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  • Picture a world with a variety of landforms.

  • It has a dense atmosphere

  • within which winds sweep across its surface

  • and rain falls.

  • It has mountains and plains,

  • rivers, lakes and seas,

  • sand dunes and some impact craters.

  • Sounds like Earth, right?

  • This is Titan.

  • In August 1981,

  • Voyager 2 captured this image of Saturn's largest moon.

  • The Voyager missions have traveled farther than ever before,

  • making the solar system and beyond

  • part of our geography.

  • But this image, this hazy moon

  • was a stark reminder of just how much mystery remained.

  • We learned an exponential amount as the Voyagers flew by it,

  • and yet we had no idea what lay beneath this atmospheric blanket.

  • Was there an icy surface with landforms like those of the other moons

  • that had been observed at Saturn and Jupiter?

  • Or perhaps simply a vast global ocean of liquid methane?

  • Shrouded by the obscuring haze,

  • Titan's surface was a huge, outstanding mystery

  • that Cassini-Huygens, an orbiter lander pair launched in 1997,

  • was designed to solve.

  • After arrival in 2004,

  • the early images Cassini sent back of Titan's surface

  • only heightened the allure.

  • It took months for us to understand what we were seeing on the surface,

  • to determine, for example,

  • that the dark stripes,

  • which were initially so unrecognizable that we referred to them as cat scratches,

  • were actually dunes made of organic sand.

  • Over the course of the 13 years Cassini spent studying Saturn

  • and its rings and moons,

  • we had the privilege

  • of going from knowing almost nothing about the surface of Titan

  • to understanding its geology,

  • the role the atmosphere plays in shaping its surface,

  • and even hints of what lies deep beneath that surface.

  • Indeed, Titan is one of several ocean worlds,

  • moons in the cold outer solar system

  • beyond the orbits of Mars and the asteroid belt

  • with immense liquid water oceans beneath their surfaces.

  • Titan's interior ocean may have more than 10 times as much liquid water

  • as all of the Earth's rivers, lakes, seas and oceans combined.

  • And at Titan, there are also exotic lakes and seas

  • of liquid methane and ethane on the surface.

  • Ocean worlds are some of the most fascinating places

  • in the solar system,

  • and we have only just begun to explore them.

  • This is Dragonfly.

  • At the Johns Hopkins Applied Physics Laboratory,

  • we're building this mission for NASA's new Frontiers program.

  • Scheduled to launch in 2026 and reach Titan in 2034,

  • Dragonfly is a rotorcraft lander,

  • similar in size to the Mars rovers or about the size of a small car.

  • Titan's dense atmosphere, combined with its low gravity,

  • make it a great place to fly,

  • and that's exactly what Dragonfly is designed to do.

  • Technically an octocopter,

  • Dragonfly is a mobile laboratory that can fly from place to place

  • taking all of its scientific instruments with it.

  • Dragonfly will investigate Titan in a truly unique way,

  • studying details of its weather and geology,

  • and even picking up samples from the surface

  • to learn what they're made of.

  • All told, Dragonfly will spend about three years exploring Titan,

  • measuring its detailed chemistry,

  • observing the atmosphere and how it interacts with the surface,

  • and even listening for earthquakes,

  • or technically titanquakes, in Titan's crust.

  • The Dragonfly team,

  • hundreds of people across North America and around the world,

  • is hard at work on the design for this mission,

  • developing the rotorcraft, its autonomous navigation system

  • and its instrumentation,

  • all of which will need to work together to make science measurements

  • on the surface of Titan.

  • Dragonfly is the next step in our exploration

  • of this fascinating natural laboratory.

  • In flying by, Voyager hinted at the possibilities.

  • In orbiting Saturn for over a decade

  • and descending through Titan's atmosphere,

  • Cassini and Huygens pulled Titan's veil back a bit further.

  • Dragonfly will live in the Titan environment,

  • where, so far, our only close-up view

  • is this image the Huygens probe took in January 2005.

  • In many ways, Titan is the closest known analogue we have to the early Earth,

  • the Earth before life developed here.

  • From Cassini-Huygens' measurements,

  • we know that the ingredients for life,

  • at least life as we know it,

  • have existed on Titan,

  • and Dragonfly will be fully immersed within this alien environment,

  • looking for compounds similar to those

  • that might have supported the development of life here on Earth

  • and teaching us about the habitability of other worlds.

  • Habitability is a fascinating concept.

  • What's necessary to make an environment suitable to host life,

  • whether life as we know it here on Earth,

  • or perhaps exotic life that has developed under very different conditions?

  • The possibility of life elsewhere

  • has inspired human imagination and exploration throughout history.

  • On a grand scale,

  • it's why the ocean worlds in the outer solar system

  • have become such important targets for study.

  • It's the "what if" that drives human exploration.

  • We don't know how chemistry took the step to biology here on Earth,

  • but similar chemical processes may have happened on Titan,

  • where organic molecules have had the opportunity

  • to mix with liquid water at the surface.

  • Has organic synthesis progressed under these conditions?

  • And if so, how far?

  • We don't know ... yet.

  • What we will learn from Dragonfly, this fundamentally human endeavor,

  • is tantalizing.

  • It's a search for building blocks, foundations, chemical steps

  • like those that ultimately led to life on Earth.

  • We're not sure exactly what we will find when we get to Titan,

  • but that's exactly why we're going.

  • In 1994, Carl Sagan wrote,

  • "On Titan, the molecules that have been raining down

  • like manna from heaven for the last four billion years

  • might still be there,

  • largely unaltered, deep-frozen, awaiting the chemists from Earth."

  • We are those chemists.

  • Dragonfly is a search for greater understanding,

  • not just of Titan and the mysteries of our solar system,

  • but of our own origins.

  • Thank you.

Picture a world with a variety of landforms.

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What Saturn's most mysterious moon could teach us about the origins of life | Elizabeth Turtle

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    林宜悉 posted on 2020/11/03
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