Astronomy HW 7

How long is a day on the Moon?

1 lunar month (the time from full moon to full moon)

The tides are strongest on the parts of Earth nearest to (D) and farthest from (B) the Moon. The reason that there are not strong tidal bulges at points A and C is because ____.

the gravitational force of the Moon at the surface at A and C is about the same as the average force of the Moon on Earth

Match the terms related to tides to their meanings.

Tides: The regular change in the height of the oceans. Tidal bulge: A bulge in ocean waters caused by the differential gravitational force of the Moon. Solar tides: Tides caused by the Sun; smaller than the Moon's tides. Tidal braking: A slowing of Earth's rotation due to drag on the tidal bulges.

Match each prediction to the appropriate hypothesis of the Moon's formation.

1. Earth captured a fully formed Moon: Earth and the Moon have very different chemical compositions. 2. Earth and Moon formed at the same time: Earth and the Moon have very similar chemical compositions. 3. The Moon formed from material spun off Earth due to Earth's rapid rotation: The Moon has a chemical composition identical to Earth's crust. 4. The Moon formed as a result of a collision between Earth and a large object: Earth and the Moon share many compositional similarities.

Arrange the following sentences to describe how impact features are formed on the Moon, from the first step at the top to the last at the bottom.

1. The impactor hits the Moon's surface at high speed. 2. The impactor disintegrates into a cloud of vaporized rock and fragments. 3. A hole forms, with a size depending on the mass and velocity of the impactor. 4. Vaporized rock forces the surrounding surface rock out into a circular, raised rim. 5. Sometimes the compressed rock beneath the crater rebounds and creates a central peak in the crater.

Apollo mission results show that Moon and Earth rocks have differences; for example, a lack of low-melting-point metals in Moon rocks. The density and structure suggest the Moon has less iron than Earth. What do these suggest is a likely model of the Moon's formation?

A Mars-sized object hit Earth after Earth differentiated, splattering low-density mantle and crust material into orbit to form the Moon.

Which is the best description of a rille?

A channel.

Which is the best explanation for the formation event shown in the picture of a region on the Moon?

An asteroid or planetesimal hit the young Moon, cracking the surface, and allowed molten rock from the interior to flow up and create a mare.

Match the descriptions with the correct layers of the Moon's internal structure.

Core: partially molten iron; slightly off center Mantle: widest internal region; contains lots of olivine Crust: where regolith is found; rich in aluminum

Select all the features that are found on Earth's Moon.

Craters Highlands Maria

Select all the lunar features thought to form as a direct or indirect result of impacts.

Craters Lunar rays Maria

Select all the choices that are true of the interiors of the Moon and Earth:

Crusts composed of silicate rocks A crust/mantle/core structure

Right now, as a result of tidal braking, ____. (Select all that apply.)

Earth only sees one side of the Moon the distance to the Moon is increasing days on Earth are slowly getting longer

Earth and the Moon are next to each other in space, so why does the Moon have so many more impact craters than Earth?

Earth's craters have been removed by erosion and plate tectonics.

The Moon exerts a tidal braking force on Earth because ____.

Earth's rotation carries the tidal bulge ahead of the Moon

What is the best account of the Moon's lack of atmosphere?

Gas present immediately after formation escaped molecule by molecule, because of the Moon's weak gravity and its proximity to the Sun.

Match the label with the layer of the Moon.

Iron core: C Iron-poor mantle: B Crust: A

Select all the processes important for forming lunar maria.

Large objects hitting the Moon Lava from the mantle flooding craters on the early Moon

Select all the statements that correctly describe the rays seen on the Moon's surface.

Long, light streaks of pulverized rock Radiate out from craters

Match the name of the feature with the letter.

Mare regions (plural maria): B Highland: A Crater: C Ray: D

The streak-like features indicated by the arrows labeled "A" are ____.

Rays.

Select all of the reasons the Moon has a heavily cratered surface but Earth does not.

The Moon has no atmosphere. The Moon has little geological activity.

Earth has an atmosphere, but the Moon doesn't. Select all the reasons why.

The Moon has too little mass so it lacks enough gravity to hold onto an atmosphere. The Moon is so cold that any gas is frozen onto the surface. The Moon has no volcanic activity producing gases.

Earth's ocean plates are rich in basalt and sink down into the mantle at continental edges (subduction zones). However, there are not subduction zones on the Moon at the edge of the maria and the highlands. Select all the reasons why.

The Moon's crust is a solid layer. The Moon's interior is cold enough that there are no convection currents.

Match the descriptions of their interiors with the Moon, Earth, or both.

The Moon: solid mantle; thinner crust on one side Earth: completely molten layer in core; strong magnetic field Both: silicate-rich crust; olivine-rich mantle

Select consequences of the Moon's lack of atmosphere.

The sky is black during the day. There are large swings in surface temperature.

Which is the cause of the Moon's synchronous rotation?

Tidal force from Earth slowed the Moon's rotation.

The difference between the strong gravitational attraction by the Moon on Earth's near side and the weak attraction on its far side is called a ______ gravitational force.

differential

Tidal interactions occur throughout the universe, between planets and moons, black holes and stars, and even between different galaxies. Tidal forces happen because the strength of ________ changes with __________.

gravity; distance

The Moon lacks the convection currents needed to power plate tectonics because ____.

it cooled off faster than Earth

The Moon's lack of atmosphere results in a ____ swing of day-night temperature than we have on Earth.

much larger

The long, straight canyon shown is an example of a lunar ____ that may have been formed by crustal shifting.

rille