezes out except near perihelion.

Eclipses have given a crude view

When will we know more? New Horizons

KBO orbits

Is Pluto just a big KBO?

Plutinos

Who is larger?

Impacts

Most of the stuff burns up

Meteor showers

intersect Earth’s orbit

same time every year

Storms

We are not the only one

Shoemaker-Levy 9 on Jupiter

Also on Callisto

Barringer about 50,000 years ago 50m object

Tunguska 1908

K-T Boundary impact