B2 中高級 美國腔 166 分類 收藏
NASA's got a new mission on the horizon.
Land an unmanned spacecraft on Titan, Saturn's largest moon, and explore the surface for evidence of potential alien life.
The billion-dollar mission will test NASA engineers like never before, because if you're going to explore Titan, there's something you need to know.
Just like our own moon, Titan orbits a planet, but it actually looks and behaves more like an Earth.
And that's why, for this mission, NASA opted for a different kind of spacecraft.
This is Dragonfly.
It's a nuclear-powered drone that's the size of a large lawn mower.
Now if NASA is going to send a space drone anywhere, it's Titan, because, similar to Earth, it has a thick atmosphere, which can keep the drone aloft.
Dragonfly is built like a helicopter, able to take short flights in between landings.
It will run on what's called a radioisotope thermoelectric generator, or RTG.
The RTG runs on radioactive decay from a reserve of plutonium-238, which not only will power the spacecraft for months on end, but will also keep it warm.
You see, the average temperature on Titan is minus 179 degrees Celsius, cold enough to freeze Dragonfly's circuits.
But a byproduct of radioactive decay is heat, which will protect the fragile electronics on board, which Dragonfly will be using to study surface composition, temperature, weather patterns, and geological activity, as well as look for water, carbon compounds, and other signs of potential life.
And NASA already has a good idea of where to explore.
Back in the 2000s, NASA's Cassini spacecraft mapped entire sections of Titan's surface, uncovering lakes of liquid methane and possible ice volcanoes.
The ice volcanoes are of special interest, because scientists think they could launch underground water to Titan's surface.
In fact, there's evidence to suggest that Titan has a vast subterranean ocean of liquid water about 80 kilometers down.
And if that water is mixed with methane-based molecules lurking in Titan's surface lakes, there's a chance for life to form, according to some experts.
And Dragonfly will have plenty of time to test that notion.
If all goes according to plan, Dragonfly will study Titan's surface for at least 2 1/2 years and is expected to travel over 175 kilometers.
That's almost double the distance covered by all the Mars rovers combined.
And whether it finds alien life or not, there's plenty more science to discover.
For instance, Titan looks a lot like how scientists think Earth looked at a young age.
So, understanding Titan may help us uncover secrets of our own planet.
What might we learn?
Well, there's only one way to find out.
NASA plans to launch the spacecraft in 2026, when it will begin its eight-year journey through the solar system towards Titan.
So mark your calendars for 2034.



NASA 花費十億美金,決心找出外星生命! (NASA's $1 Billion Mission To Search For Life On Titan, Explained)

166 分類 收藏
April Lu 發佈於 2019 年 7 月 10 日    April Lu 翻譯    Winnie Liao 審核
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