Beneath Titan II
Back to the talks this morning. I simply love this streaming format the AAS DPS is using at Cornell. Normally at a scientific conference you sit in a big conference-center room, you listen to a talk you want to hear, then when that talk runs over time you wait until its done and then you quickly run down the hall to that talk in the other session you wanted to see. Then you can’t find the room, and then there’s a big line to get in because the speaker is talking about crystal forests or snow geysers on Triton or something.
Anyway. I love this streaming format because it lets you start or stop a scientific presentation at any slide, look as long as you want at the slide, even take notes, then unpause it. You can even skip back to a previous talk. The interface allows you to navigate through the content as a video (with a progress bar and a Play/Pause/Stop button) and as a slideshow (the video jumps to whatever slide you choose, out of the list of all speakers’ slides in the session). Okay, enough gushing.
Speaking of gushing, the next talks I watched today were from the same Subsurface of Titan session I began watching last night. The third talk in the session, given by session co-chair Rosalee M. Lopes, presented Cassini radar imagery revealing what are probably cryovolcanic flows on Titan. The next talk after hers was given by the other session co-chair, Robert M. Nelson, also on the Cassini radar team, and he presented strong evidence for active cryovolcanism on Titan today.
What are cryovolcanic flows? Pretty much what they sound like: icy lava. At the temperatures found on the Titanian surface, water ice is a hard, glittering mineral and methane condenses to an oily liquid. But deep in the Titanian mantle there is heat, generated as the moon creaks and warps in Saturn’s tides. Part of the mantle is a sea of liquid water, upon which float continents of water ice, upon which pool pearlescent seas of condensed natural gas. Titan is a weird world.
When heat pulses rise from the creeping deep ice of the lower Titanian mantle, they pass through the ocean and warm it, where convection takes the heat upward and dumps it into the bottom of the floating ice continents. As on Earth, when mantle heat bakes upward into the crust, things start to melt. On Earth, the melts are made of rock. On Titan, water. Or maybe they’re more like massive slushies, blurping and shlubbing in titanic bulging blobs out of ice fissures, lava flows made of ammonia-water and crushed ice.
I love the idea of the Titanian surface being dominated by a liquid-hydrocarbon hydrology (organocryology?), above a deep marine world of conventional hydrology. At the surface Titan is hideously cold, -179 C, under a frigid blanket of 1.5 Earth atmospheres of nitrogen gas. But beneath the continents in the cthonic sea, it’s quite warm, close to 0 C, and probably warmer the deeper you dive. That’s quite a thermal gradient, from bathwater to iceworld in less than 100 km.
Cryovolcanism on Titan would establish a chemical conveyor cycle between the warm marine depths and the gellid surface – a surface where strange atmospheric chemistry and temperature combine to generate complex organic molecules on an ongoing basis. As organics build up on the surface, they’d likely form a sedimentary blanket that would isostatically sink as new icy crust piles on old. Cryovolcanism would make this possible. As new ice is delivered to the surface, it would freight down the crust there and force it to ride lower on the cthonic ocean. As the oldest, deepest ice melts into the nether sea, it would deliver its mixed baggage of organic oils and sludge and goop to warm ammonia-water.
A chemically reducing atmosphere that manufactures organic compounds, feeding the raw materials for life downwards through the crust to a relatively oxidizing, warmer ocean…. suddenly the prospects for life on Titan – or more accurately beneath Titan – just got a lot more interesting.