comets and asteroids

67 %
33 %
Information about comets and asteroids

Published on January 16, 2008

Author: Marcell


What are comets?:  What are comets? In 1704 Sir Edmond Halley hypothesized that the comets of 1456, 1532, 1607, 1682 were the same object. He calculated a 75.7 year orbit and predicted that it would return in 1758. Halley died; but comet returned. perihelion=0.59 AU; aphelion=35.3 AU (closest to Sun) (farthest from Sun) Slide2:  Halley’s comet was at perihelion in 1986 It will return in 2061. Comets are dirty iceballs!:  Comets are dirty iceballs! Nucleus (very small, about 10 km across) rock & ices (mostly H2O and CO2 [dry ice], some methane CH4 & ammonia NH3) Coma (103 to 105 km across) is gaseous. As comet approaches Sun ices sublime, change from solid to gas, dust grains loosen and move away Tails (105 km to 1 AU long)—solar wind (steady stream of solar particles) pushes gas away; dust continues to orbit Sun Slide4:  1997—Comet Hale-Bopp Can you spot the coma, gas tail, and curved dust tail? Slide5:  Asteroids show up as streaks on photos. Since they orbit the Sun, they are observed to move with respect to the stars. Most asteroids lie in the asteroid belt.:  Most asteroids lie in the asteroid belt. 1801 Ceres was discovered first. Approx. 100,000 lie between Mars and Jupiter. Asteroids are typically cratered and irregularly shaped.:  Asteroids are typically cratered and irregularly shaped. Composition Carbonaceous—containing carbon Rocky—mostly silicates Metallic—iron and nickel rich NEAR probe orbited Eros (2000) and crash landed on it (2001) Eros is a near-Earth asteroid Orbit brings it close to Earth! Slide8:  View of 3 asteroids from spacecraft 50 km Impacts on Earth:  Impacts on Earth Meteors burn up in the atmosphere; meteorites don’t; impacts can and do happen Meteor Crater, Arizona Diameter is 1.2 km; 50,000 years old Projectile was 50 meter diameter, metallic asteroid Crater diameter is 1.2 km, 200 m deep How does a small body produce a very large impact crater?:  How does a small body produce a very large impact crater? A huge amount of energy is released as the body explodes on impact. The energy released depends on a body’s mass (m) and velocity (v). Energy of motion, kinetic energy (KE) is given by the formula KE = ½ m v2 Slide11:  The projectile that exploded on impact and produced Meteor Crater was equivalent to the energy of 1000 Hiroshima bombs. 20 megatons! Slide12:  In 1908, an 80 meter stony asteroid exploded over Tunguska Siberia. The air blast knocked down trees over 30 km. Windows were broken 600 km away. People heard the noise 1000 km away Slide13:  Italian clay—65 million years old Iridium, shocked quartz, & soot in layer support impact hypothesis (Italian coin is the size of a quarter) Did an impact cause mass extinctions 65 million yrs. ago?:  Did an impact cause mass extinctions 65 million yrs. ago? Disappearance of 70% species from the fossil record, including dinosaurs Evidence for 10 km asteroid impact in Worldwide 65 million yr old clay layer with: Iridium (element #77) rare in crust, but in clay Shocked quartz—indicates heat & pressure Soot—global wildfires What happens when a large (10 km) asteroid or comet strikes?:  What happens when a large (10 km) asteroid or comet strikes? Object explodes (energy = billion megatons) on impact and vaporizes a portion of crust Molten rock is thrown into atmosphere; it falls back down as a fiery rain igniting forests Lighter dust stays suspended=>dark & cold Photosynthesis & food chain disrupted Soot, shocked quartz, iridium dust settles creating 65 million year old clay layer exposed at over 100 places on Earth Chicxulub Crater is identified off Yucatan Peninsula:  Chicxulub Crater is identified off Yucatan Peninsula 300 km diameter ringed basin About 65 million year old Could this happen again? Yes! It is estimated that more than 10,000 objects approach Earth Tunguska/Meteor Crater events happen about every 1000 years A “Big One” predicted once every 100 million years Slide17:  Crater is buried beneath Yucatan Penisula and Gulf of Mexico. This map was made by studying gravity measurements made in the region. Compressed layers show crater.

Add a comment

Related presentations

Related pages

Asteroids and Comets, Asteroids and Comets Information ...

Get information, facts, photos, news, videos, and more about the asteroids and comets in our solar system from National Geographic.
Read more

Asteroids and Comets - NASA

General Information. Asteroid Fact Sheet; Reference Books on Asteroids; General Information on Asteroids; Information on Asteroid 433 Eros; Information on ...
Read more

Asteroid and Comet Watch | NASA brings you the latest images, videos and news from America's space agency. Get the latest updates on NASA missions, watch NASA TV live, and learn ...
Read more

Comets and Asteroids! - YouTube

Our journey through the solar system continues, as Jessi gives you a close look at comets and asteroids! Like SciShow? Want to help support us ...
Read more

What is the Difference Between Asteroids and Comets ...

Asteroids and comets have a few things in common. They are both celestial bodies orbiting our Sun, and they both can have unusual orbits ...
Read more

Comets , Meteors , & Asteroids - Curious About Astronomy ...

Skip to the Questions. Comets, meteors, and asteroids are often grouped together since they are all basically the same thing: small pieces of rock and/or ...
Read more

Images of Asteroid and Comets - NASA

Target is Asteroid and Comets: Go to PIAxxxxx: Refine this list of images by: Target: Mission: Spacecraft: Instrument: Click on an image for ...
Read more

Asteroids – Facts and Information about Asteroids

Asteroids are small, ... Not everything in the main belt is an asteroid — for instance, comets have recently been discovered there, and Ceres, ...
Read more

Comets and Asteroids | Facebook

Comets and Asteroids, Vicksburg, MS. 12,726 likes · 157 talking about this. Comet and Asteroid news, info, and events from IAU MPC and for observers to...
Read more