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Small Bodies in the Solar System
• Comets
• Asteroids
• Meteorites
What is a Comet?
• A comet is a small body of ice, rock and cosmic dust
• Sometimes referred to as dirty snowballs
• The tail of a comet occurs when solar radiation heats the ice and gas is given off
What is a Comet?
• The orbits of comets are very elongated elliptical shapes.
• When a comet approaches the sun its tail can extend millions of kilometers into space
• Comets often have two tails- The ion tail, which always points away from the sun (because of solar wind) and the dust tail which can point either way
Solar Wind pushes tail away from the sunSolar Wind pushes tail away from the sun
Origin of comets
• Scientists believe comets come from two places…
• from the Oort cloud, which is a region that surrounds the solar system
• Also from the Kuiper belt, which is outside the orbit of Neptune
OriginsOort CloudKuiper Belt
What are
Asteroids?
• Large rocky bodies (objects) that orbit the sun, usually found between the orbits of Mars and Jupiter. This region is called the asteroid belt.
Types of Asteroids
• Asteroids come in many interesting shapes and sizes
• Composition of asteroids varies usually by where they are found
In the outermost region asteroids appear to be rich in organic material with reddish brown to black surfaces
Asteroids cont…
The inner most part of the asteroid belt consists of light gray asteroids with either a stony or metallic composition
Asteroid Belt and Meteors
Some 65 million years ago, a 10 to 12 km in size asteroid or comet crashed on the Yucatan platform and formed the200 km in diameter Chicxulub crater. Huge volumes of rockswere excavated, molten and vaporized in the atmosphere in matter of minute, altering the climate and triggering darkness and climatic cooling as during an nuclear winter. http://we.vub.ac.be/~dglg/Web/Claeys/Chicxulub/Chixproject.html
• When was the last asteroid strike? The last large asteroid strike was in 1908 in Siberia when a 60 meter stony body exploded in the atmosphere causing a blast that knocked over trees in an 800 mile squared area from the blast centre. Small asteroid fragments were found embedded in trees around the blast site.
Artist’s depiction
What are
Meteoroids?
• A small rocky bodies that revolves around the sun
• Much smaller than asteroids, most likely they are pieces of asteroids
Scientific
names for
meteoroids to
identify…
• A meteorite is a meteoroid that enters Earth’s atmosphere and strikes the ground
A meteor is the bright streak of light you see, sometimes called a shooting star
Meteor showers are large numbers of small meteors usually caused by Earth passing by dusty debris left by a comet
Types of Meteorites
• Three major types:
• Stony
• Metallic
• Stony iron- may contain organic materials and water
Crater in Arizona
Impacts and the Torino Scale
• Earth is protected by its atmosphere- some planets and moons with no atmosphere have many impact craters
• Craters on Earth are also weathered and eroded
• Impacts causing natural disasters are infrequent and global impacts occur about every 300,000 years.
What is the
Torino
Scale?
The Torino scale is a system allowing scientists to rate hazard level of an object moving toward Earth
