Making an Impact

Arizona's Meteor Crater

Looking around our solar system, we see evidence of impactors that have cratered the landscapes of Mars, Mercury, our Moon, and even planet Earth. What are the characteristics of impact craters and how are they formed? Using classroom models and simulations, we can investigate the factors the affect impact craters.

One of the best ways to begin a discussion of craters is by dissecting an image of a crater. Arizona's Meteor Crater provides a launching point for a study of craters and the impactors that formed them.

• How big is this crater? How wide? How deep? What evidence for scale do we see in the image?
• What are some physical features of this crater? (raised rim, steep walls, ejected material, central uplift)
• How big was the impactor?
• How fast was the impactor traveling?
• At what angle did the impactor hit?
• When did the impact happen?
• Where is the impactor?
• Why is this crater so well preserved?

From a discussion of these questions, we can begin to formulate research questions about the factors that affect impact craters:

• How does the diameter of an impactor affect the diameter and depth of a crater?
• How does the mass of an impactor affect the diameter and depth of a crater?
• How does the speed of an impactor affect the diameter and depth of a crater?
• How does the angle of an impactor affect the diameter and depth of a crater?

Impact Craters Lab

From our research questions, we can begin to plan our experiment. The lab investigation we conduct is modeled after an activity designed by NASA, outlined in their Exploring the Moon Educator Guide. Materials needed for this lab activity include Moon material (sand), impactors (marbles and golf balls), pans, balances, and metric rulers. Students test their hypotheses under controlled conditions in an attempt to better understand how an impact crater, such as the one in Arizona, could have formed and the energy involved in the impact.

Why is it important for us to understand craters? A study of geologic history reminds us that Earth has been hit by many impactors in the past. The largest of these impactors have repeatedly reset the evolutionary clock on our planet—mass extinctions of species such as dinosaurs are the result of planetary bombardment by rocks from space. It is only a matter of time before the next impactor threatens Earth.

If a large impactor is headed our way, is there anything we can do about it? While Hollywood-style scenarios involving nuclear missiles, massive explosions, and Bruce Willis single-handedly saving the day are exciting on the big screen, these solution just don't work out mathematically in real life (sorry…). For us to be prepared for a large impactor is a two-step process. We must first catalog the threat by surveying the skies around us and accurately tracking potential impactors. NASA and other organizations have begun to do this, but have not yet found everything—it is a massive undertaking. Second, we must be prepared not to simply blow an object out of space, but to gently finesse it into an orbit that harmlessly bypasses our planet. While the Hollywood excitement level is not as high, the chances for success (and the survival of our species) are much improved.

Universe Today has an excellent analysis of the many ways to deflect an asteroid, and Bad Astronomer Phil Plait explains the process of nudging a space rock out of our way should it come to pass close by. Additionally, there are multiple online resources for simulating impacts, including the Impact Calculator and Impact Earth.

Finally, while impacts have altered the landscapes of countless objects in our solar system and have changed the course of evolutionary history on planet Earth numerous times, they have also had one major positive side effect: the next time you look up in the sky and see the beautiful Moon, be awed by the massive impact between Earth and another long-gone planet-sized body that led to the Moon's formation some 4 billion years ago. Goodnight, Moon!

Earth Day 2012

Happy Earth Day! Go outside and get your hands and feet dirty...

Questions about the Moon

It was a simple query: "What questions do you have about the Moon?" A group of savvy and intelligent 8th graders (my students) pondered this question and came up with the following comprehensive list:

NASA: A New Map of the Moon

Physical Characteristics and Features

• How big is the Moon compared to the Earth?
• What is the diameter of the Moon?
• What is the Moon’s mass?
• Is the Moon smaller than Pluto?
• Why is the Moon a sphere?
• How far away is the Moon?
• Why are there craters on the Moon?
• How do craters on the Moon form?
• What is the largest crater on the Moon?
• Why is the Moon gray/white?
• What is the Moon’s temperature?
• What is the temperature difference between light and dark sides of the Moon?
• Does the Moon have a moon?
• Does the Moon have an atmosphere?
• What is the Moon’s atmosphere like?
• Is there oxygen on the Moon?
• Why isn’t there oxygen on the Moon?
• Does the Moon have weather?
• Does the Moon have wind?
• How much gravity is on the Moon?
• Does the Moon have a magnetic field?
• How strong is the Moon’s magnetic field?
• How high can you jump on the Moon?
• Can you make a fire on the Moon?
• Can you cook on the Moon?

Orbital Data

• Does the Moon rotate?
• How long does it take for the Moon to rotate?
• Does the Moon revolve around the Earth?
• How long does it take for the Moon to revolve around Earth?
• Why does the Moon orbit the Earth?
• Why do we only see one side of the Moon?
• Why are there phases of the Moon?

Lunar Composition

• What is inside the Moon?
• What is the Moon made of?
• What type of rock is the Moon made of?
• Does the Moon have layers like the Earth?
• How many layers does the Moon have?
• What’s in the Moon’s core?
• Is the core of the Moon the same as the core of the Earth?
• Does the Moon have landforms?
• Does the Moon have natural disasters (like, earthquakes, etc.)?
• Are there any fossils on the Moon?
• Is there life on the Moon?
• Does the Moon have water?
• Does the Moon have tectonic plates?
• Does the Moon have earthquakes?
• Is there lava on the Moon?
• How old is the Moon?

Lunar Formation

• How was the Moon formed?
• How did the Moon get there?
• How has the Moon changed over time?

Lunar Exploration

• How many people have landed on the Moon?
• Who else landed on the Moon?
• How many missions have we had to the Moon?
• How long does it take to get to the Moon?
• How much fuel does it take to visit the Moon?
• Where are the flags on the Moon?
• What have we accomplished by landing on the Moon?
• When did we first discover the Moon?
• Who hit the golf ball on the Moon?
• Will the Moon have livable conditions on the future?

Philosophical Questions

• What is the Moon’s purpose?
• What if we had no Moon?
• Who owns the Moon?
• Why is it called “Moon”?

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Question for educators, boards of education, policy makers, textbook publishers, et al.:

• Do your standards, curriculum, and educational materials reflect the innate curiosity and learning desires of our students?

Plate Tectonics — Putting It All Together

Why does the Earth's surface look the way it does? Why do Africa and South America look like they could fit together, like pieces of a puzzle? How could these pieces fit together? How do we know? What evidence do we have?

Earth's Tectonic Plates

One hundred years ago, plate tectonics was more of a crazy idea than a rock-solid scientific theory that explains why the Earth's surface looks the way it does. Helping students navigate how the theory was assembled bit-by-bit exposes them to both a deeper understanding of geology as well as the oft-messy nature of science itself. Theories are not always well-received when first proposed, and overwhelming evidence is needed for a fanciful idea to become a scientific theory. This is how science works.

In the classroom, we engage in a plate tectonics research map project to better understand how all of the geologic puzzle pieces fit together to complete the plate tectonics picture. Using primary and secondary internet resources, maps, posters, textbooks, and other artifacts, students add layer upon layer of geologic data and evidence onto a world map to see the patterns and mechanisms which work together in plate tectonics theory. In three to five days, students build evidence for the grand theory of geology that took more than half a century to initially develop. On the shoulders of giants we stand...

In the research project, students use the following websites to gain background knowledge about the scientific theory of plate tectonics and gather data for their world maps:

• Dynamic Earth: provides an excellent interactive overview about plate tectonics
• Optiputer Outreach: provides a wealth of images and animations to illustrate key geologic concepts
• Windows to the Universe: an always reliable source of leveled information about the Earth that can be viewed in both English and Spanish
• What on Earth Is Plate Tectonics?: the National Park Service tells the story of plate tectonics

Using these websites and other resources, students layer the following data and information onto a world map:

• prevalent earthquakes and volcanoes
• hot spots
• mid ocean ridges
• ocean trenches
• plate boundaries with their direction of movement
• plate names

Additionally, students are asked to illustrate the three major types of plate boundaries and how they work as well as assemble a Pangaea puzzle onto the back of their map. Finally, students are asked to explain in their own words what the scientific theory of plate tectonics is, how it works, and what evidence we have to support the theory. Along the way, students discover the story of Alfred Wegener—who first proposed the plate tectonics idea—and how he struggled and persevered throughout his short life to develop his ideas (which we fully accept today).