Difference between revisions of "Meteorite lesson plan"

Latest revision as of 17:06, 21 August 2014

TITLE:

What do meteorites tell us about our solar system?

AUTHOR

Phil Stokes

TOTAL TIME

Approximately 45 minutes

GOALS

Students will use microscopes to differentiate between several types of meteorites, be able to explain what makes up meteorites, and understand why meteorites are important history books for our solar system.

LEARNING OBJECTIVES

Students will be able to:

• Observe, draw, and describe thin sections of meteorites seen under a microscope
• Observe, draw, and describe hand samples of meteorites
• Explain their observations using descriptive terms
• Compare and contrast the meteorites using their explanations
• Identify the related thin sections and hand samples
• Explain why the different meteorites are important to scientists

NEXT GENERATION SCIENCE STANDARDS

HS-ESS1-6.

Apply scientific reasoning and evidence from ancient Earth materials, meteorites, and other planetary surfaces to construct an account of Earth’s formation and early history. [Clarification Statement: Emphasis is on using available evidence within the solar system to reconstruct the early history of Earth, which formed along with the rest of the solar system 4.6 billion years ago. Examples of evidence include the absolute ages of ancient materials (obtained by radiometric dating of meteorites, moon rocks, and Earth’s oldest minerals), the sizes and compositions of solar system objects, and the impact cratering record of planetary surfaces.]

Science and Engineering Practices:

2. Developing and using models

• (3-5) build and revise simple models and use models to represent events
• (6-8) develop, use, and revise models to describe, test, and predict more abstract phenomena and design systems
• (9-12) use, synthesize, and develop models to predict and show relationships among variables between systems and their components in the natural and designed worlds

4. Analyzing and interpreting data

• (3-5) introduces quantitative approaches to collecting data and conducting multiple trials of qualitative observations. When possible and feasible, digital tools should be used.
• (6-8) extend quantitative analysis to investigations, distinguishing between correlation and causation, and basic statistical techniques of data and error analysis.
• (9-12) introduce more detailed statistical analysis, the comparison of data sets for consistency, and the use of models to generate and analyze data.

6. Constructing explanations (for science) and designing solutions (for engineering)

• (3-5) use evidence in constructing explanations that specify variables that describe and predict phenomena
• (6-8) construct explanations supported by multiple sources of evidence consistent with scientific ideas, principles, and theories
• (9-12) generate explanations that are supported by multiple and independent student-generated sources of evidence consistent with scientific ideas, principles, and theories

7. Engaging in argument from evidence

• (3-5) critique the scientific explanations proposed by peers by citing relevant evidence about the natural world
• (6-8) construct a convincing argument that supports or refutes claims for explanations about the natural world
• (9-12) use appropriate and sufficient evidence and scientific reasoning to defend and critique claims and explanations about the natural world. Arguments may also come from current scientific or historical episodes in science.

Crosscutting Concepts:

3. Scale, proportion, and quantity: In considering phenomena, it is critical to recognize what is relevant at different measures of size, time, and energy and to recognize how changes in scale, proportion, or quantity affect a system’s structure or performance.

4. Systems and system models: Defining the system under study—specifying its boundaries and making explicit a model of that system—provides tools for understanding and testing ideas that are applicable throughout science and engineering.

INSTRUCTIONAL PROCESS

Materials

• Two or more microscopes that are setup with polarizing light filters
• Two or more thin sections of different meteorites
• Two or more hand samples of different meteorites
• Questions from this lesson plan ready (see bottom)
• Field journals, pencils
• Optional: Magnifying glasses and magnets

We recommend that the instructor selects meteorite thin sections that are dissimilar so that novice microscope users will be able to spot the differences. In the Sky School collection, the Millbillillie achondrite thin section contrasts well with any of the other chondrite thin sections.

Setup

• Gather hand samples and disguise any labeling that might mislead students’ interpretations
• Turn on the microscopes, place slides in viewing areas, engage polarizing light filters, set eyepieces to lowest magnification, and focus each microscope on a representative area of the slide

Introduction/Engagement

Essential questions

• What is a meteorite?
• Where do meteorites come from?
• What does the composition of a meteorite tell us about its origin?

Student misconceptions

• A meteorite is the same thing as an asteroid. Response: Asteroids are solid, minor planets in our solar system. Larger asteroids are called planetoids. Meteoroids are smaller pieces of space debris that range in size from 10 micrometers (approx. the size of a human red blood cell) to 1 meter. When meteoroids enter the Earth’s atmosphere, they become meteors. Anything that remains after traveling through the atmosphere is called a meteorite.
• There are not many asteroids in our solar system. Response: There are millions of asteroids in our solar system; most are located in a belt between Mars and Jupiter.
• Comets are the same thing as meteorites. Response: Meteorites are solid pieces of debris (e.g., rocks and metal) from space, while comets consist of rock, dust, ice, and frozen gases. Sometimes comets lose their ice and gases and turn into meteorites, but they are not the same.
• The size of a rock or mineral is a useful observation to make. Response: A larger rock can be broken into smaller pieces, so size is not very useful for measuring rocks. Minerals of the same type can form in different sizes, and size is not useful for identifying minerals.

Learning structure

• This activity works best if students observe, draw, and record on their own. After students have had a chance to individually examine all samples, a group discussion can be facilitated to discuss and summarize the findings.

Exploration

Step-by-step description

• Show a short video clip of a meteor (e.g., http://www.youtube.com/watch?v=dpmXyJrs7iU).
• Ask questions such as: What is happening? How do you know? Are these phenomena dangerous to humans? What causes the bright light and trails of steam/smoke? Why does the explosive sound take so long to reach us after the object passes by? Hint: Most meteors occur between 80 to 120 km (50 to 75 miles) in altitude and travel between 11 km/s and 72 km/s (25,000 and 160,000 mph). That’s fast! If an airplane could somehow survive the atmospheric friction at that high rate, it would circle the entire globe in 9 minutes. These speedy meteors ionize the atmosphere and leave a trail that we can use to follow the path of the meteor. Some meteorites are ejected fragments of material from the moon or Mars, but most are pieces of asteroids that have collided or broken apart.
• If students have had experiences in earth science courses, ask them if they know the age of the Earth and solar system. If not, give them the age (approx 4.5-4.6 billion years). Then, ask them how we know. If they’re not sure, provide an explanation that includes some or all of the following info:
• Scientists have found zircon crystals in western Australia that have been dated to be at least 4.4 billion years old. However, most rocks and minerals on earth have undergone many processes that make it difficult to say when they originally formed; we only know when the most recent changes occurred. But, we know that everything in our solar system formed at about the same time in a pre-solar nebula. Over tens of millions of years, the planets formed through the accretion (i.e., sticking together due to gravity) of slowly revolving matter in our solar system. Anything that didn’t become part of a planet, minor planet (e.g., Pluto), or moon remained leftover to travel around our solar system as an asteroid, comet, or other debris. We can measure the radioactive decay of uranium to lead in meteorites to give us an idea of when the meteoroid formed. These measurements give us age ranges of 4.5 to 4.6 billion years for the formation of the solar system.
• At this point, a side discussion on geological time could be included. Additionally, students could be asked if they know about the relationship between major extinction events (e.g., dinosaurs) and meteorite impacts. There is a famous impact site called Meteor Crater near Flagstaff, AZ, and some students may have visited this crater. Ask them if they can recall any relevant details about their visit to this meteor crater.
• The discussion could also be led towards understanding how atmosphere affects the visibility of impact cratering. For instance, ask students why the moon has so many craters from really big meteorite impacts while the Earth has so few visible craters. Students may speculate that the moon receives more debris than Earth, but this is an unlikely scenario. Students may suggest that the Earth’s atmosphere prevents many impacts; this scenario is partly true. While our atmosphere does prevent most meteors from reaching the surface, the really large ones still make it through. Explain that the moon lacks the erosive and tectonic forces (e.g., water, wind, and plate movement) that constantly reshape the surface of the Earth. Alternatively, the instructor could present students with images of the Earth and moon and ask the same line of questions.
• Provide the students with the following information:
• Scientists group meteorites based on composition; composition provides clues about origin. There are three main groups: stony meteorites (e.g., chondrites and achondrites), iron meteorites, and stony-iron meteorites. For this activity, we will focus on stony and iron meteorites.
• Chondrites and are named for the small and round grains that can be observed in hand sample or in thin section. Chondrites have compositions similar to silicate rocks (e.g., granite) in the Earth’s crust, but the spherical grains tell us that these rocks formed in space where gravity was not present. They represent debris from our asteroid belt that never became part of a larger planet. Note: Because chondrites have distinct appearances, we recommend using at least one chondrite sample for the activity.
• Achondrites are stony meteorites with compositions similar to basalt. These meteorites are thought to be broken off pieces of crust from the Moon, Mars, or large asteroids in the asteroid belt. They are non-metallic, dark colored, and do not have spherical grains.
• Iron meteorites contain abundant metal (e.g., iron and nickel) and probably represent the cores of asteroids and planetoids that were obliterated at some point in the history of our solar system. These meteorites may also contain small amounts of dark green mafic minerals (e.g., olivine). Scientists believe that the composition of these meteorites is very similar to the composition of the Earth’s core. Iron meteorites are magnetic.
• Now that students are primed, give them a chance to observe the samples and take notes on the handout.
• Then, ask them to determine which hand samples correspond with particular slides. The result of this step will depend on how many samples were available and on which samples were chosen by the instructor.
• Additionally, ask the students to hypothesize the origin of each sample. Encourage the students to use all of their observations to classify the meteorites and predict how each sample could have formed.
• After all students have had a chance to examine the samples, ask them to return to the discussion.
• Try to reach a consensus with the group about the dominant characteristics of each sample. While students will have different opinions about the minor details of each sample, there should be some overlying themes that emerge. Use the question prompts from the handout to initially lead the group.
• Some potential questions include: how are the samples similar and different? Do any of the samples show evidence of burning or melting? Do any of the samples have long, bladed crystals/grains? Do any of the samples have rounded grains? Does any sample show evidence of cracked or shocked grains?
• After consensus is reached for each sample, ask the students about their hypotheses. Explore and discuss each proposed hypotheses for each sample. For some samples, it may be immediately clear that the students are in agreement. For other samples, the students may take some time to reach agreement, or may not at all.
• Reveal the names and origins of the samples. Ask the students to explain how their hypotheses were correct or not based on the data that they were able to collect. To provide some historical perspective, ask the students if someone looking at these samples in 1914 might be able to reach the same conclusions. 1814? 1014? 14? Try to lead the students to think about how the development of technology has led us towards a better understanding of our solar system.
• Conclude by answering any remaining questions.

Application

Why does it matter?

• For thousands of years, humans thought that the Earth was the center of the universe and had no concept of a solar system. Meteorites were thought to be an atmospheric phenomena like clouds and lightning. Prior to the 19th century, we had only vague ideas about how the Earth and solar system formed. And, before the 1950s, we had no way to precisely date the age of the Earth or solar system. Astronomy and geology are sciences that have taken great leaps forward in the past 200 years. We are looking for the future scientists who will make the next big discoveries that help to improve our understanding of the universe.

Extensions and/or follow-up activities

• Projects that incorporate geological time and the history or Mt. Lemmon could revisit the timescales that were discussed in this activity.
• Students can attend a University of Arizona Sky Center program to learn more about our solar system and universe [1].
• Students can tour the Flandrau Science Center & Planetarium [2] on the University of Arizona campus or Meteor Crater in Arizona (http://www.meteorcrater.com/) to learn more.

Assessment

How do you know if students “got it”?

• Ask students to draw and describe the various types of meteorites that we observed.
• Ask students how they would explain, to someone else, about the formation of the solar system and why meteorites give us clues about how it formed.

RESOURCES

• Meteor types and classification [3]
• American Meteor Society: Meteor FAQs [4]
• Solar system [5]
• Meteorites [6]
• Common misconceptions about rocks and minerals [7]

Questions for field journals: What do meteorites tell us about our solar system?

Draw thin section #1.

• Describe the shapes of the individual grains.
• Can you identify any patterns in how the grains are distributed?
• How would you describe the brightness, color and texture of the individual grains?
• Rotate the slide. How does the appearance of the grains and darker (opaque) areas change?
• List any additional observations or notes:

Draw thin section #2

• Describe the shapes of the individual grains.
• Can you identify any patterns in how the grains are distributed?
• How would you describe the brightness, color and texture of the individual grains?
• Rotate the slide. How does the appearance of the grains and darker (opaque) areas change?
• List any additional observations or notes:

Draw hand sample #1

• What is the overall shape of this rock?
• Does this rock appear to have a crust? If so, describe it.
• Can you see the individual grains, minerals or crystals? If so, how would you describe them?
• How would you describe the luster (shininess) of this sample?
• Is this sample magnetic?
• List any additional observations or notes:

Draw hand sample #2

• What is the overall shape of this rock?
• Does this rock appear to have a crust? If so, describe it.
• Can you see the individual grains, minerals or crystals? If so, how would you describe them?
• How would you describe the luster (shininess) of this sample?
• Is this sample magnetic?
• List any additional observations or notes: