Small Bodies the Origin of the Solar System

Small Bodies & the Origin of the Solar System 1 1

Unused Spare Parts • Comets, asteroids, and meteors are the unused leftovers from the formation of the solar system. • Their chemical compositions and distribution yield clues as to how the solar system formed. 2 2

Asteroids – rocky leftovers of the inner solar system • Location – Asteroid Belt – Trojan or Lagrange Asteroids – Random Orbits • Types of Asteroids • Minor planets • NEO’s 3 3

Asteroid belt • Generally, just outside Mars’ orbit • 2. 7 A. U. average distance • Total mass of all asteroids is <5% of the earth’s mass (2 to 4 of our moons. ) 4 4

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Lagrange Asteroids • Clusters of asteroids co-orbit with the gas giant planets, 60 o ahead and 60 o behind the positions of the planets. • The clusters are centered on the L 4 and L 5 Lagrange points (points in space where Jupiter’s gravitational influence equals the sun’s gravitation. ) • Jupiter’s Lagrange asteroids are known as 6 the Trojan asteroids. 6

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Types of Asteroids • S – Stony • C – Carbonaceous (modified stony asteroids with dark surfaces and interiors) • M – Metallic (comparatively rare) 8 8

Stony Asteroids Gaspra – a typical stony asteroid 9 9

Some asteroids are thought to be rubble piles held together by very low gravity. 10 10

Major Asteroids or Dwarf Planets? • Over 200 objects have diameters of >100 km. • Ceres – largest, the size of Texas (1030 km). Named after the Roman goddess of the harvest (cereal). Recently named a dwarf planet. 11 11

We don’t know what the white spot is yet. Rotation of Ceres Best Model 12 12

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Major Asteroids • Vesta – smaller (450 km diameter), but much brighter. Barely visible to naked eye. • Movie of Vesta’s rotation. http: //atropos. arizona. edu/aiz/teaching/nats 102/images/Vesta. mpg • Pallas • Juno 14 14

Vesta shows signs of having been molten at one point in its history. 15 15

NEO’s (Near Earth Objects) and PHA’s (Potentially Hazardous Asteroids) • Hundreds of asteroids cross earth’s orbit ! • Several have approached within 600, 000 km of earth (2 times moon’s orbital distance) • Collisions with Earth have occurred in the past 16 16

• Barringer Crater in Arizona – from an impact within the last 50, 000 to 100, 000 years 17 17

• This asteroid has its own little moon ! 18 18

• Toutatis – one of the closest ! Toutatis spins on 2 axes. 5 km long. Passed just 29 lunar distances 19 from the earth in 2000. 19

Mission to Asteroids • Deep Space 1 flew by asteroid 1992 KD Braille in 1999. • N. E. A. R. took close-up photos of, then landed on asteroid Eros, Feb. 12, 2001. • JAXA Hayabusa visited asteroid Itokawa in 2005. It had a small lander which should have landed on the asteroid, but malfunctioned. 20 20

Asteroid 433 Eros 21 21

NEAR “landing” on Eros. 22 22

Hayabusa - ion propulsion - autonomous navigation - sample return 23 23

Comets – outer S. S. messengers • • • Structure Orbits & Types Oort Cloud vs. Kuiper Belt Famous Comets What message do they convey? 24 24

Structure • Nucleus – Water ice, frozen CO 2, N 2, methane, ammonia, HCN, (CN)2 (cyanogen), amino acids, sugars all detected. – Embedded with rocks and dust – Extremely dark, tarry surface. • Coma – Envelope of water vapor and H 2 around nucleus 25 25

Structure (2) • Ion tail – ionized gas pushed directly away from the sun by solar wind. • Dust tail – heavier particles that follow along behind the path of the comet. – The dusty path of a comet lingers for decades, even centuries. When the earth passes through the dusty path again later, a meteor shower is produced. 26 26

Structure Dirty Snowballs 27 27

Nucleus of Halley’s Comet Sunlight causes jets of gas to spew from the comet’s nucleus. This creates the coma. Jets of gas Photo by Giotto spacecraft • Dark, tarry organic coating 28 (ESA) 28

Nucleus of Borrelly 29 29

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• Direction of comet’s movement • Ion or plasma tail • Dust tail 32 32

Comet Origins & Orbits • Kuiper Belt – Short period comets (return <200 yrs) – 50 to 200 A. U. – Several billion comets – Cometary orbits are more often near the ecliptic, but may be prograde or retrograde. 33 33

Comet Origins & Orbits (2) • Oort Cloud – Long period comets (return >200 years or may only pass by sun once) – Spherical shell of matter up to 2 light years (65, 000 A. U. ) in radius. – Trillions of comets – Comets may come in from any direction, with prograde or retrograde orbits. 34 34

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Famous Comets • Halley (1984) • Shoemaker-Levy 9 (‘ 94) • Hale Bopp (’ 96) • Kohoutek (’ 75) • Hyakutake (’ 94) • West (‘ 75) 36 36

Halley’s comet 1986 37 37

Halley’s Comet Orbit • Many comets have retrograde orbits 38 38

Comet Shoemaker-Levy 9 broke into a series of fragments before impacting Jupiter. The ‘fireball’ from each impact was larger than the earth. 39 39

An atmospheric “scar” left by the impact of Shoemaker-Levy 9. These faded after several weeks. 40 40

Comet Hale Bopp, 2002 41 41

Comet Swan has been visible in our sky the past few weeks. 42 42

Past Missions to Comets • There have been 11 past missions to comets, with 2 current missions. • Giotto – examined Halley’s comet in 1986. Photographed the nucleus from a distance of only 200 km, then continued on to comet Grigg-Skellerup in 1992. 43 43

Past Missions to Comets (2) • Deep Impact – launched a 350 kg copper impactor into the nucleus of comet 9 P/Tempel 1, in July, 2005. – A 100 m x 25 m crater was created. • Visible and infrared spectrometers on the parent craft looked for the composition of the nucleus. – 250, 000 kg of water vapor were detected. 44 44

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Current Missions to Comets • Stardust – sampled the coma of P Wild 2 from a distance of 236 km above the nucleus. • Returned comet particles back to the earth for microscopic examination and chemical testing. You can help with the microscopic work by signing up at the following website. http: //stardust. jpl. nasa. gov/home/index. html 48 48

Stardust inside comet Wild’s coma. 49 49

Comet particles trapped in the aerogel (a light silicon gel). 50 50

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Current Missions to Comets (2) • Rosetta – launched 2004 to comet 67 P/Churyumov-Gerasimenko. Rosetta will fly along with the comet for 2 years as it approaches the sun, beginning in 2014. It also has a small lander which will explore the comet’s nucleus. 52 52

Formation of the solar system • Accretion from a nebula of gas and dust. • Spinning nebula flattens to a disk • Different materials condense at different distances from the sun (temperature gradient). • Other solar systems may be quite different from ours. 53 53

• A rotating cloud of gas & dust 54 54

• Rotation causes the nebula to flatten 55 55

• A star ignites in the center and a temperature gradient forms. 56 56

• Solids condense close to the star • Volatiles & ices condense farther out 57 57

We’re unsure of our model • Solar systems that we’ve observed around other stars are quite different from ours. – Planets Jupiter-sized and larger have been observed orbiting at Mercury-like distances from their stars. – Do gas giants form closer to the star and then migrate outward, or vice versa? 58 58

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http: //www. newscientist. com/data/images/ns/cms/dn 8259 -3_506. jpg http: //www. fli-cam. com/images/comet-liner. jpg http: //www. nasa. gov/images/content/116911 main_spitzer-comet-060205 -browse. jpg http: //galileo. rice. edu/images/things/comet_1532_apian-l. gif http: //www. astrocentral. co. uk/comet_diagram. gif http: //www. solarviews. com/thumb/comet. gif http: //physics. uoregon. edu/~jimbrau/Brau. Im. New/Chap 14/FG 14_06. jpg http: //www. mallorcaweb. net/masm/Aster/astervarios. JPG http: //en. wikipedia. org/wiki/Image: Ceres_Rotation. jpg http: //near. jhuapl. edu/ http: //www. isas. jaxa. jp/e/enterp/missions/hayabusa/index. shtml http: //www. daviddarling. info/encyclopedia/N/NEAR. html http: //www. nasa. gov/worldbook/comet_worldbook. html http: //herschel. jpl. nasa. gov/images/kuiper_oort. jpg http: //www 2. jpl. nasa. gov/sl 9/gif/sl 9 hst. gif http: //bluepoint. gen. tr/sagan/sholevy 9. gif http: //nssdc. gsfc. nasa. gov/planetary/sl 9/image/sl 9 g_hst 5. gif http: //www. magma. ca/ http: //www. spaceweather. com/swpod 2006/25 oct 06/lawrence. jpg http: //solarsystem. nasa. gov/missions/profile. cfm http: //www. hour 25 online. com/pix/comet-tempel 1 -orbit_01 a. jpg 60 http: //www. cfa. harvard. edu/press/Deep-Impact_lores. jpg 60

http: //deepimpact. jpl. nasa. gov/gallery/jpg/HRI_937_1. jpg http: //stardust. jpl. nasa. gov/images/gallery/Wild 2 Encounter 2. jpg http: //stardust. jpl. nasa. gov/images/gallery/aerogel_tracks. jpg http: //stardust. jpl. nasa. gov/images/gallery/aerogelhand. jpg http: //boojum. as. arizona. edu/~jill/NS 102_2006/Lectures/Lecture 6/09 -13. jpg 61 61

Meteoroids – asteroids on a collision course…with us! • Meteor – the trail of light & ionized gas left by a meteoroid • Meteorite – what’s left of a meteoroid that hits the Earth. • Bolide – a fireball or especially bright meteor. 62

Types of Meteorites • Types – just like asteroids! – stony (incl. carbonaceous chondrites) – irons & iron / nickel (90% / 10%) – stony-irons (a combination of materials) – the type of meteorite tells you where it came from. 63

• A stony meteorite (hard to find) 64

• An iron meteorite (easier to find) 65

• A carbonaceous chondrite 66

Meteoroids were formed in parent bodies (planetessimals) • Stonies were formed in the: mantle • Irons were formed in the: core 67

Meteoroids – early planet stuff • Meteoroids come from the earliest condensed stuff in the solar system. They give us the chemical composition of the earliest planetissimals. • Most are about 4. 6+ billion years old. 68