Ay [T3] - The Moon Flashcards
What’s the mean diameter of the moon?
3,500km
What’s the mean radius of the moon?
1,750km
What are maria and how are they formed?
Maria, aka seas
Dark areas on the moon
Formed by asteroids hitting the moon’s surface and breaking through the crust. Then, the molten mantle fills the impact area and cools into a basalt lake.
What are terrae and how are they formed?
Terrae, aka highlands
Bright areas higher on moon’s surface.
Formed billions of years ago, when moon underwent a time of frequent and violent impacts.
Millions of years later, when moon underwent period of high volcanic activity and lava was flowing to the surface and cooling into basalt, the lower impact areas were the ones affected, whereas the highlands were left untouched.
What are craters and how are they formed?
Impacts on the moon
Formed by asteroids and meteorites colliding with lunar surface (moon has no atmosphere to protect itself against impacts)
What are rilles and how are they formed?
Depressions (cracks/clefts) on lunar surface
Formed by lava flowing across the surface, then collapsing and cooling
What are wrinkle ridges and how are they formed?
Elevations occurring exclusively in mare (singular for maria) basalt
Formed after lava in mare cools into basalt - thought to have formed by the contracting of the mare basins, then the basalt breaking and folding to form the wrinkle ridges
What are rays and how are they formed?
Bright steaks coming out of a crater in all directions
Thought to be surface material deposited when craters are first formed
What are some similarities between the near and far side of the moon?
They both have craters
They both have maria
They both have mountain ranges
What are some differences between the near and far side of the moon?
The far side has many more craters
The craters on the far side are (in general) larger
The near side had many more maria, and they’re bigger
Why does the far side of the moon have more craters (that are generally larger)?
Due to the thicker crust on the far side, a meteor impact is less likely to break the crust and expose the mantle, therefore just leaving a crater.
Why does the far side of the moon have less maria?
Due to the thicket crust on the far side of the moon, a meteor impact would need to impact either more force in order to break the crust and expose the mantle.
What is a sidereal month and how long is it?
27.3 days
The time taken for the moon to orbit the earth once
What is a solar/synodic month and how long does it take?
29.5 days
The time between 2 full moons
What does “synchronous orbit” mean?
The period of rotation of the moon around the earth is equal to the period of rotation of the moon on its own axis.