Between the meteorites and the moons. MINOR PLANETS

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.

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”

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

Boulders to Dust THE REST OF THE OBJECTS

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.

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

IT’S OVER!!!

A CROWDED SOLAR SYSTEM? Maybe…

Not so fluffy fluff… SOLAR SYSTEM FLUFF

A CROWDED SOLAR SYSTEM? Maybe… Approximate number of asteroids ‘N’ larger than diameter ‘D ’ D 100 m300 m500 m1 km3 km5 km10 km30 km50 km100 km200 km300 km500 km900 km N25,000,0004,000,0002,000,000750,000200,00090,00010,0001,

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 * (8x10 8 ) 2 - Pi * (2x10 8 ) 2 = 2.05 x km x km 2 = x km 2 = 1,885,000,000,000,000,000 km 2 Volume = x 10^18 km 2 * 140,000 km = 2.64 x km 3 = 264,000,000,000,000,000,000,000 km 3 Space volume PER asteroid = 2.64 x km 3 / 1.0 x 10 8 = 2.64 x km 3 Average distance from asteroid to asteroid = (2.64 x km 3 ) 1/3 = ~ km QUICK VOLUME CALCULATIONS

VIEW FROM AN ASTEROID

A CROWDED SOLAR SYSTEM? Maybe… Approximate number of asteroids ‘N’ larger than diameter ‘D ’ D 100 m300 m500 m1 km3 km5 km10 km30 km50 km100 km200 km300 km500 km900 km N25,000,0004,000,0002,000,000750,000200,00090,00010,0001,

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

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?

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…

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

WHY ARE THE IRONS SO EASY TO FIND? Think about it… vs.

Not all are so easily categorized however… We sometimes get splattered with debris from distant impacts.

A METEORITE HUNTERS PARADISE!

RADIOACTIVE DATING It works.

A REMINDER ABOUT TERMINOLOGY! Meteoroid – Meteor – Meteorite. Space – Atmosphere – Ground.