Are the surfaces in permanent shadow in Moon craters 'fluffy'?

Question

I was talking to someone who anticipated digging for water ice and other volatiles would be easy in these areas because Pete Schultz of the LCROSS science team described them as 'fluffy'.

In this Universe Today article he explains that he concludes that based on how the surface reacted when the empty Centaur stage hit it to create the debris plume the LCROSS instruments measured. There was a delay before the flash of that impact in the infra-red range was detected:

We knew when it was going to hit the surface – we know how fast how we were going and where we were above the surface — and it turned out there was a delay before we saw the flash and that was really a surprise... It was about a half second delay and then it took about a third of second delay before it began to rise and get brighter. The whole thing took seven-tenths of a second before it began to get bright. That is hallmark of a fluffy surface.

Having heard a few talks by experts on polar volatile deposits, I had the impression the nature of the deposits is still unknown, and had thought it likely that digging for them would be more like digging into frozen tundra than into sort of a dirty snow. Is that fluffy surface layer a generally accepted conclusion, or are there different viewpoints?

Answer 1

It’s not a “generally accepted conclusion”, but it’s somewhat likely to be the case.

The reason I have heard from people who were involved in South Pole rover prototypes is as follows: because of the constant, low temperature of the Permanently Shaded Regions, there may not have ever been enough thermal cycling for the surface sediment to settle and compact. The rest of the moon doesn’t have this problem because it sees day/night cycles with the revolution of the moon. You can think of it the same way as a bag of chips that looks half-empty because of settling in transport.

There’s a small possibility that moonquakes are enough of an effect to induce this settling regardless of the temperature range.

NASA JSC has worked in the past to develop rover wheels that are suited to driving in low gravity with very fluffy surface sediment. Some of these designs resemble steamboat paddles.