[X] My Assistant

[Juramike]

Recent articles have invoked porous ice sands or other crustal grains as an additional potential reservoir for methane on Titan. (Selected examples: Sotin et al., 2009; Mitchell et al., 2009; Turtle et al, 2009,; Hayes et al 2008)

Last week, I set up a very simple laboratory experiment using an analogous system to try to answer the following questions:
1) How much methane could porous sands possibly hold per unit volume?
2) How will it affect the evaporation rate?
3) How could it affect the surface reflectivity?

As a laboratory analog for Titan’s hydrocarbon liquid mix (methane/ethane/nitrogen), I used solvent-grade heptane.
As an analog for Titan’s polar ice grains, I used either Flash-grade silica gel or analytical grade quartz beach sand. (The polar hydroxyl groups of the ice grains being analogous by the siloxy groups of silica)

The set-up
Three standard size 600 mL beakers were used:
Beaker A was charged with 400 mL silica gel
Beaker B was changed with 400 mL sand
Beaker C (control) was left empty.

Here are the initial images:


To initiate the experiment, a volume of Heptane was added to each beaker. Then, images and and weights were taken at key timepoints over a several day period to determine evaporation rate and monitor changes in visual appearance.

[Note: Although the temperature was held constant 298 K, the beakers were placed side-by-side in a fume hood with varying hoodflow (face velocity minimum was 100 cfm).]




Initial References:
Mitchell K.L., et al., LPSC 40 (2009) Abstract 1966. “A global sub-surface alkanifer system on Titan?”.

Hayes, A., et al. Geophysical Research Letters 35 (2008) L09204. “Hydrocarbon lakes on Titan: Distribution and interaction with a porous regolith”. doi: 10.1029/2008GL033409.

Sotin , C., et al. LPSC 40 (2009) Abstract 2088. “Ice-hydrocarbon interactions under Titan-like conditions: implications for the carbon cycle on Titan.”

Turtle, E. P., et al., Geophysical Research Letters 36 (2009) L02204. “Cassini Imaging of Titan’s High-Latitude Lakes, Clouds, and South-Polar Surface Changes.” doi: 10.1029/2008GL036186.

[nprev]

Wow! Neat experiment, Mike, thanks for sharing.

By any chance, did you try probing the slurry to see how firm it was? This sure seems to imply that Titan may have cryogenic quicksand in many spots; definite lander traps!

[Juramike]

By any chance, did you try probing the slurry to see how firm it was? This sure seems to imply that Titan may have cryogenic quicksand in many spots; definite lander traps!

Thanks! I'm amazed at how much information can be extracted from a simple experiment. (Stay tuned!)

The sand was too heavy to slurry up. The silica was nice an fluid when agitated, but if you slowed down the stirring, it would set itself up.
(Think of stomping your feet in wet sand at the surf line. All OK when your feet are moving, but let the sand settle, and you are stuck!)