Volcano Slushies and Floating Robots: Titanic Possibilities

Artist concept of a balloon-borne Titan probe. Credit: NASA, JPL/Corby Waste
Possible “cryovolcano” on Saturn’s moon, Titan! This little moon just keeps getting more and more interesting.

Since 2004, when NASA’s Cassini spacecraft and the European Huygens lander started exploring Saturn’s largest satellite, Titan, layer after layer of the mysterious moon have been peeled away, revealing what has turned out to be an awesome alien world that stands apart from all other moons in the solar system--and even holds its own with the planets.

Cryovolcanoes: cool! Imagine a 3000 foot tall mountain gushing freezing water-ammonia slush, which pours down its slopes to become solid “rock ice” flows as it freezes, and spouting a plume of water vapor that quickly turns into snow. Is that really how a volcano of cold water, ice, and maybe ammonia and methane would behave? Maybe, maybe not—but now scientists have observational evidence of what might be such a process on Titan, and the similarities in patterns to Earthly lava flows is compelling. Take a look at the video….

The thought makes me want to go and explore Titan right now!

At the annual American Geophysical Union (AGU) conference in San Francisco last December, I voiced a concern to a presenter who was describing explorations of Titan by Cassini and Huygens. My concern was that, though the images returned by Huygens from the surface of that frigid smoggy world were unprecedented up-close views of a distant alien land, I fear that with the cost of space missions and budgets and economies and all, we might not return there for further exploration within my lifetime…and I’d have to make do with the images from Huygens. (Though very cool images, they were essentially from a spot on Titan that is little more than a plane of soil and pebbles; I want lakes and volcanoes!)

Not so fast.There may be more missions to Titan’s surface yet to come. There is certainly a lot of scientific interest in Titan because of its “hydrological” cycle—that is, the liquid hydrocarbons, not water, that rain from its atmosphere and flow and collect in rivers and lakes on its surface.

Some of the possibilities the presenter suggested for surface and atmosphere probes sounded pretty interesting. One idea is another “lander,” but deliberately targeted to splash down in one of Titan’s big methane lakes, and with a longer-life battery than what powered Huygens (Huygens’ battery lasted about 90 minutes after landing). What kind of battery? Nuclear, maybe, though there are restrictions to lobbing radioactive isotopes onto the surface of another world—especially one where the existence of indigenous life hasn’t been ruled out.

Such a “floater” could drift around the lake, transported by liquid currents, taking environmental readings, pictures, and maybe sounding the lake bottom with sonar. Eventually, lake currents might be expected to naturally deliver the floater probe to a shoreline, where it could then explore Titan where land meets lake.

Another possibility on Titan is a flying aircraft probe, either winged or buoyant. Due to the thickness of Titan’s nitrogen atmosphere (four times denser than Earth’s at the surface), and the relatively low gravity of Titan itself, flight there is a very different prospect from flight on Earth. Titan’s surface gravity is only 14% that of Earth’s, so what would be a 200-pound payload on Earth would weigh 28 pounds on Titan.

A balloon-borne probe, with greater buoyancy due to Titan’s thicker atmosphere, could drift around for a long time and cover a great deal of territory at very close range, perhaps even setting down on the surface temporarily. A winged-aircraft could glide at relatively low speed, again owing to the lower gravity and higher lift from the thick air.

Yeah, I want to go and see the volcano slushy! Please, can I?