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  • [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.

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  • 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.

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  • 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.

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  • 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.

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B1 中級

美國宇航局|月球之旅 (NASA | Tour of the Moon)

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    Halu Hsieh 發佈於 2021 年 01 月 14 日