英语听力：自然百科 行星旅行：土星 Saturn—6

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Every tour itinerary² has one main attraction. With Saturn, you just can't miss the rings. As imaging team leader for Cassini, Carolyn Porco has had a ringside seat. 

 

A ring / consists of just countless³ particles. And they range from big boulders⁴, size of small apartment buildings, all the way down to the finest, finest dust particle and everything in between. And they are all orbiting like crazy around Saturn at 20,000 to 40,000 miles per hour but, it's like traffic along highway. Everybody can be going 90 miles an hour but relative to each other, they are going very slowly. If you could put a spacecraft there, you could manage to move at the same speed then the speed wouldn't be that dangerous at all. 

 

You can think of rush hour on a Friday night, you know, on the freeway that the B Ring has a lot of traffic and a lot of particles. Whereas you go to the E Ring, it's a little bit better. The C Ring is more like being out in the country. You are going to see ring particles too often. 

 

Possibly the remnants of a failed moon, the ring particles have been flattened⁵ by gravitational forces into a super thin disk, nearly 200,000 miles across. Edge to edge, that's almost the distance from the earth to the moon. 

 

I have effects imagining myself orbiting Saturn, hovering⁶ over the rings. It's hard not to. 

 

I could just imagine what it might be like to like hold a ring particle in my hand and see what it looks like. This is like a fluffy⁷ snow ball / if I start to pull it apart, what's it like on the inside? So, you can think of each of the rings, A, B, C, D, like different features. And so you want to collect samples from each of those rings.

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