hw 9
Earth's rotation is slowing down because of the tidal interaction between Earth and the Moon at a rate of 2 msec per century. If this rate remains constant at the present value, how long will it take for one day on Earth to become 2 seconds longer than it is now?
100,000 years
The rotation period of the Moon on its axis with respect to space (its absolute rotation) is
27.3 days, the sidereal revolution period
Which was the first spacecraft to land humans on the Moon?
Apollo 11
most surface rocks on Earth are younger than a few million years old, whereas ages of lunar rocks have been measured in billions of years. Why is this?
Earth's surface undergoes continuous recycling through the underlying mantle because of plate tectonics, and this does not occur on the Moon
The impact craters on Earth are younger than a few million years old, whereas ages of lunar craters extend back billions of years. Why is this?
Plate tectonics has erased older craters on Earth, whereas this process has not occurred on the Moon
The spacecraft Clementine observed the Moon in 1994 and provided evidence for ice near the South Pole. How was this information possible?
Reflections of ultraviolet, visible, and infrared from the lunar surface were analyzed
Which of the following statements is a correct description of the Moon's orbit?
The Moon is gradually spiraling away from Earth
Why are the lunar maria concentrated almost entirely on the near side of the moon?
The crust is thicker on the far side of the Moon, restricting massive lava flows after asteroid impact
By dating the Moon rocks we can determine its age How long ago did the Moon form?
We believe the Moon was formed molten and then cooled. Because the oldest rocks are about 4.3 billion years old, the formation of the Moon must have occurred around 4.5 billion years ago.
The Moon raises tides on Earth. Does Earth raise tides on the Moon?
Yes, small tidal bulges are raised on the Moon's surface as Earth's gravity distorts the Moon's shape
How quickly is the Moon spiraling away from Earth?
a few centimeters per year
The theory that seems to account most satisfactorily for the origin of the Moon at the present time is that
a large object collided with Earth and ejected the material that formed the Moon
How long is a "lunar day," or the time between two successive sunrises or sunsets on the Moon?
about 1 month
What is the current state of plate tectonics on the Moon?
absent; the Moon is a geologically dead world
The terminator on the Moon is a line
between the solar-illuminated and dark hemispheres
Most of the craters on the moon were formed by
bombardment by interplanetary meteorotic material
What kind of landing did the first spacecraft make in order to reach the surface of the Moon?
crash landing by the Ranger spacecraft
Water may have been discovered recently on the Moon in the form of
ice, in deep craters at the north and south poles, perpetually shaded from sunlight
The mountains on the Moon were mostly caused by
impacts from meteoroids from outer space
Moonquakes occur most often when the Moon is near perigee. The reason for this is
increased tidal distortion of the Moon by Earth
If you were standing on the Moon with Earth in view, how much time would elapse between two successive "Earthrises"?
infinite time, because the same side of the Moon always faces towards Earth
Maria are
large impact craters in-filled by lava
Which of the following techniques is not used to gather information about the Moon's interior?
measurements of changes in the Moon's atmosphere
The age of Moon rocks has been determined primarily by what method?
measurements of radioactive decay products
Although we do not yet know precisely how the Moon was formed, an important clue is provided by the fact that
moon rocks resemble rocks close to the surface of Earth
If astronauts set up a permanent settlement at Tranquility Base on the Moon, how many times each year would Earth rise and set as seen by a resident of this base?
never - Earth would remain essentially motionless in the sky
The Moon has
no global magnetic field, although weak magnetism in lunar rocks does show that a magnetic field existed earlier in the Moon's history
The Moon has
no measurable atmosphere or liquid water
Maria on the Moon exist
only on Earth-facing side of the Moon
To observers on Earth, the moon shows
only one side to Earth at all times
The texture of the surface of the Moon may be described as
regolith covering the entire lunar surface
What are the most common shapes of lunar craters and why?
round, because the shock wave from the impact that produced them spread out uniformly in all directions
One effect of the ocean water's tidal drag on Earth is to
slow down Earth's spin rate
Between 1966 and 1968, just prior to the manned Apollo series, five unmanned spacecraft of the Surveyor series made soft landings on the lunar surface. The main purpose of these missions was to
test the solidity of the lunar surface to see if it would support a spacecraft
What actually moves around the Sun along the path we usually call Earth's orbit?
the center of mass of Earth-Moon system
The so-called maria, or "seas" on the lunar surface, do not and could not contain water because
the water would boil and evaporate away rapidly in the vacuum of space
What is the primary cause of moonquakes?
tidal forces due to the gravitational pull of Earth
Can regions of ice exist on the surface of the Moon?
yes, because the floors of craters at the north and south poles can be permanently shaded from the Sun
