Remnants of Rock and Ice Asteroids, Comets, and Pluto Remnants of Rock and Ice

Remnants from Birth Comets, Asteroids and Meteorites carry the history of our solar system encoded in their compositions, locations, and numbers. Asteroid: a rocky leftover planetesimal orbiting the Sun. Comet: an icy leftover planetesimal orbiting the Sun-regardless of its size or whether or not it has a tail.

Meteor: a flash of light in the sky caused by a particle entering the atmosphere, whether the particle comes from an asteroid or a comet. Meteorite: any piece of rock that fell to the ground from the sky, whether from an asteroid, a comet, or even another planet.

Asteroids

The main Asteroid Belt lies between 2.2 and 3.3 AU from the Sun. Origin and Evolution of the Asteroid belt: The Asteroid belt probably formed as a result of orbital resonance. Resonance occurs whenever one object’s orbital period is a simple ratio of another object’s period. These resonances with Jupiter probably prevented a planet from ever forming in the region of the Asteroid Belt.

Another effect of the resonance is to form gaps in the orbits of the Asteroids as they orbit the Sun. These are called the Kirkwood Gaps.

The Kirkwood Gaps

Asteroids are recognizable in telescope images because they move relative to the stars in just a short time.

See SFA Observatory SFA Observatory Asteroid Discoveries

Gaspra (16 km across) Galileo Ida(53 km) and its tiny moon Galileo Mathide(59 km) NEAR Eros (40 km) NEAR

Meteorites Primitive Meteorites: Most primitive meteorites are composed of rocky minerals with an important difference from Earth rocks. The Primitive Meteorites are our best source of information about conditions in the solar nebula.

Processed Meteorites A smaller group of meteorites appears to have undergone substantial change since the formation of the solar system. These “Processed Meteorites” apparently were once part of a larger object that modified the original material into another form.

Primitive Processed Carbon-rich primitive meteorite Stony primitive meteorite Differential iron meteorite Differential stony meteorite Processed

Origin of Meteorites Carbon –rich meteorites came from the outer portion of the asteroid belt. (> 3AU) Carbon – poor meteorites formed in the inner warmer part of the asteroid belt. The processed meteorites have compositions similar to the cores, mantles, or crusts of the terrestrial worlds. These are fragments of the terrestrial worlds.

Processed meteorites with basaltic compositions must have come from lava flows.

Comets Icy Planetesimals that have been left over from the formation of the Solar System. “Sun Grazing” comet observed by The Solar and Heliospheric Observatory (SOHO).

Anatomy of a Comet

Comets exist as bare nuclei over most of their orbits and grow a coma and tails only when they approach the Sun

The Kuiper Belt and the Oort Cloud

Pluto Pluto was discovered in 1930 by an American Astronomer named Clyde Tombaugh. Pluto has long been seen to be a misfit among the planets, fitting into neither the terrestrail nor the jovian category. It has a 248 year orbit that is unusually elliptical and significantly tilted relative to the ecliptic. Other Pluto-like objects have been discovered forning a new class of planet called Dwarf Planets. Pluto falls into this class.

Cosmic Collisions The numbers of small bodies orbiting the solar system have diminished significantly since the days of early bombardment, when most impact craters were formed. However, there are still plenty of fragments left and collisions between these fragments and the planets still occur on occasion.

Comet Shoemaker -Levy 9

Comet Shoemaker-Levy 9

The End.

Comet Shoemaker-Levy 9 Was shatter by Jupiter’s gravity in 1992. All pieces hit Jupiter in the summer of 1994 leaving dark impact scars.

Images obtained by Dan Bruton in 1994

Meteor Shower

Minor Body Comparisons Property ___Asteroids _________ Comets Orbit Shape Circular to Highly elliptical elliptical Size 0.5 km to 625 km Nucleus 1 to 10 km Composition Iron or Rocky Ice and Rock Named? Named by their Named after their discoverers discoverers

Earth Impacts and Near Misses Arizona Meteor Crater measures 1 mile across from an impact 50,000 years ago by a 50 meter meteoroid

Tunguska Event in 1908 an asteroid broke up in our atmosphere leveled trees for some 30 kilometers

Frequency of Impacts versus impactor size & Effects

Chicxulub Event /cheek-shoo-loob/ 65,000,000 years ago 10 kilometer asteroid is thought to have caused a mass extinction of dinosaurs

The Oort Cloud is believed to contain: Comets Asteroids Stars All of the above

The End... Live long and prosper.