Chapter 3: Near-Earth Objects The Good Earth, Chapter 3: Near- Earth Objects Chevy Asteroid (not Chevy Astro) 1992: A football-sized meteorite crashed through the trunk of Michelle Knapp’s Chevrolet Malibu Classic in Peekskill, New York Near-Earth objects (NEOs) are asteroids or comets that approach Earth What are the chances that a larger space object will crash into Earth in the near future?
Chapter 3: Near-Earth Objects. Chevy Asteroid (not Chevy Astro) 1992: A football-sized meteorite crashed through the trunk of Michelle Knapp’s Chevrolet Malibu Classic in Peekskill, New York. Near-Earth objects (NEOs) are asteroids or comets that approach Earth - PowerPoint PPT Presentation
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Chapter 3: Near-Earth Objects
The Good Earth, Chapter 3: Near-Earth Objects
Chevy Asteroid (not Chevy Astro)
1992: A football-sized meteorite crashed through the trunk of Michelle Knapp’s Chevrolet Malibu Classic in Peekskill, New York
Near-Earth objects (NEOs) are asteroids or comets that approach Earth
What are the chances that a larger space object will crash into Earth in the near future?
Chevy Asteroid (not Chevy Astro)
Barringer (Meteor) Crater, Arizona formed approximately 50,000 years ago when a 50-meter diameter meteorite crashed to Earth.
Earth carries the scars of past impacts with asteroids and comets
A devastating collision with a 10-km wide asteroid is hypothesized to have caused a global extinction event 66 million years ago
Russia Chelyabinsk 2/15/2013http://www.wimp.com/meteorexplodes/
40,000-43,000 miles per hour
Exploded at 98,000 feet (18 miles) altitude
1,500 injured, 7,200 building damaged, 14,000 tons
Volcanic Shock Wave
http://www.wimp.com/volcanicmount/
Characteristics of Near-Earth Objects
In 2029, the asteroid Apophis is expected to come within 36,000 km of Earth . . . about here.
Most NEOs do not come close to Earth but occasionally one may approach within the moon’s orbit
Characteristics of Near-Earth Objects
Few asteroids were recognized in the inner solar system 100 years ago.
Today, more than 90,000 asteroids have been identified. (Red squares = NEOs)
Characteristics of Near-Earth Objects
Asteroids
• Size – space pebbles to 940 km in diameter (Ceres)
• Travel at ~16 km/s (36,000 mph)
• Composed of rock and/or metals− Meteor – asteroids that
burn in atmosphere
− Meteorite – an asteroid that strikes Earth’s surface
Asteroid 433 Eros
Characteristics of Near-Earth Objects
Comets
• Size – generally larger than asteroids − Many are 100s km across
• Travel faster than asteroids − ~50 km/s (112,000 mph)
• Composed of dust and ice with a rocky core
− “icy dirtballs”
Comet “tail” forms as heat from sun causes ice to change from solid to a gas. The “tail” points away from the sun
The Good Earth, Chapter 3: Near-Earth Objects
Characteristics of Near-Earth Objects
Comets
• Analysis of light from explosion on Tempel 1 revealed information on comet composition
• Common compounds present including− Cyanide
− Carbon dioxide
− Water – scientists are investigating if comets could have supplied water in Earth’s early oceans
Collision of “impactor” spacecraft with comet Temple 1, July 4, 2005
The Good Earth, Chapter 3: Near-Earth Objects
Characteristics of Near-Earth Objects
Comets
• 1908 Explosion of a comet in the atmosphere over Tunguska, Russia, destroyed forest over an area the size of a major city (2,100 km2)
Trees knocked down by a comet exploding in the atmosphere over Tunguska
The Good Earth, Chapter 3: Near-Earth Objects
Characteristics of Near-Earth Objects
Two types of comets
• Short-period comets − originate in Kuiper Belt
beyond Neptune
− Return to inner solar system every few years
• Long-period comets − Originate in the Oort
Cloud at the outer limits of the heliosphere
− Return orbits over decades to thousands of years
Oort Cloud
Kuiper Belt
The Good Earth, Chapter 3: Near-Earth Objects
Characteristics of Near-Earth Objects
• Long-period comets − Travel toward the sun with
irregular orbits that may be at a high angle to planets
• Short-period comets − Orbit sun with similar
paths to outer planets
The Good Earth, Chapter 3: Near-Earth Objects
Impact Features
• NEO collisions with rocky planets and moons formed 2 types of impact craters − Simple craters
− Complex craters
Barringer (Meteor) Crater, Arizona, a simple crater formed 50,000 years ago. This was the