People of earth. Help!!!!

Final Exam: Wednesday, May 4, 12:30 - 2:30 p.m., Swain West 119 Final Exam Review Session Tuesday, May 3, 7:15pm-9:15pm Swain West 007  

The nine planets eight

Pluto & Charon Kuiper Belt objects?

Kuiper belt objects made mostly of ice orbit beyond Neptune, in the same direction and plane as the planets

Largest known Kuiper Belt Objects

‘Falling Stars’

Meteoroids, Meteors, & Meteorites Meteoroids are simply smaller versions of asteroids. may be chunks that have been broken off asteroids by impacts. Meteors are streaks of light across the sky caused by a meteoroid entering the Earth's upper atmosphere and burning up in the process. Sometimes called "shooting" or "falling stars” Meteorites: a portion of a large meteoroid that survives its passage through the atmosphere and reaches the Earth's surface. Meteorites provided astronomers with the first good estimate of the age of the Solar System. Radiometric dating of meteorites gives them an age of about 4.5 billion years.

Two types of Meteors Sporadic Meteors Meteor showers Typically, 5 or 6 meteors are visible per hour All meteorites are thought to originate from sporadic meteors Come from random directions. Almost all of these originate from asteroids. A very small number have lunar or Martian origins. Meteor showers May produce thousands of meteors per hour. Paths can be traced back to a small area of the sky. Debris from a comet Arise from objects the size of a grain of sand or a pea No shower meteor is ever known to have reached the ground

Meteor Showers At certain times of the year, many more meteors are observed to be radiating from a particular point in space (radiant). associated with comet orbits; when the Earth crosses the "dusty" trail of a comet, many more meteors per hour can be observed. Radiant exists because of the viewing perspective There are several major meteor showers each year.

Meteor showers are named after the constellation in which their radiant is located.

Two Showers for Halley’s Comet

Meteor Shower Radiant

The 1833 storm

Leonids, 1998

1997 Leonids from Orbit

The 1966 storm

Why after midnight is the best time to view a meteor shower Towards Sun More bugs hit the front windshield of a moving automobile than hit the rear window “rear windshield” “front windshield” midnight

(originate from sporadic meteors) Primarily iron & nickel Types of Meteorites (originate from sporadic meteors) Stony meteorites Most common Iron meteorites Primarily iron & nickel Stony-Iron meteorites

Interesting Facts Sizes from microscopic dust to a few centimeters. About 2 meteorites large enough to produce visible impacts strike the Earth every day. Statistically, one meteorite is expected to strike a building somewhere on Earth every 16 months.

Over 150 impact craters found on Earth. Barringer Crater near Flagstaff, AZ: Formed ~ 50,000 years ago by a meteorite of ~ 80 – 100 m diameter

Other Impact Craters

Predicted Annual Number of Meteorite Falls Area 0.1 kg 1.0 kg 10 kg 106 km2 39 8 2 North America 920 190 38 Land area of Earth 5,800 1,200 240 Entire Earth 19,000 4,100 830

The End?

Impact Energies Kinetic Energy : 1/2 mv2 m = V 1 megaton = 4 x 1016 joules

Tunguska, 1908

The Chicxulub Crater & the demise of the dinosaurs

Activity Time!

You are the president faced with a very difficult and vitally important decision. You will be presented the situation. Members of the group are your cabinet, with whom you will debate and discuss the options. In the end, you have to make the decision and provide it in written form.

This activity should be conducted in two parts. Discussion within group, approx. 10 minutes Written individual reports, approx. 7 minutes.

The situation: An Earth crossing asteroid has just been discovered. Scientists have reported that there is a 92% chance it will impact the Earth in 2097. Given its size, these scientists say that the impact will have devastating consequences. As president, you are being urged to initiate a program designed to change the asteroid’s orbit. Such a program may be very expensive, with no guarantee of success.

Domestic & international considerations The program will an expensive proposition that will pull government resources away from programs that many consider to be very important. While the technology may exist to achieve a solution, it is untested and may not work. Many (very vocal) politicians, members of the public, and a handful of scientists, do not believe the impact will occur. Many others believe it will have only minor consequences, if it does occur. There is a good chance that the opposition to actions on your part may lead you to be a one term president. Some of your advisors are urging you to defer a decision until after the next election in two years. Given the resources needed to deal with the problem, any reasonable solution will require international cooperation, including working with countries with which we have lots of issues.