英语时差:土卫六的烃海之旅
Looking for a peaceful seaside vacation spot? You might want to consider Saturn’s largest moon, Titan. Titan is nothing like the Earth’s moon. Not only is it almost twice the size, it’s eighty-percent more massive.It's the only moon with an atmosphere, a yellow smoggy one filled with methane, ethane, and propane clouds, It also has active volcanoes and few impact craters. Scientists have long speculated that Saturn’s largest moon might have seas filled with organic compounds like ethane and methane. It wasn’t until NASA’s Cassini spacecraft reached Titan and scanned the surface with radar and an infrared mapping spectrometer that bodies of the liquid natural gases were detected.And where they ever. An ethane lake the size of Lake Ontario was found in the southern hemisphere, while a sea almost as large as the Caspian Sea and many smaller lakes were discovered in the northern hemisphere. Scientists now believe Titan has a hydrological cycle similar to Earth. But instead of water forming clouds, rain, and then evaporating to clouds again, Titan has two cycling substances: methane and ethane. Another exciting possibility is that Titan might be a cauldron for extraterrestrial life. Except for its lower temperature, 290 degrees below zero, Saturn’s largest moon has similar conditions to that of early Earth. Oceans rich in organic molecules might be home to life forms with liquid natural gas in their veins. That is why NASA hopes to look at Titan more closely in the future by sending a splashdown lander or floating air ship there. Of course, if you want to check out Titan’s seas before then, beware. There is no chance of getting sunburned, but you’ll want to take a heavy parka.
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