NASA Wants to Send a Submarine to Titan's Seas

In a sneak peek of a possible future mission to Saturn's moon Titan, NASA has showcased their vision of a robotic submersible that could explore the moon's vast lakes of liquid methane and ethane.

In a sneak peek of a possible future mission to Saturn's moon Titan, NASA has showcased their vision of a robotic submersible that could explore the moon's vast lakes of liquid methane and ethane.

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Studying Titan is thought to be looking back in time at an embryonic Earth, only a lot colder. Titan is the only moon in the solar system to have a significant atmosphere and this atmosphere is known to possess its own methane cycle, like Earth's water cycle. Methane exists in a liquid state, raining down on a landscape laced with hydrocarbons, forming rivers, valleys and seas.

Several seas have been extensively studied by NASA's Cassini spacecraft during multiple flybys, some of which average a few meters deep, whereas others have depths of over 200 meters (660 feet) - the maximum depth at which Cassini's radar instrument can penetrate.

So, if scientists are to properly explore Titan, they must find a way to dive into these seas to reveal their secrets.

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At this year's Innovative Advanced Concepts (NIAC) Symposium, a Titan submarine concept was showcased by NASA Glenn's COMPASS Team and researchers from Applied Research Lab.

Envisaged as a possible mission to Titan's largest sea, Kracken Mare, the autonomous submersible would be designed to make a 90 day, 2,000 kilometer (1,250 mile) voyage exploring the depths of this vast and very alien marine environment. As it would spend long periods under the methane sea's surface, it would have to be powered by a radioisotope generator; a source that converts the heat produced by radioactive pellets into electricity, much like missions that are currently exploring space, like Cassini and Mars rover Curiosity.

Communicating with Earth would not be possible when the vehicle is submerged, so it would need to make regular ascents to the surface to transmit science data.

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But Kracken Mare is not a tranquil lake fit for gentle sailing - it is known to have choppy waves and there is evidence of tides, all contributing to the challenge. Many of the engineering challenges have already been encountered when designing terrestrial submarines - robotic and crewed - but as these seas will be extremely cold (estimated to be close to the freezing point of methane, 90 Kelvin or -298 degrees Fahrenheit), a special piston-driven propulsion system will need to be developed and a nitrogen will be needed as ballast, for example.

This study is just that, a study, but the possibility of sending a submersible robot to another world would be as unprecedented as it is awesome.

Although it's not clear at this early stage what the mission science would focus on, it would be interesting to sample the chemicals at different depths of Kracken Mare.

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"Measurement of the trace organic components of the sea, which perhaps may exhibit prebiotic chemical evolution, will be an important objective, and a benthic sampler (a robotic grabber to sample sediment) would acquire and analyze sediment from the seabed," the authors write (PDF). "These measurements, and seafloor morphology via sidescan sonar, may shed light on the historical cycles of filling and drying of Titan's seas. Models suggest Titan's active hydrological cycle may cause the north part of Kraken to be ‘fresher' (more methane-rich) than the south, and the submarine's long traverse will explore these composition variations."

A decade after the European Huygens probe landed on the surface of Titan imaging the moon's eerily foggy atmosphere, there have been few plans to go back to this tantalizing world. It would be incredible if, in the next few decades, we could send a mission back to Titan to directly sample what is at the bottom of its seas, exploring a region where the molecules for life's chemistry may be found in abundance.

click to play video

Ten years ago,

the European Huygens probe descended through Titan's atmosphere

and became the first ever robotic mission to touch down on a world in the outer solar system. During its daring 2 hour, 27 minute descent through the murky atmosphere of Saturn's largest moon, the probe revealed an unprecedented view of of the alien environment. On landing, Huygens survived on the hydrocarbon-rich surface for only 72 minutes before its batteries drained, but the data it transmitted via NASA's Cassini spacecraft was nothing short of revolutionary -- data that continues to be analyzed 10 years after that fateful day on Jan. 14, 2005.

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Here are just a few mind-blowing images from Huygens as it gave us our first intimate look at the solar system's only moon known to possess a thick atmosphere and vast liquid methane-ethane lakes -- a world that, like Jupiter's moon Europa, invokes exciting hypotheses of extraterrestrial biology.

After traveling with the Cassini mission for seven years during its interplanetary transit from Earth to Saturn orbit, the command was given for Huygens to detach from its mothership. For 21 days, the small disk-like probe was by itself, cruising toward Titan. As Huygens ripped through Titan's atmosphere, eventually slowing down enough for its heatshield to drop away and parachutes deploy, the probe got to work, rapidly photographing its descent and collecting atmospheric data. On Wednesday, The European Space Agency released the full series of

stunning processed descent images

, showing how the moon's dune-covered surface slowly came to view as Huygens slowly drifted to the surface below.

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Looking down, Huygens also captured a slowly evolving view of its eventual landing spot. Shown here, a fish-eye view of the landscape below starts to detail some of the surface features the probe would be soon analyzing up-close. In the run-up to landing day, mission scientists were unsure whether Huygens would land on a solid surface or splash down in a methane/ethane puddle or lake. As it turned out, the probe "splatted down" in Titan's alien mud -- a mix of small grains of ice.

ANALYSIS: Titan's 'Magic Island' Appeared Mysteriously From the Depths

Photographs during descent gradually showed an alien, yet familiar, landscape. Titan is covered in dunes, valleys and lakes -- all shaped by erosion processes we'd find on Earth. The valleys are cut by liquid action and the thick atmosphere produces winds and weather systems that form dune fields of fine hydrocarbon sand. But these Titan weather systems are not driven by an Earth-like water cycle. As the atmosphere is too cold to support water in a liquid state, other chemicals, such as methane and ethane exist as a liquid, forming their own cycle. Methane rain is now known to fall onto the landscape, creating rivers that erode valleys and form deltas in vast liquid methane-ethane lakes.

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By landing a probe onto Titan's surface, the joint NASA/ESA Cassini-Huygens mission was able to get "ground proof" of flyby imaging and radar. Last year, Cassini completed its 100th Titan flyby, so in the 10 years since Huygens landed, planetary scientists have been getting a front row seat of the moon. But in 2005, Titan science was as foggy as the moon's atmosphere, so by overlaying ground-based observations with Cassini images, a better interpretation of landscape features spotted by Cassini could be made.

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Although low-resolution and grainy, the first images of the landscape surrounding Huygens after it landed at 13:34 CET (12:34 GMT) on Jan. 14, 2005, stunned the world. Rounded stones appeared to litter the grains of hydrocarbon sand and ice. The eroded rocks immediately reminded us of eroded pebbles -- rocks that have undergone liquid action for long periods of time. The landing zone resembled a dried-up lake bed and surrounding that area, evidence for rapid, transient flows of liquid could be seen.

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The Huygens lander, in its short solo mission, punched well above its weight, opening our eyes to an alien world within our solar system that is littered with prebiotic chemicals, a world that resembles a young Earth, beckoning our inquiring minds to return some day.

For more on the Huygens landing and the top 10 scientific discoveries made by the probe's continuing science, browse the special ESA anniversary news release.