Solar System Debris Asteroids Comets Meteors Oh My

  • Slides: 21
Download presentation
Solar System Debris Asteroids, Comets, Meteors, Oh My! 3 B

Solar System Debris Asteroids, Comets, Meteors, Oh My! 3 B

Asteroids • Asteroids are small, irregular, rocky bodies that orbit the sun • Most

Asteroids • Asteroids are small, irregular, rocky bodies that orbit the sun • Most are located between he orbits of Mars and Jupiter in the asteroid belt • Some are located in the same orbit as Jupiter, but are separated by 60º - Trojans • Some asteroids are in highly elliptical orbits that pass earth – Earth-crossing asteroids, Near-earth asteroids (NEAs), Near-earth objects (NEOs) 3 B

What do asteroids look like? • Too small to be seen with the naked

What do asteroids look like? • Too small to be seen with the naked eye – need large telescopes • Appear as streaks because of their motion • Three fly-bys of asteroids: – Gaspra by Galileo in 1998 – Ida by Galileo in ? ? – Mathilde by NEAR in 1999 3 B

What are asteroids made of? • Asteroids are classified into a number of types

What are asteroids made of? • Asteroids are classified into a number of types according to their spectra (and hence their chemical composition) and albedo: 1. C-type, includes more than 75% of known asteroids: 1. extremely dark (albedo 0. 03) 2. approximately the same chemical composition as the Sun minus hydrogen, helium and other volatiles 2. S-type, 17% 1. relatively bright (albedo. 10 -. 22) 2. metallic nickel-iron mixed with iron- and magnesiumsilicates 3. M-type, most of the rest 1. bright (albedo. 10 -. 18) 2. pure nickel-iron 4. There also a dozen or so other rare types 3 B

Asteroids • How many are there? – Some 5000 with well-determined orbits – Probably

Asteroids • How many are there? – Some 5000 with well-determined orbits – Probably >500, 000 larger than 1 km • How big are they? – – Largest (Ceres) is 940 km in diameter Three larger than 500 km About a dozen larger than 250 km Number increases rapidly with decreasing size • Total mass of all asteroids ~ 5% of the moon 3 B

Eros 3 B

Eros 3 B

More Eros 3 B

More Eros 3 B

Eros Landing 3 B

Eros Landing 3 B

Comets • Comets are small bodies of ice and dust that form tails as

Comets • Comets are small bodies of ice and dust that form tails as they near the sun. • What way is this comet moving? • Recall Kepler’s second law. Where do comets spend most of their time? 3 B

What are comets made of? • When they are near the Sun and active,

What are comets made of? • When they are near the Sun and active, comets have several distinct parts: – nucleus: relatively solid and stable, mostly ice and gas with a small amount of dust and other solids; – coma: dense cloud of water, carbon dioxide and other neutral gases sublimed from the nucleus; – hydrogen cloud: huge (millions of km in diameter) but very sparse envelope of neutral hydrogen; – dust tail: up to 10 million km long composed of smoke-sized dust particles driven off the nucleus by escaping gases; this is the most prominent part of a comet to the unaided eye; – ion tail: as much as several hundred million km long composed of plasma and laced with rays and streamers caused by interactions with the solar wind. 3 B

Comet Parts 3 B

Comet Parts 3 B

Where do comets live? • Short period comets come from the Kuiper belt •

Where do comets live? • Short period comets come from the Kuiper belt • Long period comets from the Oort cloud 3 B

What happens when comets loose their tails? • Meteor showers 3 B

What happens when comets loose their tails? • Meteor showers 3 B

Meteorites Three main types: • Stony – Look like ordinary earth rocks at first

Meteorites Three main types: • Stony – Look like ordinary earth rocks at first glance. If you were to look closely, you would see that the outsides of the rocks look melted. Most meteorites (93%) striking the earth are stony • Irons – These dark grey, metallic, and very dense meteorites are unlike any earth rocks that you have ever seen. Five percent of meteorites striking the earth are irons • Stony-Irons – These meteorites have clumps of both iron and stone 3 B

Asteroid – Meteorite Connection • Iron – similar to type M asteroids • Stony

Asteroid – Meteorite Connection • Iron – similar to type M asteroids • Stony Iron – like type S asteroids • Stony – Chondrite • by far the largest number of meteorites fall into this class; similar in composition to the mantles and crusts of the terrestrial planets – Carbonaceous Chondrite • similar to type C asteroids – Achondrite • similar to terrestrial basalts 3 B

Finding Meteorites • Finds – Found on earth, often long after they landed –

Finding Meteorites • Finds – Found on earth, often long after they landed – usually noticed because of their unusual appearance or their unusual location • Falls – These meteorites are seen falling, making a fireball in the sky. By following the trail, the landing site and meteorite can be found. Most of these are stony meteorites Peekskill, NY 1994 3 B

Impacts • What happens when a meteor hits the ground? – Usually nothing –

Impacts • What happens when a meteor hits the ground? – Usually nothing – Occasionally, large pieces make it to the ground and create impact craters 3 B

Impact craters 3 B

Impact craters 3 B

Impact Hazards • No person has ever been killed by a meteorite hitting earth

Impact Hazards • No person has ever been killed by a meteorite hitting earth • However, a large impact killed the dinosaurs • A smaller impact in remote Russia in 1908 knocked down trees and could have caused severe damage in a populated area 3 B

Civilization Threatening Impact Mass Extinction Impact Earth Sterilizing Impact 3 B

Civilization Threatening Impact Mass Extinction Impact Earth Sterilizing Impact 3 B

Terrestrial Impact Frequency Hiroshima year Tunguska century Tsunami danger ten thousand yr. Global catastrophe

Terrestrial Impact Frequency Hiroshima year Tunguska century Tsunami danger ten thousand yr. Global catastrophe million yr. K/T billion yr. 0. 01 1 100 10, 000 million 100 million TNT equivalent yield (MT) 3 B