22-3 Flashcards
(16 cards)
what did galileo notice about the moon?
that it wasn’t a perfect sphere and had a lot of surface features
what are craters?
depressions on the moon’s surface by meteorites, asteroids and comets that strike the surface
why do craters wear away on Earth and not on the moon?
on Earth ancient craters have worn away by erosional forces but on the moon it has not changed because no water/atmosphere
what are highlands? how are thought to have formed?
Light-colored mountains and crater rims on the moon cast dark shadows and cover much of its surface. Thought to have formed from asteroid debris that struck moon’s surface
what do seismographs allow scientists to do on the moon?
they allow scientists to study moonquakes
what is Maria?
Basaltic lava from moon’s interior flooded over and filled large basins forming dark-colored flat regions of the moon when asteroids punctured surface
what is regolith? where does it come from?
Thin gray debris that covers the Moon from space impacts; no atmosphere to burn debris and no erosion to remove it.
what is lunar regolith?
uppermost layer of regolith; made of igneous rock, beads, and fine lunar dust
What was the “capture theory” of the Moon’s origin and why was it rejected?
It said the Moon formed elsewhere and was caught by Earth’s gravity. Rejected because it couldn’t explain the Moon’s similar composition to Earth.
What was the “condensation theory” of the Moon’s formation and why was it rejected?
It claimed the Moon formed from loose material near Earth during solar system formation. Rejected due to lack of evidence and compositional differences.
What is the collision-ring theory of the Moon’s formation?
A Mars-sized object hit Earth, ejecting debris into orbit that formed the Moon. Supported by the Moon’s lack of water and a large iron core
What does crater density tell us about the Moon’s surface?
Higher crater density means an older surface. The Moon’s history has three phases
How was the Moon’s original crust (highlands) formed and affected early on?
highlands constantly hit by space debris. The impacts and heat from radioactive decay melted the Moon’s outer layer
How and when did the Moon’s maria basins form?
they formed about a billion years after the highlands; lava flows created smooth plains, some overlapping older highland areas.
What are rayed craters?
the Moon’s youngest features, bright material from impacts spreads across the surface, covering older craters.
Why do footprints on the Moon last millions of years?
The Moon has no atmosphere and no weather to cause erosion, so footprints remain unchanged except for slow wear from tiny meteoroid impacts
