Chapter 8: The Moon Flashcards
(103 cards)
1
Q
What is special about the Moon compared to other objects in the sky?
A
The only nearby object for which our eyes can ‘resolve features’ of it, meaning its the only object we can see with the naked eye and actually be able to make out it’s features
2
Q
What have we already learned about the origin of the moon in chapter 6?
A
- we learned that the moon was created as a result of an impact of earth with a mars-sized planet called Theia
- The collision resulted in a mixing of the two bodies, with Earth getting most of the metal core of the impacting body, leaving the Moon with relatively low density material richer in silicon, aluminum, magnesium and oxygen than in elements like iron and nickel.
- following the collision, the two bodies became ‘solar dance partners’, meaning that there is a gravitational
attraction between the two that dictates the physical properties of their orbital and rotational motion.
3
Q
What is tidal coupling? What is the result of the tidal coupling of the Moon and Earth?
A
- Earth’s gravitational influence on the Moon has forced the Moon into exactly the same rotational period and orbital period as Earth; this phenomenon is called tidal coupling.
- The result of the synchronized pattern is that we always see only one hemisphere of the Moon, and the ‘far side’ never rotates into a position of view.
4
Q
How is the Earth-Moon relationship changing over time in such a way that tidal coupling will be ‘complete’?
A
- the relationship between Earth and the Moon is constantly changing such that eventually tidal coupling will be complete: not only will one face of the Moon constantly point toward Earth, but one face of Earth will constantly point toward the Moon.
- To accomplish this, Earth’s rotation rate must keep slowing and the distance between Earth and the Moon must keep increasing.
- This will not happen any time soon
5
Q
has the earth always had only one satellite?
A
earth has not always had only one satellite: between September, 2006 and June, 2007, a little asteroid (named 2006 RH120) flew so close to Earth it was captured by the planet’s gravity. The little asteroid did about 4 orbits, and then continued on its way
6
Q
What is a Trojan satellite? How does this compare with the moon, which is a natural satellite?
A
A Trojan satellite is an object that stays in one position relative to a planet as it follows the same orbit as that planet.
This point at which is stays stationary relative to the planet is called a Legrangian point.
A natural satellite orbits around a planet (such as the Moon orbiting earth) wheras a Trojan satellite doesn’t orbit Earth directly; instead, it shares Earth’s orbit around the Sun but stays in a stable position either ahead of or behind Earth. It “follows” Earth as both orbit the Sun.
Earth has at least 1 Trojan.
7
Q
How many people have walked on the Moon?
A
Only 12 people have ever stood on the Moon.
8
Q
Does the Moon have an atmosphere?
A
No, the Moon is airless, which is why shadows are sharp and not softened like on Earth.
9
Q
how did we know the Moon is an airless world (no atmosphere) even before we had any samples of the Moon?
A
- our understanding of gravity tells us that a world as small as the Moon must have a low escape velocity (the initial velocity any object needs to escape gravity) – therefore gas atoms near its surface escape easily into space
- dramatic and sharp shadows between daylight and darkness, meaning there is no air on the Moon to scatter light and soften shadows.
10
Q
What other property can we infer about the Moon, knowing that it is an airless world?
A
an airless world is also a soundless world
11
Q
What is the side of the Moon that faces Earth called?
A
It is called the near side.
12
Q
What are the lighter areas on the Moon’s surface called?
A
The lighter areas are called the lunar highlands.
13
Q
What type of rock makes up the lunar highlands?
A
The lunar highlands are made of a rock called anorthosite.
14
Q
What are the darker areas on the Moon called?
A
The darker areas are called maria (the singular is mare).
15
Q
What fills the maria on the Moon?
A
The maria are filled with dark, solidified basalt lava from ancient volcanic activity.
16
Q
How long has the Moon been volcanically inactive?
A
The Moon has been volcanically dead for about 3 billion years.
17
Q
How do the craters on the highlands and maria compare?
A
Both the highlands and maria have craters from asteroid impacts, but the highlands have many more craters than the maria.
18
Q
What causes craters?
A
asteroid impacts
19
Q
Does the Moon have folded mountain ranges like Earth does?
A
No, the Moon doesn’t have folded mountain ranges. What looks like mountains are actually just heavily cratered areas of the lunar highlands.
20
Q
What does it mean that the lunar highlands are “saturated with craters”?
A
It means the highlands are so full of craters that forming a new one would destroy an old one.
21
Q
What does the saturation of craters on the highlands indicate about the highlands’ age?
A
It shows that the highlands are very old, as they have accumulated many craters over time, some of them from the early period of our solar system.
22
Q
What are the relative ages of the highlands vs maria?
A
the maria are younger than the highlands
23
Q
What are maria (singluar is mare). What are they made of? What percent of Moon’s surface do they cover?
A
The lowlands of the Moon –
The maria are areas of ancient lava flows with only a few centimetres of loose dust on their surfaces, and they cover 17% of the Moon’s surface.
24
Q
How deep is the loose dust that covers the maria?
A
The maria are covered by only a few centimeters of loose dust.
25
Did the lava that created the maria form high peaks?
No, the lava was too fluid to form high peaks.
26
What are sinuous rilles, and where are they found?
How were some sinuous rilles formed?
Sinuous rilles are long, winding channels often found near the edges of the maria, formed by flowing lava.
In some cases, such a channel may have had a roof of solid rock, forming a lava tube. When the lava drained away, meteoroid impacts collapsed the roof to form a sinuous rille.
27
How does the appearance of the far side of the Moon differ from the near side?
The far side has almost no maria and is much more heavily cratered by asteroid impacts
28
Which side is the near side of the moon and which is the far side
the near side is on the right - smoother and more maria
the far side is the left - heavily cratered and hardly any maria
29
What information can we learn from the craters of a planet?
The number and distribution of craters can tell us about the age and history of the surface, the nature of its surface material, and even aspects of its internal structure
* the more impact craters a surface has, the older that surface must be because it has been around for longer to experience more impacts
30
define meteoroid
define asteroid
meteoroid: sand size to 100m in diameter
asteroid: 100m to 1000km in diameter
31
What does the number of impact craters on a surface indicate about its age?
The more impact craters a surface has, the older it is, because it indicates a longer exposure to potential impacts.
32
How can scientists use crater counts to estimate the age of a surface?
By estimating the **rate of crater production** and **counting the total number of craters**, scientists can calculate the **relative age of the surface.** (it can not give us an age in years but we can compare which surfaces are older vs younger)
33
What can even a small telescope reveal about the Moon?
A small telescope can reveal many craters on the Moon's surface.
34
How often do objects a few tens of meters in diameter likely strike the Moon?
Are large impacts common on the Moon today?
Objects a few tens of meters in diameter probably strike the Moon every 50 years or so.]
large impacts are quite rare today, and most of the craters we see were formed during the Solar System's youth.
35
When was the first 'real-time' small meteoroid impact observed on the Moon?
The first real-time observation of a small meteoroid impact on the Moon was in 1999. we continue to see small events like that but no large impacts.
36
What is the mass of the moon?
7.4 x 10^22 kg
this is around the same mass that was accumulated by earth during Late Heavy Bombardment
37
Why do meteotoids and asteroids typically strike planets at 10 km per second or faster?
Because of the combination of orbital speed and planetary gravity, meteoroids (and asteroids) typically strike planets at 10 or more kilometres per second.
38
Why do smaller meteoroids often fail to form craters on planets like Earth?
The atmosphere can slow down or destroy smaller meteoroids before they reach the surface.
39
What types of energy are created when a meteoroid or asteroid impacts a surface?
The impact converts kinetic energy into:
* thermal energy (heat)
* acoustic energy (sound)
* and mechanical energy (rock fracturing and ejection).
40
What is a shockwave, and how does it affect the rock during an impact?
A shockwave is a zone of **highly compressed energy that compresses and deforms the rock**, making it act almost like a fluid around the impact site.
41
What happens to the rock layers below the surface during an impact?
How is the rim of a crater formed?
upon penetrating the surface, this **shockwave ‘explodes’** or releases energy below surface, any rock layers that may initially have been flat are **heaved upward and outward, bent back, and folded back over surrounding rock**
The rim around the crater is built partly from this **up-thrust rock** and partly from **excavated debris dumped around the edge.** (excavated debris refers to material that is thrown out or removed from the ground during the formation of a crater. When a meteoroid or asteroid impacts the surface, the force of the collision is so powerful that it breaks apart and ejects pieces of the surface material outward. This debris is then scattered around the crater and contributes to building the raised rim or edge of the crater.)
42
What is the rule of thumb for the size of crater an impact will form on Earth vs the Moon. Why the difference?
For Earth impacts, we use a ‘rule of thumb’ that says a crater will be roughly 15-20 times the size of the impactor.
For the Moon, that factor must be larger (perhaps 50 times) because there is no atmosphere to slow objects.
43
Explain 5 steps in crater formation and draw a diagram of the formed crater
**1. Impact of meteorite:** A meteorite strikes the surface at high speed. The initial contact generates a shock wave that starts to compress the surface material.
**2. Beginning of shock wave:** The shock wave from the impact begins to travel downwards and outwards. The subsurface layers start to react to the shock, beginning the deformation process.
**3. Compression wave:** The compression wave intensifies as it moves through the subsurface, causing the material to compress and fracture. The surrounding rock begins to crack and move, setting the stage for the crater's formation.
**4. Ejecta:** The shock wave reaches a critical point where it pushes outwards strongly, throwing up debris and material from the surface. This ejected material, known as ejecta, starts to form a curtain of debris around the impact site.
**5. Crater formation:** The area below the impact collapses into a bowl shape, forming the actual crater.
**Features of crater:**
**Ejecta blanket:** The debris thrown out during the impact settles around the new crater.
**Overturned crater rim:** The edges of the crater where the ground has been pushed up and folded back due to the impact.
**Fracture system:** Cracks and faults that appear in and around the crater due to the intense stress and deformation caused by the impact.
**Crater:** The final, bowl-shaped depression.
44
How do scientists use crater size frequency distribution (CSFD) to estimate the age of celestial surfaces like the Moon's
Scientists plot the number of craters against their sizes on a graph that typically forms a **straight line due to more small impactors than large ones,** causing more smaller craters.
**As a surface ages and collects impacts, this line shifts upward, indicating more craters.**
**Crater saturation **occurs when new impacts start obliterating old craters, which helps identify very old surfaces. This method, enhanced with age data from lunar samples, **allows scientists to calculate the relative ages of different Moon regions by observing their positions on the cratering curve.**
The term "cumulative" refers to the fact that for each point on the x-axis (crater diameter), the y-axis value represents the total number of craters per square kilometer that are equal to or larger than that diameter.
In logarithmic plots, the downward trend does not actually indicate a reduction in the cumulative total. Instead, it shows that the rate of increase in the number of craters is decreasing as crater size increases. This is because larger craters are rarer than smaller ones. The line trends downward due to the logarithmic scaling of both axes, emphasizing the rapid drop-off in frequency as crater size increases.
45
What is represented in this image?
this is a cumulative crater size frequency distribution
46
What is crater saturation and what does this concept signify?
Crater saturation occurs when we reach a point where new impacts start obliterating old craters, which helps identify very old surfaces.
47
How have scientists built a geological time scale for the moon?
By carefully counting craters on the surface different regions of the Moon and figuring out relative ages
**Pre-Nectarian Period**
Age: More than 3.92 billion years ago.
This period includes the formation of the Moon and is characterized by intense bombardment by meteorites, leading to numerous impact basins. The craters from this era are the oldest and have been heavily modified by subsequent impacts.
**Nectarian Period**
Age: About 3.92 to 3.85 billion years ago.
**Named after the Nectaris Basin,** this period features the creation of several large basins. The surface still bears signs of the heavy bombardment phase.
**Imbrian Period**
Age: 3.85 to about 3.16 billion years ago.
**Early Imbrian:** Characterized by the formation of the Imbrian and Orientale basins.
**Late Imbrian:** Known for extensive volcanic activity that led to the formation of mare basalts, which are large, dark, basaltic plains formed from ancient volcanic eruptions.
**Eratosthenian Period**
Age: About 3.2 to 1.1 billion years ago.
This period is marked by fewer basalt flows and the formation of newer craters with faint rays—ejecta that appears as light streaks emanating from craters.
**Copernican Period**
Age: 1.1 billion years ago to present.
Characterized by the most recent craters that have bright rays, indicating they are younger and have not been weathered or darkened by space weathering. This period is named after the prominent crater Copernicus.
48
What are basins
'basins' are craters that are really freaking huge like bigger than Texas
49
What does this graph illustrate?
illustrates the relationship between crater density and the age of lunar surfaces
graph starts from the right at 0 (present time) and goes to the left, the negative numbers meaning that it goes back in time.
The downward trend in crater density over time reflects a decrease in the rate at which impacts occurred.
50
Explain the formation of maria
Over time, volcanic activity on the Moon led to the formation of maria, which are large, dark, basaltic plains on the Moon's surface. These lava flows originated from the interior of the Moon and covered over earlier craters in the lowlands, effectively "resetting" the surface. This gives the maria a smoother appearance compared to the more heavily cratered highlands.
51
Who was the first human to step on the moon and when? What was the mission called?
What was the spacecraft called?
What was brought back from this mission?
**Neil Armstrong on July 20, 1969**
The first step onto the lunar surface from the **Apollo 11 Lunar Module, the Eagle**, fulfilled the promise of President John F. Kennedy that the U.S. would land a man on the Moon before the end of the decade
**The scientific return from the lunar missions was immensely important and included:**
* nearly complete high-resolution imaging of the lunar surface
* lunar samples
* topographic, seismic, and gravity data
* information on the lunar environment.
52
What was the first spacecraft that reached the moon (launched by the Soviets)?
When was it launched?
Explain what happened on this mission
**Luna 1 in 1959 (Soviet):** Luna 1 was the first spacecraft to reach the Moon, and the first of a series of Soviet automatic interplanetary stations successfully launched in the direction of the Moon.
On January 2, 1959, after reaching escape velocity, Luna 1 separated from its third stage.
On January 3, at a distance of 113,000 km from Earth, a large (1 kg) cloud of sodium gas was released by the spacecraft.
This glowing orange trail of gas, visible over the Indian Ocean with the brightness of a sixth-magnitude star, allowed astronomers to track the spacecraft. It also served as an experiment on the behaviour of gas in outer space.
Luna 1 passed within 5995 km of the Moon's surface on January 4, after 34 hours of flight. It went into orbit around Sun, between the orbits of Earth and Mars.
(this is just talking about the first spacecraft that reached the moon, not people. the first people on the moon were americans)
53
What was the first successful USA mission toward the Moon, and what was notable about its trajectory?
The first successful USA mission toward the Moon was Pioneer 4, launched within months of the USSR's Luna 1. Pioneer 4 was notable for passing too far from the Moon to activate its lunar photography experiment and eventually went into solar orbit.
54
What was the significance of the Ranger series for the USA in lunar exploration?
The Ranger series (Ranger 3, 4, 6, 7, 8, and 9) marked a streak of successes
took a stack of excellent photos and scientific instrument readings before they crashed in the lunar surface (which they were designed to do). All this was in preparation for soft landings.
55
What was Luna 9, and why was it significant in the history of space exploration?
Luna 9, launched in 1966 by the Soviets, was the first spacecraft to achieve a soft landing on another planetary body, landing in the Ocean of Storms. It transmitted panoramic photographs of the lunar surface, providing invaluable data on the lunar environment.
* the four petals, which formed the spacecraft, opened outward and stabilized the spacecraft on the lunar surface
* Spring-controlled antennas assumed operating positions, and the television camera rotatable mirror system, which operated by revolving and tilting, began a photographic survey of the lunar environment.
* Seven radio sessions, totalling 8 hours and 5 minutes, were transmitted as were three series of TV pictures.
* When assembled, the photographs provided a panoramic view of the nearby lunar surface.
* The pictures included views of nearby rocks and of the horizon 1.4 km away from the spacecraft.
56
What was unique about the Zond 5 mission by the USSR?
Zond 5, launched in 1968 by the USSR, orbited the Moon with a payload of turtles, wine flies, meal worms, plants, seeds, bacteria, and other organisms, making it the first mission to carry and return live organisms from around the Moon.
then brought the payload capsule back for a successful landing on September 21, 1968. This spacecraft was clearly the planned precursor to a manned trip. Just to show they could do this with ease, they repeated the mission a couple of months later with Zond 6.
57
What was the Surveyor mission
Within months of USSR successful soft landing with Luna 9, the USA also made a soft landing with Surveyor.
58
What achievements were made by Apollo 8 and Apollo 10 regarding manned lunar missions?
* In late 1968, the USA sent **Apollo 8 (the first manned lunar orbital mission)** around the Moon, brought the crew back successfully, and set the stage for landings.
* **With Apollo 10,** they did a complete ‘dry run’ except for the landing itself. After being pushed into a stable Earth orbit, the Command Service Module **(“Charlie Brown”),** carrying 3 astronauts (Stafford, Young and Cernan) separated from their thruster rocket, took a 3 day cruise to the Moon, and entered lunar orbit on May 21, 1969. The next day Stafford and Cernan crawled into their Lunar Module **(“Snoopy”),** separated from the CSM, **dropped into close-orbit (within 14 km!)**, and completed **31 revolutions** about the Moon. During that time they took an abundance of photos of the proposed landing site for the next mission. The two small modules rendezvoused again 8 hours after initial separation, “Snoopy” was jettisoned into a solar orbit, and **the three astronauts made it back into stable Earth orbit on May 24.** Two days later they did a parachute-controlled splash-down in the Pacific. An amazing feat for the crude technology they used! The Apollo 10 Command Module "Charlie Brown" is on display at the Science Museum, London, England.
59
Describe the Apollo 11 mission
Apollo 11 was the first mission in which humans walked on the lunar surface and returned to Earth.
On July 20, 1969, two astronauts (Apollo 11 Commander **Neil A. Armstrong** and **LM pilot Edwin E. "Buzz" Aldrin Jr.**) landed in **Mare Tranquilitatis**(the Sea of Tranquility) on the Moon in the Lunar Module (LM), while the Command Service Module (CSM) (with CM pilot Michael Collins) continued in lunar orbit. During their stay on the Moon, the astronauts set up scientific experiments, took photographs, and collected lunar samples. The LM took off from the Moon on July 21, and the astronauts returned to Earth on July 24.
60
What is this image
the Luna 9 spacecraft, the first ever spacecraft to soft land on another planetary body, launched by the Soviets
61
What is the origin of all lunar rocks brought back by the Apollo missions (and of every single solid rock on the moon's surface?)
All lunar rocks are igneous, formed from the cooling and solidification of molten rock.
62
Why are Moon rocks extremely dry?
Moon rocks contain almost no water because the Moon lacks an atmosphere and hydrosphere (earth's rocks contain some water)
63
What are the main types of rocks found on the Moon and their characteristics and compositions?
The Moon features:
* anorthosite in the highlands, which is light and rich in aluminum and calcium
* basalt in the maria, which is darker and contains more iron and magnesium.
64
How have Moon rocks contributed to our understanding of the Moon's geological history?
Moon rocks have provided key insights into the Moon's formation, its volcanic activity, and the differences between its highland and maria regions, helping to map out its geological timeline.
65
What are the most commonly identified rock type in planetary surface studied?
Igneous rocks are the most commonly identified rock type in planetary surface studies.
66
What % of earths outer few km is composed of igneous rocks? why is the high percentage of sedimentary rocks we see around us on earth misleading?
* Some 95% of Earth’s outer few kilometers is composed of igneous rocks
* the high percentage of sedimentary rocks (rocks formed from the consolidation of sediment) we see around us on Earth is misleading, because sediments and sedimentary rocks form at or close to surface but account for little depth
67
What finding was consistent with the moon never having had water on the surface?
* No sedimentary rocks were found by the astronauts, which is consistent with the Moon never having had liquid water on its surface.
68
earth rocks contain what percent water? How is this water contained in the rocks (2 possible ways)?
Has ANY trace of water been found in moon rocks?
Almost all Earth rocks contain 1 to 2% water:
* either as free water trapped in the rock or as water molecules chemically bonded with certain minerals.
Only the smallest trace of water - detected with very sensitive instruments - has been found in Moon rocks.
69
What elements are lunar maria basalts rich in, and what effect do these elements have?
Lunar maria basalts are rich in heavy elements like iron, manganese, and titanium, which give the rocks their dark color.
70
What does it mean when basalts are described as vesicular?
Vesicular basalts contain holes or vesicles, which are caused by gas bubbles that formed when the molten rock was exposed to lower pressures at the surface.
71
How do vesicles form in basalt rocks?
Vesicles in basalt rocks form when gas trapped within the molten rock expands as the magma reaches the low-pressure environment at the surface, similar to bubbles forming in a carbonated beverage when opened.
72
What are mare basalts, and how old are they?
Mare basalts are dense, dark rocks formed from volcanic activity in the lunar maria, aged between about 3.1 and 3.8 billion years.
73
How are the ages of mare basalts determined?
from the radioactive atoms they contain
74
What are highlands anorthosites and their age range?
Highlands anorthosites are lighter, less dense rocks composed of calcium-, aluminum-, and oxygen-rich minerals. They represent the Moon's original crust and are aged between 4.0 and 4.5 billion years.
75
How do mare basalts differ in origin from highlands anorthosites?
Mare basalts originated from magma that rose from the deep crust or upper mantle, forming after the Late Heavy Bombardment, whereas highlands anorthosites formed from minerals that solidified at the surface during the Moon's early formation, representing the original crust.
76
What are lunar breccias?
Lunar breccias:
* a type of rock composed of fragments of previous rocks that have been bonded together by the heat and pressure generated by meteoroid and asteroid impacts. These impacts not only shatter existing rocks but also generate enough heat and pressure to fuse the broken pieces together.
The presence of breccias on the Moon is indicative of the intense and frequent impact events that the Moon has undergone throughout its history. The repeated process of breaking and fusing underlines the dynamic and harsh environment of the lunar surface.
77
What is regolith? What is it made of?
Regolith is a layer of powdered rock and crushed fragments that covers both the highlands and the lowlands of the Moon.
Like breccias, regolith is also a product of meteoroid impacts. The continuous bombardment by space debris pulverizes the lunar surface rocks into fine particles and fragments, creating a layer that blankets the Moon.
About 1 percent of the regolith is meteorite fragments, and the rest is composed of the smashed remains of Moon rocks that have been ground down by the constant blasting by meteoroids.
78
how deep is the regolith
The regolith is about 10 m deep on the maria but over 100 m deep in certain places in the highlands. (meaning youre stepping on at least 10m of powder when youre stepping on the moon
79
What are micro-meteoroids, and what effect do they have on the Moon's surface?
Micrometeoroids are the smallest meteoroids, and they constantly "sandblast" the lunar surface, causing significant erosion over time.
80
How do micrometeoroids contribute to the formation of the lunar regolith?
The constant impact of micrometeoroids helps break down rocks on the lunar surface, contributing to the formation of the lunar regolith (the layer of dust and rock fragments).
81
What process dominates the shaping of the lunar surface?
Impact cratering dominates the shaping of the lunar surface, with meteoroid impacts responsible for the formation of craters **and the lunar regolith.**
82
What is a summary of the description of moon rocks, and why are these observations important?
In summary, Moon rocks are old, very dry, igneous, and badly shattered by impacts. We can use these facts, combined with a few more observations (to follow), to reconstruct the Moon's past.
83
How did scientists realize that some meteorites on Earth are actually from the Moon?
After the **Apollo** astronauts brought Moon rocks back to Earth, scientists were able to compare them with meteorites found on Earth and discovered that some of these meteorites were actually fragments of the Moon, **ejected during asteroid impacts on the lunar surface.**
84
What 2 parameters can we use for judging the interior characteristics of a planet that we cant see directly?
**The rate at which heat escapes from a planet** (or any Solar System body) and the **rate at which temperature increases as we go down into the interior of the body** are important parameters for judging the interior characteristics that we can’t see directly.
85
What do we know about heat flow on the moon?
While astronauts were on the Moon’s surface, they measured the heat flow, and found it to be a small fraction of that measured on Earth’s surface. (meaning much less heat escapes from the Moon's interior to the surface than from Earth's)
Obviously, the Moon’s small size means that the body never reached the relatively high temperatures of Earth.
86
what is heat flow of a planet?
measuring heat flow means measuring how much heat escapes the interior to the surface
87
What is seismology
the study of ground vibrations (from earthquakes)
88
How does the moon compare to earth seismically?
The Moon is seismically much quieter than Earth - about 100 million times less
89
what was the purpose of Apollo seismic detectors, what did they do? what did the information help us to understand?
Seismic detectors were set up by Apollo astronauts to transmit data back to Earth. These instruments operated for several years, with the final one running until 1977.
The detectors recorded both deep quakes from the Moon’s interior and surface quakes caused by meteoroid impacts. These data helped scientists understand the Moon's internal structure.
90
What does seismic data tell us about the Moon’s core?
The seismic data suggests the Moon has a **small, hot core, which may still be partially molten.**
The Moon's core is **tiny, making up only 2% to 4% of its total mass,** compared to Earth's iron core, which is about 30% of Earth’s mass. This indicates a much smaller, less geologically active core.
91
Name and describe the 4 main stages in the Moon's geological history
**Stage 1 - Formation and Differentiation:**
The Moon likely formed from a molten state after the massive impact between Earth and a body called Theia. As the Moon cooled, denser materials sank to form a small core, and lighter materials "floated" to the surface to form a crust. This differentiation process resulted in the formation of the Moon's core, mantle, and crust. The Moon's low density suggests it has a much smaller, less dense core than Earth.
* the radioactive ages of the rocks tell us that the surface solidified 4.6-4.1 billion years ago
**Stage 2 - Cratering:**
After the crust solidified, the Moon experienced intense cratering, especially during the Late Heavy Bombardment period.
The highlands were heavily bombarded, leaving behind large multi-ringed basins like Mare Orientale. These impacts shattered the Moon's crust to depths of around 10 kilometers.
**Stage 3 - Lava Flooding:**
Following the cratering, radioactive decay likely heated parts of the Moon's crust, causing magma to rise and fill the giant basins with lava, forming the dark basaltic plains known as the maria. This stage occurred from about 3.8 to 3.2 billion years ago. Famous examples of maria include Mare Imbrium. The Moon’s thinner crust on the near side (facing Earth) allowed more lava flows compared to the far side.
**Stage 4 - Slow Evolution:**
With no atmosphere or liquid water, the Moon’s surface has evolved very slowly. The primary changes have been caused by small meteoroid impacts. Unlike Earth, which experiences constant surface change due to tectonic activity and erosion, the Moon's surface has remained largely unchanged for billions of years. However, micro-meteoroids will eventually erode away features like the Apollo footprints.
92
What is the moon's average density, and what does this tell us about the likelihood of it having a massive metallic core like Earth
The Moon's average density, about 3.30 g/cm3, is similar to the measured density of lunar surface rock, virtually eliminating any chance that the Moon has a large, massive, and very dense nickel-iron core like that of Earth.
93
Why has the Moon’s surface changed very little in the last few billion years?
The Moon lacks an atmosphere and liquid water, so most changes have come from meteoroid impacts, making its surface evolution extremely slow.
94
does the moon have a magnetic field?
no evidence for any lunar magnetic field - so there is no core dynamo
95
What is represented in this image
(a) cross sections of the moon based on analysis of seismograms (c) collected by Apollo seismometers (b)
96
How deep was the Moon's crust shattered during the Late Heavy Bombardment, and what were the largest impacts?
The Moon's crust was shattered to a depth of about 10 kilometers during the bombardment, and the largest impacts formed giant multi-ringed crater basins hundreds of kilometers in diameter, such as Mare Orientale.
97
What is this image?
Lunar maria
98
Draw a diagram of moon crustal thickness variation and the proportions of its layers
99
What created the Imbrium Basin on the Moon, and how much of the surface did the impact affect?
An asteroid the size of Rhode Island struck the Moon about 4 billion years ago, creating the Imbrium Basin and blanketing 16% of the Moon’s surface with ejecta.
100
What is jumbled terrain, and how was it formed?
Jumbled terrain is a disturbed area on the Moon created by shock waves from the **Imbrium impact.** The waves traveled around the Moon and converged on the opposite side, causing the surface to violently jerk up and down.
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What is the largest impact basin in the Solar System, and where is it located?
The Aitken Basin, located near the Moon’s south pole, is the largest impact basin in the Solar System. It is about 2,500 kilometers in diameter and 13 kilometers deep.
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why is the moon's crust thinner on the side toward earth?
Studies of the Moon show that its crust is thinner on the side toward Earth.
perhaps due to tidal effects. Consequently, while lava flooded the basins on the earthward side, magma was unable to rise through the thicker crust to flood the lowlands on the far side.
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