Just from this surface image, you can figure stuff out. All those rocks (whatever they are made of - that is still a mystery), are all rounded, and the same size.

Rounding suggests erosion, those "rocks" banged together repeatedly. Likes rocks in a river or shore (hint-hint-hint).

And sorting by some type of process where bigger rocks dropped out somewhere else, and smaller rocks or pieces dropped somewhere else.

Either a flood deposit or a stream deposit.

And also what you DON'T SEE. We don't see a uniform snowscape blanket of organic molecules everywhere.

That tells us that whatever geological processes happen are faster than covering by organic molecule fallout.

That fallout happens at a rate of about same as dust builds up in your house if you have a clothes dryer in your house. Max 100 m per Gyr: 0.1 m per Myr, 0.1 mm per kyr or 0.1 microns per year. Give or take an order of magnitude.

So geology happens on Titan. It's not boring.

So. Streams or floods, rocks eroding, sorting. Faster than getting covered by atmospheric organic molecules. Got it.

But what are those rounded rocks made of?

Ahhhhh. That's still a mystery! You will read in Wikpedia or some of the literature that it is water ice.

But actually, we don't know. It could be ice, or other things: frozen benzene, solid HCN, mixed solid organics. We do not have detailed spectra or other chemical analysis of those rocks vs the sands.

(Personally, I think it's probably ice, but I want better proof.)

(The dark sands I'd lean my guess towards probably organics.)

It is good to have mysteries! Fun! Explore!

As the Huygens probe descended, it took lots of pictures on its way down to the surface. Those are just a gold mine of information.

Here is a really fun movie that we call the "bells and whistles" version. It is incredibly information rich. I love watching this over and over. You can see little cartoons showing probe orientation spin, telemetry data, instrument sequences, and images. I love to marvel at the planning that made this happen.

science.nasa.gov/resource/tita…

Titan Descent Data Movie with Bells and Whistles - NASA Science

This movie, built with data collected during the European Space Agency's Huygens probe on Jan. 14, 2005, shows the operation of the Descent Imager/Spectral Radiometer camera during its descent and after touchdown.

^{science.nasa.gov}

great thread! I still have trouble wrapping my head around the descent video, but your description helped a lot.

I saw this fantastic processing by Daniel Machacek earlier today on bsky (see also his convo with @stim3on for more details) and now I can grasp it a bit better thx!

bsky.app/profile/danielmachace…