Monday 11/6/2017

Science Log Semester 1 Week 11 Monday, November 6: How is the surface of the moon different than the surface of Earth? How is it the same? How do these differences make it hard to study impacts on the Earth?

Vocab, unit 6 pages 82-83 Complex crater: a crater with central peaks and ejecta thrown out in long rays. Flooded crater: a crater from a large impact that released magma from beneath the surface. Simple crater: small, bowl-shaped craters with a fairly uniform blanket of ejecta distributed around the rim. Answer focus question page 77

Vocab, unit 6 pages 82-83 Ejecta: the material displaced from the land when a crater is formed. Impact: the action of one object hitting another; to strike something with force Regolith: the pulverized surface material of the Moon; also known as lunar soil

6.2 Target Earth Earth Craters We’ve been modeling craters on the Moon. In reality, impacts happen throughout our solar system and universe on a regular basis. We are going to gather more data about impacts so that we can answer our focus question.

6.2 Focus Question page 87 Will Earth experience a major impact in the future?

3. Crater formation Recall from your experimentation the two major variables that affect the size of the crater created by an impacting body. Was there a relationship between the speed of the meteoroid (drop height of the marble) and the diameter of the crater? The faster the marble traveled, the larger the diameter of the crater. Was there a relationship between the size of the meteoroid (mass of the rock) and the diameter of the crater? The larger the rock, the larger the diameter of the crater. Size of the meteoroid and its speed at time of impact affect the size of the crater. The faster or larger the impactor, the larger the crater.

4. Moon Craters You found out that a crater can result when an object crashes into a surface, and larger, faster objects create larger craters when they hit. Scientists have done experiments using high-powered rifles to demonstrate that high-speed objects produce larger craters when they crash into a surface. The faster the object, the larger the crater. What do you think would happen if something really big and really fast hit the Moon? Something like an asteroid? Discuss in your groups Probably produce a larger crater with a large crater-to- object ratio.

5. 20:1 ratio Astronomers have come up with an educated approximation of a crater-to-object ratio for large-impact events. The ratio that is generally used for these calculations is 20:1---a crater with a diameter 20 times larger than the diameter of the meteoroid or asteroid that crashed into the surface. This is only an estimation because there are many factors that affect crater size, including the size of the incoming object, its speed, and its angle of impact. No astronomer has witnessed the impact of an asteroid on a Moon or Earth-size planet, but one thing astronomers do know is that most asteroids travel really fast---between 12,000 and 20,000 km per second---that’s 6,000 to 10,000 times faster than a bullet!

Poster: 20:1 Create a poster using an object and the scale factor is 20:1 Write your group names on the back

6. Impactor size NBS 37, Asteroid Size and Impacts The first four are Earth, rest are Moon

6. Impactor Size When we conduct cratering experiments, we know the size of the impact object, and we can measure the size of the crater it produces. In the real world, we can measure the crater, but the size of the object that formed it is a mystery, because it probably vaporized on impact. How can we estimate the size of the object (asteroid) that formed each of these craters? Work out the first problem on your sheet

6. Impactor Size The crater-to-object ratio is 20:1. This means that the crater is 20 times greater in diameter than the impactor. So Manicouagan Crater is 20 times larger than the impactor that created it. Manicouagan is 100 km in diameter. The impact object that created the crater is one-20th the diameter of the Manicouagan Crater. Divide the diameter of the crater into 20 parts to determine diameter of the impactor. The object that created the Manicouagan Crater was approximately 5 km in diameter. Finish the rest assuming 20:1

7. Future impacts Talk in your groups and answer the question at the bottom of the Asteroid Size and Impact sheet. Earth is much larger than the Moon, so you would think that it has been hit more often than the Moon. Why are there more craters on the Moon than on Earth? Evidence of craters on Earth weathers away and erodes due to the forces of wind, water, and tectonics. Earth craters can also be hidden by water or vegetation. Craters don’t weather or hide on the Moon, so they survive for millions of years. Some smaller ones do get burned up while passing through the atmosphere, but meteoroids large enough to damage Earth’s surface (speed and angle are also factors) get through with ease.