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23 Cards in this Set
- Front
- Back
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Describe the most widely accepted theory on how the moon originated. |
The most widely accepted theory on how the moon originated purposes that the moon formed about 4.5 billion years ago as result between Earth and a planet-sized object. |
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How did the moon develop over the half billion years since its formation? |
Over the half-billion years since the moons formation it continued to develop when debris from the impact settled into orbit around Earth, and its gravity pulled it together to form the moon. |
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What has happened on the surface of the moon for the last 3 billion years or so? |
The interior of the moon gradually cooled and became geologically inactive. |
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Sketch a cross-section of the moon showing the various layers and their depths. |
Please see diagram. |
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What is a lunar maria? |
A lunar maria is a dark area on the moon composed of great basins and level plains. These formed when lava spewed to the surface through the fractures made by earlier giant impacts |
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How does a lunar highland differ from a lunar maria? |
To the unaided eye, the moon appears as a pattern of light and dark areas. The Lunar highlands are the brighter spots which are rugged mountains pockmarked with craters. The darker spots are great basins and level plains, formed when lava spewed up to the surface through the fracture made by earlier giant impacts. |
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What are the mare basalts like? |
The mare bassalts are fine-grained crystalline rrock They are dark grey or black and contain mostly plagioclase feldspar and pyroxene. Some contain olivine and ilmenite (a mixture of oxygen, iron, titanium) The mare basalts are the youngest lunar rocks. They range in age from 3.1 to 3.8 billion years. |
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What is meant by the term mascons? How were they discovered? |
Mascons are areas of higher gravity. (Mascon is short for "mass-concentration". These were discovered in the 1960's when lunar orbiters found that the moon's gravity was greater over some of the more circular maria. |
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How are rilles thought to have formed? |
Rilles are though to have formed when a river of molten lava flowed along the surface of the maria bedrock. After a hard crust formed over he river, molten lava drained away, leaving a hollow tunnel, the roof of which caved in later. |
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Why do the lunar highlands appear brighter than the lunar maria? |
The lunar highlands appear brighter than the maria because their rocks are lighter in colour and thus reflect more sunlight. |
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Where are the lunar mountain ranges found? and what is one explanation as to how they formed? |
The lunar mountain ranges lie at the edges of maria. One explanation as to how they were formed is that the moon has no atmosphere to slow down flying particles. The second is that the moon's weak gravity does not exert the same downward force that Earth's gravity does. |
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Describe the two types of rocks retrieved from the lunar highlands? How old are they? |
The two types of rocks retrieved from the lunar highlands are breccias and a lightly coloured igneous rock. Breccias are rocks made of angular fragments cemented together with fine material. Breccias on the moon are often formed by meteoroid impacts that melted the rocks together. The igneous rocks composition is similar to gabbro and anorthosite. |
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Describe the features of a lunar crater? |
a lunar crater are circular hollows on the moon's surface. Craters are formed by the impact of meteoroid strikes. The smallest craters are microscopic pits and the largest is nearly 2100 km. |
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What is a ray? |
A ray is a bright streak of many that surrounds the fringe of a 93-km wide crater named copenicus. Some rays appear to be hundreds of km long. Recent evidence suggests that rays consist of shattered rock and dust that were splashed out by the meteoroids that formed the craters. |
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Describe the composition and characteristics of the lunar regolith. |
Lunar regolith is "lunar soil" that's not really soil (regolith means loose rock material) Regolith is a grayish brown mixture of small rock pieces and fine particles that range in size from sand grains to fine dust. Regolith contains non water or organic material. Regolith is formed by the smashing impact of meteoroids of all sizes when meteoroids explode, they mix fragments of rock over broad areas. This stirring of the regolith is called gardening. The regolith ranges in depth from 2-20 meters. |
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Describe the characteristics of the moon's orbit. |
The moon rises in the east and sets in the west. This motion is a result of Earth's turning on it's axis. The moon is in orbit around Earth, taking about 271/3 days to complete each orbit. |
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See sketch on phases of the moon
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See sketch on phases of the moon |
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Please see sketch of lunar eclipse |
Please see sketch of lunar eclipse |
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What is the difference between the umbra and the penumbra? |
The shadow cast by an object has two parts: the umbra is the area of total shadow, and the penumbra is the area of partial shadow surrounding the umbra. |
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Why doesn't a lunar eclipse occur ever month? |
A lunar eclipse does not occur every month because it can occur only at the full moon phase, even though a full moon occurs ever month, an eclipse appears less often, because of the 5 degree angle between the plane o Earth's orbit and the plan of the moon's orbit. A total lunar eclipse occurs when the moon is fully within Earth's umbra. In average, at least one total lunar eclipse occurs every year. |
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What is the difference between a partial and a total eclipse? How long might one last? |
A total lunar eclipse occurs only when the the moon is fully within Earth's umbra, an average total lunar eclipse lasts as long as two hours. A partial lunar eclipse occurs only when a portion of the moon is in Earth's umbra. In good weather it is visible from the entire nightime half of Earth. |
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See sketch of partial, total, and annular solar eclipse. |
See sketch of partial, total, and annular solar eclipse. |
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How frequently can a particular spot on Earth experience a total solar eclipse? How long will the eclipse last? |
A given area experiences a total solar eclipse only once every three or four centuries. At any one place a total solar eclipse can last most 7.5 minutes. |
