06_Comets_Dwarfs - GEL36 SOLAR SYSTEM Lecture 6: Comets,...

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1 GEL36 SOLAR SYSTEM Lecture 6: “Comets, Dwarf Planets & Outer Margins of the Solar System” (Ch. 25 p. 565-573; Ch. 24 p. 544-548; 7 th edition) Goal of the Lecture: To describe the characteristics of comets and to explain their origin and significance as remnants of the original solar nebula. We’ll talk about the outermost reaches of the solar system and the newly defined concept of dwarf planets. We’ll discuss several missions designed to investigate comets & dwarf planets that will provide inspiration for your term paper mission. Visits to Dirty Snowballs . . . comets - small icy bodies containing variable amounts of solid matter that orbit the sun in elliptical orbits, commonly discordant to the plane of the solar system. – they are pristine, icy remains of the original nebula material. - prevailing model for comets is that their nuclei are basically dirty snowballs , lumpy mixtures of ices and dust that orbit the sun in long elliptical orbits. (some consider them to be richer in dark carbonaceous particles than assumed and prefer to call them 'icy dirtballs ') - the ‘snowball’ model is probably inaccurate since the nuclei of comets have a very low density and are very dark from a black surface coating of carbon- and silicate-rich dust - the actual nucleus may be a small, fragile lump of porous rock containing various ices and lots of empty space Several comets have been visited by spacecraft, either as fly-bys or by passing through the tail . . . . In 1999, the Jet Propulsion Laboratory in Pasadena launched a space probe called Stardust to encounter a comet called Comet Wild 2 in January 2004. - close-up images showed rocky cliffs, sharp pinnacles, and deep, dark craters – Wild 2 is actually a chunk of porous rock 5 km (3.1 miles) in diameter with over 20 jets of dust spurting from the surface - Stardust snatched dust particles from the comet’s tail and returned them to Earth in January 2006 by parachute onto the salt flats of central Utah. - other than the solar wind particles abruptly returned to Earth by the Genesis mission, these are the first solar system samples returned to earth since the moon landings of the early 1970's.
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2 - analysis of Stardust particles suggest that much of the comet’s dust is rich in organic material and that the comet came from the very distant outer reaches of the early solar system Why do we care about collecting comet dust? Since comets are the icy leftovers from the original solar nebula, they hold information about the composition of that primeval material. Furthermore, comets may have delivered organic molecules and water to the very young Earth, thus providing the crucial building blocks of life. Parts of a Comet . . . Nucleus (virtually invisible from Earth), surrounded by coma (visible head), and tail extending out from the coma (the signature feature of comets) Comets do not generate their own light. When you see one, you see the Sun’s light reflected off the various layers of gas and dust that enshroud the snowball
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This note was uploaded on 05/31/2011 for the course GEL 36 taught by Professor Osleger,d during the Spring '08 term at UC Davis.

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06_Comets_Dwarfs - GEL36 SOLAR SYSTEM Lecture 6: Comets,...

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