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.
What effect causes the moon’s rate of rotation to equal its rate of revolution?
Earth’s gravitational pull
(aka Tidal Locking)
What is a revolution?
Orbiting around something
What is the perigee?
The closest point in the moon’s orbit to earth
What is the apogee?
The furthest point in the moon’s orbit to earth
What two things match up when a supermoon occurs are:
Perigee
Full moon
What are lunar librations?
Moon’s orbit is wobbly (therefore allows us to see different percentages of the moon)
What are the similarities between the structure of the earth and the structure of the moon?
Made up of same layers (crust, mantle, outer core, inner core)
Inner core is smallest region for both
Crust is thinnest layer
Mantle is molten
Mantle is largest region for both
Both outer cores are liquid
Layers all made of the same materials
What are the differences between the structure of the earth and the structure of the moon?
Outer core on moon takes up smaller fraction of moon’s volume that it does Earth’s volume
Much more uneven crust on moon
Crust thicker on far side of moon
Core of moon not in the centre- slightly shifted towards earth
Different magnetic fields - moon’s smaller due to less convection currents and smaller outer core
Why are there more maria on the near side of the moon?
There’s less crust on the near side to stop meteors from breaking the crust.
What are the main 2 reasons for lunar missions?
Collection of lunar rocks for analysis
Deployment of scientific experiments on the moon
How are the moon phases formed?
Sunlight hitting one side of the moon, and the amount of the lit up side we see changes depending on where in it’s orbit around the earth the moon is (and the earth’s orbit around the sun).
What is the giant impact theory?
Theory suggests:
- earth was hit by smaller planet while forming; debris from impact became moon
Believed because:
- moon’s orbit had similar orientation to earth’s spin
- moon samples indicate it was once molten: energy required could be supplied by giant impact
What is the fission theory?
Theory suggests:
- earth spinning so fast that material broke off and began orbiting
Not believed because:
- theorises Pacific Ocean was scar of this event, but Pacific’s crust not old enough and oceanic crust not found built up in moon
What is the capture theory?
Theory suggests:
- moon formed elsewhere as wandering body and earth’s gravitational pull captured it
Believed because:
- tidal locking, moon’s size, moon’s orbit
Not believed because:
- capture mechanism is a problem to understand
What is the co-accretion/condensation theory?
Theory suggests:
- moon and earth formed at same time as each other
Not believed because:
- hypothesis doesn’t explain angular momentum of earth-moon cycle or why moon’s iron core is relatively smaller
Where is the Tycho Crater?
Where is the Copernicus Crater?
Where is the Kepler Crater?
Where is the Apennine Mountain Range?
Where is the Sea of Crisis?
Where is the Sea of Tranquility?
Where is the Ocean of Storms?
What do each of the moon phases look like?
