Transcript Presentation

Small Bodies & the Origin of
the Solar System
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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.
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Asteroids – rocky leftovers of the
inner solar system
• Location
– Asteroid Belt
– Trojan or Lagrange Asteroids
– Random Orbits
• Types of Asteroids
• Minor planets
• NEO’s
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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.)
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Lagrange Asteroids
• Clusters of asteroids co-orbit with the gas
giant planets, 60o ahead and 60o behind
the positions of the planets.
• The clusters are centered on the L4 and
L5 Lagrange points (points in space where
Jupiter’s gravitational influence equals the
sun’s gravitation.)
• Jupiter’s Lagrange asteroids are known as
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the Trojan asteroids.
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Types of Asteroids
• S – Stony
• C – Carbonaceous (modified stony
asteroids with dark surfaces and
interiors)
• M – Metallic (comparatively rare)
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Stony Asteroids
Gaspra – a typical stony asteroid
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Some asteroids are thought to be rubble
piles held together by very low gravity.
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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.
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We don’t
know what
the white
spot is yet.
Rotation of Ceres
Best Model
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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.as.arizona.edu/aiz/teaching/nats102/images/Vesta.mpg
• Pallas
• Juno
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Vesta shows signs of having been molten
at one point in its history.
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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
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•Barringer Crater in Arizona – from an impact
within the last 50,000 to 100,000 years
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•This asteroid has its own little moon !
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•Toutatis – one of the closest !
Toutatis spins on 2 axes.
5 km long. Passed just 29 lunar distances
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from the earth in 2000.
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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.
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Asteroid 433 Eros
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NEAR “landing” on Eros.
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Hayabusa
- ion propulsion
- autonomous
navigation
- sample return
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Comets – outer S.S. messengers
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Structure
Orbits & Types
Oort Cloud vs. Kuiper Belt
Famous Comets
What message do they convey?
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Structure
• Nucleus
– Water ice, frozen CO2, N2, 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 H2 around
nucleus
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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.
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Structure
Dirty Snowballs
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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)
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Nucleus of Borrelly
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•Direction of comet’s movement
•Ion or plasma tail
•Dust tail
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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.
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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.
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Famous Comets
• Halley (1984)
• ShoemakerLevy 9 (‘94)
• Hale Bopp (’96)
• Kohoutek (’75)
• Hyakutake (’94)
• West (‘75)
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Halley’s comet
1986
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Halley’s Comet Orbit
•Many comets have retrograde orbits
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Comet Shoemaker-Levy 9 broke into a
series of fragments before impacting
Jupiter.
The ‘fireball’
from each
impact was
larger than
the earth.
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An atmospheric “scar” left by the impact
of Shoemaker-Levy 9. These faded after
several weeks.
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Comet Hale Bopp, 2002
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Comet
Swan
has been
visible
in our
sky the
past few
weeks.
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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.
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Past Missions to Comets (2)
• Deep Impact – launched a 350 kg copper
impactor into the nucleus of comet
9P/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.
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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
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Stardust inside comet Wild’s coma.
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Comet particles
trapped in the
aerogel (a light
silicon gel).
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Current Missions to Comets (2)
• Rosetta – launched 2004 to comet
67P/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.
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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.
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•A rotating cloud of gas & dust
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•Rotation causes the nebula to flatten
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•A star ignites in the center and a
temperature gradient forms.
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•Solids condense close to the star
•Volatiles & ices condense farther out
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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?
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http://www.newscientist.com/data/images/ns/cms/dn8259/dn8259-3_506.jpg
http://www.fli-cam.com/images/comet-liner.jpg
http://www.nasa.gov/images/content/116911main_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/comet.gif
http://physics.uoregon.edu/~jimbrau/BrauImNew/Chap14/FG14_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://www2.jpl.nasa.gov/sl9/gif/sl9hst.gif
http://bluepoint.gen.tr/sagan/sholevy9.gif
http://nssdc.gsfc.nasa.gov/planetary/sl9/image/sl9g_hst5.gif
http://www.magma.ca/
http://www.spaceweather.com/swpod2006/25oct06/lawrence.jpg
http://solarsystem.nasa.gov/missions/profile.cfm
http://www.hour25online.com/pix/comet-tempel1-orbit_01a.jpg
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http://www.cfa.harvard.edu/press/Deep-Impact_lores.jpg
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http://deepimpact.jpl.nasa.gov/gallery/jpg/HRI_937_1.jpg
http://stardust.jpl.nasa.gov/images/gallery/Wild2Encounter2.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/NS102_2006/Lectures/Lecture6/09-13.jpg
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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.
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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.
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•A stony meteorite (hard to find)
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•An iron meteorite (easier to find)
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•A carbonaceous chondrite
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Meteoroids were formed in
parent bodies (planetessimals)
• Stonies were formed in the:
mantle
• Irons were formed in the:
core
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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.
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