Int 1171 Folder Collection
After playing the video, you can click or select the word to look it up in the dictionary.
Report Subtitle Errors
[music] Narrator: To nearly everyone, the moon appears to be a
sterile, gray, unchanging world. But while the moon has
remained largely unchanged during human history, our own understanding of it has
evolved dramatically. Thanks to new observations,
we now have not only unprecedented views of its surface, but a whole
new tour of the moon that shows how both it and other rocky planets in our solar
system have been shaped over billions of years.
We'll start with one of the largest impacts--Orientale Basin, a feature
that's as wide as the distance from New York City to Cincinnati. Using new
elevation measurements, we can clearly see the effects of what is likely the last
giant impact event in lunar history, with its outer mountain rings
rising many kilometers above the lowest points inside the crater.
The interiors of some craters in the moon's polar regions, like Shackleton,
haven't seen sunlight in over two billion years. However, new
measurements have created our best-yet maps of these types of craters, allowing us to
see deep into the shadows of this surprisingly young-looking impact crater
in the south that's more than twice as deep as the Grand Canyon.
Some impacts are invisible for other reasons. Although the ancient South Pole-Aitken Basin
is difficult to see from orbit because it is so large,
new LRO topography maps reveal the largest impact basin in the Earth-
moon system, measuring several kilometers in depth and around 2500
kilometers in diameter. Only the Hellas basin on Mars
rivals it in size. One of the youngest
large-scale impacts on the moon is the Tycho Crater. This fresh crater
may have formed only 108 million years ago--when dinosaurs roamed the Earth.
We now also have an extreme close-up view of the crater's
central peak--revealing a mountain with sharp edges, building-sized
rocks, and a central boulder about the size of a baseball stadium.
Narrator: The Aristarchus Plateau is another recent lunar formation that has
long interested scientists and astronomers. The crater itself
formed in the same era as the Tycho Crater, and what appear to be snaking river valleys
were actually carved by ancient lava flows.
Narrator: Next, we arrive at Mare Serenitatis on the near side of the moon. In December
of 1972, the crew of Apollo 17 landed in the Taurus Littrow
valley, marking the last time humans have visited the surface of the
moon. With images from LRO's narrow-angle
camera, we can clearly see the evidence of that visit. In this
image, you can easily see the base of the lunar lander, along with the lunar
rover, parked far from the blast-off zone. You can also
clearly see the astronaut trails and the wheeltracks left on the lunar surface.
Narrator: We now head to the far side of the moon--which cannot be seen from Earth. Our
first stop is the Compton-Belkovich region, which shows evidence for young volcanic
activity in the farside highlands. This feature is unique
not only because it is isolated from other volcanoes in the area, but also
because it is located nowhere near the maria, where volcanoes are usually found.
Also, on the far side, we find
the Jackson Crater--which like the Tycho Crater on the near side, has an
extensive and complex ray system. In fact, this crater is often considered
to be like a twin to Tycho. Finally, the
Tsiolkovsky Crater stands out as an excellent example of a farside crater
filled with a sea of ancient lava--known as a mare. It is
particularly interesting to scientists and other observers because of its isolation
from other similar craters--as well as its beautiful central peak.
As we continue to study the moon, our understanding of it
improves, giving us new insights not only into how it has evolved over
time, but also how other rocky planets in our solar system have come to
look the way they do. With new missions, new instruments,
and new technologies, we will continue to improve our knowledge of the moon...
...and better understand the history of our solar system.
[music fades]
[beeping, silence]
    You must  Log in  to get the function.
Tip: Click on the article or the word in the subtitle to get translation quickly!


NASA | Tour of the Moon

1171 Folder Collection
Halu Hsieh published on September 11, 2013
More Recommended Videos
  1. 1. Search word

    Select word on the caption to look it up in the dictionary!

  2. 2. Repeat single sentence

    Repeat the same sentence to enhance listening ability

  3. 3. Shortcut


  4. 4. Close caption

    Close the English caption

  5. 5. Embed

    Embed the video to your blog

  6. 6. Unfold

    Hide right panel

  1. Listening Quiz

    Listening Quiz!

  1. Click to open your notebook

  1. UrbanDictionary 俚語字典整合查詢。一般字典查詢不到你滿意的解譯,不妨使用「俚語字典」,或許會讓你有滿意的答案喔