In this activity, you will begin to think about how a foreign body hitting the Earth could have a large-scale impact on life. Because this lesson is about impacts, it will get you to think more deeply about impacts and how they really are important for us to monitor. 

Have you ever seen a movie where the Earth was being threatened because some space object was on a collision course towards the planet? What kind of disaster was predicted to happen if that object hit the Earth? What kinds of things did people do to prevent those disasters?

In this activity you are going to think about a similar scenario. NASA needs some guidelines about what space objects they can ignore, and which ones they shouldn’t ignore. Therefore, your job is to help them figure that out. Some things could hit Earth and it wouldn’t really matter, but other things, depending on their composition and size, could wipe out a species or cause serious destruction. Your group’s job is to figure out the smallest piece of space debris that could cause an extinction event on earth.

Get into your small group and take no more than 10 minutes to answer the questions on the worksheet. This will be the start of your guidelines for NASA. Make your best guesses, as you will revisit this activity again after you know more. Also, be prepared to share their hypotheses with the class.  

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This video highlighted the three biggest collisions the Earth has experienced with celestial objects—the Tunguska Event, the Chicxulub impact, and the Vredefort impact. These impacts reshaped the Earth and had a profound effect on life in these areas.

In this video, you’ll hear about the three biggest space impacts of all time, and the catastrophic events that followed. This should help you get a better idea of the gravity of the situation if a large space object were to hit the Earth. 

Preview

This short video highlights the three biggest collisions the Earth has experienced with celestial objects. 

Key Ideas – Factual

Think about the following questions as you watch the video:

1. What was the Tunguska Event?
2. Why is the Chicxulub impact considered recent, even though it was 66 million years ago?
3. How did scientists find the biggest asteroid ever found on Earth?
4. What were the effects of the Vredefort impact on the land and life on the continent now known as Africa?
5. How did scientists figure out what caused the formation of the Sudbury Basin?

Thinking Conceptually

Do you think there have been other huge collisions that had a major impact on Earth that scientists don’t know about? If so, what leads you to believe that? If not, why not? 

Scientists discovered the presence of amino acids on a comet during the NASA Stardust mission. Amino acids are a critical building block for DNA, and thus for life. This discovery presents the possibility that this ingredient came to Earth rather than forming here on our planet. 

This article explains how NASA found amino acids on a comet. This discovery supports the theory that the building blocks of life might have come to Earth from somewhere else, rather than developing here on Earth directly.

Skimming for Gist

This article from 2009 outlines the first confirmed discovery of amino acids on a comet. Critical to the development of life here on Earth, this article outlines the role of amino acids in the development of life. Working from a tiny sample of “comet dust,” scientists were able to identify a variety of organic compounds, raising important questions about how life on Earth first formed. 

Understanding Content

By the end of the second close read, you should be able to answer the following questions about collective learning:

1. What did NASA scientists recently discover about comets?
2. What are amino acids?
3. Why do scientists feel this discovery is important?

Thinking Conceptually

Using your research and claim testing skills, decide if you accept this theory as a plausible explanation for how life began. Why does it matter where the amino acids came from? Could this mean life itself came from somewhere other than Earth? 

This activity investigates the formation of craters. You will see how the size, angle, and speed of a meteorite's impact affect the properties of craters. This should help you more deeply understand the impact of space objects on Earth, and should play into how you support your Predicting Disaster closing activity answers. 

In this activity you’re going to see the impact of craters first-hand by creating models of what it would be like if a crater hit the Earth. The findings from these experiments should help you to make a more scientific assertion for your Predicting Disaster activity.

Get into groups and fill your basin with flour (about 1 ¼ to 1 ½ inches deep), and sprinkle some cocoa on the surface. The cocoa will make the changes of the impact appear more visible. Make sure you have three different sized pebbles to be your “meteoroids.”

In this experiment, you are going to test how the size, speed, and angle of a meteoroid’s impact affect the size of the crater that is formed.

1. Pick out one of the smallest pebbles and as a group, predict what will happen to the flour when you drop that pebble from eye level. Record the prediction on the worksheet.
2. Then, have one person from the group drop (not throw) the pebble from about eye level into the flour.
3. Describe what you observe, measure the diameter of the crater, and record this information in Data Table 1.
4. If needed, smooth out the flour mixture and sprinkle a little more cocoa on top, and then drop a medium-sized pebble from the same height. Note the differences between the two craters.
5. Describe what you observe, measure the diameter of the crater, and record this information. Now, predict what will happen if you drop the largest pebble.
6. If needed, smooth out the flour mixture and sprinkle a little more cocoa on top, and then drop the largest pebble from the same height. Note the differences between the medium and large craters.
7. Describe what you observe, measure the diameter of the crater, and record this information in the data table.
8. Now that you have tried three different sizes of meteoroid, draw a conclusion about how the size of the meteoroid affects the size of the crater. Record this conclusion in Data Table 1.

Once you are done testing size, you will test speed. For this experiment, you need three or four pebbles that are about the same size. Once you have your pebbles, follow these directions:

1. Smooth out the flour and sprinkle more cocoa on top. Predict what would happen if you dropped the pebble from knee height, and write your prediction on the worksheet.
2. Then, have one person from the group drop (not throw) the pebble from about knee level into the flour.
3. Describe what you observe, measure the diameter of the crater, and record this information in Data Table 1.
4. Try to predict the appearance of a crater formed by a pebble dropped from the eye level.
5. If needed, smooth out the flour mixture and sprinkle a little more cocoa on top, and then drop the same sized pebble from the eye level. Note the differences between the crater made from dropping the pebble from knee height and a crater made from dropping a pebble from eye level.
6. Describe what you observe, measure the diameter of the crater, and record this information in the data table. Now, predict what will happen if you drop the pebble from the height of a raised hand.
7. Now, drop the pebble from over your head (hold up your arm like you are raising your hand, and drop it from that height). Note the differences between the crater made from dropping the pebble from eye level and a crater made from dropping the pebble from over your head.
8. Describe what you observe, measure the diameter of the crater, and record this information.
9. Now that you have tried three different speeds of meteoroids, draw a conclusion about how the speed of the meteoroid at impact affects the size of the crater. Record this conclusion in Data Table 1.

For the last part of the experiment, you are going to test the angle of the impact. Follow these directions:

1. Smooth out the flour and sprinkle more cocoa on top. Predict what will happen when throwing a pebble vertically into the basin.
2. Then, have one person from the group throw, with moderate force, a pebble from about waist height vertically into the basin.
3. Describe what you observe, measure the diameter of the crater, note the shape of the crater, and record this information in Data Table 1.
4. Then, try to predict the appearance of a crater formed by a pebble thrown from a slight angle.
5. If needed, smooth out the flour mixture and sprinkle a little more cocoa on top, and then have someone throw a similar sized pebble, using moderate force, into the basin. Note the differences between the crater made from dropping the pebble from knee height and a crater made from dropping a pebble from eye level. Did the shape of the crater change?
6. Describe what you observe, measure the diameter of the crater, note the shape of the crater, and record this information. Now, predict what will happen if you throw a pebble, using moderate force, at a sharper angle into the basin.
7. Now, using moderate force, throw the pebble into the flour at a sharper (more acute) angle. Note the differences between the crater made from throwing the pebble from a slight angle verses a sharper angle.
8. Describe what you observe, note the shape of the crater, measure the diameter of the crater, and record this information in the data table.
9. Now that you have tried three different angles, draw a conclusion about how the angle of the meteoroid affects the shape and size of the crater. Record this conclusion in Data Table 1.

Once everyone is done with the experiments, you’ll discuss your findings with the class. How accurate were your predictions? Did anything really surprise you about this experiment?

Most people find the results of this experiment very surprising. Usually, people expect the crater to have an oblong shape on extremely wide-angle impacts. However, all craters that have been observed on the Moon and Earth are pretty much circular. The reason is that an explosion occurs on impact and the forces associated with an explosion are always spherically symmetrical. 

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The Chelyabinsk Meteor came into Earth’s atmosphere unexpectedly on February 15, 2013. It emitted enough heat and light to cause burns to some people’s skin and retinas. Events like this suggest that we might want to be monitoring meteors in space more closely. 

In this video, we learn about the Chelyabinsk Meteor, a space object that exploded over Russia in 2013. This shows us that meteors and space objects can be a threat even before they collide into the Earth. This was a recent event and is still a surprise to everyone. Even with modern day science, we have to continue to be concerned about the objects in space that are a threat to Earth. 

Preview

In this episode of SciShow, Hank explores what we know about the meteoroid that streaked across Russian skies on February 15, 2013. 

Key Ideas – Factual

Think about the following questions as you watch the video:

1. What’s the difference between a meteor, a meteoroid, and a meteorite?
2. Why don’t we usually feel the effects of most impacts, given that it’s possible that they happen every few decades?
3. Was this impact predicted, and if not, why don’t you think it was?

Thinking Conceptually

The Chelyabinsk Meteor is the largest known object to enter the Earth’s atmosphere since 1908. Scientists were not aware of this meteor coming – if it had impacted into rather than exploded above Earth, it could have caused severe widespread damage. On the other hand, no person has ever been struck and killed by a meteorite. Do you think that we should be spending more time and resources to track meteors, or is it not really worth worrying about?

In this activity, you’re going to finish writing your guidelines for NASA about what space objects should be monitored by the agency on a regular basis. Using your new knowledge of space impacts, you will revise and strengthen your prediction regarding the smallest thing that could hit Earth and cause an extinction event. This activity has you applying the knowledge you’ve learned in this lesson.

You are responsible for putting together guidelines for NASA regarding the size specifications of space objects that they should be monitoring. If a large space object were to hit the Earth, it could be disastrous. As a way to help determine reasonable guidelines, recall that you were to estimate the smallest object that could hit the Earth and cause an extinction event. Anything smaller than this object would fall below a minimum threshold, would not be seen as a threat to mankind, and would then be ignored. NASA could then focus its efforts solely on objects larger than this threshold.  

Get into your groups from Part 1 of the activity, and make sure you have the worksheet you completed. You now have the opportunity to revise your answers. Since you have more knowledge than you did at the start of the lesson, you are going to be asked some additional questions and you are going to have to claim test some of your answers.

Complete the worksheet and be prepared to share your guidelines with the class.