Chapter 8 - The Moon and Mercury
Contents
8.1 Orbital Properties
8.2 Physical Properties
8.3 Surface Features on the Moon and
Mercury
8.4 Rotation Rates
8.5 Lunar Cratering and Surface
Composition
8.6 The Surface of Mercury
8.7 Interiors
8.8 Origin of the Moon
8.9 Evolutionary History of the Moon
and Mercury
8.10 Tidal effects on the moon
8.1 Orbital Properties
Distance between Earth and Moon has been measured to accuracy of a few centimeters using _______________________
Viewed from Earth, Mercury is never far from the Sun
___________________ of Mercury can be seen best when Mercury is at its maximum ______________________________________
8.2 Physical Properties
Moon
Mercury
Earth
Radius
6380 km
Mass
6.0 × 1024 kg
Density
3300 kg/m3
5400 kg/m3
5500 kg/m3
Escape Speed
2.4 km/s
4.2 km/s
11.2 km/s
8.3 Surface Features on the Moon and Mercury
Moon has large dark flat areas, due to lava flow, called___________________ (early observers thought they were oceans)
Moon has many craters (from ______________________________________)
There are thousands of impact craters
Smaller ones (up to a few kilometers) are _______________________________
Larger ones have a more ___________________structure: Central peaks, Concentric cliffs, Secondary impact craters, Etc.
Characteristics of Simple Crater
Characteristics of Complex Crater
_______________________________
_______________________________
_______________________________
_______________________________
_______________________________
_______________________________
The largest craters on the moon are called _____________
These giant impact sites are ___________________across or
larger.
The bottom of these huge impact craters are
filled with ______________________________________
Mare Imbrium
-Sea of ___________________
Oceanus Procellarium
-Ocean of ___________________
Mare Serenitatis
-Sea of ___________________
Mare Crisium
-Sea of
_______________
Mare
Tranquilitatis
-Sea of
_______________
___________________ of Moon has some craters but no
maria
Mercury cannot be imaged well from Earth; best
pictures are from ______________________________________
Cratering on Mercury is ___________________ to that on
Moon, although craters are less densely packed, and
___________________of surface is covered by
______________________________________
8.4 Rotation Rates
Moon is ____________________________________________ to Earth—its rotation rate is the same as the time it takes to make
one revolution, so the same side of the Moon always faces Earth
Newton’s laws of gravity state that if the moon were ____________________________________________, the longest axis would
always ________________________________________________________________________________________
It turns out that the moon is about ______________________ wider around the equator, and this keeps the equator
pointed more or less at earth
Mercury was long thought to be __________________________________________________________________; measurements in 1965
showed this to be false.
Rather, Mercury’s day and year are in a ______________________resonance; Mercury rotates
______________________ times while going around the Sun ______________________
Air molecules have high speeds due to thermal motion. If the average molecular speed is well below the escape
velocity, few molecules will escape.
Escape becomes more probable: ______________________________________________________________________________________________
____________________________________________________________________________________________________________________________________
Lunar Exploration
Soviets had first contact with Moon:
The United States is (so far) the only country to send
First spacecraft to fly past Moon: ___________________________ people to the Moon:
First spacecraft to (crash) land on Moon:
First person on Moon: ______________________________________
____________________________________________
Last person on Moon: _______________________________________
First pictures of far side of Moon: __________________________
8.5 Lunar Cratering and Surface Composition
Meteoroid strikes Moon, _________________________; explosion ejects more material, leaving _________________________
Craters are typically about _________________________as wide as the meteoroid creating them, and _______________ as deep
Rock is ___________________________________________________________________________
Most lunar craters date to at least _________________________billion years ago; much less bombardment since then
Craters come in all sizes, from the very large……to the very small
Some shown here, ___________________________________________________________________________retrieved by Apollo astronauts,
measure only _________________________mm across. (The scale at the top is in millimeters.) The beads themselves were
formed ___________________________________________________________________________following a meteoroid impact, when
surface rock was melted, ___________________________________________________________________________
__________________________________________________Thick layer of dust left by meteorite impacts
Moon is still being bombarded, especially by very small “micrometeoroids”; _____________________________________________
More than 3 billion years ago, the moon was volcanically active; the _________________________here was formed then
8.6 The Surface of Mercury
Mercury is __________________________________________________ cratered than the Moon Some distinctive features:
_________________________ (cliff), several hundred kilometers long and up to 3 km high
__________________________________________________ land features not seen anywhere else in the solar system. They appear
here as ___________________________________________________________________________ on a crater’s rim and floor.
Caloris Basin, very large impact feature on opposite side of planet from _________________________ “Weird terrain” is
thought to result from focusing of seismic waves
This weird terrain is composed of
______________________________________________________________________ that are up to 2 km high, with some slopes over 50%
8.7 Interiors
Moon’s density is relatively low, and it has __________________________________________________—cannot have sizable
iron/nickel core
Crust is much ___________________________________________________________________________
Mercury is __________________________________________________ than the Moon and has a _______________________________________.
The field is due to a molten core, similar to the Earth’s, but _______________________________________________________________
as Mercury rotates very slowly.
8.8 Origin of the Moon
Current theory of Moon’s origin: ______________________________________________________________________________________________
on the still-liquid Earth caused enough material, mostly from the mantle, to be ejected to form the Moon
8.9 Evolutionary History of the Moon and Mercury
Time before present
Event
Formation of Moon; heavy bombardment liquefies surface
3.9 billion yr
Volcanic activity ceases
Mercury much less well understood Formed about __________________________________________________billion years ago
Melted due to ____________________________________________________________________, _____________________________________________
8.10 Tidal Effects on the Moon
Gravitational forces in the Earth-Moon-Sun system cause ________________________
Tides are _____________________in the _______________________ of the earth and moon
On the moon, this causes the moon to stretch toward earth. This is called a _________________________
On the earth, the moon causes a smaller body tide
In addition, the moon also causes a ________________________
In both body and ocean tides, the bulges are on both the _________________________________________________________________
of both the earth and the moon.
This is due to the stretching along the earth-moon line, and gravitational forces trying to establish ___________________
Tidal forces have ________________________________ in the earth-moon system
They insure the moon’s orbit is _______________
They cause the earth to gradually
This is why it is also called “tidally locked”
_________________________________
They cause the moon to _________________________________
They create the _______________________________________
from the earth
The slow movement of the moon away from the earth is called ___________________________________
The earth is rotating as the moon pulls on it.
This causes the ___________________________________ to always be
slightly _________________________ of the moon’s ______________________________ The bulge leads by about ____________________
Because the bulge is actually ahead of the moon, it pulls the moon _________________________________________
This counters some of earth’s gravitational pull, so it causes the moon to ________________________________________________
About _______________________________ per year
At the same time, the fact that the tidal bulge on earth is always
slightly ahead of the moon means the moon is ____________________________________ on earth.
This causes earth’s rotation to __________________________________________.
About 3 billion years ago, the earth’s
solar day was only six hours long.
Strangely enough, the predicted length of the day (and of the lunar month) is proven out by___________________________
Diatoms make banded structures in their shells either daily or lunar-monthly
Fossils from 2.8 billion years ago show the lunar month was only _____________________________________________
Finally, tides create something called “The Roche Limit”
The Roche Limit is the distance from a planet that a satellite can not orbit without ______________________________________
For the earth-moon system,
The Roche limit is about _________________________________________________
If the moon were to cross the Roche limit, it would most likely break up into _____________________________________, like
Saturn, Jupiter, Neptune, or Uranus.
Summary of Chapter 8
 Main surface features on Moon: maria, highlands
 Both heavily cratered
 Both have no atmosphere, and large day–night
temperature excursions
 Tidal interactions responsible for synchronicity of
Moon’s orbit, and resonance of Mercury’s
 Moon’s surface has both rocky and dusty material
 Evidence for volcanic activity
 Mercury has no maria but does have extensive
intercrater plains and scarps
 Shrank, crumpling crust