Objectives:
National Science Standards:
NASA Presenter:
Advanced Preparation (Required):
To preview the presentation and to access suggested pre-conference activities on Slides 2 and 3 and Web sites for further exploration on Slide 25, click here (Powerpoint download). Please be certain to read the accompanying text in the notes of the PowerPoint presentation.
Use a web-based activity to discover what comets are made of. From the Amazing Space home page, link to Comets.
This interactive lesson focuses on what happened to all of the debris that was left behind after the initial formation of our solar system. Students are guided into discovering that rocky debris fell onto the newly formed planets, causing craters in solid surfaces, while icy debris was swept out of the solar system by the solar wind. The icy debris orbits our sun in an enormous cloud midway between our sun and the next closest stars! These condensed clots of ice, stone, and dust (dirty snowballs) are comets, according to the theoretical work of Jan Oort. We see comets when they fall inward toward the sun.
Throughout time, the solar system seems to have undergone periods of unusually heavy meteoric bombardment followed by long periods of quiet. Fossil records show that periodic mass extinctions occurred every several hundred million years or so on earth. The meteoric material may have come from great showers of comets that periodically made group excursions toward the sun. The reason for this periodic behavior is an important question in modern science. Students are challenged to arrive at the conclusion that our sun may actually have a dark companion star that passes into and out of the Oort Cloud, causing major disruptions, and sending large numbers of comets falling toward the sun.
Next, the students explore the appearance of comets in our skies and identify various cometary features. A comet is followed along its journey from deep space, around the sun, and back out to deep space again, showing changes that occur in its structure and appearance. The students are then challenged to recognize the connection between periodic meteor showers and the orbits of periodic comets.
Finally, the Age of Dinosaurs is revisited at about 65 million years ago, when a massive object struck the Yucatan Peninsula and caused the most recent mass extinction. Louis and Walter Alvarez are introduced, and their ground-breaking work with the Yucatan object is briefly discussed. (Students who have seen or read "Jurassic Park" will be familiar with the KT boundary.)
Questions and comments are an essential part of the session. The students thereby direct the speaker's comments to a level suitable to their own understanding. Pre- and post-conference activities are provided for purposes of preparation.
Suggested
post-conference activities:
Slides 24,
25, and 26 of the presentation
(powerpoint download).
NOTE: The majority of the photographs used in the presentation are taken from NASA archives.
Advanced Notice Recommended:
4 weeks
Frequency of Presentation:
Upon request
Availability of Presenter:
Varies