between the meteorites and the moons. minor planets
TRANSCRIPT
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Between the meteorites and the moons.
Minor Planets
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Dwarf Planets• A celestial body orbiting the Sun
• Massive enough to be spherical as a result of its own gravity
• Has not cleared its neighboring region of planetesimals
• Is not a satellite (does not orbit another planet).
• 5 currently recognized by the IAU: Ceres, Pluto, Haumea, Makemake, and Eris.
• 50 – 200 other current candidates.
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Asteroids• No true formal definition
• Tends to refer to minor planets within the inner solar system, larger than 10 km diameter.
• Can also be referred to as Planetoid or “Small Solar System Object”
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Trans-neptunian objects (TNO)
• ANY object that is part of the solar system and beyond the orbit of Neptune.
• Kuiper Belt:
• Objects from 30 – 50 A.U. (KBO = Kuiper Belt Object)
• Primarily Icy, with frozen volatiles (methane, ammonia, etc.)
• Scattered Disc:
• Sparse collection of larger TNOs, beyond the Kuiper Belt
• Similar in composition to Kuiper Belt Objects
• It is now believed that most comets originated from this region.
• Oort Cloud:
• Farthest reaches of the solar system
• Spherical in structure, instead of flat, disc shaped regions
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Boulders to Dust
The rest of the objects
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Comets• Highly eccentric orbits
• Believed to originate from the scattered disc
• Many come from the Kuiper Belt or Oort Cloud as well.
• Can range from “Icy mudball” to “dirty snowball” in composition.
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Meteoroids
• sand to boulder-sized particle of debris in the solar system
• Ranges from icy to rocky to metallic
• When it enters the earth’s atmosphere it becomes a METEOR
• Once it lands on the surface of the earth, it becomes a METEORITE
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IT’S OVER!!!
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A Crowded Solar system?• Maybe…
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Not so fluffy fluff…
Solar System Fluff
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A Crowded Solar system?• Maybe…
Approximate number of asteroids ‘N’ larger than diameter ‘D’
D 100 m 300 m 500 m 1 km 3 km 5 km 10 km 30 km 50 km 100 km 200 km 300 km 500 km 900 km
N 25,000,000 4,000,000 2,000,000 750,000 200,000 90,000 10,000 1,100 600 200 30 5 3 1
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• Majority of asteroids are between Mars & Jupiter
• Quick area calculation of that space to the right
• Volume?
• Assume that ALL asteroids are in a region no thicker than the diameter of Jupiter itself (140,000 km)
• Assume 100 million (100,000,000) asteroids (not nearly that many…)
• So then the average distance from one asteroid to another would be…
• That’s 1/3 the distance to the moon.
• Area = Pi * (8x108)2 - Pi * (2x108)2
= 2.05 x 1018 km2 - 1.2566 x 1017 km2
= 1.885 x 1018 km2
= 1,885,000,000,000,000,000 km2
•Volume = 1.885 x 10^18 km2 * 140,000 km
• = 2.64 x 1023 km3
• = 264,000,000,000,000,000,000,000 km3
•Space volume PER asteroid =
• 2.64 x 1023 km3 / 1.0 x 108 = 2.64 x 1015 km3
•Average distance from asteroid to asteroid =
• (2.64 x 1015 km3)1/3
• = ~140000 km
Quick Volume Calculations
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View From An Asteroid
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A Crowded Solar system?• Maybe…
Approximate number of asteroids ‘N’ larger than diameter ‘D’
D 100 m 300 m 500 m 1 km 3 km 5 km 10 km 30 km 50 km 100 km 200 km 300 km 500 km 900 km
N 25,000,000 4,000,000 2,000,000 750,000 200,000 90,000 10,000 1,100 600 200 30 5 3 1
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Differentiation• Differentiation occurs when
material accretes
• Compression and radiogenic decay produces heat
• The Planetesimal melts
• Dense material (metals) sink to the surface
• The planetesimal may collide
• Fragments become different types of meteoroids/asteroids
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What types are out there?• C - type
• Rocky (silicate) with lots of carbon compounds (think charcoal)
• S – type
• Rocky (silicate)
without the carbon compounds
• M – type
• Metallic
(Iron & Nickel)
• Why the different types?
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From the asteroids, Meteoroids
• Stony Meteorites
• Can be from C type asteroids OR S-type
• Stony – Iron Meteorites (1% of all)
• From unusual “boundary” asteroids
• Iron Meteorites (2-3% of all)
• From M type asteroids
• Make up 40% of all “finds” however…
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Chondrites
• Special meteorites – Unchanged from the beginnings of the solar system.
• 4.6 billion years old (beginning of the solar system
• Never accreted onto a larger body
• Therefore never underwent the differentiation process
• Contain chondrules
• Droplets of material leftover from initial condensation of the solar nebula
• Carbonaceous chondrites
• Contain organic molecules
• Stuff for life
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Why are the Irons so easy to find?
• Think about it…
vs.
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Not all are so easily categorized however…• We sometimes get splattered with debris from distant impacts.
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A meteorite hunters paradise!
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Radioactive Dating
• It works.
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A REMINDER about terminology!• Meteoroid – Meteor – Meteorite.
• Space – Atmosphere – Ground.